Abstract

R.E Uwadiae

The microphyto benthic assemblage in the fecal matter of a benthic gastropod Pachymelania aurita in a tropical estuarine lagoon was investigated by microscopic examination of the fecal matter. Two hundred and forty specimens comprising 120 juveniles and adults were used for this study. Comparison was made between microphyto benthos consumed by juveniles and adults. And to determine the actual source of the microphyto benthos recorded, comparison was also made between species recorded in the fecal matter of specimens direct from the wild and those exposed to sediment in the laboratory. The microphyto benthic organisms recorded consist of two major groups, blue-green algae (Anabaena, Aphanocapsa) and diatoms (Navicula, Synedra, Cyclotella, Nitzchia). Navicula and Cyclotella were the most important taxa in terms of abundance and frequency. There were no variations in the microphyto benthos consumed by the adults and juveniles. The assemblage observed in the fecal matter of specimens of P. aurita exposed to sediment in the laboratory represent a slightly different array of organisms with representation of Cyanobacteria which were absent in the fecal matter of specimens collected directly from the wild. The result of the study further buttresses the claim that benthic microalgae serve as major source of organic matter supporting benthic invertebrates.