PHYTOPLANKTON TAXONOMIC AND FUNCTIONAL RESPONSES TO A DYSTROPHIC CRISIS EVENT IN LESINA LAGOON

The extent at which species richness and composition describe the structural organization of communities is a key issue in ecology. The occurrence of a certain degree of redundancy and stochastic events have been observed and are known to be relevant under some conditions. Species occurrence within ecosystems is determined by critical functional traits, including individual body size and the related energetics, which also are likely to affect community organization. A deepening of our knowledge on community organization has direct applied implications, highlighting the key structural components describing the type and state of organization and, in turn, the level of equilibrium vs non equilibrium conditions. Here, we describe the responses of taxonomic and functional properties of phytoplankton guilds in the Lesina lagoon during an anoxic crisis, in order to address applied implication of phytoplankton community organization in the field of monitoring the ecological status of aquatic ecosystems. To this aim, following the strong dystrophic crisis that has occurred to a portion of Lesina lagoon during the summer 2008, we have analysed the spatial and temporal patterns of most of the metrics proposed so far to evaluate the status of phytoplankton guilds. They involve, simple and complex metrics, taxonomically based, functionally based and size spectra based, accounting for taxa sensitivity or considering all taxa with the same weight. The intercalibration of the different metrics and their adequacy to describe the ecological status of transitional waters is discussed.