MEPS 129:151-164 (1995)  -  doi:10.3354/meps129151

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

Parrish CC, McKenzie CH, MacDonald BA, Hatfield EA

The concentration and nutritional quality of suspended particulate matter at an experimental scallop aquaculture site on the east coast of Newfoundland, Canada, was determined at 3 depths over an 8 mo sampling period. Lipid classes and 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 juvenile scallops Placopecten magellanicus introduced to the site. The low seston concentrations observed throughout the year were punctuated by 4 large inputs: the spring diatom bloom, a resuspension event, 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 with the resuspension event and the summer bloom. The resuspended particles included the benthic pennate diatom Gyrosigma spp. which contained large lipid globules. High concentrations of polyunsaturated triacylglycerols occurred at this time; more saturated triacylglycerols were prominent in the summer. The acyl lipids contained unusually high proportions of the long-chain polyunsaturated fatty acid 20:4omega6 which was correlated (p < 0.05) with the proportion of microzooplankton in the seston. The C16 fatty acid ratio 16:1omega7/16:0, used previously as a diatom biomarker, was strongly correlated (p < 0.01) with the proportion of centric diatoms. Scallop growth appeared to be related less to the major inputs of total lipids to the water column and more to the proportion of the essential fatty acid 22:6omega3 in the acyl lipids. This fatty acid was associated principally with cryptophytes (p < 0.02).

Lipid classes . Fatty acids . Microalgae . Microzooplankton . Blooms . Resuspension

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