Seasonal studies of seston lipids in relation to microplankton species composition and scallop growth in South Broad Cove, Newfoundland

The concentration and nutritional awlity of suspended particulate matter at an experimental scallop aquaculture site on the east -1 of Newfoundland, Canada, was determined at 3 depths over an 8 mo sampling period. Lip~d r-lassaand fatty acids were measured chromatographically and the seston components were identified and quantified by microscopy. These measurements were correlated and then related to the growth of j u l -d e scallops Placopecten magellanicus introduced to the site. The low seston concentrations obsewad throughout the year were punctuated by 4 large inputs: the spring diatom bloom, a resuspension ment. a summer microzooplankton and nanoflagellate bloom, and a fall increase in zooplankton faecal :pellet and heterotrophic dinoflagellate concentrations. The largest inputs of lipids were associated w ~t h the: resuspension event and the summer bloom. The resuspended particles included the benthic permate diatom Cyrosigrna spp. which contained large lipid globules. High concentrations of polvunwrmated triacylglycerols occurred at this time; more saturated triacylglycerols were prominent ~n the sunmer The acyl lipids contained unusually high proportions of the long-chain polyunsaturated fatty acid 20:406 which was correlated (p < 0.05) with the proportion of mlcrozooplankton in the seston. n.e C,, fatty acid ratio 16:1~7/16:0, used previously as a diatom biomarker, was strongly correlated (p c O.01) with the proportion of centric diatoms. Scallop growth appeared to be related less to the major-ts of total lipids to the water column and more to the proportion of the essential fatty acid 2 2 : 6 d m the acyl lipids. This fatty acid was associated principally with cryptophytes (p < 0.02).