Exploring chlorophyll-a satellite derived data to characterise the coastal waters of the south of Portugal

• Autor(a) principal: Muche, Endalkachew Yeshewas
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/19852
• topic: Remote sensing; Chlorophyll-a; Physical-chemical variables; Inter-annual variability; Coastal waters; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

The chlorophyll-a (Chl-a) concentration can be used as the main indicator of the productivity, trophic condition, and proxy of phytoplankton biomass in coastal, and oceanic waters. This ecological indicator will provide useful information for reliable monitoring systems and government policy (e.g., European directives); however, assessment of Chl-a using in situ measurements in coastal and oceanic waters has some economic challenges and gives a restricted view of the dynamics of the phytoplankton. To overcome this limitation this study used Chl-a datasets from the Copernicus Marine Environment Monitoring Service (CMEMS), that provide merged multi-sensor ocean colour products. This study aimed to characterise the inter-annual variability of the Chl-a concentration retrieved by multi-ocean colour sensors data and relate these variabilities to the coastal environmental changes in five stations in the south coast of Portugal. Statistical analyses were performed to help the understanding and the characterisation of Chl-a at the coastal water stations along the southern Portugal coast based on 17 years of data (2002-2019). In addition, a comparison between Chl-a and physical (sea surface temperature (SST)) and chemical (nutrients) parameters were made to understand the inter-annual variability in these coastal waters. The extracted Chl-a values in the study area showed a seasonal cycle where the Chl-a is triggered in early spring. A clear negative relationship between Chl-a and SST was found in all stations. In the study area, a positive correlation was found between Chl-a and nutrients (NH4+, NO3-, PO4-3, and SiO4-4). Results show that SST and nutrients influence the Chl-a concentration availability in the study area. The Chl-a retrieved by satellite data reveals to be an efficient alternative tool and valuable approach to study environmental conditions of the coastal water, especially in response to eutrophication, which is the common management issue in coastal waters.