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1 December 2007 PHYTOPLANKTON PRODUCTIVITY IN A HIGHLY COLORED SHALLOW LAKE OF A SOUTH AMERICAN FLOODPLAIN
Patricia Rodríguez, Haydée Pizarro
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Abstract

We described phytoplankton productivity in a floodplain wetland of the Lower Paraná River, Argentina. Four samplings encompassing periods of high and low water levels were conducted in a highly colored shallow lake. Photosynthesis-irradiance (P-E) curves and the areal photosynthetic rate (PA) were estimated following the 14C assimilation technique. Likewise, physical and chemical variables and phytoplankton composition, density, and chlorophyll a concentration were measured. Phytoplankton assemblages shifted from cyanobacteria blooms in summer to cryptophycean dominance in winter, and co-dominance of cryptophytes and chlorophytes in autumn. Assimilation number Pmax ranged from 3–7.8 µg C (µg Chl a h)−1 and peaked in early summer (low water level) when water color was highest, suggesting that phytoplankton productivity was not depressed by the high content of colored humic acids. Photosynthetic efficiency (α) ranged from 0.021–1 µg C (µg Chl a h)−1 µmol photons−1 m2 s and reached its maximum value during winter even when the assemblage, dominated by cryptophyceans, did not achieve light saturation. In early and late summer and in autumn, optimal irradiance (Eopt) ranged from 544–1,397 µmol photons m−2 s−1. The highest PA (207 mg C m−2 h−1) was registered in late summer (high water level) when the lowest mean irradiance (Emean) was observed (341 µmol photons m−2 s−1). The lowest PA (28 mg C m−2 h−1) occurred in winter when Emean was maximum (1,432 µmol photons m−2 s−1). Our results indicate that productivity was similar to those recorded for other latitudes and appeared not limited by the humic content of the water because phytoplankton was dominated by algae well-adapted to low light conditions.

Patricia Rodríguez and Haydée Pizarro "PHYTOPLANKTON PRODUCTIVITY IN A HIGHLY COLORED SHALLOW LAKE OF A SOUTH AMERICAN FLOODPLAIN," Wetlands 27(4), 1153-1160, (1 December 2007). https://doi.org/10.1672/0277-5212(2007)27[1153:PPIAHC]2.0.CO;2
Received: 29 August 2006; Accepted: 1 June 2007; Published: 1 December 2007
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KEYWORDS
areal photosynthetic rate
Argentina
humic wetland
P-E curves
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