Resistance of brown mussel Perna perna to low salinities and its relation to bacteriological contamination

Abstract

The mussels are considered euryhaline species, distributed over a large area of the seashore and estuarine regions. The most important species in Brazil, in economic and productive terms, is the brown mussel Perna perna. This research aimed to study the P. perna resistance to low salinities. The animals were collected from two sites of rocky coasts. One of the sites was located in Urubuqueçaba Island (Santos í  SP), a sheltered region subjected to bacteriological contamination, and the other, in Guaraú Beach (Peruí­­be í  SP), an open sea site, free from contamination. The effects of five levels of salinity (4, 14, 24, 31 and 34%o) on the mollusk mortality were studied. The experiments were conducted at two water temperatures (19 and 28°C) during February and August 2001, with four replications of each salinity. The time to occur 50% of mortality (TM 50) and the number of dead animals in each parcel after a defined exposition time were recorded. The results show that mussels from Urubuqueçaba were less resistant to low salinities than those from Guaraú. This may point out that mussels resistance to salinity was affected by the high bacteriological contamination, even considering different sheltering conditions in both studied sites.