2010 BIOSENTINEL MERCURY MONITORINGIN THE NORTH BAY SALT PONDS

Darell Slotton Shaun AyersDepartment of Environmental Science and PolicyUniversity of California, Davis Letitia Grenier

Ben GreenfieldSan Francisco Estuary Institute

Feedback Tool for Watershed Management

Using small, young fish as localized, time-sensitive, fish based measures of methylmercury exposure

Biosentinel Mercury Monitoring

• Year-to-year trends and variability

• Within-year seasonal trends

• Spatial patterns to a local scale

• Performance measures forrestoration 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 6 ‘intensive’

seasonal sites: Dec/Mar/May/Jul

Kennedy Park

Pond 9/10

Pond 4/5

Pond 2A

Pond 2

Pond 1

Additional one-time sites: July

PetalumaMarsh

Hamilton

Wingo P 7

6A

Pre-Cullinan

Wash ponds

Multiple Individual Fish Analyses (n = 30)

• Within pre-defined size ranges with consistent Hg

• Strong statistical power

• Detailed individual information

Mean Hg±

95% C.I.

45 ± 2ng/g

0

20

40

60

80

100

120

140

30 35 40 45 50 55 60 65 70 75 80 85 90Individual silverside total length (mm)

Hg

(ng/

g w

et w

t, w

hole

bod

y)

Oct 6: 44 ± 4

Suisun Marsh Managed Seasonal Flooding:Suisun Slough North, October through February

Discharge from seasonally flooded,

managed ponds

0

20

40

60

80

100

120

140

30 35 40 45 50 55 60 65 70 75 80 85 90Individual silverside total length (mm)

Hg

(ng/

g w

et w

t, w

hole

bod

y)

Oct 18: 43 ± 3Oct 6: 44 ± 4

0

20

40

60

80

100

120

140

30 35 40 45 50 55 60 65 70 75 80 85 90Individual silverside total length (mm)

Hg

(ng/

g w

et w

t, w

hole

bod

y)

Dec 21: 75 ± 5

Oct 6: 44 ± 4Oct 18: 43 ± 3

0

20

40

60

80

100

120

140

30 35 40 45 50 55 60 65 70 75 80 85 90Individual silverside total length (mm)

Hg

(ng/

g w

et w

t, w

hole

bod

y)

Feb 7: 100 ± 5

Oct 6: 44 ± 4Oct 18: 43 ± 3

Dec 21: 75 ± 5

Sacra-mentoRiver

San Joaquin River

Merced

Tuolumne

ClearCreek

Ham-iltonCity

Cache Ck

Mud Slough Region

LowerSacramentoSeries

Vernalis

UC Davis BiosentinelMonitoring Region:2005-2007 CBDA Fish Mercury Project

• Over 3,000 individualsmall fish analyses/yr

• High precision, high cost

1 Comp40-50 mm

1 Comp50-60 mm

1 Comp60-70 mm

1 Comp70-80 mm

SFEI Compositing Approach:• 4 composites, 4 analyses (vs 30)• 5 fish per composite• 10 mm size increments

• less precise statistics• large cost saving on analytical

SFEI’s 2008-2010 RMPSmall Fish Program

Fixed, long-term sites

Potential source sites(urban, mines, POTWs)

Additional 1-time sites(12 wetland, 12 bay)

Silverside

Topsmelt

Composites(4 comps x 5 fish)

1 Comp45-50 mm

1 Comp50-55 mm

1 Comp55-60 mm

1 Comp60-65 mm

1 Comp65-70 mm

1 Comp70-75 mm

Hybrid/Compromise Plan:• 6 composites (vs 4)• 8 fish per composite (vs 5)• Narrower size range (45-75 mm vs 40-80 mm)

2010 Seasonal Silverside Mercury

KennedyPark

Pond 9/10

Pond 4/5

Pond2A

Pond 2

Pond 1

Dec-2009

Mar-2010

May

Jul

71

66

72

13875

75

68

63

54

186

83

57

8596

59

41

5446

44

78

79

55

94

46

PetalumaMarsh Wing

o

P 7Wash ponds

29

6568

63

Other species data from siteswithout silversides (July samplings)

Hamilton

Pond 7

Pond 6A

Pre-Cullinan

Silverside

Topsmelt

Killifish

Stickleback

59

24

88

16

44

5324

50

49

42

29juv. Striped Bass

North Bay Silverside Mercury Trend, Fall 2005 , Fall 2006 Dec-2009

Pond 2

Silverside Fall 2005 Mercury Spatial Distribution:Entire CBDA Range With Silversides

Pond 2

Means of Comps ± SE

Spatial patterns

Silverside

Pond 2

North Bay 2005-2006 Seasonal Silverside Mercury Trend, Oct, Feb, May, Jul, Sep, Nov

FromPond 2?

Interim Conclusions from 2010 WorkIt is possible to use small fish as biosentinels of methylmercury exposure in this region, spatially and seasonally.

Significant changes in exposure can occur both seasonally and between sites.

The lower cost, hybrid compositing approach can provide a reasonable alternative when funding is limited.

Different sites can show different patterns.