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Title:	Aquatic disposal field investigations, Duwamish Waterway disposal site, Puget Sound, Washington : Appendix G: Benthic community structural changes resulting from dredged material disposal, Elliott Bay disposal site
Authors:	Bingham, C. Rex
Keywords:	Aquatic ecology Puget Sound (Wash.) Dredging Dredging spoil Dredged material Benthos Benthic ecology Dredged Material Research Program (U.S.)
Publisher:	U.S. Army Engineer Waterways Experiment Station
Series/Report no.:	Technical Report (Dredged Material Research Program (U.S.)) ; no. Technical Report D-77-24; Appendix G
Abstract:	Benthic community changes resulting from the open-water disposal of 114,350 m³ of Duwamish River dredged material at the Elliott Bay, Puget Sound, deep-water (approximately 60 m) experimental disposal site, 7 February 1976 to 6 March 1976, were investigated. Analyses were performed on macrofaunal density, species composition, biomass, biomass/individual, frequency of occurrence, and species diversity, at several taxonomic levels for one predisposal sampling and five postdisposal samplings at 10 days, and 1, 3, 6 and 9 months after disposal. These analyses were performed on data from stratified (central, side, and corner) disposal site stations and two (east and west) reference sites. Taxonomic levels investigated were total benthic macrofauna, macrofaunal groups . (gastropods, pelecypods, errantian worms, sedentarian worms, and miscellaneous species), and individual species. Total macrofaunal densities at the disposal site showed large decreases 10 days after disposal that were unmatched by decreases at the reference sites. Disposal site total macrofaunal density gradually increased thereafter through 6 months after disposal, then decreased slightly at 9 months after disposal. The most abrupt increase occurred at 3 months. Disposal site marcofaunal densities never returned to their predisposal level nor to concurrent levels at the reference sites. Total number of species showed large decreases at 10 days and 1 month after disposal, a considerable Increase at 3 months, and a leveling off for the remainder of the study. Number of species at the reference sites remained relatively stable throughout the study. Total biomass and frequency of occurrence reacted somewhat similar to density. Species diversity indices decreased at 10 days and 1 month after disposal at the disposal site and increased thereafter for the remainder of the study. At 9 months the disposal site species diversity index exceeded both its predisposal value and concurrent values at the reference sites. Comparison of corner, side, and central disposal site stations and the two reference sites showed that the effects of dredged material disposal upon the previously discussed parameters were graded within the disposal site with central stations receiving the greatest negative impact. Side stations received a less negative effect while corner stations showed little effect. Both graphical and statistical analyses showed that there are certain species within each group except gastropoda, which suffered little or recovered rapidly from the dredged material disposal while others suffered greatly and either failed to recover or recovered slowly. Most individual species showed seasonal trends (both graphically and statistically) at the reference sites and the corner disposal site stations, indicating that rate of benthic macrofaunal recovery from dredged material disposal may be affected by seasonal parameters. Therefore, timing of dredged material disposal on similar sites may be important in reducing the severity of impact on the benthic macrofauna.
Description:	Technical Report
Gov't Doc #:	Technical Report D-77-24; Appendix G
Rights:	Approved for Public Release; Distribution is Unlimited
URI:	https://hdl.handle.net/11681/47739
Appears in Collections:	Technical Report