Benthic faunal sampling adjacent to the Barbers Point ocean outfall, Oahu, Hawaii, 1986-2010 (NODC Accession 9900098)

Benthic fauna in the vicinity of the Barbers Point (Honouliuli) ocean outfall were sampled from 1986-2010. To assess the environmental quality, sediment grain size and sediment chemistry were measured. To identify the fauna, mollusk species and non-mollusk species sitings were tabulated. 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. In summary, the response patterns of benthic fauna near the Barbers Point ocean outfall showed little or no indication of a strong influence by the diffuser effluent.

Seven stations previously established along the approximate diffuser isobath (61 m) were surveyed. In 1990 survey station names were changed from those used in the 1986 survey (Nelson et al. 1987). Survey stations (1986 station names are in parenthesis) and their locations are as follows:
Station HB1 (A) Approximately 3.5 km east of the zone of initial dilution (ZID) boundary to evaluate effects far-field and beyond the ZID
Station HB2 (B) On the northeast ZID boundary
Station HB3 (C) On the southeast ZID boundary
Station HB4 (D) On the southwest ZID boundary
Station HZ (Z) Within the ZID to evaluate diffuser effects
Station HB6 (E) Approximately 0.5 km southwest of the ZID boundary as a near-field reference station
Station HB7 (F) Approximately 3.5 km southwest of the ZID boundary as a far-field reference station

SAMPLING PERIODS:
September 1986
February 1990
July 1991
February 1992
June 1993
June 1994
January 1995
January 1996
January-February 1997
January 1998
April 1999
February-March 2000
January 2001
January 2002
January 2003
June 2004
February 2005
February 2006
July 2007
June 2008
March 2009
June 2010

missing years: 1987-89

METHODOLOGY:
The sampling methodology used in this study generally followed the recommendations of Swartz (1978) and US EPA guidelines (EPA 1987a, 1987b), hereafter refered to as EPA procedures.

A modified 0.16-m2 van Veen grab sampler deployed from a stern-mounted A-frame on the research vessel Noi I Kai was used to obtain bottom samples at all seven stations. Penetration of the sampler was adequate for all replicates. The minimum penetration depth for all grabs was 8 cm and the maximum was 15 cm.

Five van Veen grabs were taken at each station. A subsample 7.6 cm in diameter by 5 cm deep was taken from each grab sample for infaunal analysis and a subsample 4.8 cm in diameter by 5 cm deep for mollusk analysis. Subsampling was necessary because the epifauna and infauna in the area are known to be both small and abundant and processing of the entire sample would be impractical. Replicated grab samples at each station, rather than replicated subsamples from one grab sample, were used to provide information on intrastation variability. All six nonmollusk subcores were processed on a 0.5-mm screen.

Samples for geochemical analyses (total organic carbon (TOC), oxidation-reduction potential (ORP), sediment oil and grease (O&G), total Kjeldahl nitrogen (TKN), and grain size) were obtained from the grabs from which the biological subcores were taken. Each replicate van Veen grab contained more than enough sediment for both purposes (methods HI0020117). Three subsamples 7.6 cm in diameter by 5 cm deep (one from each of three differnt grab samples) were taken from all stations. The top 2 cm of sediment of each subsample were used for geochemical analysis. Samples for TOC and sediment O&G analysis were put in screw-cap jars, placed on ice, and taken to the laboratory for analysis. Sediment analyses of sediment grain size, ORP, TKN, and O&G followed EPA procedures. Analysis of TOC was carried out by PACE, Inc. Laboratory (Southern California).