COLLEGE OF AGRICULTURAL & NATURAL SCIENCES

Concentrations of heavy metals in two Ghanaian Lagoons

2011-01-01T00:00:00Z

Concentrations of heavy metals in two Ghanaian Lagoons Obodai, E.A.; Boamponsem, L.K; Adokoh, C.K; Essumang, D.K; Aheto, D.W; Debrah, J.S The study was conducated in Benya and Nakwa lagoons in the Central Region of Ghana, to assess the level of heavy metal pollution of the water and its sediment, as well as in two species of fish: the black chin tilapia (Sarotherodon melanotheron) and oyster (Crassostrea tulipa) both of which constitute one of the major sources of protein for the local people of Elmina and Nakwa. It was also to find out the effect of cooking and depuration (of oysters) on the heavy metal content of the biota. The method involves collection of samples of the species with cast net, scaled and gutted. But the oyster samples were hand–picked. Each sample was divided into two, weighing 500 g. each. One portion was boiled and the other part was dried to a constant weight. The oyster sample was similarly treated. The oyster sample was divided into two, one depurated and the other half not depurated. Water and sediment samples from the lagoons were also collected for analysis at WRI of CSIR.. The results indicated that cooking significantly reduced the concentration of Pb in Crassostrea tulipa from Nakwa but increased concentration of Cd, Pb. As and Hg in S. melanotheron, significantly. Depuration significantly reduced As and Cd concentration in C. tulipa from Benya, but raised the concentration of Pb and Hg in C. tulipa from Benya. 11p:, ill.

Composition, diversity and food habits of the fish community of a Coastal wetland in Ghana

2011-01-01T00:00:00Z

Composition, diversity and food habits of the fish community of a Coastal wetland in Ghana Okyere, Isaac; Blay, John; Aggrey-Fynn, Joseph; Aheto, Denis Worlanyo This study aims at stimulating the scientific community towards a better understanding of fish community ecology in relation to physico-chemical determinants in unmanaged coastal wetlands relevant for informed decision-making on ecosystem functioning and management in the tropical context. We investigated the diversity, size distribution and food habits of the fish community and the abiotic environmental conditions of the Kakum Estuary wetland in Ghana (5o6'N; 1 O 18 'W) from July 2009 to February 2010. Eighteen species belonging to 18 genera and 12 families of marine, brackishwater and freshwater fishes were sampled. The poecilid Aplocheilichthys spilauchen (43.31%), the cichlid Sarotherodon melanotheron (18.12%) and the freshwater shrimp Macrobrachium macrobrachion (12.37%) were dominant. Fish communities in pools in the wetland were quite close in diversity (H' ranged from 2.2 to 2.7) and highly similar (Cs > 0.6) possibly as a result of the prevailing similar environmental conditions. Smaller individuals of the cichlids Tilapia zillii, Hemichromis fasciatus and S. melanotheron measuring 2.0-3.9 cm TL, and marine species such as Elops lacerta and Liza falcipinnis measuring 6.0-7.9 cm TL constituted between 60% and 80% of the populations, suggesting the wetland as nursery and feeding grounds for the fishes. Examination of stomach contents showed that the communities included detritivorous, planktivorous, insectivorous, omnivorous and piscivorous species. It is strongly recommended to restrict fishing in the wetland during the wet season to avoid exploitation of juvenile fishes which use the wetland as nursery and feeding grounds during that period 17p:, ill.

Comparative study of tilapiine populations from two contrasting habitats in Ghana

2011-01-01T00:00:00Z

Comparative study of tilapiine populations from two contrasting habitats in Ghana Obodai, E. A; Okyere, I.; Boamponsem, L. K; Mireku, K. K; Aheto, D. W; Senu, J. K The study investigates heavy metal (Arsenic, Cadmium, Lead and Mercury) concentrations in the black chinned tilapia (Sarotherodon melanotheron) inhabiting Benya (an open lagoon) and Fosu (closed lagoon) in the Central Region of Ghana, as well as an analysis of the size –gill relations of the cichlids. The determination of heavy metal concentrations involved the use of CHRIST BETA 1 – 16 freeze drying machine to digest the fish samples which were then asprated using AAS 240fs process. The weight, standard and total lengths as well as gill length and volume of the remaining sample were determined. The results indicated that fish samples from the Fosu lagoon recorded relatively higher Cd (0.28 mg/kg) and As (0.144 mg/kg) concentrations. However, fish samples from Benya had higher concentration of Pb (0.88 mg/kg). The levels of mercury concentration in the fish from both lagoons were below detection limits (µ0.001 mg/kg). Concentrations of Cd in the fish samples from the two populations was statistically significant (p<0.000). However, the differences in the concentrations of Pb and As were not statistically significant (p>0.05). The S. melanotheron specimens from Benya lagoon were much longer than those from Fosu lagoon. There was a positive curvilinear relationship between the standard length and body weight of both populations, with the correlation coefficient being slightly higher for the Benya (r = 0.96) than the Fosu (r = 0.92). Growth was isometric in both cases (b= 2.54, t= 1.2, P> 0.05 for Benya; b= 2.51, t = 0.92, P> 0.05 for Fosu). In both populations, gill length correlated weakly with standard length in a positive linear function (r < 0.45) while gill volume showed a considerably strong linear relationship with body weight in the Benya population (r = 0.70) although this correlation was moderate for the Fosu population (r = 0.54). 11p:, ill.

Comparative study of the benthic macroinvertebrate communities of two estuaries on the Southwestern Coast of Ghana

2015-01-01T00:00:00Z

Comparative study of the benthic macroinvertebrate communities of two estuaries on the Southwestern Coast of Ghana Dzakpasu, Margaret F. A; Yankson, Kobina; Blay Jnr., John This paper on benthic macroinvertebrates of Kakum and Nyan estuaries is meant as baseline information in the wake of offshore oil drilling, mining and land use due to growing human population on the southwestern coast of Ghana. Ekman grab (0.0225 m 2 ) was used to sample benthic macroinvertebrates monthly from August 2011 to July 2012. Crustacea (58.96%) and Annelida (35.23%) dominated the 40 species encountered in the Kakum estuary while Annelida (88.15%) alone dominated the 45 species found in the Nyan estuary. The annelids Nereissp., Capitella capitata and Cossura sp. and the dipteran Chironomus sp.were the main pollution tolerant species recorded while the annelids Scoloplos sp. and Amphiglenasp. were the known pollution sensitive ones found. An unknown amphithoid (Amphithoid 'A' andaGammarussp. dominated the Kakum estuary community with mean densities ranging between 67.27 ± 30.94 ind./m 2 to 535.49 ± 275.50 ind./m 2 and 26.91 ± 10.71 ind./m 2 to 398.25 ± 143.90 ind./m 2 respectively while in the Nyan estuary, Scoloplos sp. and Cossura sp. were dominant in densities (248.91 ± 152.05 ind./m 2 to 270.44 ± 177.39 ind./m 2 and 6.73 ± 3.66 ind./m 2 to 131.85 ± 67.28 ind./m 2 Lower species diversity, richness and densities of organisms were found at the mouth of the two estuaries than stations farther from the sea. Benthic macroinvertebrate communities of the two estuaries were highly similar (Sorensen’s index, Cs = 0.706). Periodic monitoring is encouraged as a means of checking the possible impacts of human activities on these water bodies. 11p:, ill.