Spatial and temporal variability of phytoplankton and environmental factors in a temperate estuary of South America (Atlantic coast,Argentina) |
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Authors: | Cecilia A Popovich Jorge E Marcovecchio |
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Institution: | 1. Laboratorio de Ficología y Micología, Universidad Nacional del Sur (UNS), San Juan 670, 8000 Bahía Blanca, Argentina;2. Area de Oceanografía Química, Instituto Argentino de Oceanografía (IADO), CCT-CONICET-Bbca., Florida 4000, Edificio E1, Casilla de Correo 804, 8000 Bahía Blanca, Argentina;3. Universidad Tecnológica Nacional, Facultad Regional Bahía Blanca (UTN-FRBB), 11 de Abril 461, 8000 Bahía Blanca, Argentina;4. Universidad FASTA, Gascón 3145 7600 Mar del Plata, Argentina |
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Abstract: | A spatial and temporal study on data collected along the longitudinal gradient of the Principal Channel of Bahía Blanca estuary, Argentina, was carried out during 1992–1993. At nine stations, phytoplankton abundance, chlorophyll a (Chl-a) concentration, inorganic nutrient levels, Secchi disk depth, euphotic depth:mixing depth ratio (Zeu:Zm), salinity and temperature were recorded. Phytoplankton abundance, Chl-a concentration and nutrient levels decreased towards the outer zone of the estuary. The inner zone (stations 1 and 2), which was characterized by high turbidity, high nutrient concentrations and high Zeu:Zm (>0.16, critical mixing ratio]), registered the highest phytoplankton abundance and Chl-a concentrations. Temporal variability of data was also noteworthy in this zone. The highest biomass values thus corresponded to June, July, August and the beginning of spring (18 μg Chl-a L−1 and 9×106 cells L−1) concomitantly with a diatom bloom. In the middle zone (stations 3–6), a strong phytoplankton biomass decrease was observed and it coincided with both deep-mixed depths and low Zeu:Zm (<0.16). The outer zone (stations 7–9), which was characterized by low phytoplankton biomass values and low nutrient levels all along the year, was the area mostly influenced by waters from the adjacent continental shelf. In view of the above, it can be concluded that the most important primary production in the Bahía Blanca would be produced in the shallow inner zone during winter, being the spatial reach of the phytoplankton biomass principally limited to estuarine waters. Presumably, less than 5% of such biomass may reach the coastal area of the estuary. |
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Keywords: | Phytoplankton Chlorophyll a Winter diatom bloom Nutrients Euphotic depth:Mixing depth ratio Estuary Argentina |
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