Assessment of the ecological health status of river pra estuary (ghana) and adjoining wetland using physico-chemical conditions and macroinvertebrate bioindicators

Abstract

The Pra River Estuary, which is the second largest estuary in Ghana, has been under severe threat of siltation from illegal alluvial gold mining activities over a decade. To advocate the need for its conservation, the study assessed the ecological health status of the estuary and its connecting wetland using inhabitant benthic macroinvertebrates and prevailing physicochemical conditions as indicators. Physicochemical factors and macrozoobenthic fauna were sampled February 2012 to December 2013, and the macrozoobenthos were analysed for composition, richness, diversity and density. Results indicated low densities (<300 individuals/m2 ) of pollution tolerant benthic macroinvertebrates such as Capitella spp., Nereis spp., Tubifex spp. and Chironomus spp. in the estuary and wetland, suggesting a possibly low organic pollution. However, high water turbidities close to 1000 NTU remains an environmental stressor of serious concern in the estuary with possible multiplicity of repercussions on the system and its biota. A broader rehabilitation program that incorporates efforts to combat upstream illegal mining activities is therefore crucially needed to decrease turbidity levels and facilitate restoration of the estuarine ecosystem.