Laguna di S'Ena Arrubia - Italy

S’Ena Arrubia Lagoon is located along the central western coast of Sardinia (39.83° N, 8.57° E); it is 1.2 km2 in area and has a mean depth of 40 cm. Freshwater input is supplied from the watershed by two rivers: Rio Sant’Anna (also called Diversivo), which drains an area of 78.4 km2 and showed no runoff from April 2001 to March 2002; and the Canale delle Acque Basse (also called Idrovora), which drains 50 km2 mostly originating from the drying up of a pond over 3000 ha wide and dedicated mainly to farming and cattle-breeding. This channel is below sea level and water is pumped from it into the lagoon. A large part of the catchment area is used for intensive arable farming and cattle breeding, and as a result, the freshwater in the Idrovora canal is very rich in nutrients. The water in the lagoon is exchanged with sea water by means of a sea-mouth canal built in the 1970s (length = 230m, width = 25m, depth = 1.3m). Engineering works were carried out in 2000 to widen the sea mouth of the lagoon in order to improve tidal flushing and thus reduce its high trophic levels and improve its hydrodynamics. The dimensions of the new inlet vary in different places. It is 30 m wide and 0.70 m deep near the lagoon, 60 m wide and 2 m deep in the central part and 32 m wide and 1.30 m deep at the sea mouth. Climate is Mediterranean with long hot summer and short mild rainy winter, generally precipitation and consequent water inflows are low, the year average is 650 mm. S’Ena Arrubia Lagoon is very eutrophic because of the intense arable and stock-rearing activities in its watershed and dystrophic crises and fish kills occur occasionally. Anoxia and dystrophic crises were observed as early as the 1960s. The principal human activities in this wetland are fishing, outdoor recreation, education and scientific research. From 1990, a long-term series of data is available and derives from high-frequency measurements and samplings to assess environmental and biological parameters. In particular the data concern the main trophic descriptors (Secchi depth, temperature, pH, conductivity, dissolved oxygen and saturation, alkalinity, NH4-N, NO2-N, NO3-N, total nitrogen, soluble reactive phosphorus, total phosphorus, dissolved silica) and phytoplankton abundances, as chlorophyll a, cell densities and biomass, class and species composition. The collection of data was interrupted in 2003.