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PERSEUS project aims to identify the most relevant pressures exerted on the ecosystems of the Southern European Seas (SES), highlighting knowledge and data gaps that endanger the achievement of SES Good Environmental Status (GES) as mandated by the Marine Strategy Framework Directive (MSFD). A complementary approach has been adopted, by a meta-analysis of existing literature on pressure/impact/knowledge gaps summarized in tables related to the MSFD descriptors, discriminating open waters from coastal areas. A comparative assessment of the Initial Assessments (IAs) for five SES countries has been also independently performed. The comparison between meta-analysis results and IAs shows similarities for coastal areas only. Major knowledge gaps have been detected for the biodiversity, marine food web, marine litter and underwater noise descriptors. The meta-analysis also allowed the identification of additional research themes targeting research topics that are requested to the achievement of GES.

The seasonal variations of temperature, dissolved organic carbon (DOC), chlorophyll a (chl a), and bacterial and protistan abundance were investigated in an enclosed Eastern Mediterranean embayrnent over an 8 mo period. DOC levels in the gulf were high, likely due to allochthonous input through freshwater discharge. However, after the end of spring, when allochthonous input was minimal, bacterial abundance was linearly related to chl a and DOC, suggesting that during this period the remaining DOC pool (probably autochthonous DOC) was important. Bacterial abundance was significantly correlated with the biomass of the phytoplankton at the end of spring and throughout summer A correspondence of protistan abundance with bactena, especially during the warm months, when the phytoplankton biomass was low, suggests that the microbial loop is the dominant component of the food web structure during the oligotrophic period of the ycar.

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