Phytoplankton and bacterial communities patterns in a highly dynamic ecosystem (Central Mediterranean Sea)

The Straits of Messina (Southern Italy, Mediterranean Sea) is a very complex area: it connects two basins (Tyrrhenian and Ionian) with different hydrographic features and is characterised by upwelling and mixing phenomena. The aim of the study was to evaluate if and how the physical and chemical water conditions and hydrodynamics influenced the phytoplankton and bacterial patterns and the functioning of this ecosystem. During a late winter survey, size-fractionated phytoplankton (from 0.2 to 200 ?m) biomass (chlorophyll a), cell densities and species composi-tion as well as total picoplankton abundances, morphotype composition and activity levels of the enzymes leucine aminopeptidase, ?-glucosidase and alkaline phosphatase were investigated. The obtained results showed a marked diversification among the water masses identified within the Straits area. The analyses of the phytoplankton diversity indices, and particularly those based on phylogenetic relationships between species (indices of taxonomic diversity and dis-tinctness), confirmed our findings. In conclusion, phytoplankton and bacterial communities pat-terns provide a suitable approach to evaluate how microbial communities respond to changing environmental scenarios. This tool could be applied to other temperate Mediterranean ecosystems.