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

Abstract

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.