Project Report PR-94-13
Benthic Faunal Sampling Adjacent to Sand Island Ocean Outfall, Oahu, Hawaii, August 1993
Walter G. Nelson, Julie H. Bailey – Brock, William J. Cooke, and E. Alison Kay
January 1994
ABSTRACT
Benthic infauna in the vicinity of the Sand Island Ocean Outfall were sampled at seven stations along the diffuser isobath in August 1993. Stations were located both within and on the boundary of the zone of initial dilution (ZID) and at distances of 1.2 to 2 km from the ZID boundary. Values for total organic carbon, total Kjeldahl nitrogen, and oxidation-reduction potential showed no indication of significant organic buildup in sediments at any station. Sediment oil and grease values were highest at ZID station B3 and reference station B6. Nonmollusk abundance was not significantly different among stations. Nonmollusk species richness was significantly higher at Station B5 than at all other stations and was significantly higher at Station B2 than at Station B3. No other differences among stations were significant. Therefore, there was no relationship between nearness to the diffuser and mean nonmollusk species richness. Most stations differed significantly from each other in mollusk abundance. Mollusk species richness was significantly greater at Station B5 as compared to Stations B1 and B2. There was no consistent pattern in the mollusk community parameters with regard to station location. Cluster analysis of nonmollusk species composition and abundance produced two groups of stations not clearly related to outfall proximity: the five westernmost stations (B1, B2, B3, B4, and Z), and the two easternmost stations (B5 and B6). There was no overall pattern of lower diversity or evenness for either nonmollusk or mollusk groups at ZID or near-ZID stations relative to the other stations. The long-term pattern of lower species richness at Station B3 as compared to the other stations was again observed. The response patterns of benthic infauna near the Sand Island Ocean Outfall showed little indication of a strong influence by the diffuser effluent. No effects on the benthic community attributable to Hurricane Iniki were observed.