Benjamin Walker, Mark Jankowski, Kristofer Rolfhus, and Gregg Knutsen Presenting Author: Benjamin Walker – USFWS – Glacial Ridge and Rydell NWRs. 17788 349 th St. SE. Erskine, MN 56535. 218-687-2229 x12. benjamin_walker@fws.gov
2013 USGS report “the highest published water methymercury concentration in uncontaminated waters” at Glacial Ridge NWR Management regime changed at Agassiz NWR
Investigation through the food chain Sediment Invertebrate (GRNWR only) Fish (ANWR only) Insectivorous birds Agassiz NWR Compare mercury levels Successive vs. Single drawdowns Glacial Ridge NWR Compare mercury levels Restored vs. Natural wetlands Seasonal vs. Semi-permanent wetlands
Agassiz NWR Sediment Brook stickleback Tree swallows 8 locations Revisited sites from previous study Visited twice a year
Glacial Ridge NWR Sediment Odonate larvae Tree Swallows Locations 15 restored seasonal 5 natural seasonal 3 restored semi- perm.* 2 natural semi-perm.* *Visited twice a year
Total mercury Adaptation of EPA Method 7473 Milestone DMA-80 automated analyzer Methylmercury Steam distillation Cold vapor atomic fluorescence spectrophotometry
Annual drawdown Control
Total mercury (ng/g) Annual drawdown Control n=8
Methylmercury (ng/g) Annual drawdown Control n=8
Total mercury (ng/g) Annual drawdown Control n=7 n=16 n=15 n=2 n=8 n=12 n=8 n=8 n=12 n=8
Total mercury (ng/g) n=20 n=19 n=10 n=9 n=21 n=21 n=9 n=7
Methylmercury (ng/g) n=20 n=19 n=10 n=9 n=21 n=21 n=9 n=7
Total mercury (ng/g) n=20 n=19 n=10 n=8 n=21 n=20 n=9 n=7
Methylmercury (ng/g) n=20 n=19 n=10 n=8 n=21 n=20 n=9 n=7
n=45 n=49
Agassiz NWR Alter drawdown regimes Patch rotation if possible Potential bioaccumulation issues when a fishery is present Glacial Ridge NWR Differences were not found Seasonal vs. Semi-permanent Restored vs. Natural Potential exposure delay due to overwintering aquatic larvae
Recommend
More recommend
