Colonization of formulated substrates of different composition by benthic macroinvertebrate community in an estuarine ecosystem: a case study of response of benthic invertebrates to substrate alteration

摘要

Colonization of formulated artificial substrate was investigated in a tropical estuarine ecosystem for six months to determine possible response of benthic macroinvertebrates to disturbance arising from substrate alteration. Five different formulated substrates which served as content for ten cages were used for this experiment. A total of 406 individuals comprising 18 macroinvertebrate species colonized the cages. In overall, cage 1 which is the control recorded the highest number of individuals and average number (8) of colonizing species at a time, while the least number (4) was observed in cage 3. Cages 2, 4, and 5 recorded average of five species each. In terms of number of individuals, cage 1 which is the control, had the highest number (153), followed by cage 2 which recorded 122 individuals. Cages 3, 4 and 5, recorded 41, 61 and 80 individuals respectively. Analysis of temporal variability in the number of species observed in the experimental cages shows that there was a progressive decrease in the number of colonizing species after the second month. Colonizing macroinvertebrate groups were not different from the known resident species in the estuarine lagoon. However, pattern of variation in the number of individuals of colonizing species were remarkably different. The assemblage recorded in this experiment was defined by the populations of two bivalve mollusc; Macoma cumana and Tellina nymphalis , two gastropod mollusc; Pachymelina aurita and Tympanotonus fuscatus and two crustacean arthropods; Clibanarius africanus and Penaeus notialis . Among the FFGs recorded, collector-filterers dominated in number of individuals and species. Nutrient concentrations of formulated substrate had strong effects on number of colonizing individuals and species.