MEPS 310:33-46 (2006)  -  doi:10.3354/meps310033

Trophic relationships and pelagic–benthic coupling during summer in the Barents Sea Marginal Ice Zone, revealed by stable carbon and nitrogen isotope measurements

Tobias Tamelander1,2,3,*, Paul E. Renaud4,2, Haakon Hop1, Michael L. Carroll2, William G. Ambrose Jr.5,2, Keith A. Hobson6

1Norwegian Polar Institute, 9296 Tromsø, Norway
2Akvaplan-niva, 9296 Tromsø, Norway
3Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway
4University of Connecticut, 1080 Shennecossett Road, Groton, Connecticut 06340, USA
5Bates College, Lewiston, Maine 04240, USA
6Canadian Wildlife Service, 115 Perimeter Road, Saskatoon, Saskatchewan S7N OX4, Canada

ABSTRACT: Food web structure and pathways from primary production were studied in pelagic, sympagic (ice-associated) and benthic communities during summer in a seasonally ice covered region of the northern Barents Sea. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) were used as tracers of organic material through marine food webs and trophic levels of organisms, respectively. Measurements of δ15N show that sympagic amphipods occupy the lowest trophic levels (ca. 2), for primary consumers, followed by zooplankton (2.0 to 2.6), benthic suspension and deposit feeders (2.2 to 3.7), benthic carnivores (3.6 to 4.4) and fishes (3.3 to 4.4). The δ13C values indicate that zooplankton mainly graze on suspended particulate organic material (POM). Sympagic amphipods derive most of their energy from ice POM, but some species had δ13C values indicating that phytoplankton also contributes to their energy intake. δ13C values of some components of the benthic community suggest that POM settling out of the water column is efficiently exploited by the benthic fauna. Elevated δ13C values of the benthic fauna relative to zooplankton at some stations indicate that the degree of pelagic–benthic coupling at stations separated by only 90 km is determined by a combination of factors, including water-mass properties and the primary-production regime. These results may qualify findings of previous studies that have sampled from discrete locations or have pooled specimens collected from a broad area to make conclusions about food webs on a regional scale.

KEY WORDS: Stable isotopes · δ13C · δ 15N · Food web · Arctic · Barents Sea · Marginal Ice Zone · Pelagic–benthic coupling

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