Population structure and abundance of phytoplankton in three bays on the eastern Adriatic coast: Sibenik Bay, Kastela Bay and Mali Ston Bay

Present study describes the phytoplankton community structure and phytoplankton abundance in three bays on the eastern Adriatic coast (Sibenik Bay, Kastela Bay and Mali Ston Bay) during 2005. The highest phytoplankton biomass (expressed as chlorophyll a) were recorded at one station in Sibenik Bay (4.73 mg m(-3)), and in Kastela Bay (2.79 mg m(-3)), while at all other stations recorded values were generally below 1 mg m(-3). At the investigated area of Sibenik Bay a total of 114 phytoplankton taxa have been determined. The most diverse were diatoms with 61 and dinoflagellates with 37 taxa. Coccolithophorids contributed with 6, cryptophytes with 3, silicoflagellates, euglenophytes and chlorophytes with 2 taxa. In the area of Kastela Bay 193 phytoplankton taxa have been recorded. Dinoflagellate group was the most diverse with 92 taxa, followed by diatoms (80), coccolithophorids (9), silicoflagellates and euglenophytes (4), cryptophytes (2) and chlorophyte (1). In the area of Mali Ston Bay a total of 88 phytoplankton taxa have been found, with 39 diatoms, 36 dinoflagellates, 2 silicoflagellates, 4 coccolithophorids, 2 euglenophytes, 1 chllorophyte and 3 chrisophyte taxa. Abundance of dinoflagellates was very low in this area. Coccolithophorids contributed more to the community composition in Mali Ston Bay, then in other areas of research. A diverse microflagellate group was present in the whole area of investigation with a high frequency of findings. During the investigated period a relatively small number of monospecific blooms in all areas have been recorded. The largest numbers of taxa were recorded at stations that are under an influence of freshwater input from rivers and strong anthropogenic influence.