What is happening to our Lagoons? The example of Butuah Lagoon in Ghana

Abstract

Lagoons are among the most important ecosystems in the world. To find out how activities around lagoons affect their physical and chemical properties, we assessed the physicochemical properties and concentrations of seven heavy metals from samples of sediments, Tilapia fish and water of Butuah Lagoon in Ghana, as an example. The lagoon was slightly alkaline with a fairly constant temperature but increased dissolved salts and inorganic materials that have resulted in higher electric conductivity than permissible for aquatic life. There was an indication of a large quantity of organic waste in the lagoon which reflected as high biological and chemical oxygen demand. We also recorded extremely high concentrations of oil and grease that negatively correlated with all physicochemical parameters measured. Lead (Pb) concentration in the three media was higher than the permissible limits while Zinc (Zn) and Cadmium (Cd) were higher in two except the water sample. Arsenic (As) concentrations were higher than the permissible limits only in the sediments. There is a significant anthropogenic impact on the lagoon, with the midstream having extremely high degree of contamination of most of the metals. The main pollutant in the sediment was Cadmium with high enrichment factor and geo-accumulation index value. Although, the concentrations of most metals in the fish were below the highest permissible level recommended, the higher levels in the water and sediment are of concern. It will be necessary to have a long-term monitoring programme for Butuah Lagoon to prevent it from further deterioration. Also, as bioaccumulation is a gradual process, having such programmes will prevent the risk of people eating and using fish and water contaminated with such deleterious metals.