Some effects of elevated levels of chromium (III) in sediments to the mullet Chelon labrosus (R.)

An investigation into the possible toxic effects of elevated levels of chromium (III) in estuarine sediments as a result of leather tanning operations was conducted in parallel to a control study. The gray mullet Chelon labrosus (R.), which feeds directly on sediments, was monitored in a field study and in an aquarium experiment. Growth, mortality, gross tissue damage, and liver bioaccumulation were assessed. Growth was found not to be adversely affected by the elevated chromium levels in either field or aquarium studies and no macroscopic physiological damage was detected. In the aquarium experiment of 2-month duration, there were no mortalities, although significant bioaccumulation was measured in the livers of exposed mullet (P < 0.01). In contrast, the concentrations of chromium in the livers of mullet sampled from the contaminated site were not significantly elevated compared to those of controls. It is suggested that the levels of chromium in the estuary are not overtly toxic to mullet and, although short-term accumulation occurs, long-term exposure appears to lead to a stabilization in liver chromium levels.