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

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

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

North Bay UC Davis / SFEI 2010 Mercury Biosentinel Monitoring Dec-2009 – Sep 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

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

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

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: CBDA Fish Mercury Project Over 3,000 individual small fish analyses/yr High precision, high cost

1 Comp mm 1 Comp mm 1 Comp mm 1 Comp 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

SFEI’s 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)

1 Comp mm 1 Comp mm 1 Comp mm 1 Comp mm 1 Comp mm 1 Comp mm Hybrid/Compromise Plan: 6 composites (vs 4) 8 fish per composite (vs 5) Narrower size range (45-75 mm vs mm)

2010 Seasonal Silverside Mercury Kennedy Park Pond 9/10 Pond 4/5 Pond 2A Pond 2 Pond 1 Dec Mar May Jul Petaluma Marsh Wing o P 7 Wash ponds

Other species data from sites without silversides (July samplings) Hamilton Pond 7 Pond 6A Pre- Cullinan Silverside Topsmelt Killifish Stickleback juv. Striped Bass

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

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

Means of Comps ± SE Spatial patterns Silverside Pond 2

North Bay Seasonal Silverside Mercury Trend, Oct, Feb, May, Jul, Sep, Nov From Pond 2?

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.