Structural dynamics of bacterioplankton assemblages in the Lagoon of Venice

In this study we examined the spatial and temporal dynamics of planktonic bacterial assemblages at four different sites in the Lagoon of Venice. Samples were collected in January, April, July and October 2005 and several parameters (temperature, salinity, dissolved oxygen, chlorophyll a, dissolved macronutrients, dissolved and particulate organic carbon, viral and heterotrophic nanoplanktonic abundances) were determined in order to highlight the most important factors which are implied in shaping such assemblages. Furthermore we tested the relationship between similar assemblages and the patterns of activities (prokaryotic carbon production and several hydrolytic activities) that they perform in order to establish if, in this highly variable environment, similar assemblages behave in analogous ways. Results indicate that seasonality act as the main forcing on the communities. Moreover, we found a mismatch between community structure and patterns of activity possibly as a consequence of the heterogeneity of the lagoon which can affect in turn the assemblages' metabolic requirements (and thus their responses).