Authors: Doris Ugochi Obinna, Dike, Henry Ogbuagu, Enos I. Emereibeole, Chris Chibuzor Ejiogu
Abstract: The increasing anthropogenic pollution in estuarine ecosystems poses a significant threat to aquatic life and ecosystem health. This study aims to assess the pollution levels in selected estuaries of Rivers State, Nigeria, using biomarkers in Callinectes sapidus (blue crab) as an indicator of environmental contamination. In situ measurements for some water quality variables were made at the sampling locations. 48 female crabs (weight 149.20 ± 0.02 g) harvested for the estimation of biomarker levels. Mean concentrations of Total Petroleum Hydrocarbons (TPHs), Polycyclic Aromatic Hydrocarbons (PAHs), Zn and Cr (Sig. values=0.000 each), Cd, Pb, and Fe (Sig. t-values=0.003, 0.019 & 0.009 respectively) were significantly higher at the impacted than reference locations, while that of Monocyclic Aromatic Hydrocarbons (MAHs) and Fe (Sig. t- values=0.032 & 0.014 respectively) differed seasonally at p<0.05. Though there was no significant difference in accumulations of the heavy metals and hydrocarbons in tissues of the organism, numerical accumulations of Zn (5.73±2.60 µg/g) and TPHs (1.84±1.08 µg/g) were highest in the digestive than the other tissues sampled. Mean levels of Lactate Dehydrogenase (LDH), Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), Alkaline Phosphatase (ALP) and Malondialdehyde (MDA) (sig=0.000 each) at the OSD locations, and that of total proteins (Sig. t- value=0.030) in the rainy season were all markedly higher in the organism (p<0.05). Elevated MAHs appeared to induce the production of less ALT (r=-0.584) and AST (r=-0.519), Cr induced the production of less AST (r=-0.513) (p<0.05), while MAHs induced the production of less MDA (r=-0.634) (p<0.01). Lead and PAHs recorded very high Pollution indices (240,000 & 790,000) in sediments, while Zn and TPHs recorded high toxicity quotients of 1.59 and 2.83 in the organism. Allochthonous input of pollutants from petroleum sources into the creek caused biological disruptions, including tissue bioaccumulation and other biochemical disruptions in proteins and enzyme activities of C. sapidus, and these disruptions could rightly infer pollution. Treatment of oily effluents before discharge into the creek is recommended.
