Abstract
Five concentrations of water soluble fraction (WSF) of diesel fuel (1.6 ppm, 3.2ppm, 6.4ppm, 12.3ppm and 19.2ppm) were made. To each of the concentrations of the WSF, ten fingerlings of O. niloticus with an average weight of 3g were incubated for 96hours. The 96hour LC50 was determined (8.08ppm). Histopathological examination of the fish gills following exposure to the LC50 and LC100 concentrations of the WSF showed gill elongation and lamellar hyperplasia respectively. There was reduction of dissolved oxygen content (from 7.2 to 4.5 mg/l) caused by diesel that dissolved in water. This was below acceptable levels for the sustenance of aquatic life (i.e. 6.0 – 8.0 mg/L). However, the pH reading was not adversely affected. The result tended to suggest that the death of the fingerlings might be related to the decreased dissolved oxygen content of the water due to the presence of diesel. The structural changes of the gills observed may be an adaptation by the fingerlings to oxygen stress
Highlights
Two years after the release of 600,000 litres of diesel fuel into Arthur Harbour in the Antarctic peninsula, spill related contamination was still detected in the intertidal limpet Nacella concinna (Kennicutt and Sweet, 1992), and the fish, Fundulus heteroclitus collected from the Wild Harbour marsh, where a major diesel fuel spill occurred in 1969, was found to contain up to 75ppm of petroleum hydrocarbon in its tissues several year later (Sabo & Stegeman, 1977)
The current study is aimed at investigating the acute toxicological effect of the water soluble fraction of diesel fuel on tilapia (Oreochromis niloticus) fingerlings
(d) Toxicity lasting of Water soluble fraction (WSF) diesel fuel or Oreochromis niloticus fingerlings within 96 hours fingerlings were observed with 1.6 ppm (2 deaths). 3.2 ppm (3 death). 6.6ppm (5) deaths). 128 ppm ( 7 deaths) and 19.2ppm (10 deaths – all died)
Summary
Eighty fingerlings of tilapia (Oreochromis niloticus) were obtained from the African Regional Aquaculture Centre (ARAC), Aluu – Port Harcourt Nigeria the fingerlings had an average weight of 3g. PREPARATION OF WATER SOLUBLE FRACTION (WSF) One part (IL) of fresh diesel fuel obtained from a filling station, was diluted with four parts (4L) of the water with which the fingerlings were cultured (the control water), in a 6L flask in accordance with Baden (1982). A concentration of the determined LC50 value Igbigke was made by diluting the stock concentration of the WSF, and ten fingerlings were exposed to it; the gill of a dead fingerling from this group was taken out and preserved in formalin. The pH was measured with a La Motte Analogy pH meter while the dissolved oxygen content of the water was measured with a YS1® Dissolved Oxygen meter
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