Do iron and manganese affect the health of the estuarine oyster Crassostrea rhizophorae?

The metals (e.g., Fe and Mn) are not biodegradable and can be bioaccumulated in aquatic organisms. In high concentrations, Fe and Mn can cause damage in aquatic organisms, including death. Since the exposure of aquatic biota to metals can affect their health, the present study aimed to evaluate the toxicity of Fe and Mn in specimens of Crassostrea rhizophorae (oysters) through genotoxic (comet assay), biochemical (CAT and GST enzymes), and physiological (bioaccumulation of metals in tissues) biomarkers. For that, individuals of C. rhizophorae were exposed to different concentrations of Fe (0.3, 0.440 and 1.5 mg/L) and Mn (0.049, 0.1 and 0.5 mg/L) separately and in association (Mn 0.049 + Fe 0.3; Mn 0.1 + Fe 0.440; Mn 0.5 + Fe 1.5 mg/L), in order to understand the potential risk of metals together. The results indicated bioaccumulation of metals in oysters' tissues (Fe + Mn), increasing both CAT and GST activities on gills to protect oxidative stress, and damage to genetic material detected by the comet assay on hemolymph. Therefore, elevated Fe and Mn affected the health of oysters, with physiological and biochemical changes and genotoxic damage. This work provides the essential knowledge and scientific evidence to enable decision-makers to elaborate monitoring measures to expose aquatic ecosystems to Fe and Mn.

Automated summary

This study evaluated the toxicity of metals (Fe and Mn) in oysters through various biomarkers. The results showed that high concentrations of Fe and Mn caused physiological and biochemical changes, as well as genetic damage in oysters. This research provides important knowledge and scientific evidence for decision-makers to develop monitoring measures for the exposure of aquatic ecosystems to Fe and Mn.