Search

The present study investigated the levels of Manganese (Mn), Cadmium (Cd), Copper (Cu), Zinc (Zn), Lead (Pb) and Iron (Fe) in the tissues of a benthic fish (Clarias gariepinus) and a pelagic fish (Oreochromis niloticus), which are highly consumed in Ghana. The fish were collected from the Weija reservoir, which is an important source of fishery and potable water in Accra, Ghana. The results indicate heavy metal accumulation in all the tissues (gills, liver and muscles) analyzed. The bioaccumulation of all the metals was lowest in the muscles compared to the liver and gills in both species. The bioaccumulation of the metals was generally higher in the tissues of the catfish, except for Fe and Zn. Fe was higher in the gills and liver of the tilapia, and Zn was higher in the liver of the tilapia. The analysis of relationships between metal levels in the different tissues and the size of the fish showed a few significant correlations. The results also showed that all metals showed no potential health risk to consumers, as THQs and TTHQs in tilapia and catfish were less than one, and the metal levels in both species were all below the FAO/WHO maximum permissible limits., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Urban riverine systems serve as conduits for the transport of plastic waste from the terrestrial dumpsites to marine repositories. This study presented data on the occurrence of microplastics in water, sediment, Bagrid Catfish (Chrysichthys nigrodigitatus) and Black-chinned Tilapia (Sarotherodon melanotheron) from the Densu River, an urban riverine system in Ghana. Microplastics were extracted from the samples collected from both the lentic and lotic sections of the river. The results indicated widespread pollution of the Densu River with microplastics in all the compartments studied. The average numbers of microplastic particles deposited in the Dam (2.0 ± 0.58) and Delta (2.50 ± 0.48) sections of the river were not affected by the differences in their hydrology. However, the stagnant water system of the Dam promoted the floating of larger-sized microplastics while the flowing waters of the Delta did not show any selectivity in the deposition of microplastics between sediment and the water column. The number of microplastics ingestions by the Bagrid Catfish (2.88 ± 2.11) was similar to the Black-chinned Tilapia (2.38 ± 1.66) but both species ingested lower numbers of microplastics than reported for marine fish species in coastal Ghana., Competing Interests: The authors have declared that no competing interests exist.

The use of optical microscope remains the most commonly used technique for microplastic identification and quantification despite major limitations with misidentifications and biases. We evaluated the use of the 1% Rose Bengal stain in improving the identification of microplastics after a standard microplastic isolation process. The stain discriminated organic materials from potential microplastics with significant differences between numbers observed before (6.65 ± 5.73) and after staining (2.91 ± 3.43). Numbers of potential microplastics observed under the conventional method (without staining) in sediment, feacal matter of shorebirds and the lagoon water were respectively 3.55 g -1 , 0.8 g -1 and 0.13 ml -1 but reduced to 1.85 g -1 of sediment, 0.35 g -1 of feacal material and 0.09 ml -1 of water after staining. Colour composition of potential microplastics under the conventional method was brown (31.0%), black (26.5%), white (20.2%), translucent (16.7%) and red (5.6%). After staining, brown (49,2%), black (30.5%) white (2.3%) and translucent (18.0%) were retained but distinction could not be made between stained organic items and red-coloured microplastics. It was clear that the stain has the potential in improving microplastic identification but requires further investigations.

Fish and shellfish are regularly consumed and sold in Ghana, yet studies on arsenic pollution in Ghana are limited largely to ground water. This study evaluated arsenic concentrations in seven species of shellfish and 10 species of fish inhabiting the mouth of Ankobra, Densu and Volta basins in Ghana and assessed the public health implications. Arsenic levels varied from 0.2 to 2.2 mg L -1 in the three rivers and were higher than WHO recommended values of 10 μg L -1 for drinking water. Except for Periophthalmus sp. and Tympanotonus fuscatus from the Ankobra in which arsenic was not detected, concentrations in the organisms ranged from 0.2 to 2.8 mg kg -1 . The maximum quantities of the organisms considered safe for consumption ranged from 375 to 5250 g per week. Caution however needs to be exercised as PTWI for arsenic needs revision, and some heavy metals such as mercury are more toxic than arsenic.

Crustaceans, mollusks, and fish are wetland resources that constitute an important source of protein and foreign exchange for the Ghanaian population, and many species of these are sold in the open market and restaurants, yet studies on their heavy metal contents are generally scarce. This paper evaluates the levels of mercury in five species of crustaceans, two species of mollusks, and ten species of fish inhabiting three river basins with different catchment activities in Ghana. These include the Ankobra Basin, characterized with mining and agriculture, Densu Basin, associated with urban waste discharges and agriculture, and Lower Volta River Basin, associated with agricultural activities. Mercury concentration was highest in Ankobra (2.5 ± 2.59 μg g -1 ) followed by Densu (1.75 ± 1.35 μg g -1 ) and Volta (0.74 ± 1.46 μg g -1 ). The mercury load of the organisms range from <0.1 to 4 μg g -1 with the highest load in Cynoglossus senegalensis at Ankobra. Except for Panaeus notialis from Densu and Ankobra, and three other species from Ankobra (Tympanotonus fuscatus, Cardisoma armatum, Callinectes amnicola) in which mercury was not detected, mercury loads of all the organisms were above the permissible limit of 0.5 mg kg -1 established by Commission Regulation-EC (2006) for fishery products and muscle meat of fish. Weekly quantities of crustaceans and mollusks considered safe for consumption by adults ranged from 88 and 1000 g while that of the fishes were between 70 and 700 g (on a dry weight basis) depending on the species. It was clear that some caution needs to be exercised in the consumption of Ghana's fresh and brackish water fisheries.

Sakumo II is an urban wetland and a receptacle for domestic and industrial wastes from two cities in Ghana. It however supports viable populations of fish and crabs, is cultivated for food crops and grazed by farm animals. Components of the wetland can therefore accumulate pollutants, but the public health and phytoremediation implications of this are yet to be evaluated. We analysed Cd, As, Hg, Cu and Pb in the lagoon water, sediment, green algae, eight species of aquatic macrophytes, seven species of arthropods and one species of fish. The concentrations of Pb were generally below detection limit whilst Cu was detected only in the lagoon water and Pheropsophus vertialis. Cadmium ranged from 21 ± 4 ppb in algae to 69 ± 12 ppb in Typha domingensis and was generally higher than As and Hg. The highest concentration of As was 11.7 ± 2.1 ppb in Pistia stratiotes whilst Hg was highest in lagoon water (4 ± 2 ppb). The Cd concentrations generally, and Hg concentrations in macrophytes, were higher than US EPA guidelines indicating the wetland's resources were unsafe for regular consumption. Among the emergent aquatic macrophytes, T. domingensis, Ludwigia sp. and Paspalum vaginatum, respectively, had the highest accumulation capacity for Cd, As and Hg, but the floating aquatic plant P. stratiotes appeared to be a better accumulator of Cd and As.