Spatial and temporal patterns in food web accumulation of Hg San Francisco Mercury Coordination Meeting February 20, 2008

Questions addressed Spatial patterns: Where is most bioavailable mercury in the Bay? –Using small fish as biosentinels –Comparing with sediment MeHg data –Regions –Habitat types and conditions Temporal patterns: How does mercury vary in small fish from year to year?

Spatial patterns: Bay margins vs. open waters

Wetlands/margins Open waters Spatial patterns: Organized by species habits

Hg wet weight (  g/g) 2005 elevated in southern stations (significant) 2006 elevated in Pt. Isabel (significant) 2006 elevated in Pt. Isabel (significant) Spatial patterns: Regional patterns across Bay

Spatial patterns including salt pond data Includes data provided by C. Eagles-Smith and J. Ackerman

2005 elevated in southern stations (not significant) 2006 elevated in southern stations, Pt. Isabel, and Richardson Bay (significant) 2006 elevated in southern stations, Pt. Isabel, and Richardson Bay (significant)

Potential explanations for spatial patterns: –High sediment MeHg in southern stations, Richardson Bay –Suggests linkage: fish vs. sediment MeHg –Suggests spatial gradient Source: RMP

Sediment MeHg may be correlated with topsmelt Hg Topsmelt 2006 data RMP and Calfed sediment data within 1.5 km disk of fish R 2 = 0.61

Sediment MeHg: < 1 ng/g 1 – 2 ng/g > 2 ng/g Sediment MeHg higher in shallow/nearshore sites

MeHg Hotspots in Sediment Concentrations highest close to shoreline and surrounded by land < 2 ng/g > 2 ng/g

Hypothesis: Importance of enclosed areas like Pt. Isabel and Richardson Bay

Temporal Patterns

Station effect Year effect Interaction term not significant Disconnect from patterns seen in Delta/Suisun Bay (Slotton et al.) How Hg varies from year to year? Mississippi silverside

Station effect Year effect Similar to Slotton et al higher than 2005! Topsmelt

Relative importance of station vs. year effect

Summary New Interannual variation differs among species (habitat types) Elevated in some salt ponds Apparent association between sediment and biosentinel MeHg Q1 Q2 Hg entering food web at Bay margins, tributaries, wetlands, salt ponds South Bay and nearshore or enclosed hotspots (Pt. Isabel, Richardson Bay) Sediment net methylation may be locally important process for food web accumulation

Next step: more intensive survey Spatial survey of about 40 stations/yr (3 years) Annual monitoring at 8 stations to determine trends Monthly monitoring at 2 stations to determine seasonal variation External collaborations –Combining efforts with UC Davis team –Diffusive Gradient in Thinfilm Devices, Bivalves (Hintelmann and Best) –Stable Hg isotopes in fish (Blum)

Field/Lab Work and Site Access… Katie Harrold Aroon Melwani John Oram Carrie Austin Max Delaney Fred Hetzel Richard Looker April Robinson Meg Sedlak SF Bay National Wildlife Refuge USFWS Stockton USGS BRD California State Parks CA Department Fish & Game Interagency Ecological Program Collaboration/Data Sharing… Andy Jahn Mark Sandheinrich Kristen Cayce Collin Eagles-Smith Josh Ackerman Wes Heim SF Bay Regional Board

SUPPORTING INFORMATION:

Spatial survey Targeting 40 locations Multiple interrelated factors A.Land use, land cover, and Hg sources B.Spatial location in Bay C.Subtidal hydrology and bathymetry D.Sediment physical and chemical parameters

Workplan: Specific questions to address 1.Where is mercury entering the Bay food web? 2.What habitats, conditions, or factors help to identify hotspots of food web accumulation in Bay margins? 3.Are there interannual trends in MeHg bioaccumulation resulting from wetland and margin restoration activities? 4.What are the best biomonitoring tools for characterizing hotspots of MeHg bioaccumulation?

Spatial survey potential design Focus on four types of location – test hypothesis of effect Include spatial gradient from North to South Bay Also consider subtidal bathymetery/hydrology Focus on topsmelt and Mississippi silverside Land Use/Land CoverN BayS Bay Wetlands5 sites Urban outfall5 sites POTW into slough/marsh5 sites Control (upland, residential, no discharges) 5 sites

Potential sampling locations – E.g., POTW outfalls: –Fairfield-Suisun –Palo Alto –Sunnyvale –San Jose

Coordinate with SBMP sites: Improve understanding of wetland – Bay linkages Marsh fish Brine flies Song sparrows Topsmelt Silversides

Trend analysis – a multiple station BACI design

Trend Sampling Locations Alviso Slough Newark Slough Bird Island/ Steinberger Slough Eden Landing China Camp Benicia Park Control Impact (Restoration) Point Isabel Candlestick Point Hamilton Oakland Middle Harbor

Trend Sampling Locations Alviso Slough Newark Slough Bird Island/ Steinberger Slough Eden Landing China Camp Benicia Park Control Impact (Restoration) Point Isabel Candlestick Point Hamilton Oakland Middle Harbor

Monthly sampling locations Martin Luther King Shoreline Additional North Bay Station Sampled by USFWS

MLK Shoreline Location

Collection of additional parameters Aimed at better understanding mechanisms for spatial variation in bioavailable Hg GIS spatial parameters Sediment parameters

GIS spatial parameters Parameter TypeHypothesized mechanism of influence Water residence timeWater dilution and replacement and sediment advective transport may cause net loss of Hg or MeHg, and redox conditions Distance to nearest POTW and nearest storm drain discharge Loading of Hg and MeHg, as well as nutrients, fine particulates, influencing methylation potential Number of storm drains feeding into inlet (for urban stormwater outfall sites) As above. Distance to creeks and tributariesAs above. Also, movement of fish upstream to conditions favoring methylation. LatitudeLonger residence time in South Bay favoring reduced conditions and consequent methylation. Average depth near siteHigh biotic activity and repeated wetting and drying at shallow sites favoring bacterial methylation activity. Abundance of intertidal mudflat near site As above. Nearby Land Cover/Land UsesMultiple potential mechanisms

Sediment parameters Sediment parameters: redox, TON, grain size, total and methyl Hg Duplicate sediment samples at subset of 20 stations

Questions for the Workgroup Is the general approach appropriate? –Indicators selected –Allocation of effort to spatial vs. interannual vs. monthly vs. tool comparison Spatial survey design –Hypothesis testing approach –Sampling sites (wetlands, POTWs) Trend sampling –Annual sampling sites –Monthly sampling sites Additional parameters –Sediment parameters

Annual monitoring of trend stations

Station effect