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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
School of Fisheries and Ocean Sciences, University of Alaska Fairbanks
*[email protected]
Results
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 3rd 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
Preliminary Conclusions and Future Research
of food web structure across the Beaufort shelf and with other
Arctic shelves.
Introduction
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.
Warming of marine waters due to climate change has been
Fig. 2. Kate Wedemeyer (BOEM)
holding a snow crab collected
from the central Beaufort Sea
shelf.
correlated with the northward contraction of the
Bivalvia (n=12)
21
commercially important snow crab, Chionoecetes opilio, in
the Bering and Chukchi Seas1,2. Though C. opilio is not
Polychaeta (n=5)
currently commercially harvested in the Beaufort Sea,
Bryozoa (n=3)
interest in future fishing potential warrants detailed
Cnidaria (n=4)
TL 4
ecological studies of this species. While much work is
currently ongoing in the Chukchi
Sea2,
Gastropoda (n=6)
17
♂
nothing is known
goal of this study was to describe the benthic food web for
TL 3
δ15N
positioning of C. opilio within the benthic food web in this



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
CHCl3: MeOH

Measured for δ13C & δ15N ratios at Alaska Stable Isotope
Facility at UAF
♀
Amphipoda (n=2)
Porifera (n=3)
Cephlapoda (n=3)
TL 2
Ophiuroidea (n=3)
Isopoda (n=2)
9
Echinoidea (n=1)
TL 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
Decapoda (n=5)
Ascidiacea (n=3)
Methods
Samples collected from 22 Aug ̶ 3 Sept 2011 in central
Beaufort Sea (Fig. 1)
C. opilio (n= 22♂, 2♀ , 3i♀)
13
region.

Asteroidea (n=4)
i♀
about C. opilio trophic dynamics in the Beaufort Sea. The
the central Alaskan Beaufort Sea in order to assess
Four trophic levels identified based on δ15N spread of 3.4‰
enrichment per level
δ13C and δ15N 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
Holothuroidea (n=1)
Nemertea (n=1)
Crinoidea (n=1)
POM
5
-26
-24
-22
-20
-18
-16
-14
δ13C
Fig. 3. δ13C & δ15N 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.
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 communities3.
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 Sea3 and 3.4 for the Eastern
Bering Sea4). Absolute δ15N 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.
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: 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