This study was conducted in Domini and Amansuri Lagoons in the Western Region of Ghana in January, 2011 with the aim of assessing their physico-chemical and ecological health conditions using ecological indices e.g. richness and diversity of macroinvertebrate fauna along environmental gradients. Lagoon ecosystems have several physiographic attributes which increase their habitat heterogeneity for diverse fauna. The data is baseline for environmental monitoring 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 factors were determined using a Water Quality Checker. Benthic sediment samples were collected with an Ekman grab, screened in the field and examined in the laboratory. Dissolved oxygen was uniformly distributed in Domini (around 6.0 mg/l) than Amansuri 4.7- 6.5 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 Oligochaetes, leeches and Polychaetes, with hermit crab and Penaeus shrimps being rare. Invertebrate richness and diversity ranged from J’= 0.68-0.81 and H’= 0.74-1.45 respectively in Amansuri while that of Domini were J’= 0.01-0.02 and H’= 0.01-0.03 respectively. The conclusion was that the freshwater Amansuri Lagoon supports richer and diverse macrobenthic fauna than the brackishwater Domini Lagoon. Future reduction in invertebrate composition, richness and diversity would imply a change 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 current ecological and socio-economic issues around the lagoon.
