Centre for Marine and Environmental Research

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Assessing the effectiveness of management measures in the Ria Formosa coastal lagoon, Portugal

Publication . Newton, Alice; Cañedo-Argüelles, Miguel; March, David; Goela, Priscila; Cristina, Sónia; Zacarias, Marta; Icely, John

The Ria Formosa is an important transitional and coastal lagoon on the south coast of Portugal that provides valuable ecosystem services. The lagoon is a protected area under national and international conventions. There is a great potential for Blue Growth sectors, such as aquaculture and coastal tourism, but these rely on good water quality. European environmental legislation, such as the Water Framework Directive, requires member states, such as Portugal to implement management measures if a surface water body is not of good ecological status. This work addresses the effectiveness of management measures, such as wastewater treatment plant implementation and dredging, on the water quality of the Ria Formosa coastal lagoon system. This is an important social-ecological issue, since management measures can be very expensive. The ecological status of Ria Formosa was evaluated, according to the physico-chemical and biological quality elements of the Water Framework Directive. The main indicators were the physico-chemical quality elements of nutrient and oxygen condition, and the biological quality element chlorophyll a, as a proxy for phytoplankton biomass, under the Water Framework Directive. The data for these quality elements from the Ria Formosa were analyzed for consistency with the classification for the Water Framework Directive water bodies. The data after the implementation of management measures was compared with historical data to evaluate if these measures had been effective. The relation between nutrient pressures, meteorological and hydrological conditions was addressed, especially rainfall and runoff. Results showed a decrease in nutrient concentration after the management interventions, despite the increase of population and intensifying agriculture in the catchment. The Ecological Status is spatially variable with an overall moderate status, indicating the need for further management measures. There is a significant reduction in nutrient pressure on the lagoon during drought years. This indicates that climate change may alter the structure and function of the lagoon in the future.

2022Journal article

Open access

Seasonal, spatial, and high-frequency monitoring of dissolved oxygen and net ecosystem metabolism in a shallow coastal lagoon, Ria Formosa - Portugal.

Publication . Correia, Cátia; Jacob, José; Cravo, Alexandra

This study provides a detailed assessment of dissolved oxygen (DO) dynamics and net ecosystem metabolism (NEM) in the Ria Formosa coastal lagoon, highlighting how spatial and temporal variability shape mesotidal ecosystems. Complementary approaches were applied: short-term (24 h) diel oxygen open-water method at two stations (eastern and western boundaries) in comparison with the bottle incubation method, and a 2.5-year high-frequency dataset at an inner station lagoon. DO showed clear seasonal patterns, largely driven by photosynthesis and respiration, but strongly modulated by water circulation and hydrodynamics. Sporadic hypoxic events (DO ≤ 2 mg L) were observed but do not represent a risk. The boundary stations are shallower and colonized by submerged vegetation, displayed stronger diel fluctuations than at the inner station, underscoring the role of biological processes in lagoon metabolism. NEM estimates revealed strong spatial contrasts: the western station was autotrophic, while the eastern station predominantly attributed to restricted water exchange. Long-term records from the inner station indicated a slightly heterotrophic status, reinforcing the value of sustained high-frequency monitoring for capturing ecosystem trends overlooked by short-term approaches. The results also highlight lagoon-coastal ocean connectivity, suggesting dual exchanges: local production may be exported offshore to sustain adjacent coastal areas, while coastal processes, such as upwelling, can also influence lagoon metabolism. Methodological comparisons confirmed that bottle incubation method underestimated NEM relative to diel oxygen open-water method, emphasizing the role of hydrodynamics in mesotidal system metabolism. Although sampling focused on western and eastern boundaries and inner lagoon, the strong tidal renewal in the main and secondary channels suggests Ria Formosa overall is close to metabolic balance, with spatial heterogeneity shaped by hydrodynamics, vegetation, and coastal forcing. By integrating short-term, high-frequency, and long-term observations, this study advances understanding of metabolism in coastal lagoons, offering key insights for predicting ecosystem responses to climate change and for guiding management of vulnerable coastal environments.

2026Journal article

Open access

Evaluating the effects of water circulation on the modeling of wave propagation on the Southern coast of the Iberian Peninsula

Publication . Mills, Lara; Garzon, Juan L.; Martins, Flávio

Simulating wave propagation is crucial for forecasting processes offshore and near the coast. Many operational wave models consider only atmospheric and wave forcing as boundary conditions. However, waves and currents are interdependent, and simulating their interaction is crucial for accurately representing wave propagation. This study examines the influences of the current velocity and water levels on waves on the southern coast of the Iberian Peninsula. These forcing elements were simulated by a 3D hydrodynamic model (MOHID) and included in the Simulating WAves Nearshore (SWAN) model. The standalone SWAN model was calibrated and validated by comparing results of significant wave height, mean wave direction, and peak period with in situ observations. Then, the effects of water levels and current velocities on wave propagation were assessed by forcing the SWAN model with water levels as well as current velocities extracted from different depths: the surface layer and depth-averaged velocities from the surface down to 10 m, 20 m, and the full water column. The results revealed that incorporating the current velocity and water levels from MOHID into the SWAN model reduced the root mean square error (RMSE) between 1.6% and 27.6%. The most accurate results were achieved with model runs that included both the current velocity from the surface layer and water levels. Opposing currents resulted in increases in wave height, whereas following currents resulted in decreases in wave height. This work presents novel results on the effects of hydrodynamics on wave propagation along the southern coast of the Iberian Peninsula, a region of key importance for the blue economy.

2025-11-25Journal article

Open access