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- Water quality for bivalve molluscs and consumer safety: application of novel and adapted multimetric indices in a coastal lagoon system exposed to wastewater dischargesPublication . Cravo, Alexandra; Barbosa, Ana; Borlido Oliveira Lima, Maria João; Ferreira, Cristina; Correia, Cátia; Matos, André Filipe; Jacob, José; Caetano, SandraWater quality degradation associated with wastewater discharges compromises the production of marine living resources. Water quality indices (WQIs) are relevant tools for water quality management, but most applications are limited to the suitability of freshwater for drinking. In this study, a novel WQI was developed to assess the effects of urban wastewater treatment plant (WWTP) discharges on the water quality in Ria Formosa coastal lagoon, targeting the condition of bivalve molluscs and consumer food safety (WQIB). The application of WQIB was compared with an adapted version of the Canadian Council of Ministers of the Environment Water Quality Index, using similar parameters (CCME-WQIB). WQIB and CCME-WQIB were applied to four areas next to WWTPs, over a 2-year period. WQIB integrated seven sub-indices (salinity, unionized ammonia, dissolved oxygen, suspended solids, chlorophyll-a, Escherichia coli and toxigenic phytoplankton), using a weighted additive aggregation function. Water quality ranged from very poor to very good and generally improved with distance from the effluent discharge points, and during the cold period. Highest influence of WWTP discharges was detected in areas under weak hydrodynamics. In areas under strong hydrodynamics, poor water quality was caused by the advection of toxigenic phytoplankton from adjacent coastal waters during the warm period. Although correlated, the use of WQIB should be preferred over CCME-WQIB due its greater sensitivity, use of weighted parameters and application at the sampling event scale. Our novel index extends the limited number of WQIs applied to marine systems and can be adapted to other systems and water use purposes.
- Fate of microbial contamination in a South European Coastal Lagoon (Ria Formosa) under the influence of treated effluents dispersalPublication . Caetano, Sandra; Correia, Cátia; Torres, Ana Flor; Matos, André Filipe; Ferreira, Cristina; Cravo, AlexandraAim: 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.