MP8 Metals in the Environment: Dietary concerns in Aquatic Systems
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall
(BRO-1117-741616) Using biodynamics to evaluate the effect of a Cu-based herbicide on Cu uptake in Corbicula.
Brown, C.1, Croteau, M.-N.1, Luoma, S.1, 1 U.S. Geological Survey, Menlo Park, CA, USA
ABSTRACT- Copper is an ingredient in the herbicide Komeen which is being tested for the eradication of Egeria densa (a non-native submerged aquatic weed) in the San Francisco Bay Delta (California). An important question to address is whether Cu in the herbicide persists in the Delta ecosystem and affects non-target species. Trials of herbicide effects use indicators such as abundance, distribution, organism condition and levels of Cu in sediment and water. However, no indicators of Cu bioavailability have been considered. Copper concentrations were measured in the bivalve Corbicula fluminea monthly between March 2002 and April 2003 at sites near the Komeen application (Franks Tract), and once throughout the Delta (8-months after the herbicide application). Concentrations of Cu in clams near Franks Tract increased from 100 
g g-1 to over 200 g g-1 following an application, then declined slightly. After 8 months, clams from Franks Tract, sloughs and rivers located to the east of the application site had 125-200 g g-1 Cu in their tissues. In contrast, clams from locations west, southeast and north had lower concentrations (25-125 g g-1). We determined whether Cu variations in clams were due to changes in environmental Cu or clam physiology (reproduction, growth) using a biodynamic model that incorporated variables accounting for clam physiology as well as water geochemistry. Copper concentrations in clams were successfully predicted at most stations except near the Komeen application sites, where we under-predicted clam Cu concentrations. Using the biodynamic model, we showed that clam Cu concentrations increased following herbicide applications coincidently with increases in particulate Cu, suggesting that Cu is most available to Corbicula from food. It further suggests that copper is likely to accumulate to high levels in phytoplankton and zooplankton, potentially impairing primary and secondary productivity.
Key words: copper, herbicide, biodynamics, bivalves