Effect of Lowered pH on Community Composition, Growth and Cell Morphology of Freshwater Phytoplankton
Keywords: Phytoplankton, Growth rate, Biomass, Cell size, pH effects.
AbstractThis experiment studied the probable effects of lowered pH (6.5 to 5.0) on four freshwater phytoplankton species Chlorella vulgaris Beyerinck, Scenedesmus quadricauda (Turpin) Brebbison, Euglena granulata (Klebs) Schmitz and Gomphonema subtile Ehrenberg. The initial community composition was 2:2:1:1 for the four taxa respectively, which changed to 1.7:1.6:1:1 in pH 6.0, 1.6:2:1.6:1 in pH 5.5 and 1.2:2:1.8:1 in pH 5.0. The two chlorophytes showed almost gradual decreasing in growth rates and cell densities with the decreases in pH values, while diatom E. granulata showed more tolerance in a wide range of pH (6.5 to 5.5). Conspicuous changes in total biomass first observed in pH 6.0 and it reached the drastic level in pH 5.0. Moreover, significant changes in cell size of S. qaudricuada and E. granulata were found in pH 5.0 only. This lowered pH range has no effects on cell shape of the studied phytoplankton species.
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