PM06 Linking Aquatic Toxicology with Ecosystem Indicators
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM128) Sediment Quality Assessment at the LA3 Dredge Disposal Site in Southern California.
Sakamoto, K1, Armstrong, J, Thomas, C, McCarthy, M, 1 Orange County Sanitation District, Fountain Valley, California, United States
ABSTRACT- The Sediment Quality Triad (TRIAD) approach to sediment quality assessment was used to assess changes in sediment quality at the LA3 dredge disposal site in southern California. Ten quarterly assessments consisting of sediment geochemistry, infaunal community analysis, and sediment toxicity (whole-sediment and porewater) analyses were conducted from May 1999 to July 2001 on LA3 and five other sites within the Newport Canyon and one site located in the San Gabriel Submarine Canyon. Sediment toxicity was assessed using the 10-day amphipod (Eohaustorius estuarius) whole-sediment test and porewater toxicity was tested for using Microtox. Mean ER-M quotients ranged from 0.11 to 0.18 in Newport Canyon, 0.17 at LA3 and 0.22 at the San Gabriel Canyon site. Some sediment geochemistry parameters exceeded ER-L and ER-M levels, particularly organic contaminants (e.g., DDT). Most were sporadic and showed no temporal or spatial relationship to dredge operations. Benthic infaunal analyses indicate that a normal infaunal community is being maintained, with minor community alteration following the most recent disposal event suggested. Whole-sediment toxicity was moderate to high and was observed throughout the study at all stations. Porewater toxicity was low to moderate and highly variable with a trend of increasing toxicity away from LA3 towards the head of the Newport Canyon. The TRIAD evaluation indicates some chemical degradation of the sediments, mainly DDT, which may be reflected in the whole sediment toxicity tests. Overall, there is evidence of minor alteration of the infauna at the LA3 site, though diversity remained relatively high. The impact of dredge spoils disposal at the LA3 site is minimal and is not evident at other nearby sampling locations.
Key words: Toxicity, Sediment Quality Triad, Dredge, Porewater