Volume, abundance and biomass of sediment bacteria in the eastern mid Adriatic Sea

Abstract

Bacterial abundance, biomass, cell volume, and morphological diversity were studied in sediment samples collected from the coastal area of the eastern mid Adriatic Sea. Samples from the topmost 10 cm of sediment were taken monthly from January to December 2002. The number of bacteria varied from 3.54 x 10⁹ cells g^–1 in July to 8.08 x 10⁹ cells g^–1 in September. Biomass was lowest in May (78 µg C g^-1) and highest in December (378 µg C g^-1). The volume of the bacteria varied markedly with season, fluctuating from 3.87 x 10⁸ µm³ g^-1 in May to 3.12 x 10⁹ µm³ g^-1 in December. Cells with a volume smaller than 0.1 µm³ accounted for the largest number of bacteria (62%) and cocci comprised 93% of these cells. More than 80% of all rod cells had a volume smaller than 0.5 µm³. The majority of filamentous cells (63%) belonged to the 0.32 µm³ volume class. Rod-shaped cells were dominant in terms of volume (45-72%) and biomass (42-72%) and cocci in terms of abundance (52-70%). Cells smaller than 0.5 µm³ made up 88-94% of the bacteria and 68-84% of the biomass in the summer and 6-44% of the bacteria and and 21-81% biomass in the winter.