EFFECTS OF MANGANESE, COPPER AND LEAD ON SELENASTRUM-CAPRICORNUTUM AND CHLORELLA-STIGMATOPHORA

Algal assays were conducted to observe the responses of Selenastrum capricornutum and Chlorella stigmatophora to the metals manganese, copper and lead, added singly or in combination to both artificial media and natural waters. A 50% reduction in the total algal cell volume of Selenastrum in standard algal assay medium (SAAM) occurred by the addition of either 3.1 mg manganese 1-1 85 μg copper 1-2, or 140 μg lead 1-1. For Chlorella grown in 28 ppt artificial seawater plus full SAAM nutrients, the corresponding numbers were 50mg manganese 1-1, 70 μg copper 1-1 or 700 μg lead 1-1. Of the metals tested, only lead was found in higher concentrations in urban and agricultural runoff than at least one of these levels. Theoretical considerations show that a product model is a more reasonable reference for no-interaction than an additive model for experiments in which toxic metals are added in combination. Combination experiments, in which any combination of the three metals act at the same time, indicate (1) synergism between manganese and copper, (2) antagonism between manganese and lead, and (3) antagonism between copper and lead. As to the manganese-lead interaction, it is shown that the lead-induced inhibition of cell division is offset, partially for Selenastrum and completely for Chlorella by the addition of manganese. © 1979.