THE SUEZ CANAL AS A LINK AND A BARRIER IN THE MIGRATION OF PLANKTONIC ORGANISMS

ABSTRACT

Plankton affinities and differences between the Red Sea and the eastern Mediterranean are discussed in the light of the results of distribution studies of several groups of phytoplankton and zooplankton carried out over a number of years. These observations point to the role of the Suez Canal either as a connecting link or as a selective barrier in the migration of plankton organisms. While cases of migration from one marine environment to another are known to occur in either direction, those concerning species of Indo-Pacific origin succeeding in passing through the Suez Canal and reaching the eastern Mediterranean are more numerous. There is evidence that this is a continuous process and recent records indicate that species which were formerly known only from the Red Sea or the Suez Canal proper are now firmly established in the eastern Mediterranean. In other cases, the Suez Canal, in spite of a substantial drop in the salinity of the Bitter Lakes in recent years, provides a firm barrier in the migration of species of certain groups of zooplankton, notably the chaetognaths, the pelagic tunicates and the calanoids among the copepods. This fact is responsible, amongst others, for the different faunistic and floristic characteristics of the plankton of the two marine environments connected by this man-made link.