Single and Joint Toxicological Effect of Dispersit SPC 1000 and Bonny Oil on Mudskipper Fish ( PeriophthalmusPapilio  ) from the Brackish Waters of Buguma, Rivers State, Nigeria

Marine oil spillage accidents greatly impact major risks to the environment in terms of the acute and chronic adverse effects not only to the offshore, but also the coastal ecosystem. This study assessed single and joint toxicological effect of Dispersit SPC 1000 and Bonny Oil on mudskipper fish (Periophthalmus papilio) from the brackish water research station of African Regional Aquaculture Centre, Buguma, Rivers State, Nigeria. The physicochemical parameters observed throughout the study were the pH, alkalinity and salinity were 6.83 ± 0.1, 40 mg/L± 0.2 and 17,655 mg/L respectively. The temperature and Dissolved oxygen (D.O.) and specific gravity averaged 26.7 ^o C ± 0.1, 5.70 mg/L ± 0.02 and 1.008 ± 0.001, respectively. Dispersit SPC 1000 was found to be toxic to the mudskipper at various % (v/v) concentration, above 60 % (v/v) concentration no fish survived after one hour. The relation between the probit mortality and log concentration showed a strong positive correlation between the dispersant concentration and fish mortality within 3 hours, with r² = 0.813 p = 0.05;The lethal dose Lc₅₀ was 73.48%. Within 6 hours, the mortality increased as the dispersant exposure concentration was increased (r² = 0.872, p =0.05). The results of exposure of the mudskippers to the water-oil-dispersant mix (CEWAF) showed lower mortalities. Mortality was observed after 72 hours for dispersant concentration above 54 %. 63% dispersant concentrations, 20% mortalities was observed between 72 and 96 hours. Dispersit SPC 1000 alone was highly toxic, and the toxicity of CEWAF was primarily caused by the presence of dispersant. There was no joint increase in toxicity between bonny oil and the chemical dispersant, as the mixing of the dispersant by the oil resulted in diminished toxicity of CEWAF and lower mortality.