W4 PM Sediment Quality Assessment
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(HWA-1117-849553) Assessment of sediment quality in tidal salt marsh ecosystem.

Hwang, H-M¹, Green, PG¹, Higashi, RM¹, Anderson, SL¹, Young, TM¹, ¹ University of California, Davis, CA, USA

ABSTRACT- Tidal salt marshes sustain ecological diversity by providing vital food and habitat for clams, crabs, and juvenile fish. They also play buffering roles by absorbing nutrients, metals and organic contaminants before they reach the oceans and estuaries, resulting in excess levels of contaminants accumulated in marshes. Sediment samples were collected from 5 salt marshes in California and analyzed for metals and organic contaminants. Various biological measurements (e.g., comet assay, clam growth rate, crab embryo abnormality) were also conducted. Fish and clams were transplanted up to 2 months to investigate bioaccumulation of contaminants and their effects on the growth and physiological change. Chemistry data revealed that Stege Marsh located in San Francisco Bay is highly contaminated with metals and persistent organic chemicals. In order to assess toxic potential, ER-M quotients were calculated and sites were ranked to compare with biological measurement data. Fish and clam tissue analysis showed that metals and organic contaminants are readily bioavailable and bioaccumulable. No single biological indicator was able to provide enough information about overall sediment quality possibly because biological measurement conducted in this study did not respond to numerous contaminants equally. Stress-specific biomarkers such as P450 and metallothioneins in fish represent only organics and metals, respectively. Clam growth rate showed good correlation with sedimentary contaminant levels within the same marsh. However, when data from more than two marshes were compared, no good correlation was found. Some natural factors (e.g., temperature, salinity) are suspected to cause variations that are not related to contaminant gradient. It is recommended that chemical analyses and biological measurements need to be applied together to accurately assess the sediment quality. For biological measurements, integrated suite of indicators would be more valuable in assessing current condition.

Key words: Sediment quality, Bioindicators, Contaminants