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- A Geographical Information System for Ria Formosa (South Coast of Portugal)Publication . Rodrigues, Ana; Carvalho, António; Reia, João; Azevedo, Bruno; Martins, Cláudia; Duarte, Pedro; Serpa, Dalila; Falcão, Manuela
- Evaluation of ammonium and phosphate release from intertidal and subtidal sediments of a shallow coastal lagoon (Ria Formosa – Portugal): a modelling approachPublication . Serpa, Dalila; Falcão, Manuela; Duarte, Pedro; Cancela da Fonseca, Luís; Vale, CarlosDuring an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater ammonium profiles evidenced apeak in the top-most muddy sediment (380 lM) suggesting higher mineralization rate when oxygen is more available, while maximum phosphate concentration (113 lM) occurred in the sub-oxic layer probably due to phosphorus desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were always lower than in intertidal muddy sediments, ranging annually from 20 lMto 100 lM for ammonium and from 0.05 lM to 16 lM for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, inbothmuddy (104 nmol cm–2d–1––NH4+; 8 nmol cm–2 d–1––HPO4–2) and sandy sediments (26 nmol cm–2 d–1––NH4+; 1 nmol cm–2 d–1––HPO4–2), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal areas (22 ton year–1––NH4+; 2 ton year–1––HPO4–2), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH4+ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance.
- Biogeochemical Modelling of Ria Formosa (South Coast of Portugal) with EcoDynamo - Model descriptionPublication . Duarte, Pedro; Pereira, António; Falcão, Manuela; Serpa, Dalila; Ribeiro, Catarina; Bandeira, Rui; Azevedo, Bruno
- Scenario Analysis in Ria Formosa with EcoDynamoPublication . Duarte, Pedro; Azevedo, Bruno; Ribeiro, Catarina; Pereira, António; Falcão, Manuela; Serpa, Dalila; Bandeira, Rui; Reia, JoãoRia Formosa is a natural park managed partly by the Portuguese end-users of the DITTY project – Ria Formosa Natural Park authority, under “Instituto para a Conservação da Natureza (ICN)”. There are many conflicting interests over the management of this important coastal area: fishing, tourism, aquaculture, salt production, harbour activities, urban development and conservation. Furthermore, several institutions, such as the Natural Park Authority, municipalities, the Portuguese Navy, just to mention a few, are involved in decision-making over several areas of the natural park. Within DITTY, several scenarios were selected among those relevant for the management of this coastal ecosystem, considering available information from the end-users, relative importance of the mentioned scenarios, modelling and time constraints.
- Biogeochemical Modelling of Ria Formosa (South Portugal)Publication . Duarte, Pedro; Azevedo, Bruno; Guerreiro, Maria; Ribeiro, Catarina; Bandeira, Rui; Pereira, António; Falcão, Manuela; Serpa, Dalila; Reia, João; yesRia Formosa is a large (c.a. 100 km2) mesotidal lagunary system with intertidal areas with conflicting uses such as fisheries, aquaculture, tourism and nature conservation. Its watersheds cover an area of approximately 864 km2, with a perimeter of 166 km and a maximum altitude of 522 m. Land use may be classified into six major groups: 1) urban, 2) agricultural, 3) forest, 4) rangeland and pastures, 5) wetlands and 6) water bodies. The main objectives of this work are to: (i) Evaluate the relative importance of land drainage, waste water treatment plants (WTP) and water exchanges across the lagoon inlets, for nutrient dynamics; (ii) Analyse management scenarios related to changes in lagoon bathymetry and their potential effects on system dynamics. The Soil and Water Assessment Tool (SWAT model) has been applied to the catchment areas in order to simulate water discharges into Ria Formosa providing forcing to a twodimensional vertically integrated coupled physical-biogeochemical model, implemented with EcoDynamo – an object oriented modelling software. This model includes water column and sediment processes as well as their interactions and several biological sub-models (e.g. phytoplankton dynamics and bivalve growth). Obtained results suggest that the river network may have a significant effect on lagoon concentrations, in spite of the relatively low river flows, due to the high ammonium and nitrate loads. Scenarios reflecting increases in lagoon bathymetry through dredging operations suggest an increase in lagoon water washout time with potential impacts on water quality and impacts at a scale of tens of km. The obtained results are being used by the Ria Formosa Natural Park authority for management purposes and may be useful to feedback future updates of the watershed management plans, within the scope of the European Union Water Framework Directive. The use of a lagoon scale models is therefore justified in this work