The influence of organic matter and phytoplankton pigments on the distribution of bacteria in sediments of Kastela Bay (Adriatic Sea)

Bacterial abundance, biomass, Volume and morphological diversity were studied in sediments collected in the eastern Adriatic Sea (Kastela Bay) in order to investigate their relationship with changes in environmental parameters. To asses the changes in the investigated parameters oil a temporal scale and between sediment layers, the sediment samples were collected monthly in 2002 with a piston corer from the sediment surface to a depth of 10 cm. The concentrations of organic matter (OM), chloroplastic pigment equivalents (CPE), chlorophyll a (chl a) and phaeopigments (PHAEO) were used as indicators Of Substrate concentrations in sediments. Sediment depth was a significant factor influencing the distribution of bacterial abundance. biomass and volume. Granulometric properties of the sediment had no effect oil the distribution of bacteria. Bacterial abundance. biomass and volume were strongly related to the indicators of substrate concentrations oil both scales. The accumulation of labile OM in deeper layers also had a profound effect oil the size and structure of bacteria. High amounts of OM and the low proportion of labile organic fraction (CPE; chl a and PHAEO) indicate that this environment acts as a sink for accumulation of detrital material.