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Marine Ecology Progress Series

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MEPS 386:237-251 (2009)  -  DOI:

Fatty acid biomarkers in coldwater eelgrass meadows: elevated terrestrial input to the food web of age-0 Atlantic cod Gadus morhua

L. A. Copeman1,*, C. C. Parrish1, R. S. Gregory2, R. E. Jamieson2, J. Wells1, M. J. Whiticar3

1Ocean Sciences Centre, Memorial University of Newfoundland, St. John’s, Newfoundland A1C 5S7, Canada
2Fisheries and Oceans Canada, Environmental Sciences Division, 80 East White Hills Road, PO Box 5667, St. John’s, Newfoundland A1C 5X1, Canada
3School of Earth and Ocean Sciences, University of Victoria, PO Box 3055, Victoria, British Columbia V8W 3P6, Canada

ABSTRACT: Lipid classes, fatty acids (FAs), and stable carbon isotopes of FAs were used to investigate dietary sources of organic carbon for juvenile Atlantic cod Gadus morhua during settlement into eelgrass Zostera marina. Primary producers, epibenthic prey, zooplankton, and fish were collected from August to November 2002 in shallow (<10 m) eelgrass in Bonavista Bay, Newfoundland, Canada. Lipid data indicated that zooplankton (>80 µm) were associated with fresh organic material, while seston (5–80 µm) had high levels of bacterial FA and non-acyl lipids, typical of sedimentary material. Zooplankton, mysids, and amphipods showed a seasonal decrease in 22:6n-3 with a concomitant increased in the ubiquitous terrestrial indicators 18:2n-3 and 18:3n-3. Based on essential FA composition of prey, there was a decrease in the quality of food available to juvenile fish from August until November. Earlier (August) pelagic juveniles had higher levels of marine-sourced FA (22:6n-3) than late (November) arrivers. Further, in October and November settled juveniles had higher proportions of terrestrial FA biomarkers than pelagic cod, indicating an increased dietary terrestrial input at settlement. Isotopic evidence demonstrated that eelgrass was the most enriched (–14‰) source of organic carbon and supported multivariate FA analysis, confirming that eelgrass was not incorporated into the food web of juvenile cod. Increased terrestrial input of organic carbon coupled with low proportions of dietary essential FAs indicate that the functional significance of this habitat is refuge and not nutrition.

KEY WORDS: Juvenile Atlantic cod · Eelgrass · Fatty acids · Lipid classes · Stable isotopes · Terrestrial input

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Cite this article as: Copeman LA, Parrish CC, Gregory RS, Jamieson RE, Wells J, Whiticar MJ (2009) Fatty acid biomarkers in coldwater eelgrass meadows: elevated terrestrial input to the food web of age-0 Atlantic cod Gadus morhua. Mar Ecol Prog Ser 386:237-251.

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