Quantal response of Lumbricus terrestis from two oil spillage - prone sites to toxicity of Bonny Light crude oil.

Abstract

Test fauna, Lumbricus terrestis, were obtained from two oil spillage-prone sites in Rivers State, Nigeria and were treated with varying concentrations of Bonny Light crude oil with known physico-chemical properties to determine the "all or none" response of the Lumbricus terrestis to lethal doses of the test compound.

Data based on quantal response (mortality) were subjected to probit analysis using the Standard Probability Scale of three-cycle logarithm (AP-0573-GT). Toxicity Index, LC50 (median lethal concentration) of 74.14ml/L and 17.82ml/L of Bonny Light were obtained after 48 and 96 hours respectively for animals from Ogbodo-Isiokpo while 70.79ml/L and 16.98ml/L of Bonny Light were obtained after 48 and 96 hours respectively for animals from Eneka. These results imply that such concentrations of Bonny Light crude oil would be lethal to 50% of the population density of Lumbricus terrestis within the fixed periods of 48 and 96 hours respectively. One of its major highlights is the decrease in the values of LC50 with time of exposure (24 hours - 96 hours). Expectedly, higher exposure periods to the crude oil might have induced more toxicity. LC50 after 24 hours was not possibly determined because no mortality was recorded for animals exposed to the test compound within the fixed period of 24 hours.


Key words: crude oil, test fauna, toxicity index, quantal response, oil spillage prone sites.

[Global Jnl Environ Sci Vol.1(1) 2002: 59-64]