Toxicity bioassays were conducted on groovy mullet, Liza dumerili, using copper and lead, in order to assess how these metals affected their blood haematology and acid-base balance. Short-term (96 hours) exposure to lead caused significantly more haematological response [PCO2] than copper, when compared to the control. When copper and lead were applied in combination there were significant increases in bicarbonate content and red blood cell count of the fish. Long-term (28 days) exposure to copper and lead resulted in significant increases in blood glucose, haemoglobin content and the acid-base status of the fish.
The results of this study highlight the stress to which estuarine fish are exposed through the uncontrolled discharge of heavy metals and the inherent dangers posed by combinations of metals in the aquatic environment. They will also help emphasise the need to control pollution in order to protect aquatic biodiversity.
Keywords: toxicity; estuarine fish; heavy metals; copper; lead; haematology; acid-base balance
(Afr J Aqua Sci: 2002 27(1): 39-46)