2010 BIOSENTINEL MERCURY MONITORING
IN THE NORTH BAY SALT PONDS
Feedback Tool
for Watershed
Management
Darell Slotton
Shaun Ayers
Department of Environmental Science and Policy
University of California, Davis
Letitia Grenier
Ben Greenfield
San Francisco Estuary Institute
Biosentinel Mercury Monitoring
Using small, young fish as
localized, time-sensitive,
fish based measures of
methylmercury exposure
• Spatial patterns to a local scale
• Year-to-year trends and variability
• Within-year seasonal trends
• Performance measures for
restoration and remediation
UC Davis Delta Silverside Hg
• Established clear, regional pattern:
elevated periphery, lower central
• Silversides ideal biosentinels:
widespread; relatively site-specific
North Bay UC Davis / SFEI
2010 Mercury Biosentinel Monitoring
• Dec-2009 – Sep-2010
• 30 samplings total
Kennedy Park
6 ‘intensive’
seasonal sites:
Petaluma
Marsh
Dec/Mar/May/Jul
Wing
o
Additional
one-time
sites: July
P7
Pond 2 6A
Pond 4/5
Pond 2A
Pond 1
Hamilton
Pond 9/10
Wash ponds
PreCullinan
Multiple Individual Fish Analyses (n = 30)
• Within pre-defined size ranges with consistent Hg
Mean Hg
±
95% C.I.
45 ± 2
ng/g
• Strong statistical power
• Detailed individual information
Suisun Marsh Managed Seasonal Flooding:
Suisun Slough North, October through February
Hg (ng/g wet wt, whole body)
140
120
Feb 7: 100 ± 5
100
80
Dec 21: 75 ± 5
60
Oct 18: 43 ± 3
Oct 6: 44 ± 4
40
20
0
30
35
40
45
50
55
60
65
70
75
Individual silverside total length (mm)
Discharge from
seasonally flooded,
managed ponds
80
85
90
UC Davis Biosentinel
Monitoring Region:
2005-2007 CBDA
Fish Mercury Project
• Over 3,000 individual
small fish analyses/yr
Clear
Creek
Hamilton
City
Sacramento
River
Cache
Ck
Lower
Sacramento
Series
• High precision, high cost
Vernalis
Tuolumne
San
Joaquin
River
Merced
Mud Slough
Region
SFEI Compositing Approach:
• 4 composites, 4 analyses (vs 30)
• 5 fish per composite
• 10 mm size increments
1 Comp
40-50 mm
1 Comp
50-60 mm
1 Comp
60-70 mm
1 Comp
70-80 mm
• less precise statistics
• large cost saving on analytical
SFEI’s 2008-2010 RMP
Small Fish Program
Fixed, long-term sites
Silverside
Topsmelt
Composites
(4 comps x 5 fish)
Potential source sites
(urban, mines, POTWs)
Additional 1-time sites
(12 wetland, 12 bay)
Hybrid/Compromise Plan:
• 6 composites (vs 4)
• 8 fish per composite (vs 5)
• Narrower size range (45-75 mm vs 40-80 mm)
1 Comp
45-50 mm
1 Comp
50-55 mm
1 Comp
55-60 mm
1 Comp
60-65 mm
1 Comp
65-70 mm
1 Comp
70-75 mm
2010 Seasonal Silverside Mercury
94
75
46
57
186
63
Kennedy
Park
138
65
Petaluma
Marsh
Wing
o85 96
78
29
44
55
Pond 9/10
Wash ponds
72
54
46
54
P7
68
Jul
79
68
71
Dec2009
Mar2010
May
75
83
Pond 2
Pond 4/5
66
Pond 1
63
Pond
2A
59
41
Other species data from sites
without silversides (July samplings)
Stickleback
Topsmelt
Killifish
juv. Striped Bass
5
3
2
164
Silverside
Pond 7
24
Pond 6A
29
59
50
42
PreCullinan
88
44
Hamilton
49
North Bay
Silverside Mercury Trend,
Fall 2005 , Fall 2006
Pond 2
Dec-2009
Silverside Fall 2005 Mercury Spatial Distribution:
Entire CBDA Range With Silversides
Pond 2
Spatial patterns
Pond 2
Means of
Comps ± SE
Silverside
North Bay 2005-2006 Seasonal
Silverside Mercury Trend,
Oct, Feb, May, Jul, Sep, Nov
From
Pond 2?
Interim Conclusions from 2010 Work
It is possible to use small fish as biosentinels of methylmercury
exposure in this region, spatially and seasonally.
The lower cost, hybrid compositing approach can provide a
reasonable alternative when funding is limited.
Significant changes in exposure can occur
both seasonally and between sites.
Different sites can show different patterns.