Ecological Assessment of Some Coastal Lagoons and Estuaries in Ghana: Abiotic and Biotic Approaches

Abstract

This study was aimed at assessing the ecological status of six coastal water bodies using abiotic parameters and benthic macroinvertebrates as indicators. Data were collected from June 2016 to August 2017. Physico-chemical parameters were measured in situ while nutrients, heavy metals analyses, sediment organic matter and particle sizes as well as species identification were done in the laboratory. Macroinvertebrates were categorised into five functional groups namely body form, feeding habit, mobility, sexuality and sociability. A total of 45 species were recorded in the six water bodies. The abiotic parameters showed Sakumo II and Fosu lagoons are polluted systems with high conductivity, TDS, nitrate, phosphate and heavy metals concentrations. This was supported by the Bray-Curtis analyses using both taxonomic and functional traits approaches which segregated the two lagoons from the other four water bodies. Pollution tolerant species namely Chironomus sp. and Limnodrilus hoffmeisteri dominated Sakumo II while Melanoides tuberculata and Chironomus sp. were dominant in Fosu. The remaining four water bodies namely Kakum Estuary, Pra Estuary, Benya Lagoon and Muni Lagoon had higher taxonomic and functional richness and diversities than Sakumo II and Fosu. Important abiotic factors that significantly influenced the abundance of macroinvertebrates taxonomic and functional groups were conductivity, salinity, phosphate, nitrate, organic matter, arsenic, copper, chromium, iron, mercury, lead and zinc. The taxonomic and functional traits approaches used in assessing the ecological status of the water bodies in this study produced similar outcomes. In view of the advantages associated with the latter, under situations of limited resources and time, its use should be the preferred option.