Paper No. 54
Presentation Time: 8:00 AM-6:00 PM
MERCURY IN MACROINVERTEBRATES FROM THE TRUCKEE RIVER
EASTERDAY, Jill J., Unity College, 6363 Christie Ave. #2707, Emeryville, CA 94608 and PIZARRO, Claudia, University of Nevada, Reno, 6363 Christie Ave. #2707, Emeryville, CA 94608, jeasterday07@unity.edu
Mercury (Hg) concentrations in macroinvertebrates collected from the reaches of the Truckee River differ upstream and downstream of Steamboat Creek (SBC) (a source of Hg contamination). Hg concentrations of aquatic macroinvertebrates provide an indicator of bioavailability which should be greater downstream of the confluence. Three types of macroinvertebrates were collected: collectors, omnivores, and predators. Aquatic earthworms and mayflies are collectors which mean they eat plant matter and detritus. Caddisflies, crayfish and flatworms are omnivores which mean they eat smaller animals, vegetation and detritus. Damselflies, leaches and waterstriders are predators which mean they eat other animals.
After collection macroinvertebrates were separated according to order and class, lyophilized, homogenized, and total Hg determined using a Milestone Direct Mercury Analyzer 80 (U.S. EPA Method 7473). For each organism, Hg average concentrations increased below confluence of SBC with the Truckee River.
Macroinvertebrates collected at Nixon, the farthest river sampling point, had the highest Hg concentrations, except for mayflies. Macroinvertevrates collected at Tracy, the first location downstream of SBC showed predators (leaches (233 ± 34 µg/kg dry weight), water striders (158±14), and damselflies (185±4)) had higher Hg concentrations than collectors ((mayflies(89±2) and aquatic earthworms (212.6±2)), and omnivores (caddisflies (143±3), flatworms (162±6) and crayfish (140±3)).
