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 material. Samples of plankton, settling particulate matter and sediments were examined and fatty acids were used to identify their sources. Centric diatoms, as well as the dinoflagellate Ceratium tripos, were the dominant phytoplankton, producing, through primary production, large fluxes of settling particulate matter. Mean fatty acid fluxes of 8.8±7.4 mg m−2 d−1 were produced in the 1994, 1995 and 1997 seasons. Fatty acid distributions suggested that the acids were almost totally marine in origin with very few terrestrial plant indicators present and that bacterial biomass, as indicated by odd/branched chain fatty acids, was minimal. Short-term sediment trap studies with mercury chloride poisoning did not reveal a significant difference in fatty acid composition in traps with and without poison; however, dissolution of fatty acids from particles can introduce large errors in flux and concentration measurements. Fatty acid concentrations in sediments were approximately 1% of the concentration found in settling particulate matter. Fatty acids of bacterial and terrestrial origin were present at higher concentrations in the sediments and it appears that the fatty acids of marine origin are effectively recycled by diagenetic processes at the sediment–water interface. This implies that, in terms of fatty acid nutrients, the lower food web in this area is very efficient as there is a minimal loss of the high flux of fatty acids through burial in sediments.