No abstract

Impacts of decommissioning and upgrading urban wastewater treatment plants on the water quality in a shellfish farming coastal lagoon (Ria Formosa, South Portugal).

To evaluate the potential impact of an urban wastewater-treatment plant on Ria Formosa coastal lagoon, a sentinel species, the clam Ruditapes decussatus, was exposed along a gradient of the effluent's dispersal for 1 mo. Three exposure sites were selected to study the responses of 3 biomarkers: electron transport system, acetylcholinesterase, and lipid peroxidation. As complementary data, morphometric measurements, condition index, and lipid and protein content were considered together with in situ physicochemical characterization of the sites (temperature, salinity, pH, and dissolved oxygen). Electron transport system activity levels were between 35.7 and 50.5 nmol O 2 /min g protein, acetylcholinesterase activity levels ranged from 2.6 to 3.8 nmol/min g protein, and lipid peroxidation ranged from 174.7 to 246.4 nmol malondialdehyde/g protein. The exposure sites shaped the response not only of biomarkers but also of "health" parameters (protein, lipids, and condition index). Lipid peroxidation was the most responsive biomarker also associated with electron transport system, especially at the closest site to the urban wastewater-treatment plant. Because of the presence of complex mixtures of contaminants in urban effluents, biomarker responses can provide valuable information in environmental assessment. However, it is vital to identify all biological and ecological factors induced by the natural life cycle of clams. Abiotic factors can mask or overlap the response of biomarkers and should be considered in a multibiomarker approach.

Aim Assessment of the fate of microbial contamination driven from treated wastewater disposal at a highly productive zone on a South European coastal lagoon (Ria Formosa). Methods and results Microbial indicators of contamination (Total coliforms, Escherichia coli and Enterococci) were evaluated monthly during September 2018-September 2020, at three study areas (Faro, Olhão, Tavira) under different wastewater discharge flows and hydrodynamic conditions. Additional data on E. coli monitoring in bivalves, available from the national institution responsible for their surveillance was also considered. The maximum microbial contamination was found at Faro, the highest-load and less-flushed study area, contrasting the lowest contamination at Olhão, a lower-load and strongly flushed area. The wastewater impact decreased along the spatial dispersal gradients and during high water, particularly at Faro and Tavira study areas, due to a considerable dilution effect. Microbial contamination at Olhão increased during the summer while at the other study areas seasonal evidence was not clear. Data also indicate that E. coli in bivalves from BPZ next to the three study areas reflected the differentiated impact of the wastewater treatment plants effluents on the water quality of those areas. Conclusions Effluent loads together with local hydrodynamics, water temperature, solar radiation, precipitation and land runoff as well as seabirds populations and environmentally adapted faecal or renaturelized bacterial communities, contributed to microbial contamination of the study areas.