Microplásticos no ecossistema de água doce

Abstract

Microplastics are contaminants present in almost all global freshwater ecosystems. In addition to their ubiquity in water and sediments, their shape and size characteristics make them easier to be ingested by various organisms. The relationship between the content and composition of microplastics in environments (water and sediments) and freshwater organisms is still little studied. This work aims to contribute to filling this gap. It approaches this topic from two different angles. First, experimentally, it tried to understand how the bivalve Anodontites trapesialis, a filter feeder, deals with the presence of microplastics suspended in the water column. Secondly, it surveyed concentrations and compositions of microplastics in freshwater organisms and their environments produced worldwide to ascertain what can be understood about this organism-environment relationship from the world scientific literature. Specimens of Anodontites trapesialis, a freshwater filter feeder from the South American Pantanal region, were placed in 4 L aquaria with 0.3 g of polyethylene microparticles ranging in size from 55 to 110 μm. At increasing exposure times (3 h–192 h), individuals were collected to evaluate the amounts of filtered, assimilated and eliminated microplastics. A strong and significant positive correlation was found between filtered microplastics and exposure times. The probability of finding them after 24 h of exposure was 78% in gill tissues, and 90% in the eliminated material. The bivalve constitutes a potential sentinel organism for microplastic contamination. A critical review of the literature on microplastic contamination in the organism and its habitat was performed through a search in bibliographic databases of the CAPES platform. This study extracted the available data to compare the accumulation of microplastics in freshwater organisms and the environment in which they live. With 35 selected publications, we showed how the concentration of microplastics in fish and bivalves is significantly correlated with the concentrations in the sediments in which they live, but not significantly with the concentration in the water. For other organisms, such as insects, there is not enough data to make this correlation. Regarding the composition of microplastics, it seems that even when there is a correlation of concentration, the composition in the organisms may differ from the composition in their surroundings. Knowledge of the ingestion of microplastics by biota in freshwater ecosystems needs to be more systematized so that contamination relationships can be better studied and mitigation measures can be taken.