BIRDS (Chapter 4)

Lead Authors:  Barbara Ganter and Anthony J. Gaston

Contributing Authors: Tycho Anker-Nilssen, Peter Blancher, David Boertmann, Brian Collins, Violet Ford, Arnþór Garðasson, Gilles Gauthier, Maria V. Gavrilo, Grant Gilchrist, Robert E. Gill, David Irons, Elena G. Lappo, Mark Mallory, Flemming Merkel, Guy Morrison, Tero Mustonen, Aevar Petersen, Humphrey P. Sitters, Paul Smith, Hallvard Strøm, Evgeny E. Syroechkovskiy and Pavel S.  Tomkovich

SUMMARY

Photo: Jan van de KamThe Arctic is seasonally populated by roughly 200 species of birds, corresponding to about 2% of global avian species diversity. In contrast to more southerly latitudes, the dominant ecological and taxonomic groups among Arctic birds are waterfowl, shorebirds and seabirds, while songbirds are less prominent and much less diverse than at lower latitudes. The vast majority of species only spends a small portion of each year in the Arctic – but it is here that reproduction takes place. 

Of the 162 species for which more than half of their breeding range falls in the terrestrial or marine Arctic, about half have a circumpolar distribution while the others are confined to either the Nearctic or Palaearctic or to the Atlantic or Pacific ocean basins. A particularly high species richness is found on both sides of the Bering Strait. Overall, species diversity is more than twice as high in the low Arctic than in the high Arctic. 

Because of the migratory nature of most Arctic birds, these animals connect the Arctic to all other parts of the globe. Arctic birds winter as far south as the southern tips of the continents, and some even reach Antarctica. The extent of migratory behavior also means that the population sizes and trends of Arctic birds are sometimes affected, either positively or negatively, by events and activities occurring outside the Arctic. There are many examples of such extra-Arctic effects. As a consequence, conservation of Arctic birds will almost always necessitate international cooperation throughout the range of the migratory species. This is especially critical for the endangered species among Arctic birds, such as the Siberian crane Leucogeranus leucogeranus or the spoon-billed sandpiper Eurynorhynchus pygmeus, the latter currently facing extinction.

I have started to notice birds which I used to only see on TV, little birds which have multi-coloured bills, that fly home with multiple cod in their beaks and that burrow into the soil. I think these are the puffi ns, which are located some distance south migrating north due to the disappearance of the ice cover during the summer months. Pijamin: Elders Conference on Climate Change 2001.

Global climate change has the potential to influence Arctic bird populations in many ways, through effects acting in the Arctic itself as well as on migration routes or in wintering areas. However, although there are some indications that climate-induced changes are already taking place, the anthropogenic factors that are independent of climate – disturbance, habitat loss, fishing, hunting, agricultural intensification – have a much larger impact on populations at present.

INTRODUCTION

Despite its harsh environment, the Arctic is populated by a variety of different bird species. Arctic breeding birds benefit from a short but strong seasonal outburst of food availability, be it growing plants for herbivores, invertebrate biomass for insectivores or zooplankton for seabirds and their fish prey. This plentiful seasonal food supply is coupled with relative safety from predation created by continuous daylight, a low diversity of predators and the sheer numbers of prey swamping predator pressure (McKinnon et al. 2010). Diseases and parasites are also less prevalent than in warmer climates (Kutz et al. 2005). After the breeding season, however, most birds leave the Arctic to spend the winter in warmer climate zones; in fact, the majority of ’Arctic birds’ spend only a small fraction of each year on their Arctic breeding grounds (Meltofte 1996, Newton 2007). Their migrations connect the Arctic to all other parts of the globe.

 Being highly visible and audible as well as diurnally active, birds are one of the groups of organisms that are best known to humans worldwide. Hence, Arctic birds also have a strong cultural significance to the indigenous peoples of the Arctic. The arrival and departure of migratory birds marks the changing of the seasons, and in addition to their significance as a food source birds also play a role for festivals and the planning of family and community events. 

Roughly 200 bird species breed in the Arctic, amounting to 2% of the global avian biodiversity. However, the relative weight of higher taxonomic groups is different from the global total. The Anseriformes (waterfowl) and Charadriiformes (shorebirds, gulls, auks) make up the majority of avian diversity in the Arctic and are therefore treated in detail in separate sections of this chapter. By contrast, the songbirds, being the most diverse group elsewhere, are underrepresented in the Arctic and are treated together with the other ’landbirds’ below. 

Whereas some species occur mostly in temperate latitudes and only reach the Arctic at the fringes of their distribution, others are more or less confined to the Arctic during the breeding season. These ‘true Arctic’ species will be the main focus of the analyses below. Among them there are species with a circumpolar distribution while others are confined to one of the hemispheres or have even more restricted distributions. In their sum, the distributions of the single species result in patterns of species richness that differ throughout the Arctic. In this chapter we address these species richness patterns as well as the current status, trends and future prospects of individual species.

CONCLUSIONS AND RECOMMENDATIONS

With about 2% of the global species total, the Arctic supports only a small fraction of the world’s avian biodiversity, but adaptation to the harsh Arctic environment has created a variety of highly specialised species and a number of Arctic endemics. Because almost all Arctic birds are migratory, population trends for many species are driven by events outside the Arctic. For year-round resident Arctic birds, little trend information is available. Where trends are known for migratory populations, the main pattern of trends can be summarized as follows: increases in many Nearctic and W Palaearctic waterfowl populations, especially geese; and decreases in many shorebird populations and waterfowl of the E Palaearctic. For some species wintering in E Asia, habitat loss and hunting in the wintering grounds have been identified as the main causes of population decline. Problems with food supply on critical staging areas have also been diagnosed for a few shorebirds migrating through the Americas. Because of the international nature of migratory birds, conservation action for endangered Arctic breeders must include international cooperation on a flyway level both in and outside the Arctic, to ensure safeguarding of critical habitats and proper management of hunting. This is especially critical for highly endangered migratory species such as the spoon-billed sandpiper and the Siberian crane.

On the Arctic breeding grounds, known causes of population changes have been excessive harvest and climate variability, while potential threats include oil, gas and mineral exploitation. Oil exploitation at sea and increased transport of oil through Arctic waters, with its associated risks of oil spills, is especially hazardous for the great number of marine and coastal birds of the Arctic. The aggregation of very large numbers of birds in breeding colonies or molting sites, often associated with areas of high productivity and a of high diversity of other taxa (e.g. fish, marine mammals), makes the protection of such colony and molting sites and adjacent waters from the risk of oil spills a priority. Breeding and molting birds can also be negatively affected by disturbance resulting from industrial development and tourism, which can increase predation and/or keep birds from using suitable habitats. Again, this is especially severe where large concentrations of birds are affected. The overharvesting of Arctic birds is a problem mainly of inhabited regions, principally in the sub-Arctic or the fringes of the Arctic. In some cases these problems are either solved or on the way to solution: eider populations affected by over-harvesting in the late 20th century are recovering, and the greatly diminished population of thick-billed murres in Novaya Zemlya have stabilized.

In the true Arctic, some heavily harvested species, particularly geese, are increasing rapidly. Because ‘overabundant’ geese are causing degradation of sensitive habitat in some Arctic areas, management efforts have been initiated to reduce population sizes through increased hunting outside the Arctic. The problem with use of hunting as a management tool is that the massive shooting needed to significantly reduce numbers may cause high crippling rates, greatly increased shyness and create widespread disturbance of other waterfowl species on the staging and wintering grounds (Madsen & Fox 1995, Noer & Madsen 1996).

Climate change may act on Arctic bird populations in various indirect ways (Boyd & Madsen 1997). These include changes in food supply; predators, prey, parasites and diseases; mis-match between the peak of availability of food and the timing of arrival on breeding grounds, hatch, brood rearing or migration. The northward shift of vegetation zones will affect both food and habitat, as well as habitat loss due to permafrost thawing in some areas. However, even though single effects have been shown at a local scale for some bird populations, the complexity of these interacting factors makes it very hard to predict future impacts of a warming climate on Arctic bird populations. Some effects, like the impact of egg-eating by polar bears, may attenuate, as bear populations at lower latitudes decline (see Reid et al., Chapter 3).

Some species found mostly or entirely in the Arctic are showing signs of population decline which may be related to climate change (ivory gull, thick-billed murre, gyrfalcon, perhaps snowy owl). The exact causes are unknown, but may relate directly or indirectly (e.g. through changes in their food supply) to increasing temperatures. We need much more extensive monitoring, especially in Canada and Siberia, to better assess the causes of population change. Greater integration of national monitoring programmes under the Arctic Monitoring and Assessment Programme, the Arctic Breeding Bird Condition Survey (ABBCS) and the Circumpolar Seabird Data Portal (Seabird Information Network 2012) would be useful and the CAFF seabird group could provide the necessary incentive. We particularly need better information on the non-game Arctic endemics: gyrfalcon, snowy owl, shorebirds, ivory, Sabine’s and Ross’s gulls, jaegers/skuas and little auks. With their breeding distributions restricted to Arctic biomes, these birds are likely to be the first to exhibit symptoms of climate change effects. Likewise, we need regular monitoring of important wintering areas for Arctic seabirds and waterfowl, such as SW Greenland (Boertmann et al. 2004), waters off Newfoundland and Labrador (Frederiksen et al. 2011) and polynyas supporting eiders in the N Bering Sea (Petersen & Douglas 2004). 

If climate change proceeds as predicted, many of the bird species characteristic of the northern taiga and sub-Arctic are likely to expand northwards as temperatures increase. However, this cannot be viewed as an improvement in the richness of the Arctic avifauna, but rather constitutes a contraction in the area of the Arctic, as we have hitherto defined it in biological terms. Ultimately, much of the region now characterised by a high Arctic fauna may become low Arctic in character, and the eventual disappearance of typically high Arctic birds such as gyrfalcon, ivory gull and little auk seems probable.

AMPHIBIANS AND REPTILES (Chapter 5)

Authors:  Sergius L. Kuzmin and David F. Tessler

SUMMARY

Moor Frog. Photo: Konstantin Mikhailov, Nature Picture LibraryThe herpetofauna of the Arctic is depauperate relative to temperate and tropical regions. Only five amphibians and a single reptile range into the Arctic, and none are circumpolar. All Arctic amphibian and reptile taxa are currently categorized as ‘Least Concern’ according to IUCN criteria. However, basic survey and inventory data for these species are lacking across most of the Arctic, and there are few quantitative data on abundance, status or trends for Arctic herpetofauna. At the same time, isolated populations of amphibians and reptiles in the Arctic exist at or near their current physiological limits and likely face a number of escalating challenges stemming primarily from habitat alteration.

INTRODUCTION

Although amphibians and reptiles account for nearly 15,000 species worldwide, only five amphibians and a single reptile are found in the Arctic. The majority of Arctic herpetofauna are found in the eastern hemisphere; there are no circumpolar taxa (Tab. 5.1). Amphibian species richness (number of species) in the Arctic is as low as in desert regions. Amphibians and reptiles are phylogenetically the oldest of terrestrial vertebrates, and their limited representation in the Arctic is due in large measure to their poikilothermic physiology (body temperature determined by ambient conditions).

We have lizards. We have seen them this year even at the upper reaches of ‘Afanas’ki’.
Leader of the Saami indigenous obschina ‘Piras’ in the Kola Peninsula, Andrey Yulin on northwards expansion of lizards; Zavalko & Mustonen (2004).

A number of recent publications have suggested major changes to herpetological systematics (Frost et al. 2006, Roelants et al. 2007), but because these proposed changes are not yet universally accepted and many names remain in a state of flux, we follow stable herpetological taxonomy as described in Collins & Taggart (2002) and Kuzmin & Semenov (2006).

Eastern hemisphere taxa:

• Siberian newt Salamandrella keyserlingii
• Common frog Rana temporaria
• Moor frog Rana arvalis
• Siberian wood frog Rana amurensis
• Common lizard Lacerta vivipara

Western hemisphere taxa:

• Wood frog Rana sylvatica

CONCLUSIONS AND RECOMMENDATIONS

Sensitive areas and hotspots

Hotspots are difficult to identify because the distributions of Arctic amphibians and reptiles are so poorly characterized. Furthermore, these species are found in small, isolated and patchily distributed populations for a variety of reasons: (1) their Arctic range limits likely represent each species’ physiological limitations, (2) amphibians require a number of different microhabitat features to intersect in close proximity due to their limited movement potential, and (3) they may not occupy all suitable habitats within their apparent range due to the susceptibility of small populations to stochastic events and the residual effects of past disturbances (Olson 2009). Nonetheless, a few areas in the Eastern hemisphere appear to be of particular importance: the corridors and deltas of the Khadyta-Yakha River on the Yamal Peninsula, the Chaunskaya Tundra in the lowlands of the Chaunsky Administrative District of the Chukotsky Autonomous Okrug, and the Khalerchinskaya Tundra in the Kolyma lowlands.

KEY KNOWLEDGE GAPS

The principal knowledge gap is the near complete lack of survey and inventory data for status and population trends of Arctic amphibians and reptiles. Distributions are poorly and incompletely characterized, and are known only in broad general terms.

There are no reliable abundance estimates for local or regional populations for any Arctic herpetofauna, and there are no statistically meaningful monitoring efforts currently in place. General lack of understanding of the factors which limit amphibian and reptile populations in the Arctic is also a principal knowledge gap. 

Research recommendations

• Establish effective survey and inventory efforts to better define the actual distributions and ecology of these species.
• Construct statistically defensible baselines of abundance data in specific locations against which changes in abundance can be monitored.
• Establish monitoring programs with replicate schema representative of the range of habitats and microhabitats inhabited by each species. Monitoring locations should also be chosen in such a way so as to minimize the effort and expense to reach them in order to increase the likelihood that monitoring will be continued into the future. If practicable, monitoring efforts should be collocated with monitoring efforts for other taxa in order to develop economies of scale for all monitoring, and to improve our understanding of the dynamics of Arctic ecosystems.
• Conduct research into the impacts of climate-induced changes to hydrology/hydroperiod on reproduction, persistence and habitat connectivity for Arctic amphibians.
• Determine the geographic prevalence of contaminant burdens and chief pathogens for amphibians across the Arctic.
• These efforts may involve citizen science projects.

Conservation action recommendations

• Develop guidelines for human development projects that require land managers and developers to consider amphibian and reptile habitats and populations in their development plans.
• Determine which areas are of special importance for amphibian and reptile species richness and for the long-term persistence of individual taxa. Use data from survey and inventory efforts to identify hotspots and areas of likely significance by modeling species’ habitat and micro-habitat associations across the Arctic landscape.
• Establish or strengthen protections for areas of key importance to reptiles and amphibians. Arctic amphibians have complex life cycles, and require a range of habitats throughout their annual cycles and life histories. Conservation of these species will require a landscape-level approach, conserving various vital habitats at appropriate spatial scales and maintaining connectivity between conservation units, while accounting for expected wetland loss and alteration.

FISHES (Chapter 6)

Authors:  Jørgen S. Christiansen and James D. Reist  

Contributing Authors: Randy J. Brown, Vladimir A. Brykov, Guttorm Christensen, Kirsten Christoffersen, Pete Cott, Penelope Crane, J. Brian Dempson, Margaret Docker, Karen Dunmall, Anders Finstad, Vincent F. Gallucci, Johan Hammar, Les N. Harris, Jani Heino, Evgenii Ivanov, Oleg V. Karamushko, Alexander Kirillov, Alexandr Kucheryavyy, Hannu Lehtonen, Arve Lynghammar, Catherine W. Mecklenburg, Peter D.R. Møller, Tero Mustonen, Alla G. Oleinik, Michael Power, Yuri S. Reshetnikov, Vladimir I. Romanov, Odd-Terje Sandlund, Chantelle D. Sawatzky, Martin Svenning, Heidi K. Swanson and Frederick J. Wrona

SUMMARY

Large Male Dolly varden. Photo: Neil Mochnacz Having occupied Earth’s waters for about five hundred million years, fishes are the oldest group of living vertebrates. Fishes have radiated to occupy most aquatic habitats on the planet, and estimates of total biodiversity range from 28,000 up to about 35,000 species. Fishes are associated with both marine and freshwater habitats, and some migrate between these biomes. Globally, about 16,000 species occupy marine waters, 12,300 are found in fresh waters, and 225 use both habitats during their lives. It is within this global diversity context that the diversity of Arctic fishes must be assessed.

Freshwater fishes are those confined to low salinity aquatic habitats; diadromous fishes are those which regularly migrate between fresh and marine waters. The latter occur as two major groups – anadromous fishes spend much of their lives in marine waters migrating to fresh water to reproduce, and catadromous fishes do the converse. Anadromous fishes constitute the majority of diadromous fishes in the Arctic. Between 17 and 19 families (3-4% of 515 worldwide) of freshwater and diadromous fishes occur in Arctic waters with about 123-127 recognized species (1% of 12,547 extant freshwater and diadromous species globally). Many of these taxa are unresolved species complexes, consist of multiple types that have differentiated in separate glacial refugia and/or exist as multiple life history and/or ecophenotypic forms. All these forms tend to function as, and may be the equivalent of, taxonomic species. Accordingly, an estimate of simple parameters such as species richness and taxonomic and phylogenetic diversity is fraught with problems and generally under-estimates the true diversity present. To facilitate this, we will use the upper estimate (127 species) herein.

Local indigenous fishermen from Pokhodsk and Nutendli report that muksun Coregonus muksun (a freshwater fish) amounts have decreased. Fyodor Innokentyevich Sokorikov, former head of the fishing sovhoz in Pokhodsk reports that muksun was caught in the amounts of 1,500 tonnes annually in the 1980s but says that in late 1980s and early 1990s there was overfishing of muksun and that is why it has collapsed now. Mustonen 2007.

Five families (salmonids – 50+ species of chars, whitefishes (sensu Coregonus), salmons; cyprinids – 25 minnows; cottids – nine sculpins; percids – eight perches; and petromyzontids – six lampreys) account for most of the freshwater taxonomic diversity present. Ecotones, areas where distinct habitats or physiographic realms meet, exhibit high local diversity, particularly in lake and river deltas and the estuaries of the large Arctic river basins. Similarly, large water bodies with complex habitats (e.g. deep lakes, large rivers) exhibit high diversity that may be manifested at sub-specific levels. Geologically young landscapes experiencing active disturbance, taxonomically labile fishes, generalist biological strategies and inherent capacity for rapid change in many key groups result in the Arctic being an area where rapid evolution of these fishes appears to occur. This underscores their significance in a global context.

Spatially, freshwater fish diversity decreases with latitude (e.g. in North America species richness is 40 at 60° N, 31 at 70° N along the mainland margin, three at 74° N and one farther north to the maximum extent of fresh waters on land at about 84° N). Longitudinally, the greatest diversity is present in areas that were unglaciated during the last ice age (i.e. much of Siberia and Beringia; see Fig. 2.2 in Payer et al., Chapter 2), declining to low levels in the eastern Canadian Arctic and Greenland that were deglaciated last and still retain large ice sheets. Time lines are too short and monitored sites too few to document temporal trends in species diversity in the Arctic. However, recent evidence suggests northward colonizations by freshwater fishes along river corridors and diadromous species into marine environments where climatic constraints have recently decreased. At present, no documented local extirpations or extinctions of taxa are known in the Arctic, although local population declines have occurred. Anthropogenic stressors are increasing in importance as risk factors both locally and throughout the Arctic. Local ‘hotspots’ of diversity and several globally significant water bodies are present.

 Arctic freshwater and diadromous fishes are of particular importance to humans both inside the Arctic and elsewhere. Food fisheries by indigenous peoples (i.e. subsistence fisheries) are extensive throughout the Arctic and historically always have been. 

Pervasive stressors such as climate change result in significant and rapid habitat alterations (indirect effects) as well as direct effects (e.g. thermal stresses) which challenge these fishes. Productivity shifts associated with climate change may create new opportunities (i.e. increased population sizes, growth potential) for freshwater and diadromous fishes.

Localized stressors (e.g. fisheries, hydrocarbon development, industrial activities, mining, water withdrawals, hydroelectric dams) affect populations either directly (fisheries) or through habitat impacts.

Marine fishes reproduce and spawn in seawater although juveniles and adults may occur also in the low salinity waters of fjords, coastal areas and river deltas. Here, we review the marine fishes across the Arctic Ocean and adjacent Arctic seas (AOAS). Altogether 16 regions and seas are examined for species richness, including the main entrances i.e. ‘Arctic gateways’ that connect the Atlantic and Pacific Oceans with the Arctic Ocean and Arctic shelves. While nearly 250 marine fish species are known from Arctic waters sensu stricto, the AOAS encompass pro tem 633 known fish species in 106 families. Cartilaginous fishes such as sharks and skates are well represented with about 8% of the species, whereas 92% are bony fishes. From a zoogeographic point of view, only 10.6% of the bony fishes are considered genuinely Arctic and 72.2% are boreal.

The fish faunas of the Arctic gateways are relatively well known compared with the Arctic seas as they support some of the largest commercial fisheries in the world. They are undeniably also the most species-rich regions of the AOAS and include 385 species in the Bering Sea, 204 species in the Norwegian Sea and 153 species in the Barents Sea. This is in stark contrast to the Arctic Ocean and Arctic shelves where only 13-87 species are recorded to date.

Fishes of the AOAS may display extraordinary phenotypic variation, and the taxonomic status is still unsettled and controversial for several fish species, particularly within the most species-rich families: snailfishes (Liparidae), eelpouts (Zoarcidae) and sculpins (Cottidae). Moreover, new fish species are described regularly, mainly due to recent efforts in Arctic marine research, whereas others are synonymized and lose their taxonomic rank following molecular and genetic studies.

Species richness increases with sea-surface area for the relatively well studied Arctic gateways, which is to be expected. By contrast, there is no species-area relationship for the understudied Arctic seas, and they display disproportionately low numbers of species. The paucity of credible data and lack of time-series for fishes in the Arctic Central Basin and Arctic shelves clearly preclude trend analyses and elaborate studies on biodiversity.

Ocean warming in the marine Arctic has become increasingly critical for the fish fauna native to Arctic waters. The marked shifts in distribution patterns for many targeted fishes, from sub-Arctic to high latitude seas, will inevitably attract modern fishing fleets into hitherto pristine areas, and may conflict with extant subsistence livelihoods among indigenous peoples along the Arctic coasts. Fishes native to Arctic marine waters are mainly associated with the seabed, and they are particularly vulnerable to conventional bottom trawling as they end up as unwanted and unprecedented bycatch. Although of no commercial value, bycatch fishes include species that are indispensable to structuring and functioning of Arctic marine ecosystems.

Credible assessments are the scientific link to legitimate conservation actions. Scientific uncertainty is at present a hallmark for the conservation of Arctic marine fishes, and precautionary management policies are urgently needed for future Arctic fisheries.

Significant gaps exist in the knowledge base for diversity of Arctic fishes. Practical measures to document trends and conserve diversity are thus compromised.

INTRODUCTION

This chapter provides an up-to-date overview of the fish species for which occurrence is scientifically confirmed within the borders of the Arctic mainland and the Arctic Ocean and adjacent seas. We use ‘fishes’ in the wide sense of the word and include four fish and fishlike vertebrate classes: the hagfishes (Myxini), the lampreys (Petromyzontida), the cartilaginous fishes (Chondrichthyes) and the bony fishes (Actinopterygii) (Nelson 2006). In the Arctic, the four classes show some notable differences in habitat choice: the lampreys are confined to freshwaters for reproduction, the hagfishes and the cartilaginous fishes are exclusively marine, whereas the bony fishes inhabit all aquatic environments.

The genuine freshwater fishes and most diadromous fishes require freshwater for reproduction. Diadromous fishes are those species that undertake regular migrations between freshwater and marine habitats, either for refuge, feeding or reproduction (McDowall 1992). Among these are the well-known fish families: lampreys (Petromyzontidae), and whitefishes and salmonids (Salmonidae) as well as some lesser-known groups.

The marine fish fauna, on the other hand, encompasses species that spawn at sea: in the littoral zone along the coastlines, in estuaries and fjords, on the shelves and seaward. Several habitats are oligohaline (salinity < 5 practical salinity units (psu)), such as estuaries, but they are still considered within the geographic realm of the marine Arctic.

In the Arctic, the freshwater and diadromous fishes are significantly molded by glaciation, deglaciation and geological events during the late Pleistocene and Holocene epochs (i.e. ~ 126,000 and 12,000 years ago, respectively). The evolutionary history of the marine fish fauna, on the other hand, dates back to the Neogene period as the modern circulation in the Arctic Ocean began to form some 14-17 million years ago (Krylov et al. 2008, Polyak et al. 2010). For reasons of clarity and because of the marked differences in habitat choice and evolutionary history, this overview of Arctic fishes is organized into two separate subchapters: (1) freshwater and diadromous fishes of the Arctic and sub-Arctic (J.D. Reist), and (2) marine fishes in the Arctic Ocean and adjacent seas (J.S. Christiansen).

CONCLUSIONS AND RECOMMENDATIONS- FRESHWATER AND DIADROMOUS 

Conclusions

• The documentation, delineation, synonymization, uniqueness and nature of taxonomic, functional and biological types of diversity are poorly known throughout much of the Arctic and sub-Arctic for freshwater and diadromous fishes. Remote and geographically large diverse areas are particularly poorly studied. Basic information such as specific occurrences and distributional limits is generally lacking for most areas. Taxonomic confusion and unresolved complexities of diversity are apparent in many groups of these fishes and across all levels from local population structuring to that of the species.
• Similarly, both natural and anthropogenic factors that maintain (or promote), truncate or differentially affect diversity within and among these levels  are poorly known. Generally, anthropogenic factors appear to affect diversity directly (e.g. specific taxa or forms exploited in fisheries) and indirectly by altering processes by which diversity is maintained (e.g. climate change affecting productivities of water bodies). Effects of cumulative interactions are particularly problematic. 
• Association of various types and levels of diversity with particular ecosystem types, specific ‘hotspots’ and/or geographic scales is somewhat better understood, but large gaps remain. Additionally, although some distinctive types of diversity have been documented and/or locations with unique diversity are known, it is likely that many undocumented situations exist. 
• Rates of anthropogenically driven change (e.g. resource extraction, climate variability) in the Arctic suggest that much diversity will likely be lost before it is adequately understood or documented.
• Understanding of roles and relative importance of both the types of diversity and the various levels within those types is generally required. 
• Documentation of the nature and consequences of anthropogenic effects on diversity is required.
• Documentation of ecosystem roles (e.g. stability/ resiliency) and services that accrue from these fishes and their varying levels of diversity are required in terms of those directly accrued by humans (especially indigenous peoples locally) and for other valuable ecosystem components (e.g. as key prey items for marine biota). 
• Better documentation of cultural and traditional uses and relevance of fishes to indigenous peoples is required. These, and levels of use for food (7 above) and selectivity for particular forms, require better documentation. 
• Better documentation is required of local commercial and sport fisheries, both of which are often underreported.
• Development of protected areas for aquatic biota, particularly for areas where unique or highly diverse groups are present, is in its infancy (in comparison with that for terrestrial biota). Most efforts at conservation are directed towards taxonomic diversity, rather than to functional diversity or dynamic habitats, which might change over time, or to key processes which maintain diversity. Adapting existing models to a dynamic, more vaRiable and changing world is required. 
• Development and implementation of relevant and rapidly assessed indicators of effects of change on fish biodiversity are required. 
• A multitude of definitions of species coupled with highly variable taxonomic philosophies result in wide inter-regional disparity of practical definitions at the species level. This undermines spatial and temporal assessments of diversity, changes therein and linkages to causation. 
• Although many species of Arctic endemic or Arcticcentric fish species can be considered iconic, this diversity is unknown and/or under-appreciated by most. 

Recommendations

Based upon the above conclusions, the following five recommendations are made regarding research and management of Arctic freshwater and diadromous fishes:

• Concerted and coordinated effort to document and understand the roles of diversity of Arctic freshwater and diadromous fishes is rapidly required throughout much of the Arctic, at a wide range of geographic scales using a range of techniques. This includes active research to resolve taxonomic complexes and relationships among levels of diversity, issues which are especially prevalent in these fishes.
• Development and implementation of comprehensive circumpolar monitoring of freshwater and key diadromous fish populations and their supporting ecosystems (e.g. through a dispersed observatory network) is required across the range of ecosystem and diversity types present. This needs to include parallel monitoring of key locally originating and pervasive anthropogenic stressors. 
• Ecosystem-level research programs are required across the Arctic, and these must include all aspects of human interaction with the fishes and their ecosystems. Programs should be explicitly linked with stressors impinging upon biodiversity, key ecosystems and processes which maintain biodiversity, endemism or areas of high diversity. Research linking ecosystem processes to diversification of forms is a priority given the overall relevance of such understanding to global issues. 
• Alternative approaches are required which realistically reflect conservation of diversity, habitats currently used (and those possibly used in the future as change is effected) and processes relevant to maintaining and/or promoting diversity.
• Development of clear, workable circumpolar definitions of taxonomic diversity at various levels for these fishes and their relevance to human activities is required. Communication and outreach both among taxonomic experts and between these experts, users of their information and the public (both within and outside the Arctic) is required to enhance awareness, importance and conservation actions for this group of fishes.

CONCLUSIONS AND RECOMMENDATIONS- MARINE

Key knowledge gaps

Once patterns of biodiversity emerge, it is essential to identify the underlying processes to counteract negative trends. Still, patterns remain fragmentary for the majority of fishes in the Arctic Ocean and adjacent seas (AOAS). The following issues are suggested to increase present knowledge to a point where sensible hypotheses may be proposed and tested, credible forecasts made and legitimate actions executed (Christiansen et al. 2013):

• Long-term time series of real-world and diagnostic data are essential for forecasting biological and environmental trends. Therefore, key sites and baseline transects for long-term studies of functional biodiversity should be identified in the AOAS (cf. CBMP online).
• Natural history collections (NHC) hold essential information for studies of biodiversity (Harrison et al. 2011, Lister et al. 2011), and information from fishery logbooks has proven valuable in historical analysis of population trends (Alexander et al. 2009). Therefore, NHCs should be continuously upgraded and archival data critically examined and employed to reconstruct long-term time series for specific AOAS regions.
• Taxonomy and conservation are two sides of the same coin. Classic taxonomy is a critically endangered science and a craft that cannot be substituted by DNA profiles and gigabytes (Bacher 2012, Deans et al. 2012, Scotland & Wood 2012). Therefore, training programs in taxonomy sensu lato and biogeography for young researchers should be encouraged.
• Habitats of particular significance for conservation, such as breeding grounds and biodiversity hotspots, should be identified in time and space and protected accordingly, cf. the debate on Marine Protected Areas (MPAs) (Henriksen 2010, Barry & Price 2012, Rice et al. 2012). 
• Fishing gear technology designed for sustainable fisheries in Arctic waters is poorly developed. Multidecadal datasets from the North Sea unequivocally demonstrate that conventional bottom trawl fisheries for groundfishes are extremely efficient but also highly damaging to the environment, as they impoverish, perturb and change the functional composition of benthic communities (Tillin et al. 2006, Thurstan et al. 2010). Arctic fish species are largely bottomliving and territorial (Karamushko 2012), and since Arctic groundfish fisheries are expected to increase in coming years, less harmful fishing technologies should be developed and used to minimize bycatch and seabed destruction.
• Abrupt shifts in abundance trends are warning signals for conservation. Therefore, accurate bycatch statistics in upcoming Arctic fisheries are crucial and call for adaptive monitoring plans and policies to meet conservation aims (Lindenmayer et al. 2012). A range of management policies for marine fisheries are in operation worldwide (Pitcher & Lam 2010), and fisheries founded on balanced rather than selective harvesting are currently debated (Garcia et al. 2012, Borrell 2013). No single harvesting practice is foolproof. But any management policy would be desireable if it relies on the principle of full accountability– that is a procedural change from the present-day selective fishing and fixed landing quotas of targeted species to catch quotas that embrace the entire biomass extracted from the sea, i.e. targeted and non-targeted species alike. For example, catch quota management (CQM) seems a promising policy that has been tentatively implemented in the North Sea fisheries (Kindt-Larsen et al. 2011, Schou 2011). Combined with taxonomic expertise on non-targeted Arctic species, CQM may well be the immediate and first step toward obtaining credible and urgently needed bycatch data as a precautionary measure for upcoming Arctic fisheries.
• Traditional ecological knowledge (TEK) and citizen science (Hochachka et al. 2012) would generate valuable and complementary information that should be critically scrutinized to increase the legitimacy of biodiversity assessments across the marine Arctic. This would require a completely new setting, and a designated forum of TEK-informants and scientists is called for, to ensure that trust-building and respectful and equal sharing of information and methods are also put into practice.
• An ambitious interdisciplinary science plan should be outlined and implemented as a precautionary and fundamental measure to meet large-scale human intervention in understudied Arctic waters (cf. PEG 2012)

TERRESTRIAL AND FRESHWATER INVERTEBRATES (Chapter 7)

Lead Author:  Ian D. Hodkinson 

Contributing Authors: Anatoly Babenko, Valerie Behan-Pelletier, Jens Böcher, Geoffrey Boxshall, Fenja Brodo, Stephen J. Coulson, Willem De Smet, Klára Dózsa-Farkas, Scott Elias, Arne Fjellberg, Romolo Fochetti, Robert Foottit, Dag Hessen, Anders Hobaek, Martin Holmstrup, Seppo Koponen, Andrew Liston, Olga Makarova, Yuri M. Marusik, Verner Michelsen, Kauri Mikkola, Tero Mustonen, Adrian Pont, Anais Renaud, Leopoldo M. Rueda, Jade Savage, Humphrey Smith, Larysa Samchyshyna, Gaute Velle, Finn Viehberg,Veli Vikberg, Diana H. Wall, Lawrence J. Weider, Sebastian Wetterich, Qing Yu and Alexy Zinovjev 

Consulting Authors: Richard Bellerby, Howard Browman, Tore Furevik, Jacqueline M.Grebmeier, Eystein Jansen, Steingrimur Jónsson, Lis Lindal Jørgensen, Svend-Aage Malmberg, Svein Østerhus, Geir Ottersen and Koji Shimada

SUMMARY

The mirid bug Chlamydatus pullus feeding in a flower head of the dandelion Taraxacum croceum. Photo: Jens Böcher

The known terrestrial and freshwater invertebrate faunas of the Arctic comprise several thousand described species, representing over 16 major phyla. Many other species remain to be discovered and/or described. Arctic endemic species occur in many invertebrate groups. A significant proportion of Arctic species have circumpolar distributions. By comparison with better known groups such as vertebrates and plants, the invertebrates exhibit much higher biodiversity at all taxonomic levels and attain greater population densities in favorable habitats. Springtail (Collembola) numbers, for example, sometimes exceed 0.5 × 106/m² and eelworm (Nematoda) populations reach over 7.0 × 106/m² in areas of Taimyr.

Little is know about the detailed distribution and biology  of most species, and good long-term population data  on individual species, sufficient to indicate population  trends, are almost entirely lacking. Predictions of how  Arctic invertebrate communities may respond to climate  change are, of necessity, based on extrapolations from  experimental and/or distributional studies based on a  few selected species or species groups in a restricted  range of habitats.

This chapter brings together, and highlights for the first  time, baseline information on the biodiversity of all Arctic  terrestrial and freshwater invertebrates. It evaluates  the importance of habitat diversity, climatic severity and  biogeography, particularly historic patterns of glaciations,  as determinants of invertebrate biodiversity. The  significance of the Beringia refugium for biodiversity in  several groups is stressed. Invertebrates are key players  in a range of ecosystem services within the Arctic,  including herbivory, decomposition, nutrient cycling,  pollination, parasitism and predation.

Big new insects have appeared, beetles that fly. [American buring beetle] Jolene Nanouk Katchatag an Inupiaq from Unalakleet, Alaska; Mustonen & Mustonen 2009.

Changes in invertebrate communities, perhaps involving  new invasive species, may have important impacts on  several of these processes, particularly through interactions  with other groups of organisms. The key environmental  factors (drivers) determining species success in  an era of climate warming are likely to be mean summer  and winter temperatures, soil-moisture availability,  length of growing season and the frequency of freeze/  thaw events that may disrupt preparation for and emergence  from the overwintering state.Several recommendations for future action are listed.  Highest priority should be given to establishing an  inventory of Arctic invertebrate species, including their  distribution, habitat preference and ecological function.  This list should be used to identify true Arctic endemic  taxa, classify species according to IUCN Red Book  criteria and identify the vulnerability of species and their  habitats. Key indicator species that are responsive to  habitat change should be identified and monitored. For a  group as diverse as the invertebrates, conservation action  should focus on the maintenance of habitat diversity coupled  with the selection of ecologically important flagship  species that can provide a focus for raising the profile of  invertebrates as a whole.

INTRODUCTION

The observations by indigenous peoples given on the title  page of this chapter, often made in association with traditional  activities such as reindeer herding, hunting and  fishing, clearly suggest that profound changes are occurring  in the invertebrate faunas of the Arctic regions.  This chapter attempts to set a baseline for invertebrate  biodiversity within the Arctic, to document the scientific  evidence for such change and to provide a prognosis  and recommendations for the future.

Even within the scientific community, the biodiversity of invertebrates inside the Arctic is poorly understood  by non-specialists and is thus frequently underplayed or sometimes ignored. The CAFF Habitat Conservation Report No.4 (Principles and Guidelines), for example, states that “invertebrate fauna in the Arctic is scarce” (CAFF 1996), a statement far removed from reality. Collectively, the number of Arctic invertebrate species  greatly exceeds that of all other non-microbial eukaryotic  species groups combined, including the plants and the vertebrates. Furthermore, invertebrates are often found at densities of several hundred thousand, and occasionally several million, per square meter. Arctic invertebrate faunas are thus far from simple, but their complexity is less overwhelming than for many tropical ecosystems, and their diversity is perhaps more readily understandable  (Danks 1990, Vernon et al. 1998).

The mistaken idea of an overly ‘simple’ Arctic invertebrate  food web almost certainly owes its origin to a  summarizing diagram of the nutrient flow pathways  through the ecological community of Bjornøya, Svalbard, published by Charles Elton in 1923 (Hodkinson &  Coulson 2004). This diagram, erroneously interpreted  as a ‘simple’ food web, still holds sway in several modern ecology textbooks. In such diagrams, it is assumed that individual species within related invertebrate groups are ecologically interchangeable, performing similar  ecological functions or responding in similar ways to  environmental change. They are in consequence usually consigned together, for example to a ‘box’ labeled ‘ciliates’ or ‘Collembola’. This assumption of species equivalence is mistaken, and important components of biodiversity become hidden when species are aggregated and compartmentalized in this way. Take for example the unicellular ciliates, a group whose biodiversity is poorly known within much of the Arctic. Despite their relatively simple body form, the freshwater ciliates of Svalbard fall into eight different trophic groups, each feeding on different microscopic prey categories representing various  trophic levels and with individual species performing different ecological roles (Petz 2003). Similarly, species within several of the larger groups of Arctic invertebrates such as eelworms (Nematoda), springtails (Collembola), mites (Acari), flies (Diptera) and ground beetles (Coleop  tera), to name but a few, display a similarly wide range  of multi-trophic feeding specializations and adpatations (Chernov 1996, Rusek 1998, Chernov 2002, Makarova & Böcher 2009, Peneva et al. 2009). Trophic, behavioral  and physiological divergence among related species is thus  an important yet frequently overlooked component of  invertebrate biodiversity within the Arctic.

Now the black flies appear before the mosquitoes, this is something new. Komi Irina Kaneva from the Krasnochelye wilderness village on the Kola Peninsula; Mustonen 2011.

Many invertebrate species are endemic to the Arctic and  display highly restricted distributions. However, being  small and lacking the charisma of their vertebrate and  floral counterparts, few have received special conservation status, despite their vulnerability to climate change. A notable exception is the round spine tadpole shrimp Lepidurus couesii found in the American Arctic and listed as ‘endangered’ in the IUCN Red Data List. By contrast, many other Arctic invertebrate species are broadly distributed  across a wide circumpolar range and display unusually wide within-species genetic diversity, or differences in their methods of reproduction, throughout their geographical range (Hobaek & Weider 1999, Reiss et al. 1999, Hessen et al. 2004, Wheat et al. 2005). Because of their small size and mobility, terrestrial and freshwater invertebrates are well-adapted to the multiplicity of different microhabitats generated by macro- and microtopographic variations in the landscape, interacting with  climatic differences and the contrasting biotic environments created by different plant species and communities  (Coulson 2000). Many species show strict fidelity to  particular restricted microhabitat types, whereas others  are more generally distributed across a range of habitats. Such variation in habitat occupancy is an important facet  of biodiversity within the Arctic.

This chapter seeks to present a balanced assessment of invertebrate biodiversity and population trends within the Arctic regions. The quantitative data presented represent the best estimates available, but it should be recognized from the outset that our knowledge of Arctic invertebrates is far from complete, especially for many of the microscopic soil-dwelling forms. Our current understanding  of their biodiversity rests on the extent and quality of available data and the reliability of the methods used to obtain those data. For many invertebrate groups, our knowledge of their distribution is based on  a few samples taken from selected habitats at a few wellstudied sites. Often these inadequacies are compounded by taxonomic problems, particularly a lack of critical comparison of species across different regions of the Arctic. Furthermore, large areas of the Arctic remain under-sampled for many invertebrate groups. Current sampling methods may also fail to record all species present, as evidenced by divergence between studies of soil  fauna using traditional extraction techniques coupled with morphological taxonomy versus those based on the direct extraction of animal DNA from soil (Wu et al. 2009). Among ciliates and testate amoebae, for example, the number of described species may represent only a fraction of the total number of species present (Foissner  et al. 2008, Smith et al. 2008). Even in relatively well-known groups such as the springtails, molecular techniques are also beginning to reveal the presence of sibling species not discernible by traditional taxonomy based on morphology (Hogg & Hebert 2004).

Species abundance distributions for invertebrate communities  normally follow patterns in which the community is dominated by a few common species supported by a long tail of less common species, as for example in the Arctic testate amoebae on Richards Island, Canada (Dallimore  et al. 2000). From a biodiversity perspective, this  tail is highly significant but is rarely adequately sampled. The Arctic can also still produce surprises, as evidenced  by the relatively recent discovery of Limnognathia maerski, a representative of an entirely new Class of animal, the Micrognathozoa, in a cold spring on Disko Island, W  Greenland (Kristensen & Funch 2000). This species has subsequently been found on the sub-Antarctic Crozet Islands and is probably much more widely distributed than is currently recorded (De Smet 2002).

Population density estimates exist for many terrestrial  and freshwater Arctic invertebrates in a variety of  habitats (e.g. Hammer 1944, Coulson 2000, Sorensen et  al. 2006), but these are often spot estimates, and ther  are few if any data sets that reliably indicate population  trends over extended recent time periods. Even the more detailed population studies, with repeated sampling, rarely extend for periods greater than 3-5 years  (e.g. Addison 1977, Hodkinson et al. 1998, Søvik 2004). Frequently such population estimates have been made for taxonomic groups combined, such as for the total springtails or oribatid mites, rather than for individual species  It is thus difficult to identify shorter term trends in individual species populations associated with environmental change, and it is here that manipulation experiments are important. Such experiments, measuring experimentally the response of invertebrate populations to climate manipulation  and ideally linked to laboratory-based physiological studies, probably give us the best clues as to the  direction of potential future change (Hodkinson et al. 1998). The woolybear caterpillar Gynaephora groenlandica in Canada provides a good example of such a study (Kukal  & Dawson 1989, Morewood & Ring 1998, Bennett et  al. 1999). However, where a vertebrate ecologist might regard a drop of 25% in a species population density as significant, invertebrate ecologists struggle to estimate  mean population densities of even the commoner species  with an associated statistical error of less than 25%. Furthermore, invertebrate populations are often highly aggregated and frequently display wide natural fluctuation over short time scales and across topographically diverse landscapes (e.g. Høye & Forchhammer 2008). Their densities and the associated fluctuations are thus  normally expressed on the logarithmic rather than the more sensitive linear scale. Invertebrates are also capable, within limits, of shifting their population center to more suitable habitat in response to deteriorating conditions. Several species of springtails, for example, track optimum soil moisture status across a drying landscape within a given season, confusing population estimates at  any one fixed point (Hayward et al. 2001).Despite the limitations listed above, the stratigraphy of subfossil remains of invertebrate groups within the Arctic such as beetles, chironomid midge (Chironomidae)  larvae, testate amoebae and ostracod crustaceans  (Ostracoda) have successfully been used to indicate past climatic conditions and the way these conditions have changed over time (e.g. Bobrov et al. 2004, Wetterich et al. 2005, Zinovjev 2006, Thomas et al. 2008, Porinchu et al. 2009, Elias 2000a, 2000b, 2009a, 2009b). Comparison of the species composition of these subfossil assemblages with the known distribution and environmental preferences of the same species today indicates the likely conditions that prevailed when the subfossil invertebrates were deposited. Examination of the different temporal assemblages in successive strata permits the reconstruction of changing palaeoclimatic conditions at a given locality over historical time.

Judging by the last year there are almost no mosquitoes left in Lovozero [Luujavre]. It can be real evidence that climate is changing. Even some species of southern bugs and spiders appeared in tundra. Vladimir Galkin, a member of the Sámi community Piras on Lovozero Lake in the Murmansk region of Russia; Mustonen & Zavalko 2004

Large areas of the Arctic are occupied by mesic and wet tundra, grading into shallow pools, ponds and lakes where the transition between terrestrial and aquatic habitats becomes blurred. Several important groups of organisms, notably ciliates, testate amoebae, rotifers (wheel animals), tardigrades (water bears), nematodes (eelworms) and enchytraeid worms, are commonly found in both terrestrial and aquatic habitat types and several nominally terrestrial arthropod species are typical of the marine littoral zone. Some Arctic taxa, usually thought of as aquatic, such as chironomid midge larvae, contain terrestrial species, as in the genus Smittia. Similarly, the predominantly ‘terrestial’ springtails contain ‘aquatic’ species such as Heterosminthurus aquaticus, Podura aquatica and Sminthurides aquaticus (Babenko & Fjellberg 2006, Deharveng et al. 2008). For these reasons the non-marine Arctic invertebrates are considered here as an integrated whole rather than split artificially into terrestrial and aquatic groups. Invertebrates that are endoparasites of other terrestrial, freshwater and marine animals are considered by Hoberg & Kutz, Chapter 9.

Emphasis within this chapter is, of necessity, placed on documenting, essentially for the first time, the true biodiversity and abundance of the entire terrestrial Arctic invertebrate fauna and the driving factors that determine that diversity. Available knowledge of these organisms is sparse, precluding prediction of future population trends for the majority of species. Nevertheless, potentially important indicator groups are highlighted wherever possible and recommendations for future action are given.

CONCLUSIONS AND RECOMMENDATIONS

Sensitive areas and hotspots

In addition to the known major biodiversity hotspots within the Arctic, e.g. Beringia, there are many smaller biodiversity hotspots or oases with features favorable to invertebrates. Such sites may, for example, have a particularly favorable microclimate, habitat diversity or nutrient status. These sites are more likely to attract new colonizing species and to harbor source populations from which species may spread as conditions become more favorable in the surrounding areas. Several thermally favorable ‘oases’ are sheltered south or west facing sites, often with a reflective body of water in front and cliff behind (Mikkola 1992). Consequently, such sites occur most frequently at the sheltered heads of fjords or adjacent to sea coasts where climate is ameliorated by a warmer ocean current.

Examples of oases for invertebrates in the Canadian Arctic include Lake Hazen and Alexandra Fjord on Ellesmere Island and Truelove Lowland on Devon Island (Bliss 1987, Svoboda et al. 1994, Ring 2001). Greenland sites include low Arctic Disko Island with its homothermal springs, the sub-Arctic inner fjord region around Narsarsuaq on the west coast, and the high Arctic Zackenberg adjacent to Young Sund on the northeast coast (Høye & Forchammer 2008). These sites, because of their perceived diversity, have frequently been the subject of the most intensive investigations. On Svalbard, Ossinsarsfjellet oasis at the head of Kongsfjord in NW Spitsbergen supports a relatively rich flora and fauna. The moth Pyla fusca, a more typical denizen of temperate regions, is persistently found here. This is an excellent example of a species that has managed to establish a toehold within a Svalbard oasis, albeit at a single favorable site (Coulson et al. 2003c). Wrangel Island is an important biodiversity hotspot within the Russian high Arctic.

The areas on, below and in front of nesting seabird cliffs that receive high subsidies of nutrients from bird droppings, and allochthonous detritus often have greater diversity of invertebrates such as beetles. These areas may also support atypically high population densities for several invertebrate species. High total populations of mites and springtails, however, are often associated with lowered species diversity within these groups.

There is a danger that because diversity hotspots often coincide with areas of climatic favorability or historic glacial refugia, any conservation focus on such areas may result in the cold-adapted, true Arctic species with wide ranging distributions being ignored. 

Key knowledge gaps and recommendations

Our fragmentary knowledge of the biodiversity of many Arctic invertebrate taxa and the lack of good long-term data on population trends suggests the following important priorities for Arctic invertebrate diversity research:

• There is a pressing need for an increased recognition within CAFF that the invertebrates play a significant and essential role in the functioning of Arctic ecosystems. Given their dominant contribution to Arctic biodiversity and their role in providing key ecosystem services such as energy flow, decomposition, nutrient cycling and pollination (e.g. Wall et al. 2008), it is surprising how little attention has been paid to them in previous syntheses on the impact of climate change on the Arctic biota. For example, the Arctic Climate Impact Assessment barely touches on their biodiversity and makes few suggestions as to how they might respond to changing climate (Callaghan et al. 2004, 2005). Furthermore, their interaction with other organism groups through pollination (higher plants), ecto- and endo-parasitism (birds, mammals and other invertebrates) and their role as food for tundra-nesting birds or fish species at critical stages of their life cycle further emphasizes their importance to the functional health of Arctic ecosystems.
• A comprehensive inventory should be compiled for invertebrate species within the Arctic, listing their known distribution, abundance, habitat preference and functional role within the ecosystem. Traditional knowledge and expertise should be incorporated wherever feasible. Initially this inventory should be based on existing literature. It is recognized that this will be fraught with difficulties and will require the resolution of many taxonomic and nomenclature problems. This latter issue might be tackled by utilizing and further developing molecular methodologies such as the DNA Barcode of Life (BOL) initiative at the University of Guelph, Canada.
• There is a pressing need for further field survey work throughout previously neglected areas of the Arctic to ensure that the species inventory is as complete as possible and to establish more clearly the distribution patterns of species, particularly among the neglected invertebrate groups such as the eelworms and most lower invertebrates. Potential sites for long-term monitoring should be identified within these areas.
• The inventory should be used to identify and list the number and distribution patterns of the true Arctic endemic species, spread across many higher taxa, which are most likely to be most affected by a warming climate. All species, where possible, should be classified using the IUCN Red List Categories and Criteria. The inventory should also be used to identify or confirm areas of high diversity and endemism at various taxonomic levels across the invertebrates.
• There is an urgent need to establish a longer-term program monitoring population trends for selected indicator species that are likely to show both adverse and positive reactions to changing climate. It is essential that both above-ground and soil-dwelling species are included as they are likely to respond to climate change at different rates. Lake/pond dwelling species may similarly exhibit a buffered response to temperature changes. Compared with vertebrates and plants, many species/communities of invertebrates posses the attributes to act as highly sensitive indicators of changing climate. Their often effective powers of dispersal, coupled with rapid development rates leading to short generation times, ensure that they are able to rapidly shift location and re-establish populations as conditions permit (Hodkinson & Bird 1998). The potential exists to identify key indicator species/communities that may be used, through changes in phenology and distribution, to track climate changes and their impacts over time. Such changes may have cascading effects within ecosystems. Indicator species could include generalist, temperature-limited predators/scavengers such as ground and rove beetles and cold-adapted spiders including the genus Erigone (dwarf spiders), or species of host-specific herbivorous insect, such as psyllids (jumping plant lice) or leaf beetles, which currently do not occupy the full range of their host plant. The former group would be particularly easy to monitor as baseline data on their distribution along northsouth transects already exist, and their common and widespread host-plants are easy to locate. Monitoring should also examine longer term population/genetic trends in indicator species/communities at fixed locations. The indicator species should include both Arctic endemics and widespread Arctic species across a range of sites. Candidate species/groups might include chironomid midges and water beetles in lakes, herbivorous terrestrial species such as the aphid Acyrthosiphonsvalbardicum on Svalbard and the woolybear caterpillar Gynaephora in Canada, and certain widespread springtail species such as Folsomia quadrioculata and Hypogastrura tulbergi, soil-dwelling and surface-active species respectively. Inclusion of species with a long continuous history within the Arctic, such as the Beringean pill beetle Morychus viridis, could provide the longerterm context for change.
• Community change in the Arctic is likely to be driven in part by newly arrived incomer species. It would be instructive to set up a sampling program to analyze the species composition and abundance of the aerial invertebrate plankton that is carried into the Arctic from farther south by northwards-moving weather systems. These are the potential colonizing species. An inventory of newly establishing species should be developed and the extent of human mediated introductions of species into the Arctic assessed.
• The effects of climate change on economically significant biting fly populations should be evaluated throughout the Arctic in relation to alterations in the hydrology of habitats and rising temperatures. This is particularly important for the indigenous peoples of the Arctic, especially with respect to reindeer herding and other traditional activities. It also has implications for the tourism industry. Assessment should be made of the potential spread of important arthropod vectorborne diseases of humans, other mammals and birds into the Arctic.

Recommended conservation actions

Because of the sheer number of species, it is impractical to take a species-based approach to conservation of Arctic terrestrial and freshwater invertebrates. Conservation actions should focus on the maintenance of habitat diversity and protection. Nevertheless, invertebrate conservation in the Arctic has suffered from a lack of focal species that can be used to highlight the problems of conservation. Focal species, however, must be chosen for their uniqueness or for their importance in ecological processes rather than for their aesthetic appeal. Examples of the former might include the flightless aphid Sitobion calvulus with its highly restricted distribution on Svalbard or chrysomelid beetles on the high Arctic islands. Examples of the latter could include a typical widely-distributed, surface-active springtail such as Hypogastrura tullbergi or widespread Arctic species of enchytraeid worms.

Other key messages

Our knowledge of the invertebrates as a group lags far behind that of higher plants, mammals and birds, yet the invertebrates represent the dominant group in terms of species-based biodiversity. This deficiency is reflected in the paucity of data concerning numerical trends, drivers and stressors presented in the preceding sections. Invertebrates are small and, to many, aesthetically unappealing, but they are almost invariably the numerically dominant group of organisms (excluding microorganisms) at sites in the Arctic, where they serve a wide variety of ecological functions and are key players in important ecosystem processes. There is danger in overstating the importance of larger, more charismatic vertebrate species with conservation appeal at the expense of those lesser invertebrates with greater functional significance for the well being of Arctic ecosystems.

MARINE INVERTEBRATES (Chapter 8)

Lead Authors:  Alf B. Josefson and Vadim Mokievsky 

Contributing Authors:Melanie Bergmann, Martin E. Blicher, Bodil Bluhm, Sabine Cochrane, Nina V. Denisenko, Christiane Hasemann, Lis L. Jørgensen, Michael Klages, Ingo Schewe, Mikael K. Sejr, Thomas Soltwedel, Jan Marcin We¸sławski and Maria Włodarska-Kowalczuk

SUMMARY

Sea butterfly. Photo: Kevin LeeThis chapter brings together baseline information on the diversity of marine invertebrates in the Arctic Ocean and discusses the importance of factors that have shaped patterns of biodiversity.

The Arctic Ocean is here defined as the areas north of the Bering Strait on the Pacific side and areas with consistent seasonal sea ice cover on the Atlantic side. The known marine invertebrate fauna of this area comprises c. 5,000 species, representing at least 24 phyla with representatives in all three marine realms: sea ice, pelagic and benthic. About 50% of the Arctic Ocean overlays continental shelf areas at water depths ranging from 0-500 m. This Arctic Shelf constitutes 31% of the total shelf area of the world. More than 90% of the known Arctic invertebrate species occur in the benthic realm. As for terrestrial environments, the most species rich taxon in all realms is Arthropoda, with most species among crustaceans, i.e. >1,500 species according to a recent estimate. Other species-rich taxonomic groups are Annelida, mainly bristle worms (Polychaeta), moss animals (Bryozoa) and Mollusca, including bivalves (Bivalvia) and snails (Gastropoda). Among the meiobenthos (small-sized benthic metazoans, < 1 mm) the predominant groups are free-living nematodes (Nematoda), followed by harpacticoids (Copepoda: Harpacticoida). In terms of abundance and biomass, nematodes and harpacticoid copepods typically dominate the meiofauna (as they do elsewhere), while polychaetes, bivalves and amphipods typically dominate the macrofauna, and echinoderms and crustaceans dominate the megafauna.

“There are areas where the salmon is expanding north to the high Arctic as the waters are getting warmer which is the case in the Inuvialuit Home Settlement area of the Northwest Territories of Canada. Similar reports are heard from the Kolyma River in the Russian Arctic where local Indigenous fishermen have caught sea medusae in their nets. Mustonen 2007.

The number of known marine invertebrate species in the Arctic Ocean is very likely to increase in the future, because vast areas, particularly the deep-sea basins, are under-sampled. For example, a recent estimate suggests that several thousand benthic species have been missed to date. Contrary to paradigms of an impoverished Arctic fauna due to a harsh environment, as seen in the terrestrial realm, the Arctic shelf fauna is not particularly poor, but considered to be of intermediate richness, similar in overall species richness to some other shelf faunas, such as the Norwegian shelf. The pattern of declining species richness with increasing latitude, obvious in the terrestrial realm, is controversial among marine invertebrates and conclusions depend on the taxon and geographic scale studied. A latitudinal decline from the tropics to the Arctic was seen in shelf molluscs, while arthropods seem to show higher diversity in some Arctic areas compared with some non-Arctic areas.

Due to the turbulent geological history with repeated glaciation events over the last 3.5 million years, together with in ineffective isolation from adjacent oceans, in situ evolution of species has been hampered, and as a consequence there are few Arctic endemics, at least on the continental shelves. However, bryozoans contain more endemics than many other groups, possibly partly related to poor dispersal in this group.The present-day invertebrate fauna in the Arctic is a mixture of species with different origins, where the majority have distributions reaching outside the Arctic, i.e. the boreal parts of the adjacent oceans. By and large the Arctic Ocean is a sea of immigrants that have dispersed from adjacent oceans both in historical and in recent time.

Today’s biogeographic drivers of Arctic diversity are clearly seen in the distributions of origins in relation to the two major gateways into the Arctic, i.e. from the Atlantic Ocean and the Pacific Ocean. On the continental shelves the proportions of present-day Pacific and Atlantic species decrease with increasing distance from the Bering Strait and the NE Atlantic, respectively. Current inventories indicate that the Barents Sea has the highest species richness, being ‘enriched’ by sub-Arctic and boreal species. Today’s Arctic deep-sea floor is most closely related to the present North Atlantic fauna, which in a geological time perspective contains a strong Pacific influence.

Like other faunal elements in the Arctic, marine invertebrates are affected by climate warming. The most obvious effects will be on the fauna of the permanent ice (sympagic fauna) which will lose its habitat. However, detecting effects in the other realms is difficult, mainly because there are only few time series data available. It is expected that the fauna with strong boreal influence may show (perhaps temporarily) increased diversity, due to a combination of anticipated increased food availability for the benthos and immigration of species adapted to warmer waters. Signs of borealization are already seen in marginal areas of the Actic Ocean. Long-term estimates of climate change effects on diversity are challenging because of the complex interactions of changes on multiple levels of the Arctic system.

It is recommended that conservation actions are targeted towards whole systems rather than individual species. Since system-focused conservation efforts typically focus on limited regions, we need to know more about diversity patterns at a high spatial resolution, in particular the distribution of Arctic endemics in order to conserve as many unique species as possible. Also we need to identify the ‘biodiversity hotspots’ – the areas which harbor high numbers of unique species due to habitat complexity and other factors.There is a demand for research to get a better understanding of the factors and processes that affect diversity. To achieve this, regional and taxonomic gaps need to be closed and time series are needed to address temporal dynamics and changes in biodiversity. However, since time is probably short before severe effects of climate change will appear, we cannot wait for a high frequency mapping of the whole Arctic. Instead we suggest the establishment, or in some cases continuation, of time series monitoring at selected sites in species rich Arctic areas close to the major gateways, as well as in some areas distant from the gateways into the Arctic. We also suggest protection of areas with the highest proportion of Arctic endemic species, as well as the productive polynyas where pelagic-benthic coupling is strong and that are of high importance for higher taxonomic life

INTRODUCTION

In this chapter, we consider the diversity of invertebrates from the entire benthic, pelagic and sea-ice realms of the Arctic Ocean, broadly defined as areas north of the Bering Strait on the Pacific side and areas with consistent seasonal sea ice cover on the Atlantic side (Bluhm et al. 2011a). This corresponds broadly to the delineation of the Arctic waters made in Fig. 6.4 in the fish chapter (Christiansen & Reist, Chapter 6), but excluding the Bering and Norwegian Seas. We recognize, however, that the literature cited below does not always follow this delineation.

The present invertebrate diversity in the Arctic Ocean area is the net result of many factors acting both in historical and recent time. Like in other systems on Earth, species diversity in the Arctic is influenced by nichebased factors, such as adaptation to different environmental conditions and by dispersal based factors, such as immigration from species pools. The relative importance of these two types of factors is not always easy to disentangle and may vary with scale and the degree of connectivity to other ecosystems.

Niche-based factors like adaptation to different environmental conditions are likely to account for a significant part of biodiversity in the Arctic because it is far from homogeneous. In each of the three realms, invertebrate species inhabit a multitude of different habitats. The pelagic realm contains downwelling or upwelling areas, frontal zones and polynyas with a varying degree of coupling with the benthic realm below. The recent permanent ice-cover in the Central Arctic and seasonal ice in the rest of Arctic act as a specific habitat for sea-ice associated life, and within the ice realm habitats vary from highly productive ice edge areas to more oligotrophic zones in brine channels in the ice, as well as the ice-water interface on the underside of the ice.

The sea floor contains considerable large scale topographic heterogeneity, for instance intertidal coastal areas, semi-enclosed fjords with fjord basins, estuaries of different sizes, an expanded shelf zone with a number of canyons (Voronin, St. Anna) and inner isolated depressions (like Novaya Zemlya Trench), and the deep sea with several basins separated by deep-sea ridges. At smaller scales, benthic areas contain different sediment habitats such as sand and mud as well as harder substrata like boulders and bedrocks. The Arctic Ocean covers a large area, of which about 50% overlays shelf zones, which in turn constitute 31% of the total shelf area of the world (Jakobsson et al. 2004). It is well known that diversity generally increases with the extent of an area (MacArthur & Wilson 1967). If so, we would expect a high total diversity in particular of Arctic shelf fauna relative to deep sea areas.

A conspicuous feature of the sea areas of the Arctic is the strong gradient in salinity, both horizontally from river mouths out into the open sea as well as vertically, from close to fresh near the surface to fully marine at depth. Hence, in addition to seasonal ice melt, salinity gradients are highly influenced by freshwater inputs from mainly the Russian rivers, but also the MacKenzie and Yukon rivers in the western part of the Arctic Ocean. These large rivers together with smaller ones create estuarine systems of different spatial sizes which often harbor a peculiar set of species adapted to cold water of low salinity. The area of most intensive fresh water impact is regarded as a specific zoogeographical unit (Siberian brackish shallow province by Filatova 1957). A consequence of high freshwater inputs is also the permanent stratification of the central Arctic Ocean with a surface salinity of less than 32‰ and a deep water salinity of 34‰ (Gradinger et al. 2010a), thus providing different habitats for planktonic invertebrates, because pelagic organisms, like benthic ones, have different tolerances for low salinity.

Furthermore, different parts of the Arctic have different levels of productivity (Michel, Chapter 14), which also may affect diversity (Currie 1991). Productive areas often have more species than unproductive areas, but the causal relationships are still unclear (Currie et al. 2004) and firm evidence is also lacking for such effects on marine benthic diversity, although hump-shaped relationships have been reported between chlorophyll a and Arctic benthos richness (Witman et al. 2008). An example of an oligotrophic area is the Beaufort Gyre, as compared with a productive area in the Chukchi Sea shelf (Gradinger 2009) or Barents Sea shelf (Sakshaug 1997, Denisenko & Titov 2003).

The Arctic Ocean may be regarded as an open system where the strength of the connections with adjacent oceans has changed over the last 4 million years. Water currents facilitate dispersal from sub-Arctic and boreal parts of adjacent oceans, through the Fram Strait and the Barents Sea from the Atlantic, and the Bering Strait from the Pacific Ocean (e.g. We¸sławski et al. 2011). While the connection with the Pacific has opened and closed over time due to varying sea levels, the deep Atlantic entrance has been widely open. At present, there is some 10 times more Atlantic water than Pacific water flowing into the Arctic Ocean (Loeng et al. 2005).

In addition to habitat complexity and the importance of recent dispersal from adjacent oceans, the turbulent geological history has also been important in shaping present day diversity of Arctic invertebrates. In the comparatively young Arctic Ocean, the evolutionary origin of marine invertebrates reflects a Pacific origin dating back to the opening of the Bering Strait 3.5 million years ago (Adey et al. 2008). Throughout most of the Tertiary, the Arctic Ocean region supported a temperate biota, and fully Arctic conditions developed only during the latest part of this period. Sea ice cover formed c. 3-5 million years ago (Briggs 2003). Over the last 3-5 million years, a series of glaciation periods with intermittent de-glaciations has created an unstable environment with a series of extinction and immigration events shaping present day diversity. These extinction events are thought to have precluded extensive local evolution or endemism on the shelves (Dunton 1992). Furthermore, events during the last 3.5 Myr have allowed great re-distributions of species in the boreal part of the northern hemisphere likely still affecting Arctic diversity today. The most pervasive change occurred during the late ice-free Pliocene, after the opening of the Bering Strait, when extensive transgressions of invertebrates species across the Arctic occurred (Vermeij 1989, 1991, Mironov & Dilman 2010), mainly from the species-rich Pacific center of diversity (Briggs 2003) to the Northern Atlantic, an event called ‘The Great Trans- Arctic Biotic Interchange’ (Briggs 1995). As contended by Briggs (2007), there is little evidence from the marine realm that invasions have decreased native diversity, but rather that they have added to the native diversity, resulting in an overall increased diversity. A result of this major transfer was therefore likely an enrichment of the Northern Atlantic pool of species with Pacific species. This pool of species may be the source of immigration into the Arctic Ocean in recent time.

Against this background we expect that invertebrate diversity in the Arctic Ocean has been shaped to a high degree by dispersal based factors like immigration and a low degree of endemism. We expect the Arctic Ocean to be dominated by wide-range boreal species. In this respect, it is interesting to compare the degrees of endemism in the Arctic with those in the Antarctic, another cold region with similar glaciation history (Krylov et al. 2008), but which has been much more isolated from adjacent oceans by the strong Antarctic Circumpolar Current (ACC). The ACC, formed in the Miocene, is the only current on Earth extending from the sea surface to the sea floor, unimpeded by any landmasses (Hassold et al. 2009). We certainly would predict a much higher degree of endemism in the Antarctic, which as we will see is in fact the case. Furthermore, given that connectivity is strong between the Arctic Ocean and the boreal parts of the Pacific and the Atlantic oceans, we would not expect a markedly lower richness in the Arctic, but fairly similar levels of species richness as in the other oceans, at least in proximity to the two gateways.

In addition to the natural structuring factors, diversity patterns in the Arctic Ocean likely are influenced by variation in sampling methods as well as sampling frequency. For instance, some areas have been extensively investigated for more than a century (Barents Sea), while other less accessible areas (deep Arctic basins) have been relatively poorly studied. This creates a challenge when estimating total numbers of species in the Arctic.

The main questions addressed in this review are:

• Is the marine invertebrate diversity in the Arctic Ocean impoverished compared with adjacent areas?
• Are there large scale diversity patterns within the AO area that can be attributed to dispersal rather than niche adaptation?
• Is the turbulent geological history and openness to adjacent oceans mirrored by a low degree of endemism?
• Are there ‘hotspot’ areas that by virtue of their species diversity should be protected?
• Can we predict what the effects of global warming on invertebrate species diversity?

CONCLUSIONS AND RECOMMENDATIONS

Conclusions

The Arctic Ocean area hosts c. 5,000 species of marine invertebrates, which is a similar level as is found in the other polar environment, Antarctica, and is considered intermediate on a global scale. Arthropoda, mainly crustaeans, is the most speciose group and does not exhibit the decreasing richness with increasing latitude as found in Mollusca.

Although the Arctic contains great morphological heterogeneity and a vast number of environmental gradients, giving the opportunity for extensive niche adaptation, Arctic diversity seems largely a result of extinctions and dispersal events over the last c. 4 million years. Most species have origins from outside the Arctic, and overall there are few species endemic to the Arctic. The degree of endemism varies greatly among different taxonomic groups, where bryozoans for example seem to have a relatively high degree of endemism possibly partly due to their sessile habits and, maybe more importantly, poor dispersal ability.

The glaciation history of the two polar oceans seems fairly similar, but unlike the Antarctic which has a long history of geographic isolation, the Arctic has been, and is, open towards the two major oceans, the Pacific and the Atlantic, although the strength of the connections have varied over the last c. 4 million years. This is a likely explanation for the very low degree of endemism in the Arctic compared with the Antarctic. Today’s biogeographic drivers of Arctic diversity are clearly seen in the distributions of origins in relation to the two major gateways into the Arctic, i.e. from the Atlantic and Pacific Oceans, respectively. On the continental shelves, the proportions of present-day Pacific and Atlantic species decrease with increasing distance from the Bering Strait and the NE Atlantic, respectively. Current inventories indicate that the Barents Sea has the highest species richness, being ‘enriched’ by boreal and sub-Arctic species. Today’s Arctic deep-sea floor is most closely related to the present North Atlantic fauna, which in a geological time perspective contains a strong Pacific influence. The regional species richness is highest in Arctic regions close to the two gateways, the Chukchi Sea for the Pacific and, even higher, the Barents Sea/ Kara Sea for the Atlantic. These observations together with the distribution patterns of zoogeographical affinities indicate the importance of dispersal through the gateways into the Arctic Ocean.

While areas within the Arctic with high species richness have been identified, such as the Barents Sea, it is uncertain if there are real ‘hotspots’ of diversity, i.e. areas with high diversity of unique or endemic species in the Arctic. This is because many of these species may be abundant in waters to the south and thus not unique. The polynyas, ice-free areas within the area of sea ice, may be hot spots in terms of energy flow (Michel, Chapter 14), where benthic and pelagic invertebrates provide food for dense aggregations of birds and mammals.

There are already clear signs of global warming effects on invertebrates, for instance northward expansion of several boreal species. As would be predicted, this borealization has so far occurred in the margins of the Arctic Ocean, primarily at the two major gateways to the boreal parts of the Atlantic and Pacific. The rapidly melting sea ice means loss of habitat for sympagic fauna.

In addition to temperature rise, global change will acidify the oceans, and there is a great concern that this will negatively affect calciferous invertebrates like several benthic as well as pelagic molluscs. Experimental work shows that acidification hampers shell formation in wing snails.

Recommendations

It is recommended that conservation measures are targeted towards whole systems rather than individual species. Specifically, there are urgent needs to document and understand Arctic biodiversity patterns and processes to be able to prioritize conservation efforts.

We need more inventories

This includes the need to know where the highest diversity occurs in the Arctic, particularly for endemic species, in order to conserve as many unique species as possible. Hence, there is a need for:

• Detailed surveys of diversity in hitherto understudied areas like the East Siberian Sea and the Canadian Arctic, together with deep-sea areas of the Central Arctic Basin and at the Arctic-Atlantic frontier. Studies are also needed in the shallow subtidal to 12 meters, which still is an understudied area.
• Increased sampling and taxonomic effort on poorly investigated groups, including several among the meiofauna.
• Establishing and continuing several observation sites for long-term monitoring of marine ecosystems in different parts of the Arctic proper to obtain a more holistic view of the changing Arctic. The existing biological stations together with marine protected areas could serve as a base for such long-term observations.
• A priority focus on consistent time series monitoring at sites in the species-rich Arctic areas close to the major gateways, as well as in some areas distant from the gateways. Given the likelihood of little time before more severe climate change effects will be manifested, this entails both the establishment of some new sites and the continuation of monitoring at existing sites such as the White Sea Biological Station, the Greenland Ecosystem Monitoring in Godthåbsfjorden in W Greenland and Young Sund in NE Greenland, and the HAUSGARTEN observatory west of Svalbard. The number of observatories in both deep and shallow waters has to be increased to include a wide spectrum of testing areas and communities. Repeated sampling should be conducted in the places of former studies, like those of Golikov (1990, 1994a, 1994b, 1994c) in the Laptev and West Siberian Seas. These studies provide a sufficient background to evaluate any changes in recent community structure and composition.

We need research to understand maintenance of diversity so it is recommended:

• To quantify immigration rates of boreal species into the Arctic and investigate the possible influence of global warming on these rates.
• To investigate whether or not immigration of boreal species ‘enriches’ native diversity, and whether immigrants have a negative influence on the native fauna.
• To further implement molecular taxonomy to discover the likely presence of sibling species and to reveal historical migration patterns. The most optimistic estimates predict a diversity of ‘molecular operational taxonomic units’ as much as three times the number of described morphological species, even in such well studied groups as the Polychaeta (Carr et al. 2011).
• To investigate how increased primary production, which may be one consequence of shrinking ice cover, affects species diversity both in the pelagic and the benthic systems. This could be performed in connection with polar fronts and productive polynyas.
• To investigate how climate change influences changes in biogeographic distributions, specifically the borealization process, habitat loss for sympagic fauna and the distribution of calciferous fauna.

Based on present knowledge we recommend protection of the following areas:

• Polynyas which are areas known to be important for maintaining seabird and mammal populations. These areas should be closed for fishing as well as petroleum extraction. The latter is necessary because it is virtually impossible to clean up oil in waters with broken ice.
• Large estuaries, which harbor several of the unique Arctic species.

PLANTS (Chapter 9)

Lead Authors:  Fred J.A. Daniëls, Lynn Gillespie and Michel Poulin 

Contributing Authors: Olga M. Afonina, Inger Greve Alsos, Mora Aronsson, Helga Bültmann, Stefanie Ickert-Bond, Nadya A. Konstantinova, Connie Lovejoy, Henry Väre and Kristine Bakke Westergaard

SUMMARY

Photo: Erik Thomsen

Based on published scientific literature, the diversity of plants in the Arctic is reviewed. The plants are divided into three main groups according to essential differences in anatomy, morphology and reproduction. These are vascular plants, bryophytes (mosses and liverworts) and algae (micro- and macroalgae). As a whole, these three plant groups have the ability to perform photosynthesis. As primary producers they play a key role in the environment, since photosynthesis provides resources for all other organisms. Vascular plants and bryophytes (together with the lichenized fungi, the lichens) are the main structural components of terrestrial vegetation and ecosystems, while algae are more abundant in fresh water and marine ecosystems.

Our knowledge of the taxonomic diversity of these three main groups is very uneven. Although serious knowledge gaps still exist, our understanding of vascular plant diversity in the Arctic was recently improved considerably by the publication of the Annotated Checklist of the Panarctic Flora (PAF) Vascular plants (Elven 2011), a result of many years of laborious research by taxonomists associated with the Panarctic Flora Project. The Arctic bryoflora is relatively well known, but a circumpolar Arctic checklist of mosses and liverworts has not yet been finalized. Knowledge of the circumpolar Arctic taxonomic diversity of algae is still rather fragmentary. Preliminary biodiversity assessments have been made for Arctic marine algae, but there has been no attempt yet to synthesize knowledge of the diversity of Arctic freshwater algae. Knowledge of the biodiversity of terrestrial algae in the Arctic is also very fragmentary.

 

Willows grow much faster now on the banks of Kolyma. As well in the summer pasture areas along the Arctic Ocean tundra willows are more plentiful and more now. On River Suharnaya the willow bushes are much bigger. Reindeer herders of the Chukchi community of Nutendli, northeastern Sakha-Yakutia, Siberia; Mustonen 2007

 

The main difficulties in assessing biological diversity at subgeneric levels are the dissimilarities that exist in the taxonomic species concept and classification between the Arctic countries. Moreover, current species concepts from traditional morphological assessments are challenged by the latest molecular phylogenetic analyses, which sometimes conflict with traditional classification.

The vascular plant flora of the Arctic is relatively poor. Approximately 2,218 vascular plant species (including subspecies, apomictic aggregates and some collective species) are recognized. This is less than 1% of the known vascular plant species in the world (c. 0.85% based on an estimated total of 260,000 species; Raven et al. 2005). Arctic vascular plants belong to 430 genera and 91 families, almost all within the flowering plants (angiosperms). Gymnosperms are rare and species diversity per genus and family is low. Species-rich families with more than 100 species include Asteraceae (composite family), Poaceae (grass family), Cyperaceae (sedge family), Brassicaceae (mustard family), Rosaceae (rose family), Fabaceae (pea family), Ranunculaceae (buttercup family) and Caryophyllaceae (pink family). The genera Carex (sedge), Salix (willow), Oxytropis (oxytrope) and Potentilla (cinquefoil) are well represented, with each having more than 50 species. The majority of the Arctic species have a circumpolar distribution.

The Arctic territory is divided into 21 floristic provinces and five subzones. These strongly differ in species richness and composition. There is a pronounced increase in species numbers from the northernmost high Arctic subzone A (102 species) to the southernmost low Arctic subzone E (2180 species). A comparison of species numbers per floristic province showed a range from approximately 200 species for the rather heavily glaciated and northern floristic province Ellesmere Land-N Greenland to more than 800 species for Beringian W Alaska.

Endemism is well developed. One hundred six species (and subspecies), or around 5% of the Arctic vascular plant flora, are endemic to the Arctic. The genera Papaver (poppy), Puccinellia (salt marsh-grass, goose grass), Oxytropis, Potentilla and Draba (draba, whitlow-grass) are particularly rich in endemic species, and almost all endemic species are forbs and grasses, whereas there are no endemic woody species. Though the absolute number of Arctic endemic species increases from north to south, i.e. from the high Arctic to the low Arctic, the relative percentage of endemic species decreases.

The floras of the northern floristic provinces Ellesmere Land-N Greenland, Svalbard-Franz Joseph Land and Wrangel Island are relatively rich in Arctic endemic species. Ten Arctic endemic species are restricted to Wrangel Island and underline the hotspot character of this high Arctic island. Twenty Arctic endemic species are very rare, and as such are possibly threatened. Polyploidy1 (allopolyploidy) levels are high in Arctic plants.

Borderline species are primarily non-Arctic species just reaching the southernmost extent of the Arctic (subzone E). Taxonomically this is a rather diverse group of 136 vascular plant species in 91 genera and 45 families.

Non-native species that occur as persisting stabilized introductions in the Arctic account for 5% of the flora (101 species). In addition there are 89 species native to the Arctic that also occur as stabilized introductions in other parts of the Arctic. In addition, more than 205 non-native species have been recorded in the Arctic only as casual introductions that do not persist. Non-native species mainly occur in and around settlements and towns, in particular in climatologically favorable parts of the Euro-Siberian Arctic.

No single, predominantly Arctic vascular plant species is known to have gone extinct due to human activities in the last 250 years. There are no species in the Arctic that are considered to be seriously invasive, but some are at risk of becoming it with increasing human traffic combined with climate change. The Arctic flora is considered taxonomically, ecologically, biologically and genetically a coherent and distinctive complex of young and dynamic species that occupies a vast natural area characterized by a cold climate. The present Arctic vegetation shows climate change related changes such as greening, shrub expansion and floristical changes.

Local plants always played an essential role in the lives and cultures of Arctic indigenous peoples. The most useful plants have indigenous names, including not only vascular plants, but bryophytes and algae as well.

There are an estimated 900 species of Arctic bryophytes (mosses and liverworts). Distributional types are similar to those observed for vascular plants. Arctic endemism is not common among bryophyte species, but many widely distributed species in the Arctic show considerable morphological plasticity representing subspecies, variants or forms. The bryoflora is in general rather uniform. Almost 80% of the species have a circumboreal distribution. In rather stable, moist to wet sites, bryophytes contribute substantially to vegetation biomass, and they contribute significantly to species richness of many vegetation types in other habitats. Very few vegetation types in the Arctic occur without bryophytes, and single shoots occur almost everywhere, in particular in the high Arctic. The ecosystem function of bryophytes is poorly studied, and the bryofloras of several Arctic regions are still incompletely known. The most speciesrich families include Bryaceae (threadmoss family), Dicranaceae (forkmoss family), Amblystegiaceae (feathermoss family), Pottiaceae (tuftmoss family), Grimmiaceae (Grimmia family), Sphagnaceae (bogmoss family), Hypnaceae (feathermoss family), Mniaceae (thyme-moss family), Brachytheciaceae (feathermoss family), Polytrichaceae (haircap family) and Splachnaceae (dung moss family), which collectively account for 70% of the total moss flora. Bryum (Bryum moss), Sphagnum (bogmoss), Pohlia (nodding moss) and Dicranum (forkmoss) are among the most species-rich genera. Species-rich liverwort families include the leafy liverworts Scapaniaceae (earwort family), Jungermanniaceae (flapwort family), Gymnomitriaceae (frostwort family), Cephaloziaceae (pincerwort family) and Cephaloziellaceae (threadwort family), whereas Scapania (earthwort) and Lophozia (notchwort) are prominent genera. The use of bryophytes by indigenous people is very limited. There are no known threatened bryophyte species.

Algae are ubiquitous, ecologically important and constitute the first layer of marine and freshwater food webs. They occur either free floating in the upper water column (pelagic), associated with sea ice (sympagic), or attached to bottom substrates (benthic). Phaeophyta (brown algae) range in size from less than 2 μm to more than 100 m long in giant kelps. Pelagic algae, known as phytoplankton, and sea ice algae are autotrophic, singlecelled eukaryotes ranging in size from 0.2 to 200 μm. Benthic algae mainly refer to marine macroalgae characteristic of coastal regions, but also include microalgae attached to various substrates along the seashore. Algae, including the autotrophic prokaryote cyanobacteria (blue-green algae), are classified into different groups or phyla, depending on the classification system used.

The following groups have been recognized in this review: (1) Archaeplastida, including Chlorophyta (green algae), Streptophyta, Glaucophyta, Rhodophyta (red algae), (2) Chromalveolata, with Cryptophyta, Haptophyta, Dinophyta, Stramenopiles (including Dictyochophyceae, Eustigmatophyceae, Pelagophyceae, Bacillariophyta (diatoms), Phaeophyceae (brown algae), Xanthophyceae, Chrysophyceae (yellow-green algae), Rhaphidophyceae), (3) Excavata (Euglenophyta), (4) Opisthokonta (Choanoflagellida), (5) Rhizaria (Chlorarachniophyta) and (6) Cyanophyceae (blue-green algae).

There is a conservative estimate of 4000 algal species reported from the circumpolar Arctic, including both freshwater and marine habitats. The species diversity of microalgae and cyanobacteria for the Arctic is still largely unknown, especially in terrestrial and freshwater environments, but it is assumed to be much lower than in warmer regions of comparable size. In Arctic regions, marine diatoms are very diverse and abundant in annual sea ice, pelagic waters and benthic environments. Recent molecular studies reported a high diversity in the smallest-sized fraction of the phytoplankton in polar regions, frequently contributing to more than 50% of total phytoplankton biomass and production. In the western Canadian Arctic alone, 10,000 species of singlecelled phytoplankton species were documented through molecular analyses, at least half of which are likely autotrophic. There are c. 200-215 seaweed (macroalgae) taxa in the Arctic, with endemism poorly developed. A major challenge facing biodiversity assessments will be matching morphology of a single-celled alga to a given gene sequence, which will require development of better sampling strategies and culture techniques for these small-sized microalgae.

INTRODUCTION

This plant chapter deals with the taxonomical biodiversity of organisms that are able to perform photosynthesis. They use light energy for conversion of carbon dioxide and water into chemical energy in the form of sugar and other organic substances under release of oxygen. Most of them are photoautotrophic, using carbon dioxide as their carbon source.

They include three main groups based on differences in anatomy, morphology, physiology and reproduction, and phylogenetic relationships.

The kingdom Plantae of the eukaryotic life domain comprises the green land plants. These are the vascular plants – Tracheophyta (section 9.2) and the bryophytes – Bryophyta (section 9.3). The vascular plants are subdivided into spore-producing plants (clubmosses – Lycopodiophyta and ferns – Pteridophyta) and seed producing plants (Gymnospermae with uncovered seeds, Angiospermae with covered seeds). The bryophytes are divided into the hornworts (Anthocerophyta), liverworts (Hepatophyta) and mosses sensu stricto (Bryophyta) (Raven et al. 2005).

The photoautotrophic algae (section 9.4) of the kingdom Protista comprise eukaryotic organisms which cannot be attributed to the kingdoms Fungi, Plantae or Animalia. The green algae (Chlorophyta) are ancestral to the algal Streptophyta and hence to the kingdom Plantae, the bryophytes – Bryophyta and vascular plants – Tracheophyta. Some other algae are both autotrophic and heterotrophic (Poulin et al. 2011).

The blue-green algae belong to the prokaryotic life domain Bacteria and are classified as Cyanobacteria (Raven et al. 2005).

As primary producers, all groups play a key role in the environment, since photosynthesis provides resources for all other organisms. Vascular plants and bryophytes (together with the lichenized fungi, the lichens; see Dahlberg & Bültmann, Chapter 10) are the main structural components of terrestrial vegetation and ecosystems, while algae are more abundant in freshwater and marine ecosystems.

The state of knowledge of Arctic vascular plants, bryophytes, and algae differs among countries, regions, and floristic provinces, and there remain many differences in taxonomic opinions among botanists on different continents. The data presented here should be viewed as a preliminary assessment.

Scientific names are used throughout the manuscript since there are no standardized common or vernacular names for plants, and many species (e.g. algae) lack common names altogether. For taxa with common names, these are provided in parentheses following the scientific names the first time a taxon is mentioned. These names are derived from several sources (among others Clapham et al. 1962, Böcher et al. 1968, Hultén 1968, Porsild & Cody 1980, Rønning 1996, Smith 2004 and Edwards 2012).

The total land surface of the Arctic is estimated at 7.11 million km², with an estimated 5 million km² covered by vegetation; the remainder is ice-covered (Walker et al. 2005). The Arctic territory has been and still is sparsely populated. While there was almost no impact by human populations on Arctic flora and vegetation prior to the 1960s, human impacts now pose an increasing threat in certain areas. Nevertheless, these impacts are minor compared with human impacts in the adjacent boreal zone.

CONCLUSIONS AND RECOMMENDATIONS

Vascular plants

There is a great need for intensifying biodiversity research on Arctic flora with emphasis on molecular phylogenetic taxonomy, vegetation classification, monitoring and modelling. Coordination and cooperation between researchers must be improved. Baseline information on the distribution of Arctic plant species, including population number and size, is essential for accurately determining species status. Given the almost complete lack of population trend data for Arctic plant species, monitoring programs should be established in order to gather trend data. The conservation status of Arctic plant species can only be objectively assessed once information becomes available on the population status and trends of individual species and their plant community types. Due to their small-scale climatic and biotic diversity, Arctic hotspot complexes are strongly recommended as Arctic field laboratories for climate change-related research (see Elvebakk 2005) and for consideration as protected areas. In particular, monitoring of species ranges along altitudinal gradients in Arctic mountains is strongly recommended. Here we might expect above all species response to climate warming due to the relatively steep climate gradient (e.g. Elvebakk 2005, Schwarzenbach 2006, Pauli et al. 2007, Jedrzejek et al. 2012).

Bryophytes

The estimated species number of the bryophyte flora of the Arctic is moderate (c. 900) compared with that of lichens (c. 1750) and vascular plants (c. 2,218). But it is likely that this number will increase significantly in the course of future studies. Arctic endemism is not strongly pronounced, and is displayed mainly on an infraspecies level. The Arctic bryoflora is rather uniform. Almost 80% of the species have a broad circumboreal and circumpolar distribution. In rather stable, wet-to-moist sites they strongly contribute to vegetation biomass, and they also contribute to species richness of many vegetation types in other habitats. Their ecosystem function is poorly studied, and overall the bryofloras of most Arctic regions are still incompletely known. Moreover, Arctic material in the majority of taxonomic groups needs revision using modern molecular phylogenetic approaches (cf. Konstantinova & Vilnet 2009, Söderström et al. 2010). Records of localities of rare and recently described species need verification. There are no known threatened species. The use of bryophytes by indigenous people is very restricted. A circumpolar checklist according to uniform taxonomic concepts and nomenclature is urgently needed and will be highly beneficial for vegetation and ecosystem studies, especially for monitoring and interpretation of change in the face of climate change.

Algae

The total number of recognized algal species for the Arctic is at present likely around 4000, which represents 10% of the world’s recognized species. There are between 30,000 and 40,000 described species of algae worldwide, which correspond to only a small fraction of the estimated number of about 400,000 species (Poulin & Williams 2002). The total species number of algae and cyanobacteria in the Arctic is still largely unknown, especially in terrestrial and freshwater environments. Regarding their huge ecological importance for all life on earth, both in the sea and on land, better inventories and monitoring of algae are strongly needed, particularly considering that the Arctic regions are and will be severely impacted by global warming.

A major effort should be undertaken to establish a complete baseline of the biodiversity of marine and freshwater phytoplankton and macroalgae and polar sea ice microalgae, especially since these algae will become part of the CAFF Circumpolar Biodiversity Monitoring Program (CBMP). Reaching that goal requires more taxonomic studies in order to elucidate the species concept and harmonize it across the Arctic. The fields of taxonomy and systematics should be considered more than a descriptive exercise and rather as fundamental tools of discovery, conservation and management. Future efforts should focus particularly on the biodiversity of small-celled (< 20 μm) microalgae. Finally, all this research effort should be undertaken through international networks leveraging the costs associated with such pan-Arctic programs.