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Biodiversity - Status and Trends of Benthic Organisms

B. A. Bluhm1 and J. M. Grebmeier2

1School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK, USA
2Center for Environmental Science, University of Maryland, Solomons, MD, USA

November 21, 2011

Highlights

  • A recent (2010-2011) inventory documented the occurrence of at least 4600 benthic animal species in the Arctic, with at least hundreds of species yet to be discovered.
  • Recent studies indicate changes in benthic community composition and biomass in relation to climate warming in both the Pacific and Atlantic sectors.
  • Changes in the benthic biomass in some Arctic seas, or parts thereof, likely reflect shifts in energy flux patterns related to regional sea ice loss.
  • Snow crab populations have expanded northward and commercially-harvestable size specimens have been observed in both the Barents Sea and on the Beaufort Sea slope.

The newest estimate of Arctic benthic faunal species indicates at least 4600 species inhabit the Arctic sea floor (Bluhm et al. 2011). Several hundred species, if not thousands, are estimated to still be discovered (Piepenburg et al. 2011), in particular in the Arctic deep sea and within small size classes. As a result of concentrated efforts related primarily to the International Polar Year and the Census of Marine Life, several dozen benthic species were newly described in the past few years (of at least 100 discovered). Taxa included a broad range of groups such as bristle worms, moss animals, snails and crustaceans, and were discovered in poorly-charted territory such as the Canada Basin as well as well-sampled areas such as Svalbard's Hornsund Fjord.

A good 10% of all known Arctic benthic species now have part of their genetic make-up, the so-called COI (cytochrome c oxidase sub-unit 1 mitochondrial region) 'barcode' gene, archived in publicly-accessible online databases. These and other new sequence data confirm past morphological analyses in documenting high population connectivity of the Arctic fauna to Atlantic and Pacific faunas.

A gradually increasing body of literature documents recent changes in Arctic benthic biodiversity, community composition and biomass, interpreted in the light of climate warming (Grebmeier 2012). In several cases, switches from longer-lived and slow-growing Arctic species and/or communities to faster-growing temperate species and/or communities reflect increasing water temperatures. Similarly, northern range extensions of several sea floor dwellers likely are tied to the warming habitat. In the Atlantic Arctic, this process is anticipated to result in the 'Atlantification' of the benthos. New research on sediment-associated microbes, including bacteria, archaea, viruses and microscopic fungi, are currently expanding our knowledge of this topic.

An example species of high interest is the snow crab, a crustacean commercially harvested in the southeastern Bering Sea and Canadian north Atlantic Ocean. A self-sustaining population of snow crab has recently established itself in the Barents Sea, and specimens of harvestable size were recently found on the western Beaufort Sea slope.

A new data-rich estimate of global benthic biomass distribution confirms historic data documenting comparatively high biomass on Arctic shelves compared to lower latitudes. Recent changes in benthic biomass in some Arctic seas, or parts thereof, probably reflect shifts in energy flux patterns, regionally related to sea ice loss. Biomass changes over the past one to three decades include decreases in infaunal biomass in parts of the Bering Sea, increase in epifaunal biomass in parts of the Bering and Chukchi seas, decrease in epifaunal biomass in deep Fram Strait, and no changes in a Svalbard fjord system.

Examples of the sparse but much-needed long-term observations that are documenting changes in the benthos include those from: (1) the HAUSGARTEN deep sea observatory, which has been in operation since 1999 in Fram Strait; and (2) the Pacific Arctic shelves (Fig. ME3 where observations have been made for almost 30 years (see the essay on Marine Ecology: Biological Responses to Changing Sea Ice and Hydrographic Conditions in the Pacific Arctic Region).

Fig. 3 -- Dominant benthic infaunal taxa and biomass
Fig. ME3. Dominant benthic infaunal taxa and biomass for stations sampled in the northern Bering and Chukchi seas and into the Canada Basin from 1973-2010 (updated from Grebmeier et al. 2006, plus unpublished data through 2010, and data from Bluhm et al. 2011).

References

Bluhm B. A., Gebruk A.V., Gradinger R., Hopcroft R. R., Huettmann F., Kosobokova K. N., Sirenko S. I., Weslawski J. M. (2011) Arctic marine biodiversity - an update of species richness and examples of biodiversity change. Oceanography 24:232-248.

Grebmeier J. M. (2012) Shifting patterns of life in the Pacific Arctic and Sub-Arctic seas. Ann Rev Mar Sci 4:16.1-16.16 (in press, doi: 10.1146/annurev-marine-120710-100926).

Piepenburg D., Archambault P., Ambrose W. G. Jr., Blanchard A., Bluhm B. A., Carroll M. L., Conlan K., Cusson M., Feder H. M., Grebmeier J. M., Jewett S. C., Lévesque M., Petryashev V. V., Sejr M. K., Sirenko B., Włodarska-Kowalczuk M. (2011) Towards a pan-Arctic inventory of the species diversity of the macro- and megabenthic fauna of the Arctic shelf seas. Marine Biodiversity 41:51-70.