A Chemotaxonomical approach towards synthetic indicators of phytoplankton composition in the context of the Marine Strategy Framework Directive (MSFD).

In order to pursue the Good Environmental Status (GES) with the aim to reduce the negative effects of anthropogenic eutrophication, the MSFD includes several criteria to be followed, among which, for Descriptor 5 (Eutrophication), total chlorophyll concentrations and the shift in the diatom-to-flagellate ratio. Within this Descriptor, the assessment is based on the nutrient concentrations in the water column and their direct and indirect effect on Chl a concentration and species shift in floristic composition (e.g. diatom to flagellate ratio) used as indicators. However, the tools to reach the described criteria are not clearly defined neither agreed upon. In recent years, the chemotaxonomical approach to phytoplankton community composition is spreading. This is based on the observation that some pigments can be mainly attributed to specific algal classes and/or types and are therefore used as taxonomical markers (Wrigth S.W. and Jeffrey S.W., 2006, Mangoni O. et al., 2008). In some cases these can also be species-specific (Mangoni O. et al., 2011). This approach allows to map the main functional groups including smaller size groups usually underestimated by microscopical counts. This works aims at analyzing the temporal dynamics of main phytoplankton groups along the water column at a fixed station in the Gulf of Naples from 2003 to 2010 as related to macro-nutrients and water column dynamics.