Duarte-dos-Santos et al.: Spatial-seasonal variation of microphytoplankton 356 Spatial and seasonal variation of microphytoplankton community and the correlation with environmental parameters in a hypereutrophic tropical estuary -Maranhão -BrazilThe Bacanga River Estuary has a hydrodynamic behavior and its tidal flow is limited by a dam. It is considered as a hypertrophic environment that receives daily high loads of domestic sewage without treatment. This study aimed to evaluate the spatial and temporal variation of phytoplankton community and its relationship with environmental parameters. Bi-monthly sampling campaigns were carried out at six fixed sites between 2012 and 2013. Physical-chemical and biological parameters were collected (chlorophyll a, phytoplankton composition and abundance) to perform the statistical correlations. The results indicate that phytoplankton community is mostly represented by diatoms, with Skeletonema costatum being the dominant species responsible for bloom in April and June of 2012. The dominance of this species is related to the high silicate concentrations, pH and turbidity. Other blooms events as well as the Euglena gracilis and Chlamydomonas sp. were recorded in February 2013, when the total phosphorus concentrations were high and the dissolved oxygen concentrations were higher. Dinoflagellates, cyanobacteria and diatom Thallassiosira sp. were widely distributed in the dry period and highly correlated with salinity, water transparency and nutrients. Hence, the distribution of phytoplankton community is more defined seasonally, rather than spatially. AbstrActDescriptors: Algal bloom, Microalgae, Nutrients.O estuário do rio Bacanga apresenta um comportamento hidrodinâmico com fluxo de marés limitado por uma barragem. Ele é considerado como um ambiente hipereutrófico que recebe diariamente altas cargas de esgoto doméstico sem tratamento. Este trabalho teve como objetivo avaliar a variação espaço-sazonal da comunidade fitoplanctônica e suas relações com parâmetros ambientais. Amostragens bimestrais foram realizadas em seis pontos fixos entre 2012 e 2013, obtendo valores dos parâmetros físico-químicos e biológicos (clorofila a, composição e abundância do fitoplâncton) para realização das análises estatísticas. Os resultados indicam que a comunidade fitoplanctônica é representada por diatomáceas, sendo Skeletonema costatum a espécie dominante responsável por pulsos de florações em abril e junho de 2012. O predomínio dessa espécie está relacionado aos elevados teores de silicato, pH e turbidez da água. Outros eventos de florações como da Euglena gracilis e Chlamydomonas sp. foram registrados em fevereiro de 2013, quando os teores de fósforo total estiveram elevados e as taxas de oxigênio dissolvido foram superiores. Os dinoflagelados, cianobactérias e a diatomácea Thallassiosira sp. apresentaram ampla distribuição no período de estiagem e estão altamente correlacionados com a salinidade, transparência da água e nutrientes. Desta forma, a distribuição da comunidade fitoplanctônica é ...

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This study evaluated metal contamination in surface sediments and macroalgae of mangroves and port complexes on the Brazilian equatorial margin. Samples were collected between August 2020 and February 2021 at seven points in a mangrove swamp under the influence of port activity and at two points without port activity. Metal concentrations in the macroalgae and sediments were determined using inductively coupled plasma optical emission spectrometry. All macroalgal species bioaccumulated metals, as demonstrated by their bioaccumulation factors. The geochemical contamination indices indicated that the estuarine complex was influenced by port activity as moderately contaminated by Pb, Cr, Mn, and Fe, and considerably contaminated by Zn and Cu. The enrichment factor confirmed significant mineral enrichment of Zn and Cu in this environment. The concentrations of the metals in the sediment followed the order Fe > Mn > Cr > Zn > Cu > Pb at most collection points. Cladophoropsis membranacea recorded the highest bioaccumulation values for Pb (0.44), Rhizoclonium africanum for Zn (1.08), Cr (0.55), and Fe (0.30), and Bostrychia radicans for Mn (2.22). The bioaccumulation pattern of metals in the most abundant macroalgal species followed the order Bostrychia radicans (Mn > Zn > Cu > Cr > Pb > Fe) and Rhizoclonium africanum (Zn > Mn > Cr > Cu > Pb > Fe).