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Polychaetes Associated with a Tropical Ocean Outfall: Synthesis of a Biomonitoring Program off O'ahu, Hawai'i

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Title:Polychaetes Associated with a Tropical Ocean Outfall: Synthesis of a Biomonitoring Program off O'ahu, Hawai'i
Authors:Bailey-Brock, J.H.
Paavo, B.
Barrett, B.M.
Dreyer, J.
Date Issued:Oct 2002
Publisher:University of Hawai'i Press
Citation:Bailey-Brock JH, Paavo B, Barrett BM, Dreyer J. 2002. Polychaetes associated with a tropical ocean outfall: synthesis of a biomonitoring program off O'ahu, Hawai'i. Pac Sci 56(4): 459-479.
Abstract:A comparison of benthic polychaete communities off the Sand Island
Wastewater Outfall was undertaken to recognize organic enrichment indicator
species for Hawaiian waters. Primary-treatment sewage is discharged off the
south shore of O'ahu at 70 m depth. A historical data set spanning 9 yr for seven
sites at 70 m and two recent studies at 20, 50, and 100 m depths were analyzed.
Geochemical data did not support the assumption that the outfall is an important
source of organic enrichment in nutrient-poor sandy sediments within
oligotrophic tropical waters. Five polychaete species, however, appeared particularly
sensitive, positively or negatively, to environmental conditions near the
outfall. Neanthes arenaceodentata (Nereididae) and Ophryotrocha adherens (Dorvilleidae)
have been dominant at sites within the outfall's zone of initial dilution
(ZID). Since 1993, N arenaceodentata has virtually disappeared, and 0. adherens
concurrently became abundant and continued to flourish at ZID sites. Well known
indicators within the Capitella capitata complex (Capitellidae) were present
at ZID and control (far field) sites though their ZID abundance was greater.
Two sabellids, Euchone sp. Band Augeneriella dubia were inversely distributed,
the smaller Euchone sp. B at far field sites and larger A. dubia within ZID stations.
The former was most likely restricted to a greater proportion of fine sediment
particles at two far field sites. The most abundant and widespread
polychaete off O'ahu's south shore was Pionosyllis heterocirrata (Syllidae), which
does not seem to represent a sensitive indicator species. Ophryotrocha adherens
was the most abundant indicator species within the ZID; P. heterocirrata was the
most ubiquitous species at all sites and should always be expected in these sediments.
Traditional measurements of numerical abundance, species richness, and
diversity (H') have not shown a clear distinction between ZID and far field sites
in annual analyses. An examination of composited data over an 11-yr period
does support such a distinction. Multidimensional scaling (MDS) analyses
clearly delineate different assemblages. We suggest that MDS analyses are sensitive
to the community differences present near the outfall. The ZID community
is clearly contained within the Environmental Protection Agency-approved
ZID boundary. Because each ZID and far field site supports a diverse and
coarsely similar polychaete fauna, no pollution level effects seem to be present.
Appears in Collections: Pacific Science Volume 56, Number 4, 2002

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