The Structure Of Zooplankton Population In The Jabuka Pit Area (Eastern Mediterranean)

The paper presents data on the structure of total zooplankton according to comparison of microfraction and mesofraction of quantitatively important zooplankton groups in the Jabuka Pit region. Research work was carried out during six cruises from 1986 to 1992 in the framework of the Adriatic Scientific Coordinating Programme (ASCOP). The samples were collected by vertical tows in three layers (50 to 0 meters, 100 to 50 meters and bottom to 100 meters). The microzooplankton was sampled with a 53 mu m Nansen net equipped with a closing device and mesozooplankton with a Juday-Bogorov 250 mu m net. There was no significant difference in zooplankton abundances between the eastern and western part of Jabuka Pit. The differences in the vertical distribution pattern, precisely between the surface and near the bottom samples were significant. Qualitative composition of some of the zooplankton groups differ between the western and eastern part of the Pit primarily due to the appearance of oceanic species in its eastern part, carried with mediterranean and south Adriatic water masses. This influence was most pronounced in December 1986 and August 1992. It should be noted that in September 1987 and in August 1992, small Oithona and Oncaea genera's copepods prevailed, whereas in December 1986, May 1987 and August 1990, the calanoids were the dominant group.