The Effects of Caging on the Colonization of Fouling Organisms in the Upper Bonny Estuary

Abstract

The effects of caging on the colonization and development of the fouling community in the upper Bonny estuary was studied. The experimental design was such that sets of wooden panels (20x20 cm) were screened with cages constructed with plastic netting while another set was left uncaged. Both sets of panels were submerged below low tide level and sampled fortnightly for seventy-four days. The species settling on the panels (as well as on the mesh of the cage) were identified and examined for percentage cover. Data obtained were subjected to Analyis of Variance or t-tests after arc-sine transformation. Faunal abundance was found to be significantly higher on the mesh of the cage than on the panels (p<0.001). Differences between the caged and uncaged panels were influenced by time as total cover was found to decline with time on the caged panels. Pennaria distichia, Styela sp. and Sabella sp. achieved significantly higher cover on the mesh of the cage than the panels (p<0.001). Some species that settled on the panels (Balanus sp., Membranipora membranacea, Serpula sp, Halichondria sp, Crassostrea gasar) were not found on the mesh of the cage, and both Balanus and M. membranacea showed significantly higher abundance on uncaged panels (p<0.05). Current speed and sedimentation may have accounted for much of the difference in settlement between cagaed and uncaged panels.


(Journal of Applied Sciences & Environmental Management: 2002 6(1): 29-33)