Reactions of Plankton Organisms to Water Stratification

A survey of the literature indicates that zooplankton aggregate at salinity or temperature interfaces. The experiments reported here offer evidence that such interfaces may be preferential sites for certain marine organisms. Experiments were made by layering water of various densities and introducing planktonic organisms into the layers. The zooplankters under study included protozoa, and adults or larvae, or both, of ctenophores, chaetognaths, cirripeds, amphipods, polychaetes, brachiopods, mysids, molluscs, appendicularians, and teleost eggs. Almost all organisms tested accumulated at the interfaces of water layers.