Repopulation of the polychaete fauna of an intertidal habitat following natural defaunation: Species equilibrium.

During summer, 1971, a massive outbreak of red tide resulted in defaunation of a previously characterized sandy, intertidal habitat in upper Old Tampa Bay, Tampa, Florida. Repopulation of the polychaete fauna was studied from August, 1971, to July, 1973. A transect composed of 4 stations running from just below mean high water to just below mean low water was quantitatively sampled each month for species composition, densities of individual populations, biomass, and distribution of age classes.Analysis of the rates of immigration and extinction, and the resulting colonization curve showed that repopulation conformed to the species equilibrium model of MacArthur and Wilson. Immigration was rapid with an equilibrium number of species becoming established in the 11th month. Although species composition was fairly constant, the distribution of individuals among species changed greatly.In contrast to the ideas of Thorson, adult dispersal was shown to be a significant factor in the establishment of benthic populations with larval settlement being more significant in maintenance of the populations.The community is viewed as a system in which species composition is determined primarily by the physical attributes of the area, and the density dominance of any species is dampened by the vagaries of adult dispersal and larval settlement. Such a system could be used to explain the relatively large number of species which belong to the same trophic type and yet occupy the same habitat.