Microplastics integrating the coastal planktonic community in the inner zone of the Río de la Plata estuary (South America).

This study explores in plankton samples the abundance, distribution, size, types (fibres and fragments), colours of the microplastics (MPs) and its relation with the characteristics of the plankton (size and morphology) of the Río de la Plata estuary. Water samples were collected in triplicate in freshwater-mixohaline tidal zone of the estuary, in ten sampling sites located along 150 km of coast, in two periods (September-November 2016 and April-June 2017). The results revealed the presence of MPs in all the samples analysed, with a dominance of fibres and sizes >500 ≤ 1000 µm, and blue colour being more frequent. The MPs distribution was significantly different among sampling sites, being more abundant in the most urbanized sites, sewage discharges and near the maximum turbidity front. The mean density, in the two samplings analysed, were 164 and 114 MPs m-3. The fibres amount was significantly different among sites. The MPs integrated a planktonic community dominated by pico-microphytoplankton, mainly conformed by filaments/chains and solitary forms and by micro-mesozooplankton. The comparative analysis of plankton and MPs demonstrated that a fraction of the latter showed a frequency range of size that coincides with the most common sizes of plankton (≤500 µm). The mean percentage of MPs items in relation to zooplankton was 0.36% (sampling 1) and 1.20% (sampling 2) and for phytoplankton was 0.0002% (sampling 1) and 0.0005% (sampling 2). The correlations between the MPs concentration and habitat quality (IHRPlata index) were statistically significant, on the contrary correlations between the MPs concentration and measured environmental variables were not found. The findings of this study emphasises the need for a better treatment of urban waste, which would contribute to reducing the entry of this pollutant into the ecosystem. The presence of microplastics in plankton samples on the coast of the Río de la Plata estuary.

Biofilms coating Schoenoplectus californicus as indicators of water quality in the Río de la Plata Estuary (Argentina).

Community composition, structure, biomass and tolerance to pollution of biofilms growing on Schoenoplectus californicus were assessed, together with physico-chemical parameters of the water, to evaluate their usefulness as water quality indicators along the Argentinian shore of the freshwater zone of the Río de la Plata Estuary. Monthly sampling was carried out at three sites, one of which, located in a nature reserve, was considered as the reference site while the others were affected by sewage outlets and port activity. The reference site had higher dissolved oxygen and turbidity values, the polluted sites greater conductivity, oxygen demands, phosphate, ammonium and nitrite values. Diatoms dominated the biofilms at the reference site; ciliates reached higher densities at the polluted sites. Significant differences were found in species numbers, species diversity index, biomass, tolerance to pollution of the taxa, and the Pampean Diatom Index, between the reference and the impacted sites. This study shows that the biofilms growing on Schoenoplectus californicus are good indicators of the changes in the water quality of their environment.