Mercury in Biosentinel Fish in San Francisco Bay

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Mercury in Biosentinel Fish in San Francisco Bay

• Ben Greenfield1, Andrew Jahn2,
• Letitia Grenier1, Mark Sandheinrich3
• 1. San Francisco Estuary Institute, Oakland, CA
• 2. 1000 Riverside Drive, Ukiah, CA
• 3. River Studies Center, University of Wisconsin
  La Crosse

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Key Management Questions

• Assessment of ecological risk to fish and
  wildlife
• Spatial and temporal mercury trends in the
  Estuary
• Is risk of mercury exposure spatially variable,
  and are these risks predictable?
• What are trends in bioaccumulation of Hg vs.
  wetland restoration and TMDL activities
• Building upon conceptual models of Hg exposure

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Sampling Design

• Multiple sites in San Francisco Bay margins
• Wetland restorations vs. extant marshes
• Benthic and pelagic species
• Topsmelt, Mississippi (inland) silversides
• Arrow and cheekspot goby
• Additional collection in Bay shoals and channels
• Bay goby, herring, anchovy (IEP Bay Study)
• Partnering with USFWS performing individual
  analyses on 4 southernmost stations

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Compositing Design

• 5-10 individuals per composite
• 4 composites per species per site to allow
  statistical comparison
• Used size limits to reduce influence of any
  lengthHg relationships

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Primary Sampling Locations
Benicia Park
China Camp
Extant Marsh
Point Isabel
Restoration Area
Oakland Middle Harbor
Candlestick Point
Eden Landing
Bird Island/ Steinberger Slough
Newark Slough
Alviso Slough
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Opportunistic Locations
USFWS Survey
IEP Bay Study
Primary Location
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Preliminary Results

• Results from 97 samples in 2005 and preliminary
  results from 114 samples in 2006
• 17 seining locations and 9 trawling locations
  (IEP)
• 10 Species

Inland silversides Animal Diversity Web
Image by Mami Odaya, SFEI
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Patterns among pelagic species
Hg wet weight (?g/g)
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Patterns among pelagic species
Effects threshold for fish (Beckvar et al. 2003)
Hg wet weight (?g/g)
TMDL Target for prey fish to protect piscivorous
wildlife
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Patterns among benthic species
Hg wet weight (?g/g)
TMDL Target
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Conceptual model

• Variation among species
• Mississippi Silverside gt Topsmelt and wetland
  gobies gt Bay Goby
• Spatial patterns
• Alviso Slough elevated in cheekspot goby
• South Bay elevated in silversides

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Why were arrow and cheekspot gobies higher in
2006?
Hg wet weight (?g/g)
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Broader size range in 2006
Arrow goby
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Broader size range in 2006
Cheekspot goby
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Comparison to fish/wildliferisk thresholds
Tissue concentration dry weight
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Spatial Patterns
USFWS Survey 06
(Topsmelt)
Primary
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• 2005 cheekspot goby significantly elevated in
  Alviso Slough

Letters indicate results of ANOVA followed by
Student-Newman-Keuls test
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• 2006 arrow goby elevated in southern stations

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Hg wet weight (?g/g)

• 2005 silverside significantly elevated in
  southern stations

• 2006 silverside elevated in Point Isabel

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• Mississippi silverside 2005
• Combine FMP and RMP data from 2005
• Results indicate relatively high concentrations
  in South Bay fish

Unpublished data provided by Darell Slotton
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• 2005 topsmelt elevated in southern stations (not
  significant)

• 2006 elevated in southern stations, Pt. Isabel,
  and Tiburon

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• Why are concentrations often elevated in southern
  stations and Pt. Isabel?

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• Southern stations
• RMP data indicate higher sediment MeHg in
  southern stations
• High sediment MeHg in Tiburon

Source RMP
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Point Isabel

• Enclosed wetland with long drainage canal
• Recall conceptual model wetland methylation
• Urban dump with disposal of car batteries and
  other metal waste

Source Google Earth
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Steinberger Slough/Bird Island
Source Google Earth
Source Google Earth
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Point Isabel Pilot Project collaboration with
Regional Board
Sediment Hg and MeHg Sediment, fish and water

• Is the Point Isabel effect localized to within
  the wetland or representative of this portion of
  the Bay?
• Help distinguish wetland effect from other
  factors (conceptual model)

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Results Summary

• Some samples above TMDL risk threshold for
  wildlife risk
• Variation among species related to conceptual
  model
• Mississippi silverside gt topsmelt, anchovy,
  herring
• Arrow and cheekspot goby gt Bay goby
• Spatial patterns
• Southern locations higher trend
• Pt. Isabel interior wetland

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Whats the big picture?

• Variable wildlife risk as a function of target
  prey and habitat
• Conceptual model different exposure in Bay
  margins vs. open-water areas
• Are there more Point Isabels throughout the
  Bay?
• What drives spatial variation?
• Sources (e.g., historic Hg mining in South Bay
  watershed)
• Net Methyl Hg production in sediments (many
  drivers may vary sulfur, reducing bacteria,
  salinity, water retention time)

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Plans for 2007 and beyond

• Same general sampling design funded through 2008
  begin trends analysis
• Organics analyses in 6 composite samples
• PCBs, PBDEs, legacy pesticides
• Pt. Isabel pilot study
• In 2008, change in contract lab may be required
  will result in 10,000 cost increase or require
  much smaller sample sizes

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Thanks to April Robinson Aroon Melwani John
Oram Rick Wilder Steve Slater Carrie
Austin Collin Eagles-Smith Darell Slotten Max
Delaney Fred Hetzel Meg Sedlak Mami Odaya Arthur
Fong SF Bay National Wildlife Refuge USFWS
Stockton USGS BRD California State Parks CA
Department Fish Game Interagency Ecological
Program
Image by Mami Odaya, SFEI
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Lab cost increase

• Current lab (70/sample) having staffing issues
• Going rate for contract lab is 140/sample (can
  solicit more bids)
• To continue at current level (128 analyses/yr)
  would increase lab budget from 10,000 to 18,500
• Could reduce sample size
• Hesitant to reduce labor budget since it is final
  year of 4 year project will want to publish
  results

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Topsmelt also no obvious difference between
years
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External Coordination

• This project Margins of South, Central, and
  North Bay
• Fish Mercury Project Central Valley, Delta, and
  North Bay more freshwater focus
• South Bay Salt Pond Hg Project Marshes, ponds,
  and sloughs
• CBDA Bird Hg Project Avian forage fish
• Petaluma Hg Project Marsh fish in Petaluma
• Produce comparable data sets by sampling same
  species

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Fish vs. Sediments
South Bay
San Pablo Bay
Hg wet weight (?g/g)
Silversides 2005 Sediment
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Small Fish Hg Project
3
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Topsmelt 2005
Mississippi Silverside 2005
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• Bay goby
• Spatial pattern confounded by fish size
• Try to limit size range

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• Cheekspot goby

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Striped bass Hg concentrations in SF Estuary
over time
For more information on sport fish monitoring,
see poster 27
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Small Fish Hg Project

• Background
• Mercury (Hg) in N. California waters a
  longstanding management concern due to historic
  mining
• Elevated concentrations in sport fish
• San Francisco Estuary site of extensive wetland
  restoration activity
• Sensitive wildlife in region

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Why Small Fish?

• Most sport fish over health advisory threshold
  (0.3 ppm)
• TMDL has small fish targets but there are limited
  data from Bay
• Contaminant pathway to sport fish poorly known
• Effect of extensive wetland restoration

Hg, ppm wet wt.
2.0
0.2
Jacksmelt
Ca. halibut
Shiner perch
Wt. sturgeon
Wt. croaker
Striped bass
Leopard shark
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Regional Monitoring Program Small Fish Project
Goals

• Monitor food-web mercury at fine spatial and
  temporal scales
• Assess regional trends in bioaccumulation of Hg
  related to wetland restoration
• Develop conceptual model of Hg availability to
  prey fishes
• Collect prey fish appropriate for wildlife risk
  evaluations