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Temporal variability of physico-chemical parameters acquired in a real-time monitoring station in an inner area of Ria Formosa
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As lagoas costeiras estão entre os ambientes mais produtivos da Terra, fornecendo múltiplos serviços ecossistémicos. No entanto, o aumento da pressão humanas, juntamente com as alterações climáticas, podem aumentar os perigos, resultando em alterações da sua dinâmica. Apesar do aumento do número de estudos de processos físicos, químicos e biológicos em lagoas costeiras, ainda é difícil obter conjuntos de dados de séries temporais longas. Neste trabalho, foi efectuada uma análise do conjunto de dados registados em tempo real ao longo de dois anos, por uma estação de monitorização fixa localizada na costa sul de Portugal, numa zona interior da Ria Formosa, onde a pressão humana é maior. O intervalo de amostragem de alta frequência 15 min) permitiu descrever a variabilidade temporal da temperatura, salinidade, oxigénio dissolvido (concentração e saturação), pH, clorofila a, e turbidez, a várias escalas temporais, desde a diurnae a semi-diurna, até à quinzenal e à sazonal. Os resultados da análise espectral revelaram que a variabilidade típica dos parâmetros estudados foi induzida principalmente por forças astronómicas, tais como as constituintes principal lunar semi-diurna M2 e lunisolar sinódica quinzenal MSF, mas também por outros factores relacionados com a configuração do sistema, tais como a constituinte lunar quarto-diurna M4 e o componente diurna associada aos efeitos da radiação solar. Além disso, os dados adquiridos permitiram a identificar processos marinhos, e eventos episódicos, desde o desenvolvimento de fitoplâncton, a ocorrências de mesoscala, tais como tempestades, afloramento costeiro e contracorrente costeira. Utilizando uma correlação cruzada entre os dados de vento de hora em hora e as séries temporais de temperatura quase em tempo real, foi possível identificar a alternância entre eventos de afloramento e de contracorrente, ambos suportados pela análise de imagens de satélite. Estes eventos de mesoscala tiveram um impacto importante nos parâmetros da água da Ria Formosa, o que reflectiu a influência das trocas de água através do sistema de múltiplas barras. A estação de monitorização fixa revelou ser uma equipamento eficaz em termos de variação da qualidade da água, permitindo ter uma imagem mais abrangente dos processos e eventos que ocorrem na área da Ria Formosa e que pode representar uma ferramenta muito útil numa perspectiva de gestão ambiental.
Coastal lagoons are among the most productive environments on Earth, providing multiple ecosystem services. However, the increase of human pressures, together with climate changes, may increase the hazards resulting in changes of their dynamics. Despite growing of number of studies in physical, chemical, and biological processes in coastal lagoons, long term temporal data sets are still difficult to obtain. In this work analysis of data set recorded in a real-time mode along two years was performed, by a fixed monitoring station located in the south coast of Portugal, in an inner area of Ria Formosa, a sector more influenced by pressures from the surround populations. The high frequency sampling interval permitted to describe the temporal variability of temperature, salinity, dissolved oxygen (concentration and saturation), pH, chlorophyll a, and turbidity, at several temporal scales, from diurnal and semidiurnal, to fortnightly (spring tide vs neap tide) and seasonal. The spectral analysis’s results revealed that the typical variability of the studied parameters was induced principally by astronomical forces, such as the principal lunar semidiurnal constituent M2, the lunisolar synodic fortnightly constituent MSF, and to other factors related with the system configuration such as the shallow water overtides of principal lunar constituent M4 and the radiational tidal constituent associated with solar radiation effects. Moreover, the data acquired allowed to capture marine processes and episodic events, from phytoplankton growth to mesoscale occurrences, such as storm, coastal upwelling, and countercurrents. Using a cross-correlation between hourly wind data and almost real-time temperature timeseries, it was possible to identify the alternation between upwelling and countercurrent events, both supported by the satellite images analysis. Those mesoscale events had an important impact on Ria Formosa water parameters which reflected the influence of the water exchanges through the multi-inlets system. The fixed monitoring station revealed to be an effective tool in terms of water quality control, enabling to have a more comprehensive picture of the processes and events occuring in the area of Ria Formosa resulting a very useful tool from an environmental management perspective.
Coastal lagoons are among the most productive environments on Earth, providing multiple ecosystem services. However, the increase of human pressures, together with climate changes, may increase the hazards resulting in changes of their dynamics. Despite growing of number of studies in physical, chemical, and biological processes in coastal lagoons, long term temporal data sets are still difficult to obtain. In this work analysis of data set recorded in a real-time mode along two years was performed, by a fixed monitoring station located in the south coast of Portugal, in an inner area of Ria Formosa, a sector more influenced by pressures from the surround populations. The high frequency sampling interval permitted to describe the temporal variability of temperature, salinity, dissolved oxygen (concentration and saturation), pH, chlorophyll a, and turbidity, at several temporal scales, from diurnal and semidiurnal, to fortnightly (spring tide vs neap tide) and seasonal. The spectral analysis’s results revealed that the typical variability of the studied parameters was induced principally by astronomical forces, such as the principal lunar semidiurnal constituent M2, the lunisolar synodic fortnightly constituent MSF, and to other factors related with the system configuration such as the shallow water overtides of principal lunar constituent M4 and the radiational tidal constituent associated with solar radiation effects. Moreover, the data acquired allowed to capture marine processes and episodic events, from phytoplankton growth to mesoscale occurrences, such as storm, coastal upwelling, and countercurrents. Using a cross-correlation between hourly wind data and almost real-time temperature timeseries, it was possible to identify the alternation between upwelling and countercurrent events, both supported by the satellite images analysis. Those mesoscale events had an important impact on Ria Formosa water parameters which reflected the influence of the water exchanges through the multi-inlets system. The fixed monitoring station revealed to be an effective tool in terms of water quality control, enabling to have a more comprehensive picture of the processes and events occuring in the area of Ria Formosa resulting a very useful tool from an environmental management perspective.
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Keywords
Lagoa costeira Ria Fformosa Propriedades físicas e biogeoquímicas da água Monitorização em tempo real