Seasonal Composition of Temperate Plankton Communities: Fatty Acids

Fatty acid composition of the plankton in Narragansett Bay, Rhode Island, varies in relation to the seasonal succession and productivity of populations. The ratio of palmitoleic acid to palmitic acid declines during vernal warming from 2.0 to ca. 0.3, reflecting the change in dominance from diatoms to flagellates. In the zooplankton, the ratio is twice as high in Acartia clausi, the winter dominant copepod, as in the summer species, Acartia tonsa. Palmitoleic acid and palmitic acid vary reciprocally throughout the year; so do oleic and stearidonic acids. If palmitic and oleic acids, the less saturated members of each covariate pair, are related by multiple linear regression to zooplankton standing crop, 52% of the variation over an annual cycle is explained. During a poor year for Calanus finmarchicus in Rhode Island Sound, the fatty acids vary independently of each other, in agreement with previous findings for free amino acids.