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Fitting snow crabs (Chionoecetes opilio) into the benthic food web of the central Alaskan Beaufort Sea Lauren M. Divine*, Katrin Iken, and Bodil A. Bluhm.

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Presentation on theme: "Fitting snow crabs (Chionoecetes opilio) into the benthic food web of the central Alaskan Beaufort Sea Lauren M. Divine*, Katrin Iken, and Bodil A. Bluhm."— Presentation transcript:

1 Fitting snow crabs (Chionoecetes opilio) into the benthic food web of the central Alaskan Beaufort Sea Lauren M. Divine*, Katrin Iken, and Bodil A. Bluhm School of Fisheries and Ocean Sciences, University of Alaska Fairbanks Introduction Warming of marine waters due to climate change has been correlated with the northward contraction of the commercially important snow crab, Chionoecetes opilio, in the Bering and Chukchi Seas 1,2. Though C. opilio is not currently commercially harvested in the Beaufort Sea, interest in future fishing potential warrants detailed ecological studies of this species. While much work is currently ongoing in the Chukchi Sea 2, nothing is known about C. opilio trophic dynamics in the Beaufort Sea. The goal of this study was to describe the benthic food web for the central Alaskan Beaufort Sea in order to assess positioning of C. opilio within the benthic food web in this region. Methods  Samples collected from 22 Aug ̶ 3 Sept 2011 in central Beaufort Sea (Fig. 1)  Particulate organic matter (POM) samples collected with CTD rosette from ~10 m surface water in replicates of 3  Invertebrate species collected with trawl from depths ranging from m  61 putative species representing 18 higher taxa sampled (Fig. 2)  Muscle tissue, body wall, or whole organisms dissected  Carbonates removed with HCl; lipids extracted with 2:1 CHCl 3 : MeOH  Measured for δ 13 C & δ 15 N ratios at Alaska Stable Isotope Facility at UAF Results  Four trophic levels identified based on δ 15 N spread of 3.4‰ enrichment per level  δ 13 C and δ 15 N spreads for 61 benthic invertebrate species were 13.9‰ and 12.7‰, respectively  First trophic level (TL 1) was occupied by primary consumers such as bivalves and bryozoans  TL 2 was occupied by a variety of surface and subsurface deposit feeders, as well as suspension feeders  C. opilio occupied TL 3.7 indicating predatory/ omnivorous strategy based on the detrital food chain  C. opilio shared TL 3 with other decapods (e.g. Eualus gaimardii, Hyas coarctatus, Sabinea septemcarinata, blue king crab), asteroids, sponges, and cephalopods Fig. 1. A total of 31 stations within the outlined box were sampled in the central Beaufort Sea during Aug-Sept 2011 cruise on the R/V Norseman II. Fig. 3. δ 13 C & δ 15 N ratios of benthic taxa found in the central Beaufort Sea. N= Number of species sampled for each taxon; for C. opilio n= number of individuals per male, immature females, and mature females. Preliminary Conclusions and Future Research This study is the first to describe the benthic food web of the central Alaskan Beaufort Sea shelf. The food web presented here is similar to those for other nearby benthic shelf communities 3. Trophic positioning of snow crab for the central Alaskan Beaufort Sea was among the highest of TL established for other shelf communities ( for the Chukchi Sea 3 and 3.4 for the Eastern Bering Sea 4 ). Absolute δ 15 N values ( ) were more enriched than those for the Chukchi Sea ( ) 3, but within the range of values for the Bering Sea ( ). The data from this study will be used in a large-scale benthic food web comparison of the eastern, central, and western Beaufort Sea and other Arctic shelves. Beaufort Sea food web structure will also be compared with patterns in the physical and biological parameters including depth, salinity, temperature, chlorophyll a, and substrate type to gain a more thorough understanding of the influence of environmental influences on benthic food web structure. Fig. 2. Kate Wedemeyer (BOEM) holding a snow crab collected from the central Beaufort Sea shelf. Literature Cited 1. Orensanz J, Ernst B, Armstrong DA, Stabeno P, Livingston P (2004) Contraction of the geographic range of distribution of snow crab (Chionoecetes opilio) in the eastern Bering Sea: An environmental ratchet? CalCOFI Rep 44:65–79 2. Bluhm BA, Iken K, Hardy SM, Sirenko BI, Holladay BA (2009) Community structure of epibenthic megafauna in the Chukchi Sea. Aquat Biol 7: Iken K, Bluhm BA, Dunton KH (2010) Benthic food-web structure under differing water mass properties in the southern Chukchi Sea. Deep-Sea Res 57: Aydin K, Mueter F (2007) The Bering Sea- A dynamic food web perspective. Deep-Sea Res 54: Lovvorn J (2010) Predicting snow crab growth and size with climate warming in the northern Bering Sea. NPRB Project 713 Final Report. 28 pp Funding for this project was provided by: BOEM, the Coastal Marine Institute, and the NSF-IGERT MESAS Fellowship Abstract Understanding the biology and ecology of species of potential commercial importance in the Arctic is essential, especially in light of the rapidly changing marine environment. This study sought to provide a first assessment of the trophic positioning of snow crab, Chionoecetes opilio, on the Arctic Beaufort Sea shelf. A total of 4 trophic levels were identified with snow crab occupying the 3 rd trophic level. No differences in trophic position existed between sexes. Food web and snow crab trophic level agree with similar studies in the Chukchi and Eastern Bering Seas. Future research will expand the study area in the Beaufort Sea to present a large- scale comparison of food web structure across the Beaufort shelf and with other Arctic shelves Bivalvia (n=12) Polychaeta (n=5) Bryozoa (n=3) Cnidaria (n=4) Gastropoda (n=6) Asteroidea (n=4) C. opilio (n= 22 ♂, 2 ♀, 3i ♀ ) Decapoda (n=5) Amphipoda (n=2) Ascidiacea (n=3) Porifera (n=3) Cephlapoda (n=3) Ophiuroidea (n=3) Isopoda (n=2) Echinoidea (n=1) Holothuroidea (n=1) Nemertea (n=1) Crinoidea (n=1) ♂ i♀i♀ ♀ TL 1 TL 2 TL 3 TL 4


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