FATTY-ACID SIGNATURES FROM BACTERIA AT THE FRESHWATER SEAWATER BOUNDARY OF THE KRKA ESTUARY IN WINTER, SPRING AND AUTUMN/

Distribution of fatty acids was determined at the halocline and in adj acent brackish and marine waters in the Krka Estuary, on the East coas t of the Adriatic Sea, in winter 1987, spring 1988 and fall 1990. Part iculate matter (> 0.7 mu m) was extracted and analyzed for fatty acids by gas chromatography and gas chromatography/mass spectrometry. Diffe rent groups of fatty acids were examined: branched and monounsaturated (vaccenic). Bacterial signatures were highly variable in the estuary, depending on season and the extent of accumulation of organic matter at the halocline. Imprint of branched fatty acids, probably representa tive for the largest bacterial populations, varied by three orders of magnitude. This imprint was generally low at marine stations with an e xception of fall 1990, and high in river/brackish waters. Bacterial si gnatures were interpreted in terms of relationship between their occur rence and growth conditions expressed as suspended matter, organic car bon and chlorophyll a concentrations, as well as nature of organic mat ter in various water types, fresh, brackish and marine.