T4 PM Endangered Species and Environmental Contaminants: Status of the Science (Part 2)
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(WAR-1117-829576) Risk assessment of water quality in streams supporting federally-endangered freshwater mussels in North Carolina.

Ward, S¹, Augspurger, T¹, ¹ US Fish and Wildlife Service, Raleigh, NC

ABSTRACT- To determine if impaired water quality is a limiting factor in the recovery of endangered freshwater mussels, site-specific water quality data were collected from Goose Creek, Swift Creek, and Tar River in North Carolina. These streams support the endangered Carolina heelsplitter (Lasmigona decorata) and dwarf wedgemussel (Alasmidonta heterodon). Metals, total residual chlorine, and ammonia concentrations were measured bimonthly in 2002 and 2003 at sites bracketing known wastewater sources and mussel habitats. Results were compared to estimates of chemical concentrations likely to be protective of mussels (when freshwater mussel toxicity data were available), site-specific screening values (adjusted for local hardness and pH conditions for metals and ammonia, respectively), and appropriate water quality criteria and state standards. Water chemistry results were also compared to existing datasets from local and state monitoring networks. In all drainages, our total copper concentrations exceeded the federal ambient water quality criteria (adjusted for local hardness) for acute exposures in 10 to 41% of samples. In addition, copper concentrations in the Goose Creek and Tar River drainages exceeding the state action level for copper (7 ug/l) were found in 26 and 10% of samples, respectively, while no exceedences were observed in Swift Creek. State ambient data for stations within these watersheds confirm that the 75th percentile values (ranging between 3.2 and 6.0 ug/L) for the period of record are above acute screening values at three of four stations. Chlorine concentrations exceeding federal water quality criteria and the State water quality standard of 17 ug/l were observed in 14 and 35 percent of samples from Goose Creek and Tar River drainages, respectively; they were never exceeded in Swift Creek. Acute and chronic site-specific ammonia screening values derived for protection of freshwater mussels were exceeded in 6 and 15 percent of samples, respectively, in Goose Creek; however, ammonia concentrations were generally below levels of concern in the remaining two drainages.

Key words: mussel, water quality, instream monitoring