Effects of a short-term environmental change on a brackish-water polychaete community (Aquatina, Lecce, Italy).

Acquatina lake is a brackish basin, connected with the Adriatic Sea along the coast of Apulia (Italy), with a mean salinity of 26 parts per thousand. The abundance and biomass of fifteen polychaete species were recorded by monthly samples in a pilot area of the lake from February 1989 to February 1990. Naineris laevigata was dominant, both in number of individuals and biomass. During 1990, obstruction of freshwater inflow to the lake caused an increase in salinity up to 40 parts per thousand, followed by some changes in the polychaete community. Notomastus latericeus became dominant, and the abundances of the other species decreased except for Naineris laevigata. Salinity assumed normal values after three months, but community responded slowly because the massive presence of N. latericeus inhibited the recovery of other species. An abiotic disturbance, followed by a biotic disturbance, altered the structure of the polychaete community.