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Comunidades de microfitoplâncton no Arquipélago dos Açores: possíveis influências das ilhas na sua distribuição
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O presente estudo teve como objetivo caracterizar as comunidades de
microfitoplâncton no Arquipélago dos Açores e avaliar possíveis influências das
ilhas na sua distribuição, composição e biomassa de carbono. Foram analisadas
31 amostras recolhidas durante a expedição M150 BIODIAZ de 2018,
distribuídas pelas ilhas das Flores, Terceira e Santa Maria, e pelos montes
submarinos Banco Princesa Alice e Banco das Formigas. Estas foram obtidas à
profundidade da máxima concentração de clorofila (DCM) e analisadas em
termos de abundância, biomassa de carbono, composição taxonómica e índices
ecológicos, em articulação com os parâmetros físico-químicos da temperatura,
salinidade, oxigénio dissolvido, nutrientes, profundidade média da camada de
mistura (MLD) e intensidade do vento. As análises estatísticas revelaram uma
elevada variabilidade espacial, com diferenças significativas entre as ilhas e
montes submarinos, rejeitando-se a hipótese nula de ausência de influência das
ilhas. Santa Maria destacou-se com os maiores valores médios de biomassa de
carbono, seguida da Terceira e do Banco das Formigas. Este evidenciou-se em
relação ao Banco Princesa Alice, demonstrando haver um efeito de monte
submarino. As análises multivariadas e as regressões lineares entre biomassa e
variáveis ambientais (como temperatura, oxigénio e MLD) reforçaram o papel
dos gradientes físico-químicos locais. Foi detetado um padrão espacial de
aumento da biomassa ao longo de um gradiente oeste-leste, com maior
biomassa nas ilhas central e oriental do arquipélago. Pelo contrário, não se
observaram diferenças significativas entre locais próximos e afastados da costa,
não sendo rejeitada a segunda hipótese nula. A tempestade tropical Helene,
ocorrida durante a campanha oceanográfica, poderá ter contribuído para a
intensificação de processos de mesoescala, como o upwelling e a retenção
localizada de biomassa. Estes resultados reforçam o papel de processos físicos
locais, como o efeito da massa insular (Island Mass Effect), na modulação da
produtividade e estrutura do microfitoplâncton em sistemas marinhos
oligotróficos.
The present study aimed to characterize microphytoplankton communities in the Azores Archipelago and to assess possible influences of the islands on their distribution, composition, and carbon biomass. A total of 31 samples collected during the 2018 M150 BIODIAZ expedition were analysed, distributed across the islands of Flores, Terceira, and Santa Maria, as well as the submarine banks Princesa Alice Bank and Formigas Bank. These samples were obtained at the depth of maximum chlorophyll concentration (DCM) and analysed in terms of abundance, carbon biomass, taxonomic composition, and ecological indices, in conjunction with physicochemical parameters, namely temperature, salinity, dissolved oxygen, nutrients, mean mixed layer depth (MLD), and wind intensity. Statistical analyses revealed high spatial variability, with significant differences between islands and submarine banks, leading to the rejection of the null hypothesis of no island influence. Santa Maria stood out with the highest mean carbon biomass values, followed by Terceira and Formigas Bank. The latter was more pronounced in comparison with Princesa Alice Bank, demonstrating the presence of a seamount effect. Multivariate analyses and linear regressions between biomass and environmental variables, such as temperature, oxygen, and MLD, reinforced the role of local physicochemical gradients. A spatial pattern of increasing biomass from west to east was detected, with higher biomass in the central and eastern islands of the archipelago. In contrast, no significant differences were observed between sites located close to and far from the coast, and the second null hypothesis was not rejected. Tropical storm Helene, which occurred during the oceanographic campaign, may have contributed to the intensification of mesoscale processes, such as upwelling and localized biomass retention. These results reinforce the role of local physical processes, such as the Island Mass Effect, in modulating microphytoplankton productivity and structure in oligotrophic marine systems.
The present study aimed to characterize microphytoplankton communities in the Azores Archipelago and to assess possible influences of the islands on their distribution, composition, and carbon biomass. A total of 31 samples collected during the 2018 M150 BIODIAZ expedition were analysed, distributed across the islands of Flores, Terceira, and Santa Maria, as well as the submarine banks Princesa Alice Bank and Formigas Bank. These samples were obtained at the depth of maximum chlorophyll concentration (DCM) and analysed in terms of abundance, carbon biomass, taxonomic composition, and ecological indices, in conjunction with physicochemical parameters, namely temperature, salinity, dissolved oxygen, nutrients, mean mixed layer depth (MLD), and wind intensity. Statistical analyses revealed high spatial variability, with significant differences between islands and submarine banks, leading to the rejection of the null hypothesis of no island influence. Santa Maria stood out with the highest mean carbon biomass values, followed by Terceira and Formigas Bank. The latter was more pronounced in comparison with Princesa Alice Bank, demonstrating the presence of a seamount effect. Multivariate analyses and linear regressions between biomass and environmental variables, such as temperature, oxygen, and MLD, reinforced the role of local physicochemical gradients. A spatial pattern of increasing biomass from west to east was detected, with higher biomass in the central and eastern islands of the archipelago. In contrast, no significant differences were observed between sites located close to and far from the coast, and the second null hypothesis was not rejected. Tropical storm Helene, which occurred during the oceanographic campaign, may have contributed to the intensification of mesoscale processes, such as upwelling and localized biomass retention. These results reinforce the role of local physical processes, such as the Island Mass Effect, in modulating microphytoplankton productivity and structure in oligotrophic marine systems.
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Microfitoplâncton Biomassa de carbono Arquipélago dos Açores Island Mass Effect Montes submarinos Mesoescala Açores (Portugal) Microphytoplankton Carbon biomass Azores Archipelago Seamounts Mesoscale Biologia Aplicada . Faculdade das Ciências da Vida