Thermal and biocidal (chlorine) effects on select freshwater plankton.

Impact of select levels of temperature, individually and in combination, with different initial chlorine concentrations on the growth and reproduction of phytoplankter Chlorella vulgaris and zooplankton C. reticulata, C. viridis, and Diaptomus forbesi was evaluated. During the experiment, optimum growth temperature for the alga was estimated as 26 degrees C, even though alga showed considerable growth up to 36 degrees C. However, initial chlorine at concentrations >or=0.25 mg l(-1) adversely affected growth (P < 0.05 to 0.001) at all select temperature levels (26 degrees C, 31 degrees C, 33 degrees C, 36 degrees C, 39 degrees C, 42 degrees C, and 45 degrees C). Investigations toward effects of different temperatures (26 degrees C, 31 degrees C, 33 degrees C, and 36 degrees C) on zooplankton indicated that survivability of these organisms was affected at temperatures >or=33 degrees C. However, the percent growth rates of zooplankters at 26 degrees C were significantly higher (P < 0.05) than those at 31 degrees C, 33 degrees C, and 36 degrees C. Initial chlorine levels of 0.5 and 0.25 mg l(-1) were lethal to zooplankton; however, zooplankton survival was not affected at 0.06 mg l(-1) chlorinated water at all selected temperatures.