Fitting snow crabs (Chionoecetes opilio) into the benthic food web of the central Alaskan Beaufort...
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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
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 *[email protected] 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 16-220 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 13 C & 15
N ratios at Alaska Stable Isotope Facility at UAF Results Four
trophic levels identified based on 15 N spread of 3.4 enrichment
per level 13 C and 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. 13 C & 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
(3.3-3.6 for the Chukchi Sea 3 and 3.4 for the Eastern Bering Sea 4
). Absolute 15 N values (14.5-15.36) were more enriched than those
for the Chukchi Sea (12.7-14.8) 3, but within the range of values
for the Bering Sea (13.3-16.2). 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 44:6579 2. Bluhm
BA, Iken K, Hardy SM, Sirenko BI, Holladay BA (2009) Community
structure of epibenthic megafauna in the Chukchi Sea. Aquat Biol 7:
269-293 3. 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: 71-85 4. Aydin K, Mueter F (2007) The
Bering Sea- A dynamic food web perspective. Deep-Sea Res 54:
2501-2525 5. 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.
5 9 13 17 21 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) ii TL 1 TL
2 TL 3 TL 4