Heterotrophic bacterial production in the Cretan Sea (NE Mediterranean)

In March and September 1995, bacterial production was measured by the ³H-leucine method in the oligotrophic Cretan Sea (Aegean Sea, Eastern Mediterranean) in the framework of the CINCS/MTP program. Samples were obtained from four stations (a coastal, a continental shelf and 2 open-sea stations) for the construction of vertical profiles of bacterial abundance and production. Bacterial production ranged from 0.1 μg C m⁻³ h⁻¹ at 1500 m depth, to 82 μg C m⁻³ h⁻¹ in March at 50 m at the coastal station. Higher bacterial integrated production was observed in March at the coastal station (131 mg C m⁻² d⁻¹ for the 0–100 m layer). Bacterial production, integrated through the water-column, was similar in March and September for the open-sea stations (60–70 mg C m⁻² d⁻¹). Relative to production, bacterial concentrations varied little between stations and seasons ranging from 9×10⁵ ml⁻¹ to 3×10⁵ ml⁻¹. Relationships between bacterial biomass and bacterial production indicated seasonal differences, likely reflecting resource limitation of bacterial biomass in March (bloom situation), and predator limitation of bacterial biomass in September (post-bloom situation).