Distribution of Planktonic diatoms in Pelorus sound, South Island, New Zealand

Abstract

Planktonic diatom populations from the waters of Pelorus Sound and Admiralty Bay were analysed throughout a complete tidal cycle in August 1974. Two species, Thalassiosira hyalina and Thalassionema nitzschioides, alternate as dominants of the populations. The changes in dominance reflect salinity changes. Other diatom species are consistently present, but only in small numbers. The distribution of all diatom species throughout the sound and Admiralty Bay has been correlated with depth and salinity. The diatoms arc divided into two categories: those resident in Pelorus Sound and those washed into the sound from Cook Strait on the tidal flow. There is considerable variation in the numbers and kinds of species at the same geographical location, but at different times in the tidal cycle; thus errors may arise from single‐sample analysis or use of microfossil assemblages for reconstructing paleocnvironments in great detail. Most diatom species dealt with are illustrated by stereoscan electron micrographs and light microscope, under phase‐contrast, for comparison with past work, on the light microscope only.