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Mercury and Methylmercury Processes in North SF Bay Tidal Wetland Ecosystems San Francisco Estuary Institute USGS BRD WERC Vallejo, CA USGS WRD Menlo Park,

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Presentation on theme: "Mercury and Methylmercury Processes in North SF Bay Tidal Wetland Ecosystems San Francisco Estuary Institute USGS BRD WERC Vallejo, CA USGS WRD Menlo Park,"— Presentation transcript:

1 Mercury and Methylmercury Processes in North SF Bay Tidal Wetland Ecosystems San Francisco Estuary Institute USGS BRD WERC Vallejo, CA USGS WRD Menlo Park, CA USGS WRD Middleton, WI Avocet Research Associates

2 Background: The Good? Tidal wetland restoration plans Adding 12,000+ acres North Bay Tidal wetlands Habitat for threatened & other wildlife Wetland restoration = good but…

3 The Bad? Mercury (Hg) already in Bay- Delta levels of concern human & wildlife health Hg in biota correlates to watershed % wetlands Mostly freshwater systems Similar in tidal marshes? Attractive nuisance? Wildlife check in, but …? x

4 The Ugly? Not just a matter of reducing Hg…

5 What (Me)Hg Worry? Not just Hg, need to worry about reducing methylmercury (MeHg) Most bioaccumulative form Formed by sulfate reducing bacteria under reducing conditions But is subject to degradation- Microbial Abiotic (photolytic)

6 Ask Questions First (Me)Hg in wetlands: where, when, how much? What influences (Me)Hg distribution & production? How does (Me)Hg accumulate in tidal wetland food webs? How does (Me)Hg get there: wetlands to bay (or vice versa)?

7 Approach: General Spatial distribution of (Me)Hg (water, sediments, biota) Differences in (Me)Hg concentrations Differences in (de)methylation processes Temporal distribution Seasonal differences in methylation rates and concentrations

8 Spatial Distribution 3 wetlands along Petaluma River Gambinini Ranch (Mid-)Petaluma Marsh Black John Slough Salinity gradient along Petaluma main stem

9 Spatial Distribution Within wetlands: habitat elements Medium channels (2 nd - 3 rd order) High marsh plain Transect composites (some grabs) Replicates of habitat elements

10 Food Web Charismatic Critter: California Black Rail (USGS- BRD CA) - capture, tag, track Identify distribution, habitat use, range, diet

11 Bioaccumulation Examine (Me)Hg in biota: High marsh food web: Hg in California Black Rails (blood, feathers) (Me)Hg in probable/potential diet items Channel biota food web Channel fish and invertebrates to compare

12 MeHg Processes Sediment processes (USGS-Menlo Park CA) (De)Methylation rates in channel and high marsh Lab incubations of sediment composites Microbially available (reactive) Hg Sediment quality (sulfur, carbon) Water processes (USGS-Middleton WI) Demethylation rates Photo-incubation experiments

13 Results: Hg Distribution Sediment Hg all sites >>ancient Hg levels comparable to Bay sediments High marsh < channel

14 Sediment MeHg Distribution High marsh Highest at mid- Petaluma Channel MeHg Opposite of salinity gradient < high marsh

15 Vertical MeHg Distribution MeHg highest in high marsh surface layers Black John Gambinini MidPetaluma

16 MeHg in Sediments Net = methylation - demethylation Sediment MeHg parallels sulfate reduction

17 What Drives Sediment MeHg? Sulfate reducing bacteria need food!

18 (Me)Hg in Water Water MeHg similar to channel sediments MeHg lowest near Bay end of Petaluma MeHg & Hg mostly (80%+) in particulate phase

19 Where do Biota Fit? Are black rails in areas w/ high MeHg? Small ranges (avg.24ha) in spring Black John Slough Mid Petaluma

20 Habitat Usage Primarily in high marsh pickleweed

21 Does It Add Up? BJSMPGAM MeHg (ng/g) High Marsh Slough High Marsh sediment MeHg ~2x higher Mid-Petaluma MeHg is bioaccumulative form of Hg

22 Black Rail (Feather) Hg Black rails reside and feed in high marsh, therefore… Rail Hg differs among wetlands (Mid-Petaluma ~2x)

23 Implications for Management MP feather Hg up to 10ng/g, is it bad? Other birds background in feather ~1-5ng/g Can we do anything about it? Less (or more) reducing conditions? Less organic matter? Other goals and priorities? (Me)Hg not the only factor Newer marsh Hg < ancient marsh (problem in 2000 years?)

24 Closing Credits Funding: CBDA Ecosystem Restoration Program grant ERP-02D-P62 Site Access: CDFG, the Phelans Project Partners: SFEI: (Don Yee), Josh Collins, Letitia Grenier, S. Pearce USGS WRD-CA: Mark Marvin-DiPasquale, Jennifer Agee, Le Kieu, Nick Ladizinski, Lisa Windham USGS WRD-WI: Dave Krabbenhoft, Shane Olund, Tom Sabin USGS BRD- John Takekawa, Isa Woo, Danika Tsao-Melcer Avocet Associates: Jules Evens


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