Abstract
Synthetic analogues of natural metabolites (antimetabolites) have been used to assess the sensitivity to inhibition of marine unicellular algae in laboratory cultures and also of more open-sea species grown in mixed culture in nutrient enriched sea waters. Different species show a different pattern of response to a range of antimetabolites. The presence of vitamins and metabolites in the medium influences inhibition of a species by an antimetabolite. The extent by which various sea waters influence inhibition is perhaps capable of development as a measure of the natural metabolites present. Species which are related or which occur together in the sea at the same time of year tend to show similar patterns of response. It is suggested that there may be a connexion between the susceptibility of species to antimetabolites and phytoplankton ‘succession’ in the sea.