U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION 9, WATER DIVISION

Supplemental Information: 

Selenium in the San Francisco

Bay and Delta

Comparison of the Proposed Selenium Water Quality 

Criteria to Dissolved and Particulate Selenium in 

Seaward and Landward Transects and the Proposed 

Selenium Tissue Criteria to Selenium in Sturgeon and 

Clam Tissues

DANIEL R. OROS and DIANE FLECK

June 8, 2016

Available data on dissolved and particulate selenium (Se) concentrations in water column 

samples of seaward and landward transects and Se in sturgeon and clam tissues in the San 

Francisco Bay and Delta were analyzed. Figures 1-4 show the Se concentrations and the 

percent of water sample analyses that exceeded the proposed dissolved Se criterion of 0.2 μg/L 

(ppb) and proposed particulate Se criterion of 1.0 μg/g dw (ppm). Figures 5-9 show the Se

concentrations and the percent of sturgeon muscle tissue analyses that exceeded the proposed 

fish muscle tissue selenium criterion of 11.3 μg/g dw. Figure 10 summarizes the percent of 

sturgeon muscle tissue analyses that exceeded the proposed fish muscle tissue selenium 

criterion from 1989 to 2015. Figure 11 shows the Se concentrations and the percent of clam 

tissue analyses that exceeded the proposed clam tissue selenium criterion of 15 μg/g dw. 

Figure 12 summarizes the percent of clam tissue analyses that exceeded the proposed clam

tissue selenium criterion from 1995 to 2012. The sources of the environmental and tissue data 

are listed in the references section. 
1

Figure 1. Dissolved Selenium Concentrations by Seaward Transects. The dashed line represents 

the proposed dissolved selenium criterion of 0.2 μg/L. For the 2010 to 2012 data there were no 

exceedances of the proposed dissolved selenium criterion, while for the 1998 to 1999 data 5% of 

the analyses exceeded the proposed dissolved selenium criterion. References: Tetra Tech, Inc. 

(2012); Cutter and Cutter (2004); and Doblin et al. (2006).

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Dissolved Se (μg/L)

Number of Analyses (n)

Dissolved Selenium Concentrations by 

Seaward Transects

Dissolved Se (μg/L) Tetra Tech Sep 2010 to Apr 2012

Dissolved Se (μg/L) Cutter & Doblin Jun 1998 to Nov 1999

5% > 0.2 μg/L

(n = 74)

0% > 0.2 μg/L

(n = 71)
2

Figure 2. Particulate Selenium Concentrations by Seaward Transects. The dashed line 

represents the proposed particulate selenium criterion of 1.0 μg/g dw. For the 2010 to 2012 data 

there were no exceedances of the proposed particulate selenium criterion, while for the 1998 to 

1999 data 12% of the analyses exceeded the proposed particulate selenium criterion. References: 

Tetra Tech, Inc. (2012); Cutter and Cutter (2004); and Doblin et al. (2006).

0.0

0.5

1.0

1.5

2.0

2.5

Particulate Se (μg/g dw)

Number of Analyses (n)

Particulate Selenium Concentrations by 

Seaward Transects

Particulate Se (μg/g dw) Tetra Tech Sep 2010 to Apr 2012

Particulate Se (μg/g dw) Cutter & Doblin Jun 1998 to Nov 1999

12% > 1.0 μg/g dw

(n = 73)

0% > 1.0 μg/g dw

(n = 70)
3

Figure 3. Dissolved Selenium Concentrations by Landward Transects. The dashed line 

represents the proposed dissolved selenium criterion of 0.2 μg/L. For the 2010 to 2012 data 25% 

of the analyses exceeded the proposed dissolved selenium criterion, while for the 2003 to 2004 

data 23% of the analyses exceeded the proposed dissolved selenium criterion. References: Tetra 

Tech, Inc. (2012); and Lucas and Stewart (2007).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Dissolved Se (μg/L)

Number of Analyses (n)

Dissolved Selenium Concentrations by 

Landward Transects

Dissolved Se (μg/L) Tetra Tech Sep 2010 to Apr 2012

Dissolved Se (μg/L) Lucas & Stewart Jan 2003 to Jan 2004

25% > 0.2 μg/L

(n = 24)

23% > 0.2 μg/L

(n = 47)
4

Figure 4. Particulate Selenium Concentrations by Landward Transects. The dashed line 

represents the proposed particulate selenium criterion of 1.0 μg/g dw. For the 2010 to 2012 data 

16% of the analyses exceeded the proposed particulate selenium criterion, while for the 2003 to 

2004 data 11% exceeded the proposed particulate selenium criterion. References: Tetra Tech, 

Inc. (2012); and Lucas and Stewart (2007).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Particulate Se (μg/g dw)

Number of Analyses (n)

Particulate Selenium Concentrations by 

Landward Transects

Particulate Se (μg/g dw) Tetra Tech Sep 2010 to Apr 2012

Particulate Se (μg/g dw) Lucas & Stewart Jan 2003 to Jan 2004

16% > 1.0 μg/g dw

(n = 24)

11% > 1.0 μg/g dw

(n = 47)
5

Figure 5. Sturgeon Muscle Selenium Concentrations. The dashed line represents the proposed 

fish muscle tissue selenium criterion of 11.3 μg/g dw. For the 1989 to 1990 data 55% of the 

analyses exceeded the proposed fish muscle tissue selenium criterion. Reference: CDFG (1991).

0

10

20

30

40

50

60

Muscle Se (μg/g dw)

Number of Analyses (n)

Sturgeon Muscle Selenium Concentrations: 

1989 - 1990

Sturgeon Muscle Se (μg/g dw) CDFG Feb 1989 to Mar 1990

55% > 11.3 μg/g dw

(n = 60)
6

Figure 6. Sturgeon Muscle Selenium Concentrations. The dashed line represents the proposed 

fish muscle tissue selenium criterion of 11.3 μg/g dw. For the 2002 to 2005 data 15% of the 

analyses exceeded the proposed fish muscle tissue selenium criterion, while for the 1999 to 2001 

data 21% exceeded the proposed fish muscle tissue selenium criterion. References: LinaresCasenave et al. (2015); and Steward et al. (2004).

0

5

10

15

20

25

30

35

Muscle Se (μg/g dw)

Number of Analyses (n)

Sturgeon Muscle Selenium Concentrations: 

1991-2001 and 2002-2005

Sturgeon Muscle Se (μg/g dw) Linares-Casenave Oct 2002 to May

2005

Sturgeon Muscle Se (μg/g dw) Stewart 1999 to 2001

15% > 11.3 μg/g dw

(n = 47)

21% > 11.3 μg/g dw

(n = 34)
7

Figure 7. Sturgeon Muscle Selenium Concentrations. The dashed line represents the proposed 

fish muscle tissue selenium criterion of 11.3 μg/g dw. For the 2009 data 8% of the analyses 

exceeded the proposed fish muscle tissue selenium criterion. Reference: SFEI (2015a).

0

2

4

6

8

10

12

14

16

18

Muscle Se (μg/g dw)

Number of Analyses (n)

Sturgeon Muscle Selenium Concentrations: 

2009

Sturgeon Muscle Se (μg/g dw) SFEI RMP Status and Trends 2009

8% > 11.3 μg/g dw

(n = 13)
8

Figure 8. Sturgeon Muscle Selenium Concentrations. The dashed line represents the proposed 

fish muscle tissue criterion of 11.3 μg/g dw. For the 2014 data 22% of the analyses exceeded the 

proposed fish muscle tissue selenium criterion. Reference: SFEI (2016).

0

5

10

15

20

25

30

Muscle Se (μg/g dw)

Number of Analyses (n)

Sturgeon Muscle Selenium Concentrations: 

2014

Sturgeon Muscle Se (μg/g dw) SFEI RMP Muscle Plug 2014

22% > 11.3 μg/g dw

(n = 9)
9

Figure 9. Sturgeon Muscle Selenium Concentrations. The dashed line represents the proposed 

fish muscle tissue selenium criterion of 11.3 μg/g dw. For the 2015 data 38% of the analyses 

exceeded the proposed fish muscle tissue selenium criterion. Reference: SFEI (2015b).

0

5

10

15

20

25

Muscle Se (μg/g dw)

Number of Analyses (n)

Sturgeon Muscle Selenium Concentrations: 

2015

Sturgeon Muscle Se (μg/g dw) SFEI 2015 Derby Report Jan 2015 to Feb 2015

38% > 11.3 μg/g dw

(n = 8)
10

Figure 10. Sturgeon Muscle Selenium Concentrations. The bar chart shows the percent of 

analyses that exceeded the proposed fish muscle tissue selenium criterion of 11.3 μg/g dw from

1989 to 2015.

28

69

0

13

29 33

0

19

38

8

22

38

0

10

20

30

40

50

60

70

80

1989 (n=25)1990 (n=35)

1991 (n=0)1992 (n=0)1993 (n=0)1994 (n=0)1995 (n=0)1996 (n=0)1997 (n=0)1998 (n=0)1999 (n=2)

2000 (n=15)2001 (n=17)

2002 (n=3)

2003 (n=20)2004 (n=16)

2005 (n=8)2006 (n=0)2007 (n=0)2008 (n=0)

2009 (n=13)

2010 (n=0)2011 (n=0)2012 (n=0)2013 (n=0)2014 (n=9)2015 (n=8)

Percent (%)

Year (n = number of analyses)

Sturgeon Muscle Selenium Concentrations % > 11.3 μg/g dw

% > 11.3 μg/g dw
11

Figure 11. Clam Tissue Selenium Concentrations. The dashed line represents the proposed clam 

tissue selenium criterion of 15 μg/g dw. For the 1995 to 2012 data 9.4% of the analyses 

exceeded the proposed clam tissue selenium criterion. References: Kleckner et al. (2010); and 

Stewart et al. (2013).

0

5

10

15

20

25

Clam Se (μg/g dw)

Number of Analyses (n)

Clam Tissue Selenium Concentrations: 

1995 - 2012

Clam Se (μg/g dw) Kleckner May 1995 to Feb 2012

9.4% > 15 μg/g dw

(n = 921)
12

Figure 12. Clam Tissue Selenium Concentrations. The bar chart shows the percent of analyses 

that exceeded the proposed clam tissue selenium criterion of 15 μg/g dw from 1995 to 2012.

20

24

15

4

8 9

27

4 5

0 0 0

8

17

2

18

6

23

0

5

10

15

20

25

30

1995 (n=15)1996 (n=70)1997 (n=33)1998 (n=25)1999 (n=89)2000 (n=34)2001 (n=41)2002 (n=70)2003 (n=60)2004 (n=66)2005 (n=63)2006 (n=39)2007 (n=48)2008 (n=48)2009 (n=66)2010 (n=76)

2011 (n=65

2012 (n=13)

Percent (%)

Year (n = number of analyses)

Clam Tissue Selenium Concentrations % > 15 μg/g dw

%>15 μg/g dw
13

References:

CDFG. California Department of Fish and Game. 1991. Selenium Verification Study 1988-1990. 

91-2-WQ May 1991. Water Resources Control Board, State of California. Pages B-1-39, B-1-40 

and B-1-43.

Cutter, G.A. and Cutter, L.S. 2004. The biogeochemistry of selenium in the San Francisco Bay 

estuary: changes in water column behavior. Estuarine, Coastal and Shelf Science 61: 463-476. 

Doblin, M.A., Baines, S.B., Cutter, L.S., and Cutter, G.A. 2006. Sources and biogeochemical 

cycling of particulate selenium in the San Francisco Bay estuary. Estuarine, Coastal and Shelf 

Science 67: 681-694. 

Kleckner, A.E., Stewart, A.R., Elrick, K., and Luoma, S.N. 2010. Selenium concentrations and 

stable isotopic compositions of carbon and nitrogen in the benthic clam Corbula amurensis from 

Northern San Francisco Bay, California, May 1995 to February 2010. U.S. Geological Survey 

Open-File Report 2010-1252. 34 p.

Linares-Casenave, J., Linville, R., Van Eenennaam, J.P., Muguet, J.B., and Doroshov, S.I. 2015. 

Selenium tissue burden compartmentalization in resident white sturgeon (Acipenser 

transmontanus) of the San Francisco Bay Delta Estuary. Environmental Toxicology and 

Chemistry 34: 152-160.

Lucas, L. and Stewart, A.R. 2007. Transport, transformation, and effects of selenium and carbon 

in the delta of the Sacramento-San Joaquin Rivers: Implications for ecosystem restoration. U.S. 

Geological Survey, Menlo Park, CA. Ecosystem Restoration Program Agreement No.

4600001955, Project No. ERP-01-C07. 515 pp.

SFEI. San Francisco Estuary Institute. 2015a. SFEI RMP 2009 Status and Trends Program 

database. See: http://ceden.org/

SFEI. San Francisco Estuary Institute. 2015b. Draft 2015 Sturgeon Derby Report. Authors: 

Jennifer Sun, April Robinson, Jay Davis, Phil Trowbridge, Robin Stewart, Vince Palace, and 

Zachary Jackson.

SFEI. San Francisco Estuary Institute-Aquatic Science Center, by J Sun, A. Robinson, and J.A. 

Davis. 2016. Selenium in White Sturgeon Muscle Plugs: 2014, Contribution #774. Richmond, 

California.

Stewart, A.R., Luoma, S.N., Schlekat, C.E., Doblin, M.A., and Hieb, K.A. 2004. Food web 

pathway determines how selenium affects aquatic ecosystems: A San Francisco Bay case study. 

Environmental Science and Technology 38: 4519-4526.

Stewart A.R., Luoma, S.N., Elrick, K.A., Carter, J.L., and van der Wegen, M. 2013. Influence of 

estuarine processes on spatiotemporal variation in bioavailable selenium. Marine Ecology 

Progress Series 492: 41-56.

Tetra Tech, Inc. 2012. North San Francisco Bay Selenium Characterization Study. Final Report. 

October 5, 2012.