Effects of salinity on growth and on valve morphology of five estuarine diatoms

SUMMARY The effects of salinity on the growth and valve morphology of five benthic estuarine diatoms ( Nitzschia pusilla , N. frustulum , N. palea , N. filiformis var. conferta and Eolimna subminuscula ), isolated from both freshwater and brackish/marine habitats, were investigated. The four Nitzschia strains grew well over a broad salinity range, though some ( N. pusilla, N. frustulum ) showed a broader salinity range tolerance (from fully saline down to at least 9.5 ppt) than others ( N. palea, N. filiformis var. conferta had reduced growth at salinities of 16 ppt and above). Salinity significantly affected the valve morphology of the five strains studied. However, there was no consistent pattern in either the morphological characters affected or the direction of the effects. Although significant, the effects of salinity on valve morphology were very small and therefore it seems that the taxonomic usefulness of some of the classical taxonomical characters is not undermined.