Benjamin Walker, Mark Jankowski, Kristofer Rolfhus, and Gregg - - PowerPoint PPT Presentation

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Nov 06, 2023 30 likes •243 views

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

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Benjamin Walker, Mark Jankowski, Kristofer Rolfhus, and Gregg Knutsen

Presenting Author: Benjamin Walker – USFWS – Glacial Ridge and Rydell NWRs. 17788 349th St. SE. Erskine, MN 56535. 218-687-2229 x12. benjamin_walker@fws.gov

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 2013 USGS report “the highest published water

methymercury concentration in uncontaminated waters” at Glacial Ridge NWR

 Management regime changed at Agassiz NWR

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 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

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 Agassiz NWR

 Sediment  Brook stickleback  Tree swallows

 8 locations

 Revisited sites

from previous study

 Visited twice a

year

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 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

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 Total mercury

 Adaptation of EPA

Method 7473

 Milestone DMA-80

automated analyzer

 Methylmercury

 Steam distillation  Cold vapor atomic

fluorescence spectrophotometry

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Annual drawdown Control

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Total mercury (ng/g)

n=8 Annual drawdown Control

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Methylmercury (ng/g)

n=8 Annual drawdown Control

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Total mercury (ng/g)

n=8 n=8 n=12 n=8 n=7 n=2 n=16 n=15 n=12 n=8

Annual drawdown Control

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Total mercury (ng/g) n=20 n=19 n=10 n=9 n=21 n=21 n=9 n=7

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Methylmercury (ng/g) n=20 n=19 n=10 n=9 n=21 n=21 n=9 n=7

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Total mercury (ng/g)

n=20 n=19 n=10 n=8 n=21 n=20 n=9 n=7

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Methylmercury (ng/g)

n=20 n=19 n=10 n=8 n=21 n=20 n=9 n=7

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n=45 n=49

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 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

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