Effects of salinity changes on growth and metabolism of the marine centric diatom Cyclotella cryptica

Cyclotella cryptica grows well over a wide range of salinities and can therefore be considered a euryhaline species. The content of chlorophylls a and c of this diatom varies little in the medium salinity range but declines markedly in long-term experiments at both the high and low salinity extremes.Transfer of cells from low to high salinities causes a stress condition evidenced by a lag phase in growth, probably resulting from temporary plasmolysis and decreased photosynthetic and protein synthesis capacities. These stress conditions are also associated with rapid accumulation of free amino acids, including proline, either from photoassimilated carbon or from heterotrophic assimilation of glucose in the dark. Transfer of cells back to low salinity conditions results in rapid decreases in these amino acids.