1. 2010 BIOSENTINEL MERCURY MONITORING IN THE NORTH BAY SALT PONDS Darell Slotton Shaun Ayers Department of Environmental Science and Policy University of California, Davis Letitia Grenier Ben Greenfield San Francisco Estuary Institute Feedback Tool for Watershed Management

2. Using small, young fish as localized, time-sensitive, fish based measures of methylmercury exposure Biosentinel Mercury Monitoring Year-to-year trends and variability Within-year seasonal trends Spatial patterns to a local scale Performance measures for restoration and remediation

3. UC Davis Delta Silverside Hg Established clear, regional pattern: elevated periphery, lower central Silversides ideal biosentinels: widespread; relatively site-specific

4. North Bay UC Davis / SFEI 2010 Mercury Biosentinel Monitoring Dec-2009 – Sep-2010 30 samplings total 6 ‘intensive’ seasonal sites: Dec/Mar/May/Jul Kennedy Park Pond 9/10 Pond 4/5 Pond 2A Pond 2 Pond 1 Additional one-time sites: July Petaluma Marsh Hamilton Wing o P 7 6A Pre- Cullinan Wash ponds

5. Multiple Individual Fish Analyses (n = 30) Within pre-defined size ranges with consistent Hg Strong statistical power Detailed individual information Mean Hg ± 95% C.I. 45 ± 2 ng/g

6. Oct 6: 44 ± 4 Suisun Marsh Managed Seasonal Flooding: Suisun Slough North, October through February Discharge from seasonally flooded, managed ponds Oct 18: 43 ± 3 Oct 6: 44 ± 4 Dec 21: 75 ± 5 Oct 6: 44 ± 4 Oct 18: 43 ± 3 Feb 7: 100 ± 5 Oct 6: 44 ± 4 Oct 18: 43 ± 3 Dec 21: 75 ± 5

7. Sacra- mento River San Joaquin River Merced Tuolumne Clear Creek Ham- ilton City Cache Ck Mud Slough Region Lower Sacramento Series Vernalis UC Davis Biosentinel Monitoring Region: 2005-2007 CBDA Fish Mercury Project Over 3,000 individual small fish analyses/yr High precision, high cost

8. 1 Comp 40-50 mm 1 Comp 50-60 mm 1 Comp 60-70 mm 1 Comp 70-80 mm SFEI Compositing Approach: 4 composites, 4 analyses (vs 30) 5 fish per composite 10 mm size increments less precise statistics large cost saving on analytical

9. SFEI’s 2008-2010 RMP Small Fish Program Fixed, long-term sites Potential source sites (urban, mines, POTWs) Additional 1-time sites (12 wetland, 12 bay) Silverside Topsmelt Composites (4 comps x 5 fish)

10. 1 Comp 45-50 mm 1 Comp 50-55 mm 1 Comp 55-60 mm 1 Comp 60-65 mm 1 Comp 65-70 mm 1 Comp 70-75 mm Hybrid/Compromise Plan: 6 composites (vs 4) 8 fish per composite (vs 5) Narrower size range (45-75 mm vs 40-80 mm)

11. 2010 Seasonal Silverside Mercury Kennedy Park Pond 9/10 Pond 4/5 Pond 2A Pond 2 Pond 1 Dec- 2009 Mar- 2010 May Jul 71 66 72 138 75 68 63 54 186 83 57 85 96 59 41 54 46 44 78 79 55 94 46 Petaluma Marsh Wing o P 7 Wash ponds 29 65 68 63

12. Other species data from sites without silversides (July samplings) Hamilton Pond 7 Pond 6A Pre- Cullinan Silverside Topsmelt Killifish Stickleback 59 24 88 16 44 5353 2424 50 49 42 29 juv. Striped Bass

13. North Bay Silverside Mercury Trend, Fall 2005, Fall 2006 Dec-2009 Pond 2

14. Silverside Fall 2005 Mercury Spatial Distribution: Entire CBDA Range With Silversides Pond 2

15. Means of Comps ± SE Spatial patterns Silverside Pond 2

16. North Bay 2005-2006 Seasonal Silverside Mercury Trend, Oct, Feb, May, Jul, Sep, Nov From Pond 2?

17. Interim Conclusions from 2010 Work It is possible to use small fish as biosentinels of methylmercury exposure in this region, spatially and seasonally. Significant changes in exposure can occur both seasonally and between sites. The lower cost, hybrid compositing approach can provide a reasonable alternative when funding is limited. Different sites can show different patterns.