Hydrological and trophic characterization of the inlet Lesina Lagoon system

The importance of lagoons depends on its high productivity mainly due to the euryhaline fish species use such shallow protected embayment for feeding, to hide from predators and, most importantly, as nursery grounds. Lesina Lagoon is a shallow water body located on the southern Adriatic Sea coast, it communicates with the sea through two channels: Acquarotta and Schiapparo. The first one, on the west side, is 2km long; Schiapparo is located on the east side, it is 1km long and wider and deeper than Acquarotta. This work shows hydrological and trophic characteristics of both of two entrance channels as an important passage area for fry ascent. Hydrological conditions, turbidity, nutrients and chlorophyll a concentrations were monitored in one station for each inlet, from September 2006 to May 2007 (every 2 weeks) during recruitment period of 0-group migrant euryhaline species. The very low saltwater input is due to the weak tidal oscillations and to the presence of fish traps situated to the inlets. The higher values of salinity, turbidity and lower DIN concentration at the Acquarotta showed major exchange with the sea compared to Schiapparo. Moreover, Acquarotta inlet ammonium concentration is higher than nitrate suggesting that nitrogen source is the result of biogeochemical processes or it is related with resuspension of sediment rather than freshwater input. Schiapparo inlet is much influenced by freshwater streams flowing along southern side of the lagoon.