Spatial and temporal dynamics and potential pathogenicity of fecal coliforms in coastal shallow groundwater wells.

Access to water through shallow groundwater wells is a common practice in coastal settlements. This, coupled with a lack of planning for wastewater disposal promotes fecal contamination of groundwater and poses a threat to human health. Here, the spatial and temporal dynamics of groundwater fecal contamination was evaluated during summer and winter (2013 and 2014) in a coastal protected area having a high touristic relevance (Cabo Polonio, Uruguay). Fecal coliforms (FC) abundance in groundwater was significantly higher during summer, related to an influx of ~ 1000 tourists per day. A significant spatial autocorrelation was found in 2014, when the abundance of FC in a well was influenced by its three nearest wells (Moran and Geary tests). The applied statistical models (mixed models) indicated that total phosphorus and organic matter were the variables significantly explaining FC abundance. The risk for human health was estimated using groundwater-extracted DNA and qPCR of genes encoding for E. coli virulence factors (stx1, stx2, and eae). Potential Shiga toxin-producing enteropathogenic and enterohemorrhagic pathotypes were detected, even at FC abundances ≤ 1 CFU (100 mL-1). Moreover, we found that contaminated groundwater reached the beach, being the presence of FC in sand detected even in winter and showing its highest frequency nearby groundwater wells consistently having high FC abundance (hot spots). Altogether, the results show that fecal contamination of shallow groundwater in Cabo Polonio involves a risk for human health that intensifies during summer (associated to a significant increase of tourists). This contamination also impacts the beach, where FC can remain through the whole year.

Trophic assessment in South American Atlantic coastal lagoons: Linking water, sediment and diatom indicators.

Within two coastal shallow lagoons, trophic state was assessed by integrating water and sediment chemical indicators such as the TRIX and the benthic biopolymeric carbon (BPC) trophic indicator, altogether with biological environmental indicators (diatom species characterization). Spatial and temporal behavior of TRIX and BPC indices suggest that water column trophic indicators reflect rather short-term variations in water quality changes, while benthic trophic indicators rather reflect consistent long-term trends which make them useful as enduring indicators of eutrophication. Canonical Correspondence Analysis (CCA) showed that both sediment and transitional water trophic state indices increased eutrophic conditions with a decreasing salinity and increasing total nutrients. Diatom species associated with elevated eutrophic condition such as Staurosirella martyi, Staurosira breviestriata, Amphora copulata, Amphora veneta, Nitzschia sp., and Bacillaria paradoxa, showed a positive correlation with both trophic indices. We highlight the need for considering sediment eutrophication indicators towards in monitoring programmes within shallow coastal lagoons.

Basin-scale monitoring and risk assessment of emerging contaminants in South American Atlantic coastal lagoons.

Emerging contaminants (ECs) such as pharmaceuticals, personal care products, drugs of abuse and polar pesticides are under particular attention due to their high consumption, frequent detection in the environment and reported ecotoxicological risk. This study investigates the occurrence and distribution of multiclass of ECs in surface waters at basin scale of two Atlantic coastal lagoons of Uruguay, South America. For this purpose, a target screening approach covering up to 362 compounds was employed using nanoflow liquid chromatography - high resolution mass spectrometry (nanoLC/HRMS). 56 compounds were identified including five banned pesticides in the European Union: atrazine, carbendazim, chlorpyrifos ethyl, diazinon, and ethion. Pharmaceuticals, hormones and drugs of abuse showed maximum detection frequencies and concentrations downstream cities. The highest occurrence of pesticides was found in lagoons and streams with neighboring agricultural activity. ECs were also found in coastal sea. Environmental risk assessment revealed that the hormones 17α-ethinylestradiol and 17-ß-estradiol showed the highest risk to aquatic organisms in these basins. This study represents the first basin- scale monitoring of ECs in superficial waters encompassing streams, lagoons, and coastal seas in Uruguay, South America.

Temperature and precipitation shape the distribution of harmful cyanobacteria in subtropical lotic and lentic ecosystems.

Cyanobacterial blooms are expected to become more frequent in freshwaters globally due to eutrophication and climate change effects. However, our knowledge about cyanobacterial biogeography in the subtropics, particularly in lotic ecosystems, is still very limited and the relationship of blooms to temperature and precipitation remains unclear. We took advantage of a comprehensive database of field data compiled over several years (1997 to 2015) to compare cyanobacteria biomass and distribution between lentic and lotic subtropical freshwaters (36 ecosystems, 30°-35°S) and to investigate the role of water temperature and precipitation as significant predictors in eutrophic ecosystems. A filamentous Nostocales, Dolichospermum (Anabaena), was the most widely distributed and frequent genus in the region of the study, followed by the colonial Microcystis, supporting observations of a global latitudinal pattern. Similar total cyanobacteria biovolumes (TCB) were found in lentic and lotic ecosystems, but the proportion of Dolichospermum was higher in lotic ecosystems. Using generalized linear models (GLMs), we found that temperature and rainfall explained 27% of the variation in TCB in lotic ecosystems, while temperature explained 19 and 28% of Dolichospermum and Microcystis biovolume, respectively. In lentic ecosystems, accumulated rainfall explained 34% of the variation of Microcystis biovolume while temperature explained 64%. Our results imply that the increase in extreme meteorological events and temperature predicted by climate models will promote increasingly severe cyanobacterial blooms in eutrophic subtropical freshwaters. Our analysis provides new information about the occurrence of bloom-forming cyanobacteria for southeastern South America and thus fills an important knowledge gap for subtropical freshwaters.

Land suitability assessment in the catchment area of four Southwestern Atlantic coastal lagoons: multicriteria and optimization modeling.

In the present study, a land suitability assessment was conducted in the basin of four Uruguayan coastal lagoons (Southwestern Atlantic) to analyze the productive development while minimizing eutrophication, biodiversity loss and conflicts among different land uses. Suitable land for agriculture, forest, livestock ranching, tourism and conservation sectors were initially established based on a multi-attribute model developed using a geographic information system. Experts were consulted to determine the requirements for each land use sector and the incompatibilities among land use types. The current and potential conflicts among incompatible land use sectors were analyzed by overlapping land suitability maps. We subsequently applied a multi-objective model where land (pixels) with similar suitability was clustered into "land suitability groups", using a two-phase cluster analysis and the Akaike Information Criterion. Finally, a linear programming optimization procedure was applied to allocate land use sectors into land suitable groups, maximizing total suitability and minimizing interference among sectors. Results indicated that current land use overlapped by 4.7 % with suitable land of other incompatible sectors. However, the suitable land of incompatible sectors overlapped in 20.3 % of the study area, indicating a high potential for the occurrence of future conflict. The highest competition was between agriculture and conservation, followed by forest and agriculture. We explored scenarios where livestock ranching and tourism intensified, and found that interference with conservation and agriculture notably increased. This methodology allowed us to analyze current and potential land use conflicts and to contribute to the strategic planning of the study area.