Seasonal Composition of Temperate Plankton Communities: Free Amino Acids

In marine plankton, the patterns of seasonal succession and free amino acid composition reveal several features in common. Free amino acids levels are generally higher in summer than in winter communities: major changes occur during periods of community change in late spring and early winter. These levels also appear to be an index of physiological condition and productive capacity. The variations are quantitative in terms of concentration per unit tissue weight; relative compositions are the same in both the summer and the winter dominant copepods (Acartia tonsa and Acartia clausi). Factor analysis reveals an extremely high degree of intercorrelation within the free amino acid pools. The phytoplankton-microzooplankton, consisting primarily of diatoms and larval crustaceans in varying proportins, has greater consistency of quantitative change (one amino acid in relation to all others) than does the zooplankton. Furthermore, the amino acid communality of an estuarine phytoplankton-microzooplankton community is surprisingly high.