The toxic effect of copper on algae and rotifers from a Soda Lake (Lake Nakuru, East Africa)

The effect of Cu(II) ions on the photosynthetic oxygen production of the phytoplankton, the growth rate of the blue-green algae Spirulina platensis and the population of rotifers (Brachionus sp.) in water from the soda lake Nakuru in Kenya was investigated experimentally. The photosynthetic production was reduced to 80% of the control by the addition of 0.1 mg Cu l⁻¹ and 50% by addition of 0.15–0.20 mg Cu l⁻¹. The growth rate of Spirulina platensis was more affected by copper than the photosynthesis of phytoplankton. Addition of 0.05 mg Cu l⁻¹ reduced the growth rate to about 40% of the control. The rotifiers were less sensitive to copper than the algae, but after 8 days exposure to 0.5 mg Cu l⁻¹ or more the population was severely affected.