spatial and temporal patterns in food web accumulation of hg san francisco mercury coordination...
TRANSCRIPT
Spatial and temporal patterns in food web accumulation of Hg
San Francisco Mercury Coordination MeetingFebruary 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
Total Length (mm)
0 20 40 60 80 100 120
Hg
(g/
g w
et)
0.01
0.1 ARROW GOBYCHEEKSPOT GOBYMISSISSIPPI SILVERSIDESHIMOFURI GOBYTOPSMELTYELLOWFIN GOBYBAY GOBYSTRIPED BASSNORTHERN ANCHOVYPACIFIC HERRING
0.4
0.003
Spatial patterns: Bay margins vs. open waters
Total Length (mm)
0 20 40 60 80 100 120
Hg
(g/
g w
et)
0.01
0.1 ARROW GOBYCHEEKSPOT GOBYMISSISSIPPI SILVERSIDESHIMOFURI GOBYTOPSMELTYELLOWFIN GOBYBAY GOBYSTRIPED BASSNORTHERN ANCHOVYPACIFIC HERRING
0.4
0.003
Wetlands/margins
Open waters
Spatial patterns: Organized by species habits
0 20Miles
Mississippi silverside 2005
Hg
(ug/
g w
et)
0.05
0.1
0.15
0.2
Hg
wet
weig
ht
(g
/g)
Mississippi Silverside 2006
0 20Miles
Hg
(ug/
g w
et)
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
• 2005 elevated in southern stations (significant)
2006 elevated in Pt. 2006 elevated in Pt. Isabel (significant)Isabel (significant)
Spatial patterns: Regional patterns across Bay
Spatial patterns including salt pond data
Includes data provided by C. Eagles-Smith and J. Ackerman
0 20Miles
Topsmelt 2005
Hg
(ug/
g w
et)
0.028
0.03
0.032
0.034
0.036
0.038
0.04
0.042
0.044
0.046
0.048
Topsmelt 2006
0 20Miles
Hg
(ug/
g w
et)
0.025
0.03
0.035
0.04
0.045
0.05
0.055
• 2005 elevated in southern stations (not significant)
2006 elevated in 2006 elevated in southern stations, southern stations, Pt. Isabel, and Pt. Isabel, and Richardson Bay Richardson Bay (significant)(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
0.5 1.0 1.5 2.0 2.53.03.5
MeHg in sediment (ng/g)
0.02
0.03
0.04
0.05
0.06
0.070.08
Hg
in f
ish
(u
g/g
)
•Topsmelt 2006 data
•RMP and Calfed sediment data within 1.5 km disk of fish
•R2 = 0.61
-122.6 -122.3 -122.0 -121.7Longitude
37.4
37.5
37.6
37.7
37.8
37.9
38.0
38.1
38.2La
titud
e
-3-2-1012
LOGMEHG
0.00.51.01.52.02.5
MEHG_HIGH1
Sediment MeHg: < 1 ng/g 1 – 2 ng/g > 2 ng/g
Sediment MeHg higher in shallow/nearshore sites
MeHg Hotspots in SedimentSediment MeHg Hotspots
0.2 0.4 0.6 0.8 1.0Proportion Land Within 2 KM Buffer
1000
2000
3000
40005000600070008000
Dis
tanc
e F
rom
Nea
r est
Sho
reli n
e (m
)
10
HIGHMEHG
Concentrations highest closeto shoreline and surrounded by land
< 2 ng/g> 2 ng/g
Hypothesis: Importance of enclosed areas like Pt. Isabel and Richardson Bay
Temporal Patterns
ALVSL
BENPK
CHINA
EDENL
NEWSL
STATION
0.0
0.1
0.2
0.3H
GW
W
20062005
YEAR
•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
ALVSL
BIRDI
EDENL
NEWSL
OMHEA
STATION
0.02
0.03
0.04
0.05
0.06
0.07
0.08H
GW
W
20062005
YEAR
•Station effect•Year effect•Similar to Slotton et al.
2006 higher than 2005!
Topsmelt
Relative importance of station vs. year effect
Species Station R2 Year R2Station/Year
Topsmelt 0.30 0.43 0.7Mississippi Silverside 0.58 0.05 11.6
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 HarroldAroon MelwaniJohn OramCarrie AustinMax DelaneyFred HetzelRichard LookerApril RobinsonMeg SedlakSF Bay National Wildlife RefugeUSFWS StocktonUSGS BRDCalifornia State ParksCA Department Fish & GameInteragency Ecological Program
Collaboration/Data Sharing…Andy JahnMark SandheinrichKristen CayceCollin Eagles-SmithJosh AckermanWes HeimSF Bay Regional Board
SUPPORTING INFORMATION:
Spatial survey• Targeting 40 locations
• Multiple interrelated factorsA. 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 Cover N Bay S Bay
Wetlands 5 sites 5 sites
Urban outfall 5 sites 5 sites
POTW into slough/marsh 5 sites 5 sites
Control (upland, residential, no discharges)
5 sites 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 fishBrine fliesSong sparrows
TopsmeltSilversides
Trend analysis – a multiple station BACI design
0
0.05
0.1
0.15
0.2
0.25
0.3
1 2 3 4 5 6 7 8 9
Year
Mer
cury
Con
cent
ratio
ns Control 1
Impact 1
Control 2
Impact 2
Control 3
Impact 3
Control 4
Impact 4
Trend Sampling Locations
Alviso Slough
Newark Slough
Bird Island/Steinberger Slough
Eden Landing
China Camp
Benicia Park
Control
Impact (Restoration)Point Isabel
CandlestickPoint
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
CandlestickPoint
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 parametersParameter Type Hypothesized mechanism of influence
Water residence time Water 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 tributaries As above. Also, movement of fish upstream to conditions favoring methylation.
Latitude Longer residence time in South Bay favoring reduced conditions and consequent methylation.
Average depth near site High 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 Uses Multiple 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
0.5 1.0 1.5 2.0 2.53.03.5
SEDIMENT
0.02
0.03
0.04
0.05
0.06
0.070.08
FIS
H
SQ
Pt Isabel
Tiburon
Alviso
Newark
Oakland Harb
Treasure Isl
China Camp
Least Squares Means
ALVSL
BENPKCHIN
A
EDENL
NEWSL
STATION
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
LOG
HG
DW
Station effect