PT07 Contaminated Harbor and River Sediment
Exhibit Hall
8:00 AM - Tuesday, 11 November 2003
(PT111) Integrated assessment of agricultural drain water impacts in the Santa Maria River watershed.
Anderson, B1, Phillips, B1, Nicely, P1, Hunt, J1, Tjeerdema, R1, Worcester, K2, Adams, M2, Richard, N3, 1 University of California, Davis, CA, USA2 Central Coast Regional Water Quality Control Board, San Luis Obispo, CA, USA3 California State Water Resources Control Board, Sacramento, CA, USA
ABSTRACT- The lower Santa Maria River watershed supports rapidly growing urban areas and intensive agriculture. The lower river and its lagoon provide critical aquatic habitat in the arid central California coast. In this study, six stations were monitored for a number of physical, chemical, toxicologic, and ecological characteristics as part of an investigation designed to assess the ecotoxicologic effects of agricultural drainage creeks on the River. Stations were monitored on four separate occasions from July 2002 through May 2003. Temporal variability of water column toxicity to Ceriodaphnia dubia was observed at several stations, and Ceriodaphnia mortality was associated with elevated concentrations of organophosphate pesticides (Chlorpyrifos, diazinon, malathion). Sediments in the river lagoon and two of the drainage creeks were also significantly toxic to the amphipod Hyalella azteca, a resident species, and sediment toxicity was associated with elevated concentrations of OP pesticides in the sediment interstitial water, as well as pyrethroid and organochlorine pesticides in bulk-phase samples. These data were combined with Toxicity Identification Evaluations of sediment and water, and macroinvertebrate bioassessments, in a weight-of-evidence assessment of the effects of polluted drain water on the lower Santa Maria River ecosystem.
Key words: TIEs, toxicity, Pesticides, sediments