Cabras Lagoon is located on the west coast of Sardinia (Italy), in the Gulf of Oristano (39°56’37’’N, 08°28’43’’E), and occupies about 2280 ha, with a mean water depth and maximum of 1.6 and 3 m respectively. The watershed of the site extends over approximately 430 km2. The input of freshwater into the lagoon is scarce and irregular because of the semi-arid Mediterranean climate. Most of the freshwater comes from the small Mare ‘e Foghe River, located in the north.
The predominance of agriculture in the region and the release of poorly depurated urban waste account for the high nutrient loads deposited in Cabras Lagoon. The resident population of about 38,000 inhabitants is grouped in 19 urban centres, the largest being Cabras, which is located on the southeast coastal side of the lagoon.
During the twentieth century, the lagoon and its watershed underwent several modifications as a consequence of human activities that affected the hydrology and hydraulics of the region. In addition, in the late 1970s, water exchange with the sea was altered by the dredging of a large canal, the Scolmatore (spillway), which connected the lagoon with the adjacent Gulf of Oristano. The canal was constructed to avoid flooding of adjacent land during the heavy rainfall that occurs in winter. In addition, a cement dam was built into the Scolmatore to prevent further increases in the lagoon’s salinity and artificial barriers were constructed to control the fish catch, thereby impeding direct communication between the lagoon and the sea. Now the only link to the sea is via four very narrow creeks that flow into the large canal from the southern part of the lagoon over the barrier.
The lagoon has a high economic rating due to ex¬tensive fishery activities, involving about 300 people and those involved in related enterprises. In the site, in addition to the guard houses and warehouses of fishermen, there is also a restaurant, where the products of fishery in the lagoon are offered. In 1998, fish productivity reached 40,000 kg km-2, corresponding to a catch of 850 tonnes but these values fell to around 20,000 kg km-2 and less than 80 tonnes after 1999. In fact, its high trophic status has often exposed the lagoon to important dystrophic crises, which have caused large reductions in its fishing productivity. Scientific monitoring has been carried out since the strong dystrophic crisis that affected Cabras Lagoon during the summer of 1999, killing the whole aquatic biota. 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 activity was interrupted in 2009.
