Total mercury in Pema perna mussels from Guanabara Bay--10 years later.

Guanabara Bay (GB) is an important estuary in regard to the productivity of the southeastern Brazilian coast. It is heavily polluted by oil, land runoff, and sewage, had large areas reclaimed, and its basin has been seriously deforested. The objective of the present work is to compare the total mercury levels in mussels from the bay, measured at the beginning and at the end of a 10-year interval (1988 and 1998). The commonly occurring species of bivalve in the bay is the mussel Perna perna. The total mercury content in mussels from GB has probably remained constant for the last 10 years (17.3-74.1 microg Hg kg(-1)), with possible isolated fluctuations attributed to occasional changes in water quality. Mussels have a good potential as biomonitors of water quality in GB. The need for the establishment of long-term biomonitoring programs is also commented.