Toxicity test data used in a weightofevidence Sediment
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Toxicity test data used in a weight-of-evidence: Sediment contamination Sediment Quality Assessment Sediment toxicity Benthic community structure Results used to identify and map areas of unimpacted to clearly impacted sediments Current RMP toxicity tests are those recommended for the accepted statewide SQO methods for bays and estuaries, EXCEPT… Draft Data - Do not cite or quote
Excerpt from SQO Staff Report - Table 5. 2 List of candidate sediment toxicity tests The SQO recommends the use of sediment water interface (SWI) samples Draft Data - Do not cite or quote
Mussel embryo development 48 -h exposure Sublethal endpoint Sediment elutriate. Draft Data - Do not cite or quote VS. Sediment-water interface exposure
The TRC needs to decide if the RMP should adopt, add, or study the sediment-water interface (SWI) bivalve test in 2008. Draft Data - Do not cite or quote
What are the issues? • Comparison to historic RMP/other programs • Interpretation (Ecological Relevance) • Cost Draft Data - Do not cite or quote
Comparison to historic RMP data 1999 - 2001 Bivalve Methods Study • 48 -hr. sublethal development test • Elutriate (1: 4 dil. VS. SWI intact cores) • 14 stations (52 samples). Draft Data - Do not cite or quote
RMP 1999 -2001 Elutriate & SWI bivalve development tests (N=52) Davis Point Napa River Grizzly Bay Rivers Red Rock Yerba Buena Is Horseshoe Bay Alameda San Bruno Shoal San Jose (LEMP) Redwood Creek South Bay Draft Data - Do not cite or quote Coyote Creek
Amphipod and Bivalve Sediment Toxicity Results 1993 -2001 Davis Point Napa River Grizzly Bay(BF 21) Rivers Horseshoe Bay Legend: Yerba Buena Island Redwood Creek San Jose South Bay (BA 21) Coyote Creek Draft Data - Do not cite or quote Pulse of the Estuary, 2003
Interpretation • SWI tests are thought to be more ecologically relevant • However, not much in known about contaminant flux and exposure • SCCWRP study (4 samples) to determine if homogenized sediments can be left to equilibrate and used in the SWI test. Draft Data - Do not cite or quote
Recommendation • RMP S&T should switch to the intact SWI method to be comparable to recommended SQO methods that have been endorsed by a panel of national experts – However, this will result in a NEW toxicity measure and will not be comparable with historic RMP data (largely an issue in Suisun Bay & Lower South Bay Regions) • Consider adding elutriate tests in Suisun Bay and Lower South Bay Regions and evaluate chemistry in the test water of both tests to begin to understand differences in contaminant exposures. Draft Data - Do not cite or quote
Cost $20 more per sample Draft Data - Do not cite or quote
Cost Draft Data - Do not cite or quote
RMP 1999 -2001 Elutriate & SWI bivalve development tests (N=52) Davis Point Napa River Grizzly Bay Rivers Red Rock Yerba Buena Is Horseshoe Bay Alameda San Bruno Shoal San Jose (LEMP) Redwood Creek South Bay Draft Data - Do not cite or quote Coyote Creek
Further Study • Evaluate the comparability of intact SWI cores vs homogenized sediment on a variety of sediments in order to make a confident assessment that the two sampling methods can be used and are equally ecologically relevant. – SCCWRP is beginning to investigate (4 samples) – RMP? Draft Data - Do not cite or quote