Effects of moderate sewage input on benthic polychaete populations

Abstract

The polychaete fauna of a sandy intertidal habitat receiving effluent from a sewage treatment plant was compared to that of a control site. The total number of individuals, total biomass, and average species numbers were significantly greater at the sewage-affected site. The response of individual species to nutrient enrichment varied. Some species showed significantly greater numbers of individuals at the sewage-affected site while other species' densities showed no difference. All species maintained greater biomass at the enriched site, most biomass differences were significant. Those species which did not show density differences between sites tended to have the greatest difference in average weight per individual. In general, species with either benthic development or some form of brooding behavior were best able to exploit the enriched condition by increased densities, or greater average biomass per individual. It was concluded that for moderate increases in nutrient concentrations, benthic productivity will be most enhanced in those sediments with very low concentrations of fine sized particles.