RESOURCE COMPETITION BETWEEN MACROBENTHIC EPIFAUNA AND INFAUNA IN A KENYAN AVICENNIA-MARINA MANGROVE FOREST

A cage exclusion experiment was used to examine the interaction betwee n the epibenthos (permanent and visiting) and the macroinfauna of a hi gh intertidal Kenyan Avicennia marina mangrove sediment. Densities of Oligochaeta (families Tubificidae and Enchytraeidae), Amphipoda, Insec ta larvae, Polychaeta and macro-Nematoda, and a broad range of environ mental factors were followed over 5 mo of caging. A significant increa se of amphipod and insect larvae densities in the cages indicated a po sitive exclusion effect, while no such effect was observed for oligoch aetes (Tubificidae in particular), polychaetes or macronematodes. Reso urce competitive interactions were a plausible explanation for the sta tus of the amphipod community. This was supported by the parallel posi tive exclusion effect detected for microalgal densities. It is therefo re hypothesized that competition for microalgae and deposited food sou rces is the determining structuring force exerted by the epibenthos on the macrobenthic infauna. However, the presence of epibenthic predati on cannot be excluded.