Spatial Changes in the Polychaete Infaunal Community at Barbers Point Ocean Outfall, Oahu, Hawaii.

It is important to determine the water quality at the ocean outfall at Barbers Point using the approach of spatial and temporal bio-monitoring of the benthic polychaete community. The objective of this study is to evaluate the ecological effect of the ocean outfall on the polychaete community. Seven sampling sites were designed and sampled during 1994-2008, and the polychaete community was determined by sorting and counting the numbers of species and individuals. Based on the direct observation of 5 indicator species and trophic categories at the seven sites, we divided the seven sites into three site groups: non-ZID (far away from outfall as control), ZID (very close to the outfall as treatment zone), and near-ZID (between non-ZID and ZID as transition zone). Results showed that Myriochele oculata and Capitella capitata were found at all the three site groups but Ophryotrocha adherens was found only at the site group ZID, which indicated that the ZID has organic enrichment according to the theory of successive indicator species at different level of organic enrichment developed by Lee, Bailey-Brock and McGurr (2006). This evaluation was confirmed by the Pearson-Rosenberg’s model (Pearson and Rosenberg, 1978) with observations of decreased number of individuals of polychaetes but close number of species and similar indices of Shannon-Wiener diversity and Pielou’s evenness at ZID compared with non-ZID. The results of nMDS and ANOSIM also showed difference between the polychaete community at ZID and non-ZID groups. Overall, there was little evidence of any adverse effects on species diversity/richness and abundance at the Barbers Point Ocean Outfall in the 15 years of monitoring.