The Abereke River, situated in Araromi, Ondo State, Nigeria, plays a vital role in supporting a diverse range of species and providing important seafood resources, especially prawns (Melicertus plebejus), for the local population. Unfortunately, increasing human activities, particularly oil exploration and urbanization, have raised concerns about the ecological health and safety of these aquatic resources.
This study aimed to assess the microbiological quality, proximate composition, and concentrations of selected heavy metals; lead (Pb), zinc (Zn), manganese (Mn), copper (Cu), mercury (Hg), and cadmium (Cd), in samples of water, sediment, and prawns collected from the Abereke River. Microbial analyses were conducted using the pour plate method to determine total viable counts (TVC) and utilized membrane filtration for Enterobacteriaceae, following standard protocols. The proximate composition of prawn tissues was analyzed using standard procedures. Heavy metal concentrations were measured using Atomic Absorption Spectrophotometry (AAS).
The results indicated that the TVC and Enterobacteriaceae counts in both prawn and water samples fell within acceptable ranges, reflecting satisfactory microbiological quality. The proximate analysis of prawns showed a moisture content of 10.51 ± 0.01%, crude protein at 73.83 ± 0.07%, ether extract at 4.23 ± 0.01%, ash at 10.12 ± 0.01%, and carbohydrate at 1.22 ± 0.01%, indicating a high nutritional value. In the water samples, manganese was detected at 0.36 ± 0.02 mg/L, exceeding the WHO permissible limit of 0.1 mg/L, while other metals were absent. Sediment analysis revealed zinc levels at 33.60 ± 2.00 mg/kg, surpassing the permissible threshold of 0.6 mg/kg, while copper levels were within acceptable limits at 0.01 ± 0.00 mg/kg; mercury, lead, and cadmium were undetected. Prawn tissues showed zinc and manganese levels at 76.55 ± 4.00 mg/kg and 28.70 ± 0.12 mg/kg, respectively, both exceeding the FAO/WHO maximum allowable limits of 30 mg/kg for zinc and 1 mg/kg for manganese, while copper was acceptable at 0.40 ± 0.01 mg/kg; mercury, lead, and cadmium were not found.
These findings portray the effect of human activities on the Abereke River ecosystem, with elevated heavy metal levels posing potential health risks to consumers and threatening aquatic biodiversity. While the microbiological quality seems satisfactory, the presence of heavy metals reveals the necessity for continuous monitoring and stringent environmental regulations to safeguard the ecosystem. The results also suggest the potential for sustainable aquaculture development in the area, provided that environmental pollutants are effectively managed to ensure the safety and quality of aquatic products.
Keywords: Abereke River, Aquaculture Potential, Aquatic Biodiversity,