Investigations of phytoplankton in the Montenegrin coastal sea through summer (June, July, August) 2003 are described in this paper. They represent continuation from the previous years, and especially from 2001 and 2002. Maximum microphytoplankton quantity is found in the area of the bay (Kotor Bay) during June 3.9 x 10**6 cell/cubic dm, with the dominance of Nitzschia delicatissima (99%). This species was found with high percentage (more than 50%) during July and August, too. Leptocylindrus minimus and Skeletonema costatum, which were dominant in the previous period, through this year were slightly presented. In the area outside the Bay of Boka Kotorska, microphytoplankton was presented with quantities cell between 10**3 and 10**5 cell/cubic dm. Mean values of microphytoplankton in the area of the Boka Kotorska Bay were in 2003 year 4.6 times higher than outside the Bay. The same ratio was found for nanophytoplankton, too.

Studies of the plankton copepods also included the area of continental shelf and the Southern Adriatic deep valley with pronounced ocean characteristics. The deep waters of Southern Adriatic are inhabited by numerous species of all depth zones, with a pronounced domination of ocean forms, similar to the Mediterranean. The quantity of copepods in the area of open surface waters shows a pronounced spring maximum of abundance. The abundance of overall copepod population decreases from the shore toward the open sea of Southern Adriatic valley, with an increase of species abundance in plankton. That area is governed by stenothermal and stenohaline conditions. The Copepoda community is characterized by stenothermic and stenohaline species. Ranges of many of these are not increased horizontally toward the northern parts of Adriatic, and the individuals carried north by water currents quickly die.