THE ASCIDIAN MICROCOSMUS EXASPERATUS AS BIOINDICATOR FOR THE EVALUATION OF WATER QUALITY IN ESTUARIES.

Anthropogenic activities cause a great impact in marine biota. In estuarine environments, the sea squirts, sessile marine invertebrates, can be used as bioindicators and environmental quality biomonitors. The ascidian Microcosmus exasperatus was used in this study to compare two sites with different pollution stress. In the laboratory the individuals were dissected separating the inner soft body and the tunic. This body parts were weighed and processed to determine the concentration of various chemicals, including heavy metals. The water content of tissues showed significant differences between sites, with higher values in antropized site, indicating stress of pollution. Similarly, the condition factor presented differences between sites, which may be related to factors such as hydrodynamics, tidal cycle, but also indicate environmental pollution. In chemical analysis, it was observed that the ascidian retains higher concentration of certain chemicals in inner body than in tunic. Some chemical also showed different concentrations between places. The species studied is able to absorb a significant percentage of highly toxic elements, showing to be a good biomonitor for some metals.