Structure of microphytoplankton community and environmental variables in a macrotidal estuarine complex, São Marcos Bay, Maranhão - Brazil

Abstract

Cavalcanti et al.: Microphytoplankton of a macrotidal estuarine complex 283 Structure of microphytoplankton community and environmental variables in a macrotidal estuarine complex, São Marcos Bay, Maranhão -BrazilSão Marcos Bay is an estuarine complex with semidiurnal tides that can reach more than 7 m during equinoctial spring tides. It is situated in the second largest Brazilian coastline and is subjected to continuous human activities holding an important port complex of Latin America. In order to contribute to the knowledge about the structure of the phytoplankton in a macrotidal systems, this study aims to evaluate the phytoplankton community and its relationship with environmental conditions in the São Marcos Bay. Five surveys in 2010 and 2011 were carried out on four sampling points during the rainy and dry seasons. Samples were taken during the flood and ebb phases at neap tides. Hydrological parameters were correlated with biological data (phytoplankton composition, abundance and biomass) using statistical analysis. The phytoplankton biomass (chlorophyll a) characterized the bay as quite productive (10.43±7.62 mg m -3 ) with the nanophytoplankton as the dominant fraction. Seasonal variation was observed in phytoplankton abundance with higher values (34,262±18,422 cells L -1 ) in the rainy season. Diatoms were the most important phytoplankton group, pointing out Nitzschia sp., Diploneis weissflogii and Synedra sp. as the dominant species. This study revealed that the composition of phytoplankton community was mainly influenced by the local dynamics, governed by macrotides, and precipitation regime that mostly contributed to the seasonal fluctuations of the environmental conditions, such as salinity, dissolved oxygen, and nutrients.

Outwelling of nutrients into the Pasur River estuary from the Sundarbans mangrove creeks

“…In comparison to neap tide, spring tide concentrations of DIN, DIP, salinity, silica, and chlorophyll-a were substantially higher. Similar trends have been identified for a few additional tropical estuaries around the coast of Brazil ( Silva and Sampaio, 1998 ; Dittmar, 1999 ; Tanaka and Choo, 2000 ; Cohen et al., 2004 ; Cavalcanti et al., 2018 ). Other methods of nitrogen and phosphate retention used by mangroves include a vast pool of dead roots and tight immobilization of accessible solutes.…”

“…Chlorophyll-a levels peaked at 6.85 μg/L at the spring tide in the tidal mangrove creeks. Chlorophyll-a levels at neap tides, however, were less than 4.89 μg/L, which is also supported by Tanaka and Choo (2000) ; Sodre et al., (2011) ; and Cavalcanti et al., (2018) . The high phytoplankton biomass in the spring tide may represent the nutrients outwelling from the mangrove area by the inundation and tidal mixing of the spring tide.…”

DIATOMÁCEAS CÊNTRICAS (Coscinodiscophyceae e Mediophyceae) PLANCTÔNICAS EM DOIS ESTUÁRIOS TROPICAIS BRASILEIROS: LEVANTAMENTO FLORÍSTICO E NOVOS REGISTROS

“…Novo registro para o estado de Pernambuco. Espécie encontrada no Maranhão (Cavalcanti et al, 2018), Sergipe e São Paulo (Garcia & Odebrecht, 2009). Características e dimensões de acordo com Herzig e Fryxell (1986).…”

Dissolved nutrient fluxes in macrotidal estuary in the Amazonian region, Brazil

“…SMB has a central channel with depths up to 90 m and a width of ∼55 km, which narrows to 1.5 km at the intersection of Pindaré and Mearim rivers. It has the biggest mangrove area of the country with 5,414.31 km2 (Cavalcanti et al, 2018;Rodrigues et al, 2016). It is characterized by semi-diurnal tidal, with tidal current speeds up to 2.5 m s-1 that influences areas up to 150 km from the coast (Chagas, 2013;De Morais, 1977).…”