Assessment of the environmental conditions and benthic macroinvertebrate communities in two coastal lagoons in Ghana

Abstract

This study was conducted in Domini and Amansuri Lag oons in the Western Region of Ghana in January, 2011 with the aim of assessing their physico-chemic al and ecological health conditions using ecologica l indices e.g. richness and diversity of macroinverte brate fauna along environmental gradients. Lagoon ecosystems have several physiographic attributes wh ich increase their habitat heterogeneity for divers e fauna. The data is baseline for environmental monit oring assessment since the Domini Lagoon lies at a proposed site for the establishment of a petroleum gas processing facility while the Amansuri Lagoon serves as eco-tourism site. The physico-chemical fa ctors were determined using a Water Quality Checker . Benthic sediment samples were collected with an Ekm an grab, screened in the field and examined in the laboratory. Dissolved oxygen was uniformly distribu ted in Domini (around 6.0 mg/l) than Amansuri 4.76.5 mg/l; pH range at Amansuri was 5.5 ‐ 6.0 while Domini was 7.4‐7.7; turbidity range at Amansuri 15.1‐20.0 ppm and Domini was 0 to 98.3 ppm. Insects encountered belonged to the orders Diptera and Trichoptera while the worms present included Oligoc haetes, leeches and Polychaetes, with hermit crab and Penaeus shrimps being rare. Invertebrate richne ss and diversity ranged from J’= 0.68-0.81 and H’= 0.74-1.45 respectively in Amansuri while that of Do mini were J’= 0.01-0.02 and H’= 0.01-0.03 respectively. The conclusion was that the freshwate r Amansuri Lagoon supports richer and diverse macrobenthic fauna than the brackishwater Domini La goon. Future reduction in invertebrate composition, richness and diversity would imply a c hange or deterioration in environmental conditions of the lagoon. Serious efforts should be made to step up environmental improvement measures in and around the Domini Lagoon in the light of the curren t ecological and socio-economic issues around the lagoon.