Lysosomal stability in oysters Crassostrea sp. from three different populations from the coast of São Paulo, Brazil

Abstract

Coastal zones continuously receive inputs of contaminants, which greatly affect its quality. Biological effects resulting from environmental pollution are complex and have not been properly estimated by chemical analysis and toxicity tests. A reliable form to assess the environmental quality consists of analyzing organisms exposed to constant, complex and diffuse sources of contamination. The appropriate use of biomarkers in sentinel organisms may provide an estimate of the potential risk associated with contamination. This study aims to evaluate if different levels of potential contamination affect differently the stress responses in oysters from three sites along the coast of São Paulo state. The physiological condition of oysters Crassostrea sp. from Cananéia (reference site), Santos and Bertioga was studied by analyzing the lysosomal membrane stability in haemocytes, measured using the neutral red retention time (NRRT) assay. Adult organisms were collected in spring (August, September, and October/2016) and autumn (April and May/2017). During the spring, the times of retention of the neutral red dye were similar in oysters from different sites and the reference area (p > 0.05). Interestingly, an uncommon red tide occurred along the coast of the state mainly affecting Cananéia, which may have influenced the reduction of the NRRT for oysters from this region. Such biological events (algal blooms) are more likely to occur at this time of year due to the typical climatic conditions, and may have the potential to even the adverse effects of pollution on distinct bivalve populations subject to different levels of contamination. During the autumn campaign, organisms from both contaminated sites (Santos and Bertioga) showed significant reduction in the mean NRRT relative to the reference site (p < 0.05). A previous study in the same region (Catharino et al., 2015) observed that in both seasons the oysters from Cananéia had a higher NRRT than the oysters from the other two sites. Overall, the NRRT were lower in the present study. These results may be due to the exposure of the organisms to pollutants, since lysosomes are organelles that absorb a wide variety of organic and inorganic substances. However, further investigations are required and being carried out to confirm this hypothesis.