Vertical and horizontal distribution of oceanic copepods in the Adriatic sea

Abstract

        This report is based od the planktonic material collected during 4 seasonal cruises covering the entire Adriatic and on previous, partly published data on the vertical distribution of South Adriatic oceanic copepods.

        The oceanic community of the South Adriatic is comprised of species associated with 3 depth distribution zones. The upper zone includes sub-surface copepods which have a mean annual maximum abundance from 100-200 m. The middle zone includes intermediate-water copepods. They are most abundant in the layer od 300-400 m range. The lower zone of deep-sea copepods have a mean annual maximum abundance below the 400 m depth. Sub-surface and especially intermediate-water species show pronounced seasonal and diurnal migrations, being found in more surface waters during the winter.

        A general characteristic of oceanic community is the winter widening of the distribution range from the South Adriatic to the North. These seasonal differences in areal distribution are particularly evident for sub-surface copepods (Figs. 6 and 7). On the contrary deep-sea copepods show very feeble seasonal differences in horizontal distribution.

       It is concluded that seasonal differences in horizontal distribution are associated with the dynamic of the hydrographic conditions of Adriatic Sea. However, the extent to which the copepods will spread northwards is related to the vertical distribution pattern of the single species and the amplitude of their seasonal and diurnal migrations.