MEPS 220:13-23 (2001)  -  doi:10.3354/meps220013

Feeding relationships in Mediterranean bathyal assemblages elucidated by stable nitrogen and carbon isotope data

N. V. C. Polunin1,*, B. Morales-Nin2, W. E. Pawsey1, J. E. Cartes3, J. K. Pinnegar1, J. Moranta2

1Department of Marine Sciences & Coastal Management, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom
2Consejo Superior de Investigaciones Cientificas-Universitat de les Illes Balears, Institut Mediterrani d¹Estudis Avançats, Miguel Marqes 21, 07190 Esporles, Mallorca, Spain
3Consejo Superior de Investigaciones Cientificas, Instituto de Ciencias del Mar, Paseo Juan de Borbón s/n, 08039 Barcelona, Spain

ABSTRACT: Fishes and invertebrates were collected from the continental slope southwest of the Balearic Islands, Mediterranean, in October 1996 and May 1998 from 3 faunally-distinct depth zones: 200 to 800 m (upper slope), 800 to 1425 m (middle slope) and 1425 to 1800 m (lower slope). Differences in δ15N and δ13C between October 1996 and May 1998 were observed only in the crustaceans Aristeus antennatus and Nematocarcinus exilis. There were few differences among depths in δ15N or δ13C of benthic fishes or crustaceans: the shrimps A. antennatus and Acanthephyra eximia showed higher δ15N values at greater depth, and δ13C values of the fishes Alepocephalus rostratus (Alepocephalidae) and Coelorhynchus coelorhynchus (Macrouridae) also tended to increase with increasing depth. Differences in plankton and suprabenthos were also observed among zones (at depth, greater δ15N values of gelatinous plankton, calanoid copepods and peracarids were recorded, along with smaller δ13C values of gelatinous plankton and peracarids). These are attributed to a microbially-mediated increase in δ15N and a reduction in δ13C of the particulate material remaining after preferential utilization of labile organic matter in the stable and relatively high (13°C) temperature of the Mediterranean water column. Strong positive correlations between δ15N and δ13C data for plankton, fishes and crustaceans indicated a single primary source material for these communities, which is attributed to marine snow.

KEY WORDS: Deep-sea · Mesozooplankton · Fishes · Crustaceans · Suprabenthos · Mediterranean · Bathyal

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