The relationship of the zoogeographic distributions of the planktonic ostracods in the North-east Atlantic to the water masses

Abstract

The quantitative zoogeography of pelagic zooplankton is a subject very much in its infancy. This is due to a number of causes; firstly, the taxonomy of a large number of animal groups has not been finalized and new species are still being regularly discovered. Secondly, many samples, especially from the earlier expeditions, were obtained from broad depth ranges and without accurate depth measurements or the use of opening-closing nets. This latter problem has been overcome by modern sampling devices (e.g. Baker, Clarke & Harris, 1973).Underlying the thinking of a lot of previous workers has been the hypothesis that the water masses of the various oceans (usually delineated by means of temperature-salinity relationships (Sverdrup, Johnson & Fleming, 1942)) support a distinct fauna. This point of view has been summarized by Johnson & Brinton (1963), Banse (1964) and Beklemishev (1966, 1971). Examples of studies in which the relationship of species distributions to water masses have been studied are Pickford (1946; the cephalopodVampyroteuthis infernalis), David (1958,1963; chaetognaths), Bieri (1959; Pacific chaetognaths), Brinton (1962; Pacific euphausiids), McGowan (i960; the wormPoebius meseres) and Haffner (1952; the fish genusChauliodus). In the last case it was suggested that the oxygen content of the water was also an important factor.