Intertidal community responses following the decommissioning of a sewer outfall: Owhiro Bay, Wellington, December 1994 - March 1996

Abstract

The intertidal community at the Owhiro Bay Sewage outfall was observed from December 1994 to March 1996 following the decommissioning of the outfall. The community exhibited characteristics typical of sewage affected communities, namely few species, dominated by opportunistic, quick growing, pollution-tolerant algal and invertebrate species. Following the decommissioning of the outfall, the Owhiro Bay Sewer community exhibited a rapid increase in the number of species present and a change in the species composition. By the conclusion of the study the community structure at the outfall showed indications of returning to a more typical state when compared to 'unpolluted' sites along the Wellington south coast. The initial differences in community composition and the subsequent changes in community composition with respect to biomass were examined using Multivariate Analysis of Variance, Canonical Discriminant Analysis, and Analysis of Similarities. These tests determined that the Owhiro Bay Sewer site was significantly different to the three control sites, while they also indicated that with increasing time after decommissioning the sewer site exhibited trends of increasing similarity to the control sites. A gradient of increasing community complexity was also detetected.