Title: Mercury Risk to Avian Reproduction in San Francisco Bay: Implications for TMDL Implementation
1Mercury Risk to Avian Reproduction in San
Francisco Bay Implications for TMDL
Implementation
- Collin Eagles-Smith, Josh Ackerman, Terry
Adelsbach, John Takekawa, Keith Miles, Steve
Schwarzbach, and Tom Suchanek
U. S. Fish and Wildlife Service, Environmental
Contaminants Division U. S. Geological Survey,
Western Ecological Research Center
2Mercury in San Francisco Bay-Delta Birds Trophic
Pathways, Bioaccumulation, and Ecotoxicological
Risk to Avian Reproduction
Hg
3San Francisco Bay Estuary HEMISPHERIC IMPORTANCE
FOR WATERBIRDS
4Wildlife Sensitive to Methyl Mercury Toxicity
- Central nervous system effects
- Altered behavior
- Impaired vision, hearing, and motor skills
- Endocrine effects
- Reduced breeding effort
- Embryo death
- Embryo deformities
- Chick death
Forsters Tern Nest
MeHg Reduces Reproductive Success
5Bird Mercury Questions
- Mercury differences among species.
- Spatial and temporal trends in bird and egg
mercury. - Relate mercury concentrations to reproductive
risk. - Fish as wildlife indicators?
- Implications for TMDL implementation.
6Species Studied
- Littoral Foragers insects crustaceans
- American avocet
- Black-necked stilt
- Obligate Piscivores - fish
- Forsters tern
- Caspian tern
7Study Sites
North Bay
- 3 regions
- North Bay (Napa-Sonoma Marsh)
- Central Bay (Eden Landing, Newark)
- South Bay (Don Edwards SFB NWR)
Central Bay
South Bay
8Methods
- Mercury Analyzed at USGS Davis Field Station
Mercury Lab
9Methods Continued
- Prey fish collected
- Telemetry based
10Birds Captured
Total Captures 668
11Bird Mercury Concentrations
1. Mercury differed among species
P 2. Mercury concentrations differed among
regions
P 3. Mercury concentrations increased over time
Forsters tern
10
Blood Hg (ppm ww)
1
0.1
4/10
5/20
5/30
4/1
4/30
5/10
4/20
Date
12Forsters Tern
Male Hg Female Hg (P 0.003)
Breeding Pre-breeding (P Female
Pre-breed
Male
Breed
10
Blood Hg (ppm ww)
1
0.1
North Bay
Central Bay
South Bay
North Bay Central Bay
13What Does this Mean for Birds?Risk Factor
Analysis
Based on Evers et al. 2004 (common loon) Heinz
and Hoffman 2003 (mallard)
Hg Concentration (ppm)
Impact
Risk Category
Blood (ww)
Eggs (dw)
Undocumented Minimal Effects
Low
Potential Effects Reduced Egg
Hatchability
13
Moderate
3.26.8
Documented Effects Molecular, Cellular,
Behavioral, Potential Population Effects
34
High
6.88
Documented Effects at Population Level
4
Extra High
8
14Forsters Tern
Risk Category
Female
Pre-breed
Male
Breed
10
Extra high
High
Moderate
Blood Hg (ppm ww)
1
Low
0.1
North Bay
Central Bay
South Bay
15Stilt
Risk Category
10
Female,
pre-breeding
Male,
pre-breeding
Extra high
Female,
breeding
High
Moderate
Blood Hg (ppm ww)
1
Low
0.1
North Bay
Central Bay
South Bay
16Percent of Population at Risk Site Specific
Risk Factor High Extra High
0
Avocet
2
Stilt
North Bay
4
Caspian tern
29
Forsters tern
0
Avocet
Stilt
Central Bay
0
Forsters tern
0
Avocet
1
Stilt
22
South Bay
Caspian tern
10
27
Forsters tern
17Percent of Population at Risk Breeding Birds Only
Risk Factor High Extra High
6
5
10
58
18Mercury in Eggs
Avocets Stilts Forsters Terns
Risk Category
Extra High
High
Moderate
Low
19Percent of Population at Risk All Eggs
Risk Factor High Extra High
0
10
46
Percent of Population at Risk
20Management Regulatory Implications
- Differences in space and habitat use
- Differences in diet
- Differences in prey Hg
Differences in mercury exposure
21Telemetry Map Stilts 2005
South
22Telemetry Map Avocets 2005
South
23Telemetry Map Forsters Terns 2005
South
24Forsters Tern Diet by Colony-Estimated from
colony returns-
25Forsters Tern Diet by Colony-Estimated from
colony returns-
26Prey Fish Hg Concentrations
Pond A7
Pond A8
Pond A16
North Bay
27Fish vs. Egg Mercury Relationships
28Fish vs. Egg Mercury Relationships
3
3
3
3
)
)
)
)
ww
ww
ww
ww
ppm
ppm
ppm
ppm
2
2
2
2
Colony Egg Mercury (
Colony Egg Mercury (
Colony Egg Mercury (
Colony Egg Mercury (
1
1
1
1
R2 0.07 P 0.57
R2 0.04 P 0.65
0
0
0
0
0
0.1
0
0.1
0
0
0.2
0.3
0.2
0.3
0.1
0.2
0.1
0.2
Silverside Mercury (
ppm
ww
)
Silverside Mercury (
ppm
ww
)
Mudsucker
Mercury (
ppm
ww
)
Mudsucker
Mercury (
ppm
ww
)
3
3
)
)
ww
ww
ppm
ppm
2
2
Colony Egg Mercury (
Colony Egg Mercury (
1
1
R2 0.19 P 0.33
R2 0.10 P 0.31
0
0
0
0.1
0.2
0
0.1
0.2
Stickleback Mercury
(ppm ww)
Goby Mercury
(ppm ww)
29Diet-weighted Fish vs. Egg Mercury Spatially
Explicit
3.5
3.0
2.5
2.0
Colony Egg Mercury (ppm ww)
1.5
1.0
0.5
0.0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Diet-weighted Fish Mercury (ppm ww)
30Diet-weighted Fish vs. Egg Mercury Spatially
Explicit
3.5
- Need to know bird space use
- Need to know bird-specific diet
- Need to know bird prey Hg concentrations
R2 0.68 P 0.01
3.0
2.5
2.0
Colony Egg Mercury (ppm ww)
1.5
1.0
0.5
0.0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Diet-weighted Fish Mercury (ppm ww)
31Diet-weighted Fish vs. Egg Mercury TMDL
implications
3.5
- Wildlife target exceeds LOAEL
- Is wildlife target
- non-protective?
- Does LOAEL need refinement?
- OR
- Are fish inadequate indicators of avian risk?
R2 0.68 P 0.01
3.0
2.5
2.0
Colony Egg Mercury (ppm ww)
1.5
1.0
Avian egg LOAEL
0.5
0.0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Diet-weighted Fish Mercury (ppm ww)
TMDL Wildlife Target
32Eggs as indicators of wildlife risk
Fail-to-Hatch
Trophic Transfer
Maternal Transfer
Hatch
Survive
Mortality (
33Eggs as indicators of wildlife risk
Fail-to-Hatch
Trophic Transfer
Maternal Transfer
Hatch
Mortality (Survive
34Conclusions
- Birds show high site fidelity
- Birds are good bioindicators of Hg at small
spatial and temporal scales - Birds useful for Hg monitoring
35ConclusionsCurrent mercury levels are above
toxic thresholds
- In breeding birds
- Especially Forsters terns and potentially other
fish-eating birds - In eggs
- Especially Stilts and Forsters terns
36Conclusions
- Individual fish species do not adequately
represent wildlife exposure. -
- Spatially explicit data on bird habitat use, diet
and prey mercury to predict exposure. - Eggs are valuable tools for monitoring mercury in
Bay-Delta wildlife.
37Acknowledgements
- CALFED Ecosystem Restoration Program
- Carol Atkins and Donna Podger
- Logistical Support
- Don Edwards SF Bay NWR (USFWS) Clyde Morris, Joy
Albertson, Mendel Stewart, Joelle Buffa, Eric
Mruz - Eden Landing Ecological Reserve John Krause
- Napa/Sonoma Marsh Wildlife Area Tom Huffman,
Larry Wyckoff, Carl Wilcox, Karen Taylor - Bird Mercury Project Principles
- USGS Steve Schwarzbach, Tom Suchanek, John
Takekawa, A. Keith Miles, Susan De La Cruz - US FWS Tom Maurer, Dan Welsh
- SFBBO Cheryl Strong, Janet Hansen
- PRBO Conservation Science Nils Warnock, Mark
Herzog - Field Support
- Jill Bluso, Scott Demers, Sarah Stoner-Duncan,
Angela Rex, John Henderson, Joe Northrup, Brooke
Hill, Kristen Dybala, Eli French, Ross Wilming,
Lindsay Dembosz, Cathy Johnson, Lani Stinson,
Kevin Aceituno Emily Eppinger, Mychal Truwe,
River Gates, Mali Nakhai, - Lab Support
- Robin Keister, Sarah Spring, Liz Bowen