Relationships between benthic infauna and groundwater eutrophication on a sandy beach in southern Brazil.

Urban expansion in Brazilian coastal zones has caused various anthropic impacts on coastal marine ecosystems that have resulted from unorganized use and the lack of infrastructure projects. The inadequate disposal of domestic and industrial effluents in coastal waterbodies is notable, which can cause severe environmental problems. For sandy beaches, the relationships between the contamination of groundwater with domestic sewage and the possible effects on spatial and temporal variations in the density and composition of benthic infauna are still poorly understood. This work aimed to relate variations in benthic infaunal associations with the concentrations of groundwater nutrients in summer and winter on Enseada Beach. The greater concentrations of nutrients in water percolating through the sediment in the summer, increasing of domestic effluents, and periods of intense precipitation increased the contamination of the surface and groundwater. This contributes to an increase in the population density of Thoracophelia furcifera, demonstrating its use as an indicator of eutrophication of the groundwater, allowing monitoring and contribution to actions aimed at improving the environmental quality of sandy beaches.

Plastic floating debris along a summer-winter estuarine environmental gradient in a coastal lagoon: how does plastic debris arrive in a conservation unit?

Improper management of plastic waste is an important contributor to the pollution in water bodies. However, how floating plastic debris is transported to coastal lagoons and marine conservation units is still poorly understood. This work determined the level of contamination due to floating plastic debris in Acaraí Lagoon by establishing density distribution patterns along the lagoon ecocline in the winter and summer. Four areas were chosen that followed the estuarine gradient of the lagoon (external, lower, middle, and upper), and in each area, three samples of were collected by trawling with a plankton net. The plastic debris was classified into paint fragments, hard solids, plastic filaments, and soft plastics, and the plastic debris density and surface area were determined in each sampling area. The concentrations of the plastics in the downstream and upstream areas resulted from the high density of debris that occurred during the winter due to the absence of rain and the entry of coastal waters into the lagoon. The reduced abundance and surface area of the plastics in the summer were related to the substantial output of water from the interior of the lagoon to the mouth of the lagoon due to high rainfall during this season. The absence of plastic waste management actions and developed areas at the mouth of the lagoon that were associated with the spatial and temporal fluctuations in the environmental variables favored the occurrence and high abundance of plastic debris in the water column, contaminating the entire system of Acaraí State Park.