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Sources of anthropogenic nutrients and their implications on nutrient chemistry and ecological conditions of Ria Formosa lagoon, Portugal

Publication . Oduor, Nancy A.; Cristina, Sónia; Goela, Priscila

Shallow coastal waters receive high anthropogenic nutrients (nitrogen-N and phosphorus-P) from land that can change their nutrient chemistry, algal composition, and food webs with serious effects on marine life, human health, and local livelihoods. Managing anthropogenic nutrient inputs is thus key to ensuring healthy and productive coastal ecosystems. This study conducted a bimonthly sampling for eight months between 2014 and 2015 to determine the influence of agriculture, sewage, and natural nutrient sources on nutrient chemistry, ecological status, and possible implications for aquaculture production in the western side of Ria Formosa lagoon. Ecological Quality Ratios (EQR) were calculated from nutrient ratios (N: P: Si) computed from nutrient concentrations with the Redfield ratio (N: P: Si =16:1:16) used as a reference for ecological status determination. A mean of 3.7, 1.0, and 4.6 mu mol/L; 6.7, 1.12, and 5.5 mu mol/L; and 4.6, 0.7, and 2.8 mu mol/L were recorded for dissolved inorganic nitrogen, phosphorus and silicates concentrations at sewage, agriculture, and natural sites respectively. The site mean EQR values ranged between 0.55 and 0.69. The overall ecological status of the west part of the lagoon was 'Moderate', with all the sites grouped under 'Good'/'Moderate' and 'Moderate'/'Poor' classes based on nutrient ratios. This study demonstrates that the western part of the lagoon's nutrient chemistry is highly influenced by the nutrient sources with agricultural run-off and sewage discharges associated with nitrates, and ammonia and phosphates respectively. The elevated ammonium and phosphates registered can transform the phytoplankton composition to non-diatomic species and affect the current ecological functions of the lagoon. We recommend further studies, including biological quality elements, to get more comprehensive results on the study area.(c) 2023 Elsevier B.V. All rights reserved.

2023-07Journal article

Restricted access

Cliff vulnerability assessment on rocky coasts in southern Portugal.

Publication . Moura, Delminda; Cristina, Sónia

Rocky cliffs are widely distributed around the world’s coasts and are subject to natural and anthropogenic pressures. The coastal evolution and erosional processes of the southern Algarve coast in Portugal have been previously studied. However, a detailed analysis of the relationship between lithological characteristics and cliff vulnerability to erosion is lacking. Therefore, in this work we focused on lithological facies variation and structures of the cliffs from Olhos de Água to Albandeira. We combined a variety of data, including those derived from traditional field-based and laboratory analysis, remote sensing (UAV image analysis) and photogrammetry. We identified multiple key forcers concerning cliff vulnerability to erosion: high vertical facies variation, intense karstification, multiple notches and marine caves. Furthermore, our lab analysis revealed differences in CaCO3 content for each lithofacies, resulting in alternating rock strength and leading to the formation of multiple structural notches into the cliff face. A classification of cliff vulnerability was developed based on a combination of these lithological and geomorphological factors. The sector Arrifes - Galé was classified as most vulnerable; Sector Galé - Armação de Pêra Bay was classified as least vulnerable in the study area.

2021-07-21Conference object

Open access

Application of free satellite imagery to map ecosystem services in Ungwana Bay, Kenya

Publication . Mathai, Daina; Vitorino Cristina, Sónia; Owuor, Margaret Awuor

A major obstacle to mapping Ecosystem Services (ES) and the application of the ES concept has been the inadequacy of data at the landscape level necessary for their quantification. This study takes advantage of free satellite imagery to map and provide relevant information regarding ES and contribute to the sustainable management of natural resources in developing countries. The aim is to assess the flow of ES in mangrove ecosystem of Ungwana Bay, located on the northern coast of Kenya, by adopting the Land Use Land Cover (LULC) matrix approach. This study characterized LULC classes present in the study area, identified the most important ES, and collected data on expert opinions via a survey on ES flow supplied by the mangrove ecosystem. A qualitative and quantitative analysis of the expert scoring produced a LULC matrix which, when integrated with the LULC maps, showed the spatial distribution of ES flow. The assessment indicates very high flow (5.0) for the regulating and supporting services, high flow (4.0) for the cultural services, and medium flow (3.0) for the provisioning services as supplied by mangroves. In addition, the analysis indicates there are sixteen major ES supplied by the mangrove ecosystem of Ungwana bay as of the year 2021. This study highlights the importance of mangroves as a coastal ecosystem and how the visualization of the spatial distribution of ES flow using maps can be useful in informing natural resource management. In addition, the study shows the possibilities of using freely accessible satellite imagery and software to bolster the ES assessment studies lacking in developing countries.

2023-03-28Journal article

Open access

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

Exploring open-source multispectral satellite remote sensing as a tool to map long-term evolution of salt marsh shorelines

Publication . Blount, Tegan R.; Carrasco, A. Rita; Cristina, Sónia; Silvestri, Sonia

From an ecological and socio-economic perspective, salt marshes are one of the most valuable natural assets on Earth. As external pressures are causing their extensive degradation and loss globally, the ability to monitor salt marshes on a long-term scale and identify drivers of change is essential for their conservation. Remote sensing has been demonstrated to be one of the most adept methods for this purpose and open-source multispectral satellite remote sensing missions have the potential to provide worldwide long-term time-series coverage that is non-cost-prohibitive. This study derives the long-term lateral evolution of four salt marsh patches in the Ria Formosa coastal lagoon (Portugal) using data from the Sentinel-2 and Landsat missions as well as from aerial photography surveys to quantitatively examine the accuracy and associated uncertainty in using open-source multispectral satellite remote sensing for this purpose. The results show that these open-source satellite archives can be a useful tool for tracking long-term salt marsh extent dynamics. During 1976-2020, there was a net loss of salt marsh in the study area, with erosion rates reaching an average of-3.3 m/yr opposite a tidal inlet. The main source of error in the satellite results was the dataset spatial resolution limits, but the specific salt marsh shoreline environment contributed to the relative magnitude of that error. The study notes the influence of eco-geomorphological dynamics on the mapping of sedimentary environments, so far not extensively discussed in scientific literature, highlighting the difference between mapping a morphological process and a sedimentary environment.

2022Journal article

Open access