Μαύρη Θάλασσα-Βόρειο Αιγαίο Πέλαγος: μια συγκριτική μελέτη της χωρικής και χρονικής κατανομής της ιικής και βακτηριακής αφθονίας και βιομάζας

The North Aegean Sea is a unique marine environment that combines the oligotrophic character of the Eastern Mediterranean and the eutrophic character of the Black Sea Water (BSW) outflow. In a five-month timeframe, viral abundance and bacterial abundance and biomass were measured in order to determine the influence that the BSW exerted on the North Aegean. For this purpose, a transect of three stations displaying high (MD1), moderate (MD2) and low (MD3) impact by the BSW was chosen. Synechococcus spp. were found to be the most abundant cyanobacteria, outcompeting Prochlorococcus in all stations and months. However, at depths greater than 100m, the latter overcame Synechococcus, reaching some of the highest abundances and biomasses during spring. The pico-phytoplankton bloom that took place in late spring in MD2 and MD3 was of half the intensity of MD1 and occurred at different depth layers, revealing that the role of the BSW changes as distance from the Dardanelles Strait increases. Total bacterial biomass was especially low in March, while in the remaining months, it was largely dominated by small heterotrophs. Viruses always dominated the surface waters, showing disparate levels of correlation with cyanobacteria and heterotrophic bacteria. The highest correlation was recorded in MD1, which also exhibited some of the highest viral abundances recorded in the Mediterranean.