Changes in the plankton community of the Western English Channel

Abstract

MARINE biologists and oceanographers will probably be familiar with the story of the biological and chemical changes that occurred in the Channel waters off Plymouth during the 1930s: a summary of how the plankton community altered, the numbers of young fish declined, adult demersal fish became scarcer and herring were replaced by pilchard can be found in many textbooks. The most striking feature, and one of the first to be detected, was the changeover from a plankton community characterised by the chaetognath Sagitta elegans and associated ‘plankton indicators’ to a much poorer community characterised by Sagitta setosa^1–3.