Avaliação do impacto do sistema de resfriamento da Usina Nuclear de Angra dos Reis, através de censo visual, na comunidade de peixes de costões rochosos

Abstract

The influence of thermal pollution of the Angra dos Reis nuclear power station on the rocky shore fish community and structure of the habitat was assessed by sub-aquatic visual census. Six impacted sites from water cooling form power station (I1 to I6) and two controls (C1 and C2) were sampled between 2006 and 2008. Significant differences in ichthyofauna richness and diversity were found among the sites, which were associated to benthic cover and habitat structural complexity. Sites next to the thermal discharge (I1 and I2) were the most affected by thermal pollution, showing low fish species richness and diversity and low benthic cover. Other sites (I3, I5 and C2) were more structured with higher species richness and benthic cover, suggesting the importance of both structure of habitat and benthic cover, and decreased influence of thermal pollution at the more depth sites. Average surface temperature at the more affected sites (I1 e I2) ranged from 31 to 30.5 ºC, while in the controls, ranged from 25.5 to 28.5 ºC. Higher abundances of Eucinostomus argenteus, Mugil curema and Sphoeroides greeleyi were associated to high temperatures typical of the most impacted sites I1 and I2, indicating that these species are tolerant and opportunistic. The remain sites were characterized by high occurrences of typical rocky shore coastal species, such as Abudefduf saxatilis, Haemulon steindachneri, Haemulon aurolineatum, Diplodus argenteus and Stegastes fuscus. Structural physical habitat complexity when associated to benthic cover enable the presence of a rich fish and diverse fish community. No evident gradient of thermal alteration from the source of the discharge, was found, with the hypothesis that the thermal discharge did not alter habitat structure have being, at least partially, corroborate in the present study, since higher depth from more structured sites minimizes the effects of the impact, which was more evident at superficial layers.