Spatial and temporal patterns in food web accumulation of Hg

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Spatial and temporal patterns in food web
accumulation of Hg

• Project Update
• RMP Technical Review Committee March 18, 2008

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Workplan Specific questions to address

• Where is mercury entering the Bay food web?
• What habitats, conditions, or factors help to
  identify hotspots of food web accumulation in Bay
  margins?
• Are there interannual trends in MeHg
  bioaccumulation resulting from wetland and margin
  restoration activities?
• What are the best biomonitoring tools for
  characterizing hotspots of MeHg bioaccumulation?

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General approach

• Spatial analysis
• Stratified random design
• Identify hotspots based on conceptual model
• Seasonal trend evaluation
• Interannual trend detection
• Field sampling for Hg isotopes and for DGT study

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Allocation of effort

• Total of 70 sampling events per year to evaluate
  spatial, seasonal, and interannual patterns

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Spatial survey

• Test hypotheses of MeHg entry points and food web
  accumulation hotspots
• Hg source sites
• Wetlands and wetland type
• Enclosed subembayments and estuarine creeks
• Sediment parameters

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Spatial survey design - hypothesis testing
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Spatial survey sites chosen probabilistically

• Same GRTS method as Status and Trends Program
• More powerful inference than with sites of
  convenience
• What types of conditions Bay-wide higher
  Hg
• Identify spatial gradients (e.g., South/North?)
• Even if all our hypotheses are wrong, we are
  still characterizing conditions and identifying
  hotspots Bay-wide

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So What Are the Areas Sampled?

• Entire shoreline of Bay
• Lower South Bay to Suisun Bay
• Estuarine tributaries
• All subtidal wetlands
• Not sampling
• Offshore locations
• Salt ponds (weak connection to Bay)
• Marine lakes (e.g., Aquatic Park, Anza Lagoon)
• Islands within Bay (e.g., Angel Island, Red Rock)

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How separating different site types?
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Preliminary map of areas to be sampled

• GIS based on morphology, size, depth
• Strata 1
• Open Shorelines
• -Strata 2
• Submbayments

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Identifying Hg source areas
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Source site selection

• Mining sources
• Creeks draining La Joya, Bella Oaks, Borges, and
  New Almaden Mines
• POTW discharges
• 11 shallow-water wastewater treatment plants
  recommended by RB NPDES Permitting Staff
• Creeks draining urban/industrial areas
• Identified for part of Bay by Prop 13 Stormwater
  BMP project
• Based on historic industrial area and railway
  lines, auto recycling facilities, and Hg hotspots
• Industrial areas with high sediment THg
• BPTCP sites having sediment THg gt 0.7 ppm
• Total of about 50 sites

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Wetland site selection
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Wetland site selection

• Oversight by Josh Collins and Letitia Grenier
• Based on GRTS sampling performed for SBMP and
  CRAM
• Stratified based on relative wetland elevation
  and age

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Coordination and Collaboration

• University of Michigan RMP Hg stable isotope
  study (Joel Blum, Gretchen Gehrke)
• Hg isotope sites characterize specific sources
• Urban runoff, mining, waste water, atmospheric
  deposition
• Sites will be chosen from small fish source sites
  after probabilistic site selection is complete
• Augment with small number additional sites (e.g.,
  Guadalupe Reservoir to represent mine signal)
• Sediment Hg and isotope analysis

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Coordination and Collaboration

• Trent University Diffusive Gradient in Thinfilm
  devices (Holger Hintelmann)
• Just completing analyses of the pilot study data
  (2007)
• Year 1 - validation
• 15 small fish sites varying in chemistry and
  expected bioaccumulation
• Likely overlap with mercury isotope sites
• Year 2 process studies
• Source sites of interest including fishless
  locations
• Likely include SPL sites (e.g., Z4LA)
• Report available February 2010
• Addition of water column DOC as correlate

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Discussion points

• Other suggested source sites?
• Agree with area and types of sites covered?
• Entire shoreline of Bay
• Lower South Bay to Suisun Bay
• Estuarine tributaries
• All subtidal wetlands
• Not salt ponds, marine lakes, offshore, or small
  islands
• Phased plan for DGT study

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END OF TALK

• REST IS ANCILLARY MATERIAL IN EVENT OF DISCUSSION

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Sediment MeHg may be correlated with topsmelt Hg

• Topsmelt 2006 data
• RMP and Calfed
• sediment data within 1.5 km disk of fish
• R2 0.61

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Trend analysis a multiple station BACI design
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Trend Sampling Locations
Hamilton
Benicia Park
China Camp
Control
Point Isabel
Impact (Restoration)
Oakland Middle Harbor
Candlestick Point
Eden Landing
Bird Island/ Steinberger Slough
Newark Slough
Alviso Slough
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Trend Sampling Locations
Hamilton
Benicia Park
China Camp
Control
Point Isabel
Impact (Restoration)
Oakland Middle Harbor
Candlestick Point
Eden Landing
Bird Island/ Steinberger Slough
Newark Slough
Alviso Slough
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Monthly sampling locations
Additional North Bay Station Sampled by USFWS
Martin Luther King Shoreline
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MLK Shoreline Location
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Collection of additional parameters

• Aimed at better understanding mechanisms for
  spatial variation in bioavailable Hg
• GIS spatial parameters
• Sediment parameters

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Sediment parameters

• Sediment parameters redox, TON, grain size,
  total and methyl Hg
• Samples at subset of 20 Sites

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Sediment MeHg lt 1 ng/g 1 2 ng/g
gt 2 ng/g
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Annual monitoring of trend stations
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