2010 BIOSENTINEL MERCURY MONITORING IN THE NORTH BAY SALT PONDS Feedback Tool for Watershed Management Darell Slotton Shaun Ayers Department of Environmental Science and Policy University of California, Davis Letitia Grenier Ben Greenfield San Francisco Estuary Institute Biosentinel Mercury Monitoring Using small, young fish as localized, time-sensitive, fish based measures of methylmercury exposure • Spatial patterns to a local scale • Year-to-year trends and variability • Within-year seasonal trends • 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-2010 • 30 samplings total Kennedy Park 6 ‘intensive’ seasonal sites: Petaluma Marsh Dec/Mar/May/Jul Wing o Additional one-time sites: July P7 Pond 2 6A Pond 4/5 Pond 2A Pond 1 Hamilton Pond 9/10 Wash ponds PreCullinan Multiple Individual Fish Analyses (n = 30) • Within pre-defined size ranges with consistent Hg Mean Hg ± 95% C.I. 45 ± 2 ng/g • Strong statistical power • Detailed individual information Suisun Marsh Managed Seasonal Flooding: Suisun Slough North, October through February Hg (ng/g wet wt, whole body) 140 120 Feb 7: 100 ± 5 100 80 Dec 21: 75 ± 5 60 Oct 18: 43 ± 3 Oct 6: 44 ± 4 40 20 0 30 35 40 45 50 55 60 65 70 75 Individual silverside total length (mm) Discharge from seasonally flooded, managed ponds 80 85 90 UC Davis Biosentinel Monitoring Region: 2005-2007 CBDA Fish Mercury Project • Over 3,000 individual small fish analyses/yr Clear Creek Hamilton City Sacramento River Cache Ck Lower Sacramento Series • High precision, high cost Vernalis Tuolumne San Joaquin River Merced Mud Slough Region SFEI Compositing Approach: • 4 composites, 4 analyses (vs 30) • 5 fish per composite • 10 mm size increments 1 Comp 40-50 mm 1 Comp 50-60 mm 1 Comp 60-70 mm 1 Comp 70-80 mm • less precise statistics • large cost saving on analytical SFEI’s 2008-2010 RMP Small Fish Program Fixed, long-term sites Silverside Topsmelt Composites (4 comps x 5 fish) Potential source sites (urban, mines, POTWs) Additional 1-time sites (12 wetland, 12 bay) Hybrid/Compromise Plan: • 6 composites (vs 4) • 8 fish per composite (vs 5) • Narrower size range (45-75 mm vs 40-80 mm) 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 2010 Seasonal Silverside Mercury 94 75 46 57 186 63 Kennedy Park 138 65 Petaluma Marsh Wing o85 96 78 29 44 55 Pond 9/10 Wash ponds 72 54 46 54 P7 68 Jul 79 68 71 Dec2009 Mar2010 May 75 83 Pond 2 Pond 4/5 66 Pond 1 63 Pond 2A 59 41 Other species data from sites without silversides (July samplings) Stickleback Topsmelt Killifish juv. Striped Bass 5 3 2 164 Silverside Pond 7 24 Pond 6A 29 59 50 42 PreCullinan 88 44 Hamilton 49 North Bay Silverside Mercury Trend, Fall 2005 , Fall 2006 Pond 2 Dec-2009 Silverside Fall 2005 Mercury Spatial Distribution: Entire CBDA Range With Silversides Pond 2 Spatial patterns Pond 2 Means of Comps ± SE Silverside North Bay 2005-2006 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. The lower cost, hybrid compositing approach can provide a reasonable alternative when funding is limited. Significant changes in exposure can occur both seasonally and between sites. Different sites can show different patterns.