Josh Ackerman 1, Collin Eagles-Smith 1, Mark Marvin-DiPasquale 2, Cheryl Strong 3, and Eric Mruz 3 1

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1 Managing Salt Ponds to Increase Waterbird Nesting Habitat While Minimizing Methyl Mercury Biomagnification: Implications for the South Bay Salt Pond Restoration Project Josh Ackerman 1, Collin Eagles-Smith 1, Mark Marvin-DiPasquale 2, Cheryl Strong 3, and Eric Mruz 3 1 U.S. Geological Survey, University of California, Davis, CA; 2 U.S. Geological Survey, Menlo Park, CA; 3 U.S. Fish and Wildlife Service, San Francisco Bay National Wildlife Refuge Complex, Newark, CA (16 September 2009)

2 South Bay Salt Pond Restoration Project Plans to convert 50-90% of salt ponds (~25,000 acres ) into tidal marsh Salt ponds are preferred habitat for waterbirds Need to enhance remaining salt ponds to maintain current waterbird populations But unclear how to manage salt ponds to increase waterbird foraging and nesting opportunities while minimizing methyl mercury production

3 Waterbird Nesting Colonies in South San Francisco Bay N=5,874 nests Avocet Stilt Forster s tern % of nests in A8/A7 which will be flooded for restoration

4 Pond Bathymetry Foxgrover et al A9 A14 A15 A17 A10 A11 A13 A16 A5 A7 current A8 A12 future?

5 Pond A12 Water Management Before After High-salinity Water levels lowered Deep water Substrate exposed suitable No nesting habitat for nesting islands No prior history of nesting

6 Pond A12 Nesting Islands Monitored: waterbird nesting response Hg in water over time Hg in fish over time Hg in waterbird eggs

7 Waterbird Nesting Effort A8 and A12 Avocet Stilt Forster s s tern A8 Avocet=211 Stilt=6 Tern=69 A12 Avocet=321 Stilt=5 Tern=73

8 Waterbird Abundance Over Time A A of Wate erbirds Number Jan Mar May Jul Sep Nov Jan Mar May July Sept Nov A A Jan Mar May Jul Sep Nov water lowered 10 Jan Mar May July Sept Nov water lowered Athearn & Takekawa

9 THg (ng g/l) Total Mercury A. Filtered THg B. Particulate THg 160 THg (ng/ /L) A11 A A11 B A12 A A12 B Most THg in the particulate fraction THg higher in A12 (July peak)

10 Methylmercury MeHg (n ng/l) A. Filtered MeHg B. Particulate MeHg A11 A A11 B A12 A A12 B MeHg (n ng/l) Most MeHg in the particulate fraction Higher MeHg in A12 (July peak)

11 Mercury Bioaccumulation in Fish Muds sucker THg (µ µg/g dw) Pond da11 Pond da12 Pond da Jan Feb Mar Apr May Jun Jul Aug Fish mercury concentrations before altered water management

12 Mercury Bioaccumulation in Waterbird Eggs 7 Forster s Tern Stilt Avocet dw) A12 A8 A7 B4 A16 A1 AB1 Pond 2 A12 NCM AB1 A16 A2W N4/N5 A7 A12 A8 NCM N4/N5 R1 A2W AB1 A1 Eggg THg (µg/g Wetland Site Photos by Ken Phenicie

13 What Drives These Trends in MeHg? 1) Salinity was higher in 2) Total Suspended Solids A12 and peaked in July and chlorophyll track salinity Co onductivity (m ms) A11 A A11 B A12 A A12 B TS SS (mg/l) R² = 0.76 July Peak in A12 3) Particulate MeHg tracks 40 salinity (ng/l) ) Conductivity (ms) R² = 0.80 ulate MeHg Partic R² = 0.87 July Peak in A Conductivity (ms) hl-a (mg/m 3 ) C July Peak in A Conductivity (ms)

14 Fish Mercury Among Habitats N=3,033 fish 10 species Moffet West Alviso Central Alviso East Alviso Newark South Bay Sloughs North Bay <0.50 ppm dw ppm dw ppm dw >1.0 ppm dw Fish THg (µg/g dw)* A1 A2W A2E AB1 AB2 A5 A7 A8 A12 A13 A16 A17 A18 New Chicago Marsh A19 A20 A21 M1 M2 N2A N4A N6 N9 Alviso Sl. Charleston Sl. Coyote Cr. South Bay Pond 1 Pond 2 Pond 3 Pond 4 North Bay Mowry *least-square means controlling for species, year, date, site, length, & body condition *0.8=fish effects; 1.2=bird effects

15 Fish Mercury Correlated Pond Salinity? N=16 ponds over 4 years Fish TH Hg (µg/g dw w) Mudsucker Stickleback R 2 = R 2 = Pond Salinity (ppt)

16 Mercury Bioaccumulation in Waterbird Eggs 7 Forster s Tern Stilt Avocet dw) A12 A8 A7 B4 A16 A1 AB1 Pond 2 A12 NCM AB1 A16 A2W N4/N5 A7 A12 A8 NCM N4/N5 R1 A2W AB1 A1 Eggg THg (µg/g Wetland Site Photos by Ken Phenicie

17 Percent of Population at Risk Breeding Birds Only Risk Factor: High + Extra High Avocet 6% Stilt 5% Caspian tern 10% Forster s tern 58% Percent of Breeding Population at Risk *B Based on breeding adult ltblood dhg concentrations ti Low Risk Moderate Risk High Risk Extra-High Risk

18 Effects of Mercury on Egg Hatchability Forster s Terns fww) P<0.001* F 2,341 =13.58 N=73 failed eggs in successful nests Egg [T THg] (μg/g *Statistically controlled for effects of colony site and year

19 Summary We successfully created waterbird nesting habitat (+400 nests) by lowering water levels But, methyl mercury production was elevated Methyl mercury subsequently biomagnified ifi up the food web, with waterbird egg concentrations highest in Pond A12 than in other ponds Further study is necessary to determine if similar water management actions will increase methyl mercury bioaccumulation within other salt pond habitats as the South Bay Salt Pond Restoration Project proceeds

20 Funding U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service Coastal Program U.S. Geological Survey Support Staff of Don Edwards San Francisco Bay National Wildlife Refuge Contact