Avaliação dos impactos ambientais através das respostas bioquímicas em ostras Crassostrea sp. (Bivalvia, Ostreidae) na baía de São José - Maranhão

Abstract

The responses of organisms as an environmental monitoring tool have been used by organisms sensitive to changes that occur in the environment. Among the organisms used as biomonitors, oysters stand out, which accumulate large amounts of contaminants in their tissues. In this sense, this research aimed to determine the physical-chemical parameters of seawater at three points in São José Bay, Maranhão - Brazil, perform biometry of oysters of the genus Crassostrea, evaluate the anthropic impact through the quantification of nitrites (NO2) and identify oyster species through molecular analysis. For this, oysters of the genus Crassostrea were collected in the dry season in October 2022 and the rainy season in March 2023 at three points in São José Bay, point S1 (cultivation - Raposa), S2 (extractivism - Paço do Lumiar) and S3 ( urban area- São José de Ribamar). During the time of each collection (low tide), the physical-chemical parameters of the water were recorded at all sampling points and compared with CONAMA Resolution No. 357/2005, 2 ml of seawater was also collected at the three sampling points for NO2 quantification. The nitrite present in the oysters' supernatant was analyzed indirectly through the Griess reaction, which quantifies nitrites. For molecular analysis, DNA extraction techniques using the saline protocol and the Polymerase Chain Reaction were used. Analyzes of the physical-chemical parameters of seawater demonstrated that pH and temperature remained within established limits, except during the rainy season in the extractive area. The concentration of dissolved oxygen remained low at points S2 and S3. In the biometric analysis, it is possible to observe that oysters from extractivism are smaller in all dimensions, especially in the rainy season. The result of nitrite quantification in the oyster supernatant revealed significantly higher concentrations in the extraction area (dry period 0.41 ± 0.7 mg/L and rainy period 0.28 ± 0.11 mg/L), showing that this area is the most impacted. Regarding molecular identification, it was possible to observe a pattern of bands that correspond to Crassostrea gasar and Crassostrea rhizophorae. Therefore, the results found indicate that the quantification of nitrites is an innovative, simple, effective and lowcost tool that can be used in environmental monitoring in addition to the physicalchemical parameters of water and biometric analysis.