Abstract
Edible periwinkle, Tympanotonus fuscata, was collected from the Cross River estuary, allowed to acclimate to laboratory conditions for a week and then exposed to Nigerian light crude oil at different concentrations of 50ml, 100ml, and 150ml per litre of water for a period of 96 hours. Mud (80g) was added to all the 4-litre aquaria used for the experiment. The oil was thoroughly mixed with the estuarine water by stirring vigorously. During the 4-days experimental period, most of the specimens suffered suffocation and became moribund and mortality recorded. Within the first 24 hours mortality was absent in the 50ml and 100ml concentrations, although most specimens moved out of the medium by creeping up the aquaria. Specimens in the control seemed lively and unaffected by oiling throughout the duration of the experiment. Mortalities were as high as 117 out of 180 individuals during the entire experimental period, with higher concentrations recording higher mortalities. There was steady increase in mortality from 4 individuals in the first 24 hours to 12 individuals after 72 hours in the 150ml/l concentration. The LC50 values were obtained by graphical interpolation. It is concluded that the soluble fraction of the Nigerian light crude oil could be detrimental to shellfish even at a concentration as low as 1000ml/l of the estuarine water.KEYWORDS: Crude Oil, Water Soluble Fraction, Tympanotonus fuscata, Cross River estuary, Nigeria.
Highlights
Exploration, exploitation, drilling transportation, processing and storage of crude oil have greatly affected the marine environment (Richard et al, 1978; Doerter, 1992; Ewa-oboho and Abby Kalio, 1994)
Enin (1997) reports that offshore petroleum production facilities located adjacent to the mouth of the Cross River estuary introduce small-scale oil spills and leakages into the estuary by wave and tides
Table 3b: Percentage Transformed number of total mortality of periwinkle exposed to Water Soluble Fraction (WSF). These experiments showed that the Water Soluble Fractions (WSF) of the Nigeria light crude oil could be detrimental to Tympanotomus fuscata even at a concentration as low as 100ml per litre of estuarine water
Summary
Exploration, exploitation, drilling transportation, processing and storage of crude oil have greatly affected the marine environment (Richard et al, 1978; Doerter, 1992; Ewa-oboho and Abby Kalio, 1994). The majority of oil pollution occurs in the estuaries and near shore waters (Richard et al, 1978; Brown et al, 1990). Petroleum hydrocarbons are the major contaminants of the estuarine and coastal environments (Lee et al, 1980; Widdows et al., 1982). In Nigerian waters, cases of oil spillage have been recorded between 1958 to date releasing about 2.4 million barrels of crude oil into coastal aquatic environment. Of importance are the Exxon Mobil spills, Idoho disaster, 1998, Ogoni oil spills disasters, 1958-2005 (Udo, 2007)
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