Lipid biogeochemistry of plankton, settling matter and sediments in Trinity Bay, Newfoundland. II. Fatty acids

The fatty acid biogeochemistry of a fjord-like bay in eastern Newfoundland, Canada, was investigated to determine sources and fates of organic materia l. Samples of plankton. settling particulate matter and sediments were exam ined and fatty acids were used to identify their sources. Centric diatoms. as well as the dinoflagellate Ceratium tripos, were the dominant phytoplank ton, producing, through primary production, large fluxes of settling partic ulate matter. Mean fatty acid fluxes of 8.8 +/- 7.4 mg m(-2) d(-1) were pro duced in the 1994, 1995 and 1997 seasons. Fatty acid distributions suggeste d that the acids were almost totally marine in origin with very few terrest rial plant indicators present and that bacterial biomass, as indicated by o dd/branched chain fatty acids, was minimal. Shortterm sediment trap studies with mercury chloride poisoning did not reveal a significant difference in fatty acid composition in traps with and without poison: however, dissolut ion of fatty acids from particles can introduce large errors in flux and co ncentration measurements. Fatty acid concentrations in sediments were appro ximately 1% of the concentration found in settling particulate matter. Fatt y acids of bacterial and terrestrial origin were present at higher concentr ations in the sediments and it appears that the Fatty acids of marine origi n are effectively recycled by diagenetic processes at the sediment water in terface. This implies that, in terms of fatty acid nutrients, the lower foo d web in this area is very efficient as there is a minimal loss of the high flux of fatty acids through burial in sediments. (C) 1998 Elsevier Science Ltd. All rights reserved.