Contamination by microplastics in oysters shows a widespread but patchy occurrence in a subtropical estuarine system.

Microplastics (MPs) have been widely documented in marine biota, with a notable presence in bivalve species. This study examines microplastic (MP) contamination in oysters across a subtropical estuarine system, revealing widespread and highly variable levels of contamination. Our results indicate a general trend of higher contamination in areas with greater anthropogenic impact, and unexpectedly high values in remote Marine Protected Areas, suggesting alternative sources of MPs. We observed a 94.31 % frequency of occurrence and an average contamination level of 8.16 ± 6.39 MP.ind-1, 1.06 ± 1.28 MP.g-1ww, and 7.54 ± 6.55 MP.g-1dw. Transparent fibers, predominantly composed of polyester and polyethylene from likely textile origins, were the most common. The findings underscore the significance of MP pollution in marine environments, even in protected zones. For enhanced spatial assessment and consistent data comparison, we recommend that future studies include MP quantities in terms of dry weight (MP.g-1dw) and biometric data such as size and weight.

First record of Perkinsus marinus infecting Crassostrea sp. in Rio Grande do Norte, Brazil, using real-time PCR.

A pathogen with high virulence potential in some host species, Perkinsus marinus remains a challenge for the ecological integrity of marine ecosystems and the health of bivalve molluscs. This study investigates the occurrence of P. marinus in Crassostrea sp. in estuaries of the Potengi River and the Guaraíras lagoon in Rio Grande do Norte, Brazil. A total of 203 oyster samples that tested positive for Perkinsus sp. in Ray's fluid thioglycollate medium (RFTM) were subjected to species-specific quantitiative PCR, where 61 animals (30.05 %) presented amplification graphs with a melting temperature of 80.1 ± 0.6 °C matching the positive control. This was the first record of P. marinus in oysters in these estuaries using qPCR as a diagnostic tool.

Comparison of biochemical composition, nutritional quality, and metals concentrations between males and females of three different Crassostrea sp.

Gametogenesis can significantly affect the biochemical composition of oysters, but little research on the difference between sexes. Therefore, we conducted the first in-depth study on the composition differences between males and females of three different Crassostrea sp.. The results showed that females had higher glycogen, lipid, Cu and Zn contents than males, while males had higher protein and taurine contents than females at maturity, which might be related to special meiosis pattern of eggs and less energy was required for female gametogenesis. In addition, both males and females had well-balanced essential amino acid compositions. The omega-3: omega-6 (n-3: n-6) ratio of males was significantly higher than that of females, indicating that the nutritional quality of males was higher. These results provide a reliable and refined theoretical and research basis for revealing the nutritional quality, extracting beneficial ingredients, and developing functional food of Crassostrea sp., and provide data support for the sex-regulated breeding of oysters.

Linkage between speciation of Cd in mangrove sediment and its bioaccumulation in total soft tissue of oyster from the west coast of India.

This study established a mechanistic linkage between Cd speciation and bioavailability in mangrove system from the west coast of India. High bioaccumulation of Cd was found in the oyster (Crassostrea sp.) even at low Cd loading in the bottom sediment. Bioaccumulation of Cd in the oyster gradually increased with the increasing concentrations of water soluble, exchangeable and carbonate/bicarbonate forms of Cd in the sediments. Fe/Mn oxyhydroxide phase was found to control Cd bioavailability in the sediment system. Cd-associated with sedimentary organic matter was bioavailable and organic ligands in the sediments were poor chelating agents for Cd. This study suggests that bioaccumulation of Cd in oyster (Crassostrea sp.) depends not on the total Cd concentration but on the speciation of Cd in the system.

Densidade colimétrica das áreas de extrativismo de ostras em relação aos fatores ambientais em Cananeia (SP) / Colimetric density assays of oyster harvesting areas in relation to environmental factors in Cananeia (SP)

A água nas áreas de extrativismo de ostras do Estuário de Cananeia foi avaliada por meio da análise colimétrica durante o período de 2005 a 2011. Averiguou-se que a média geométrica dos coliformes termotolerantes (18,80 NMP.100mL-1) está dentro dos limites permitidos pelo CONAMA 357/2005, mas o percentil não alcançou o mínimo estabelecido pela Resolução (80%). Verificou-se que houve correlação positiva entre coliformes com o fator pluviosidade e correlação negativa com a salinidade. Constatou-se também que a preamar de sizígia apresentou menor densidade de coliformes e diferiu significativamente dos outros estofos analisados. Concluiu-se que a concentração de coliformes nos locais analisados demonstrou variabilidade temporal e que sofre influência direta de salinidade, pluviosidade e amplitude de maré.

The water in oysters harvesting areas of Cananeia Estuary was assessed by coliforms analysis throughout the 2005 to 2011 period. The thermotolerant coliforms presented geometric averages (18.80 NMP.100mL-1) within the limits allowed by CONAMA 357/2005, but it did not reach the minimum percentile established by the Resolution (80%). It was observed that there was a positive correlation between coliforms with rainfall factor and a negative one correlated with salinity factor. It was found also that the high tide showed lower density of coliforms and significantly differed from other upholstery analyzed. The analysis of the upholstery water showed variations in coliforms density and it is concluded that the concentration of coliforms in oyster production areas is directly influenced by salinity, rainfall and tidal range.