Annual Variation of Environmental Variables, Phytoplankton Species Composition and Photosynthetic Parameters in a Coastal Lagoon |
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Authors: | Macedo M F; Duarte P; Mendes P; Ferreira J G |
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Institution: | 1 Department Of Environmental Sciences And Engineering, Faculty Of Sciences And Technology, New University Of Lisbon, P-2825 Monte De Caparica, Portugal And
2 Centre For Modelling And Analysis Of Environmental Systems, Fernando Pessoa University, Praça 9 De Abril 349, P-4200 Porto, Portugal |
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Abstract: | Physicalchemical variables, phytoplankton biomass, speciescomposition and photosynthesisirradiance (P-I) parameterswere analysed during 1 year in the Santo André Lagoon,SouthwestPortugal a land-locked coastal ecosystem withtemporary connections with the sea. When the lagoon stayed closedthe observed phytoplankton blooms were mainly caused by Prorocentrumminimum, a potentially toxic dinoflagellate. It was dominantduring most of the year but the seawater inflow to the lagoontriggered a decrease in phytoplankton biomass and an abruptshift in species composition. The maximum photosynthetic rate(Pmax) ranged from 2.0 to 22.5 mg C (mg chlorophyll a)1h1 and the light saturation index (Ik), ranged from 5.2to 335.0 µE m2 s1, with winter minima andsummer maxima. Pmax and Ik were both positively correlated totemperature. Abundance ofP. minimum was associated with highnitrate concentrations whereas diatoms appear when ammonium,salinity and wind velocity are high. A mathematical model todescribe photosynthetic rate as a function of irradiance andtemperature P (I, t)] was applied to the samples in which P.minimum was the dominant species |
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