The Photosynthesis of Diatom Cultures in the Sea

Abstract

Photosynthesis in the open sea is due mainly to two groups of organisms, the diatoms and the dinoflagellates. In British seas the diatoms are so much more numerous that the chemical changes which are due to photosynthetic activity can be almost entirely ascribed to their influence. Recent work on these chemical changes has shown that they do not extend deeper than about 30 metres. Of the external limiting factors light is among the most important and the depth to which photosynthesis can go on must, of course, depend on the light intensity. In the study of the phytoplankton under natural conditions the results are complicated by the interaction of many other factors such as temperature, viscosity, or lack of food salts, so that it is difficult to come to definite conclusions on the effect of light alone.