SPATIAL AND TEMPORAL DESCRIPTION OF THE DYSTROPHIC CRISIS IN LESINA LAGOON DURING SUMMER 2008.

Mediterranean lagoons, being shallow and very productive area, are naturally exposed to anoxic and dystrophic events during the summer period of high temperature and reduced water exchange. Urban, agricultural and industrial nutrient load act as facilitating factors for the dystrophic events. During summer 2008 the North-Western part of the Lesina lagoon was affected by a dystrophic crisis lasting several weeks. During the same period a group of laboratories of the University of Salento, CNR-ISMAR of Lesina and ARPA Puglia, that were involved in a monitoring activity on the ecological status of the lagoon, had the opportunity to follow the entire events with weekly observations of many abiotic and biotic parameters. Here, we describe the dystrophic event focusing on the spatial and temporal dynamics of the crisis as well as on both some potential drivers and the most commonly used chemicalphysical markers. The dystrophic crisis involved rapidly an area up to 4 Km2 as shown by a satellite images analysis, with a slower decrease at the end of August 2008. A general chemical-physical analysis is reported. An analysis of the main meteorological factors during the event compared with the data of the past 4 years showed a strong influence of wind intensity and directions on the dystrophic event probably influencing the mixing dynamic of waters. A comparison with previous dystrophic events in Lesina lagoon is also presented for a better understanding of the causes that can arise these dystrophic events.