Salinity and its variability in the Lagoon of Venice, 2000–2009

Yearly averages computed from monthly and bimonthly salinity data collected between 2000 and 2009 from 13 broadly spaced stations in the Venice Lagoon were analysed in view of 30 min data collected semi-continuously during 2009 at nine similarly located stations. Data from all stations and all years indicate that, based on yearly averages, the lagoon may be divided along its major (long) axis into three areas: 1) a northern, freshwater impacted area (S = 32 PSU of low, tidally-caused, variability, and 3) an intermediate zone. Salinity changes are closely associated with rainfall events, and the incoming freshwater is consistently distributed throughout the lagoon by tidal action. Much variability is simply a result of the forward and backward motion of the tides and is not caused by a salinity change in the water itself. The consistency of the 2000–2009 data and the historical (to 1961) watershed record support the hypothesis that the Venice Lagoon has been and is currently at steady-state with respect to its salinity distribution. As such, it is conducive to the development of (at least) three separate ecosystems.