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- Dissolved oxygen dynamics in Ria Formosa Lagoon (South Portugal) - A real time monitoring station observatoryPublication . Cravo, Alexandra; Rosa, Alexandra; Jacob, J.; Correia, CátiaDissolved oxygen (DO) is considered one of the most important environmental variables of water quality. This work aimed to provide, for the first time, insights regarding DO dynamics on a representative site of the productive Ria Formosa coastal lagoon, south Europe, using a real time monitoring station observatory (acquiring data every 15 min) deployed for a period of two and a half years. This comprehensive data set represents an added value contributing to a better understanding of the DO variability throughout analyzing semidiurnal, daily, fortnightly tidal cycles (spring tide vs. neap tide), seasonal and interannual periods. This observational station was able to capture distinct temporal signatures, including episodic upwelling and meteorological events advancing the knowledge about the functioning of Ria Formosa. DO was highly variable presenting an evident seasonal distribution with the maximum concentration in spring and the minimum in summer night periods. Critical values < 5 mg/L were recorded only in 3% of the global data set with negligible hypoxia events, showing infrequent DO stressful conditions in the study area. In addition, the disclosure of its did dynamics over long periods, provided by this data set, allows to determine the impact of biological activity upon the DO variability and related ecosystem metabolism behavior (autotrophic vs. heterotrophic), through the metric estimation of Net Ecosystem Metabolism (NEM). NEM in the study area revealed to be slightly heterotrophic along one year of observation, reflecting the median percentage of DO saturation (93%). The acquired data set is highly valuable and can contribute to Ria Formosa management and protection, which is imperative for building knowledge-based societies.
- Qual a importância das trocas entre a Ria Formosa e o oceano adjacente para a produtividade biológica destes sistemas?Publication . Cravo, Alexandra; Jacob, J.A Ria Formosa é a lagoa costeira mais importante do sul de Portugal, com grande influência nas trocas de água e de matéria com o oceano adjacente, as quais controlam a produtividade biológica destes ecossistemas intimamente ligados. Neste capítulo são apresentadas as características geomorfológicas da Ria Formosa e as características dinâmicas que a tornam um sistema bastante produtivo e peculiar, com forte impacto no oceano adjacente. São ainda apresentadas, pela primeira vez, as trocas através das três barras do setor oeste da Ria Formosa, em condições de maior produtividade biológica, típicas de Primavera, evidenciando a importância da interligação entre estes dois sistemas, particularmente num período sob afloramento costeiro.
- Impacts of decommissioning and upgrading urban wastewater treatment plants on the water quality in a shellfish farming coastal lagoon (Ria Formosa, South Portugal)Publication . Jacob, J.; Correia, Cátia; Torres, Ana Flor; Xufre, Gustavo; Matos, André Filipe; Ferreira, Cristina; Reis, Margarida; Caetano, Sandra; Freitas, Carla; Barbosa, Ana B.; Cravo, AlexandraRia Formosa is a productive coastal lagoon, located on the south coast of Portugal, and represents the largest national producer of shellfish bivalves (ca. 90% production). This ecosystem is subjected to various anthropogenic pressures, including the discharge of urban wastewater treatment plants (UWWTP), which impacts the lagoon water quality. This study aimed to assess the impact of alterations in the functioning of two UWWTP on the water quality of Ria Formosa, based on chemical variables, phytoplankton composition ( including potential harmful species) and faecal contamination. During the period September 2018 - October 2019, water sampling was conducted along dominant longitudinal gradients of the effluent dispersion from the discharge point (1-2 km), for two sites: a decommissioned (OP) and a modified (FO) UWWTP. After modification, the later started receiving a higher influent volume (ca. 40%), under an innovative technology system (biological treatment in aerobic granular sludge). Based on chemical water quality variables, phytoplankton and indicators of faecal contamination, a significant improvement along the longitudinal gradient from the discharge point was observed after OP decommissioning. This improvement was fast, being detected two months after decommissioning, positively affecting areas used as shellfish farming grounds. However, distribution patterns of bacteriological indicators and regular shellfish harvesting interdictions suggested an alternative source of faecal contamination after OP decommissioning. At FO, both chemical variables and bacteriological indicators of faecal contamination revealed a slower improvement, only six-months after the UWWTP alteration. Before that, increased and highly variable ammonium, chlorophyll a concentration, phytoplankton abundances and Escherichia coli densities, revealed an unstable phase. Overall, a lower water quality at FO in respect to OP reflected not only a higher effluent volume but also more restricted water circulation for the former.
- Unravelling the effects of treated wastewater discharges on the water quality in a coastal lagoon system (Ria Formosa, South Portugal): Relevance of hydrodynamic conditionsPublication . Cravo, Alexandra; Barbosa, A.B.; Correia, C.; Matos, A.; Caetano, S.; Lima, M.J.; Jacob, J.This study aimed to assess the influence of treated wastewater disposal on Ria Formosa coastal lagoon (South Portugal), the largest national producer of bivalve mollusks. Water quality was evaluated at two areas under different wastewater loads and hydrodynamic conditions, using physico-chemical variables, bacterial indicators of contamination, chlorophyll-a concentration, phytoplankton abundance and composition. Samples were collected monthly, between October 2018 and September 2019. Minor influence of effluent discharge was detected at the eastern Olhao ˜ area, exposed to stronger hydrodynamics and higher wastewater load than the northwestern Faro area (ca. 2–4-fold total nitrogen and phosphorus). The lower load weakly flushed area showed a poorer water quality, up to 500 m from the discharge point, more marked during the spring-summer period. The intensity, persistence, and spatial extent of the wastewater footprint, lower for the highest-loading area, reflected the role of local hydrodynamic conditions, modulating the influence of wastewater discharge on lagoonal water quality.
- Effects of climate change and anthropogenic pressures in the water quality of a coastal lagoon (Ria Formosa, Portugal)Publication . Rodrigues, Marta; Rosa, Alexandra; Cravo, Alexandra; Jacob, J.; Fortunato, André B.Understanding how climatic and anthropogenic drivers will influence coastal lagoons is fundamental to guarantee their preservation and sustainability. The Ria Formosa (coastal lagoon, South coast of Portugal) is a very important ecosystem that supports diverse economic activities in the region. The 3D coupled hydrodynamic-biogeochemical model SCHISM was validated and used to assess the influence of climate change and anthropogenic pressures on the water quality of the Ria Formosa. Five scenarios were simulated: reference scenario (S0), mean sea level rise (SLR) of 0.5 m (S1), increase of the air temperature of 1.68 °C (S2), increase of the outflow from the wastewater treatment plants (WWTP) by 50% (S3) and a combined scenario (S4). Results suggest that SLR of 0.5 m promotes an increase of 0.5-3 in the salinity near the area of influence of the WWTP. SLR decreases the inorganic nutrient concentrations in these areas by about 40-60%, due to an increase of the dilution. In contrast, the increase of the outflow from the WWTP by 50% increases the nutrients concentrations by about 20-40%. The increase of the air temperature alone by 1.68 °C increases the water temperature by 0-1 °C. The combined scenario suggests antagonist effects in the nutrient concentrations. Overall, the trophic index (TRIX) of the lagoon calculated for the scenarios exhibits only minor differences relative to the reference scenario, except in some areas near the WWTP discharges. In these areas, TRIX tends to increase with the increase of the outflow from the WWTP in scenario S3. These results provide further insight into the response of coastal lagoons, and the Ria Formosa in particular, to future changes and contribute to support their management.
- Export of dissolved and suspended matter from the main estuaries in South Portugal during winter conditionsPublication . Correia, C.; Torres, A. F.; Rosa, A.; Cravo, Alexandra; Jacob, J.; de Oliveira Junior, L.; Garel, ErwanEstuaries are essential drivers of primary productivity in coastal waters through the export of dissolved and suspended material. This study aims at quantifying this fertilization process at the two main estuaries in South Portugal, where typical low river discharge conditions occur in winter due to strong flow regulation by upstream dams and seldom-local rain events. Data were collected across the channel of the lower Arade (10/01/2018) and Guadiana (04/02/2019) estuaries during a semi-diurnal tidal cycle with intermediate tidal ranges (1.5 m and 2.2 m, respectively). Current velocity records were completed with hourly water quality measurements (temperature, salinity, pH, dissolved oxygen, suspended solids, chlorophyll a and nutrients) for determination of the along channel fluxes and residual mass transport of dissolved and suspended matter across the channel sections. The results show that the two estuaries were characterized by distinct water circulation patterns and tidal properties (e.g., standing wave at the Arade, mixed wave at the Guadiana). The concentration of dissolved and particulate matter displayed a general similar anti-phase pattern of variations with tidal height at both sites. The corresponding fluxes were generally strongest during the ebb phase. Thus, the residual mass transport was seaward, indicating that both estuaries contribute to fertilize adjacent coastal waters by exporting nutrients (order of kg), chlorophyll a (order of kg) and suspended solids (up to tons). Moreover, transport differences at both estuaries reflect specific discharge flow and environmental conditions as well as contamination sources close to the study areas. In particular, the signatures of a discharge event from a water treatment plant at the Arade and of coastal upwelling at the Guadiana were identified.
- Integrating physical and biogeochemical processes and oceanic exchanges at a coastal lagoon in Southern West EuropePublication . Cravo, Alexandra; Jacob, José; Rosa, Alexandra; Correia, CátiaCoastal lagoons are highly productive systems and the quantification of mass fluxes, which is of paramount importance for the sustainable management of these systems, remains poorly studied. In this context, a detailed study was conducted to better understand the exchanges between the productive coastal lagoon Ria Formosa (South-West Europe) and the ocean. The exchanges of water, nutrients, chlorophyll-a and suspended solids between the main inlets (Faro-Olhao inlet - BFO; Armona inlet - BAR; and Ancao inlet - BAN) and adjacent channels (Faro - CF and Olhao - CO) and the adjacent ocean were estimated along complete semidiurnal tidal cycles, under extreme fortnightly tidal ranges and different seasonal and environmental/oceanographic conditions. The net tidal prism was highest during spring tides. Among the three inlets, BFO was the most important in terms of exchange, followed by BAR and BAN. Net transport at BFO was lowest during the Summer campaign, although it exported material that fertilised the adjacent coast. The persistent net export of suspended solids and ammonium suggests the higher biological productivity of Ria Formosa compared to that found in coastal waters. In the Winter campaign, after a period of rainfall and increased land runoff, there was a remarkable export of matter, on which, ammonium and suspended particles exported can exceed 0.3 times and almost 0.9 times, respectively, those imported from coastal water. However, the import of phosphate and nitrate can be attributed to a weak coastal upwelling event, as well to low consumption and nitrification at this period of low temperature. During the Spring and Autumn campaigns, the Ria Formosa was fertilised either by upwelling events or due to rapid consumption of nutrients by phytoplankton in this shallow system. BFO and the other two inlets of the western sector of Ria Formosa are interconnected by CF and CO. The higher nutrient transport was recorded at CF, despite the highest nutrients concentrations was recorded at CO. The data show the strong link between physical and biogeochemical processes with meteorological/oceanographic factors. The study showed that associated biological processes are superimposed on the tidal effect in this system. Data from this study could be used as a reference, particularly important for management of Ria Formosa, a productive system where bivalves production depends deeply on water quality. In addition, the nutrient concentrations and mass exchanges resulting from the different processes can be used as a reference for other lagoon systems where shellfish production is practised.
- Water quality of a southwest Iberian coastal lagoon: Spatial and temporal variabilityPublication . Rosa, Alexandra; Cravo, Alexandra; Correia, Cátia; Jacob, JoséThe present work aims to characterize Ria Formosa water quality considering its spatial, and temporal variability at two scales: short-term (among seasons) and long-term to evaluate its evolution over the past 40 years, by comparing six historical datasets with data obtained in this study. To attain these goals, four field surveys under different seasons and/or weather conditions were conducted between 2017 and 2019 at seven sites along the Ria Formosa, covering the water bodies specified for this system. In situ measurements (temperature, salinity, pH and dissolved oxygen) and water sampling for determination of nutrients, chlorophyll a and suspended solids were taken every 2 h at each site, during complete semidiurnal tidal cycles. Moreover, these data were complemented with in situ data acquired at a high frequency (every 15 min) by a real time observational station deployed at an inner area, close to a main channel, where the anthmpogenic pressure is more intense. Data analysis clearly depict a spatial variability pattern along the Ria Formosa, as well as a temporal heterogeneity, influenced by the contribution of precipitation, sediments, wind and water exchanges with the adjacent ocean. Between sampling sites, the lowest variability of water quality parameters occurred at the boundary coastal station, at the main inlet, in permanent connection with the ocean, while the maximum variability was found at both the lagoon edges, mainly due to the shallowness of the water column. Temporally, the highest concentrations of nutrients were obtained during the Wet/rainy conditions survey, under the influence of runoff. The lowest concentrations of nutrients were attained during the Summer, except for phosphate, due to consumption by phytoplankton. Although the sampling frequency along time has been limited, Ria Formosa water quality data from the last 40 years shows a decreasing trend in nutrients concentration and a marginal increase of dissolved oxygen, suggesting a water quality improvement over time, in contrast with other coastal lagoons that are showing a water quality deterioration due to an increasing anthropogenic pressure. Altogether, these are relevant aspects to consider regarding Ria Formosa present and future management, including climate change and anthropogenic pressures susceptibility assessment and to use them within an international context by comparison with other similar systems.
- 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.