Environmental impact of organic and inorganic contaminants on aquatic species population structure and water quality in the reservoirs

Aquatic environmental quality plays an essential role in the growth, survival, and abundance of flora and fauna species in the ecosystems. Change in the physiochemical properties and biological quality of the ecosystem has a deleterious effect on the organisms in their habitat. Due to increasing levels of anthropogenic activities that range from agriculture, mining, fishing, and aquaculture, toxicity burdens have been imposed on the environment, forcing organisms to migrate or face extinction. Waste generated from agriculture through organic and inorganic means and pesticides washed from farmland periphery to the boundaries of reservoirs into the aquatic habitat have compromised the quality of water acceptable for organisms’ survival. Adding to the load of waste draining from outside the water is the direct deposition of organic feed waste, excreta of the cultured fish, and washed mine waste, which exacerbate the water quality by increasing the nutrients and heavy metals level, causing eutrophication and lethal toxicity of the water. These have affected the biodiversity of the freshwater ecosystem in Ghana, leading to declining numbers of macroinvertebrates. Recently, pesticide levels in water have been found to be low, such as organophosphate/synthetic pyrethroid and organochlorines, which were <0.01 µg/L and <0.005 µg/L, respectively. While in the sediment, there were high levels of zinc, with 7.5 ± 0.86 mg/L, and lead, with 0.4 ± 0.03 mg/L, reported. As a result, a narrative review was conducted on peer-reviewed studies and systematically analyzed using databases like Google Scholar, Web of Science, PubMed, and EBSCO. The results revealed an increasing concentration of ammonia, nitrates, nitrites, organophosphates, and organochlorines. Again, the result found that biodiversity, such as fisheries and other macroinvertebrates, was declining in the reservoirs. The study observes a lack of coordinated policies and commitment to regulate the use of these contaminants near the reservoirs. Hence, the study recommends proper management practices, regulation, and enforcement of laws on how these contaminants should be utilized. Designing policies and educating farmers on the need for collaborative management of the reservoir would help maintain its productivity and contribute to sustainability in practice around the reservoirs.