Details:

Personal Author:
Brock, Richard E.
Corporate Authors:
University of Hawaii at Manoa. Sea Grant College Program
NOAA Program & Office:
Sea Grant ; OAR (Oceanic and Atmospheric Research)
Sea Grant ; OAR (Oceanic and Atmospheric Research) Less -
Sea Grant Program:
HAWAU (Hawaii Sea Grant)
Description:
This report provides the results of the fourteenth year of an annual quantitative monitoring of shallow marine communities inshore of the Barbers Point Ocean Outfall located in 61 m of water offshore of 'Ewa Beach, O'ahu, Hawai'i. The monitoring effort focuses on benthic and fish community structure and is designed to detect changes in these communities. Field sampling was first carried out in August 1991 when three study stations were established: Station BP-1, a control station 2.2 km inshore and east of the outfall terminus; Station BP-2, an experimental station about 1.6 km inshore of the terminus; and Station BP-3, an experimental station about 2.9 km west and inshore of the terminus. The second field effort, completed in May and September 1993, resurveyed the above stations as well as established a fourth station (BP-4) on and adjacent to the basalt armor caprock protecting the discharge pipe in 13 m of water and directly inshore of the outfall terminus. Subsequent field surveys were completed in March and April 1994, in June 1995, in May 1996, in February and April 1997, in January and March 1998, in January 1999, in May 2000, in June 2001, in May 2002, in March 2003, in February 2004, and the most recent in May 2005. The permanently marked stations are sited to capitalize on presumed gradients of impact that may be created by the discharge and movement of treated sewage effluent toward the shore and the coral reef communities. Data from the first survey suggested that marine communities offshore of 'Ewa Beach receive disturbance from a number of possible sources, with the largest perturbation probably coming from natural disturbance caused by occasional wave impact. This was most evident at the station directly inshore of the outfall. Data from Station BP-4 showed that benthic communities situated on armor rock which rises above the flat limestone substratum are not subjected to the same sand scour as those situated on the limestone; thus the coral communities on the elevated caprock are better developed on this substrate. A comparison of the data from the fourteen annual surveys indicated that no statistically significant change has occurred in the measured biological parameters at the four permanent stations that would suggest an impact from the operation of the wastewater outfall, despite the imposition of a major hurricane on these marine communities in September 1992. However, the mean number of macroinvertebra​te species seen per transect was significantly greater in 2002 (8.5 species/transec​t) than in 1991 (5.0 species/transec​t), with other years showing no significant change. In addition, coral coverage at Transect BP-4-B, which is located directly adjacent to the outfall pipe, has shown a steady and significant increase from the first survey after Hurricane Iniki (1993 mean = 0.1%) to the most recent survey (2005 mean = 12.6%). Thus the data to date support the contention that the operation of the Barbers Point deep-ocean outfall is not having a quantifiable impact on the coral reef resources situated inshore of the outfall terminus.
Series:
Project Report PR-2005-11
Sea Grant Document Number:
HAWAU-S-05-003
Document Type:
Technical Report
Funding:
Contract no.: C00983
Rights Information:
Public Domain
Compliance:
Library
Main Document Checksum:
[+]
urn:sha256:efb02180e6a74dd0509a717ba3696f95591a7f436c2002fc19ead5ad8402b339
Download URL:
https://repository.library.noaa.gov/view/noaa/39918/noaa_39918_DS1.pdf
File Type:

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