Effects of Dietary Selenium and Methylmercury on Green and White Sturgeon

Bioenergetics in Response to Changed Environmental Conditions.

1,2Robert C. Kaufman, 1Ann G. Houck, and 1Joseph J. Cech, Jr.

1Wildlife Fish and Conservation Biology, UC Davis

2Pharmacology and Toxicology Graduate Group, UC Davis

SF Bay-Delta is a multiply-stressed ecosystem

•Water diversions

•Salinity fluctuations

•Pollutants e.g., agricultural, industrial, storm-water runoff. Selenium (SeMet) and Mercury (MeHg) are toxicants of concern

•Introduced species, e.g., Asian clam

•Several species are currently imperiled e.g., POD & salmon

•Green and white sturgeon numbers are in decline

•Green sturgeon listed as threatened in 2006

Problems

• Little is known of the effects of Hg on wildlife

• Aquatic food web recognized as the most

efficient process of bioaccumulation of Hg

• Studies have shown reduced capacity for:

– Reproduction when exposed as juveniles

– Growth

– Ability to avoid predators

– Shoaling

– Swimming performance

Problems cont.:

• Selenium: nutritional versus toxicity

• Effects on wildlife well documented

• Studies have shown that Se:

– Teratogenic in fish and avian species e.g., Belews Lake, NC and Kesterson, CA.

– Decreased reproduction

– Concentrations in North SF Bay-Delta are a concern

– Multiple sources of input e.g., agriculture and refining

processes

menlocampus.wr.usgs.gov/.../agricul

ture.html

Objectives

• Determine effects of SeMet and MeHg on

sturgeon bioenergetics

• Determine the effects of environmental

stressors, temperature and salinity, on

previously exposed (SeMet & MeHg) individuals’

bioenergetics

• Determine the feasibility of using non-listed, and

domesticated white sturgeon as a surrogate for

green sturgeon in toxicity testing

56-Day Growth Experiment

Elevated Temperature•25°C

•Gradual increase from ambient to 25°C over 12 hours•Maintain 25°C for all performance experiments

Ambient•18º C

•Air-equlibratedwell water•Hold fish for 24 hours prior to start of experiments

Elevated Salinity•Ambient Temperature

•Increase from 0 ppt to 18 ppt over 8 hours•Maintain 18 pptsalinity for all experiments

Predator avoidance

Routine & Active metabolic rates

Critical SwimmingVelocity

Tissue samples for Se, Hg, & glycogen content

Tissue samples for Proteomic analysis

Dietary MeHg effects on white sturgeon predator

avoidance

0

0.1

0.2

0.3

0.4

0.5

0.6

MeHg-0 ppm MeHg-25 ppm MeHg-50 ppm

MeHg dose (ppm)

qu

ad

ran

ts p

er

seco

nd

ambient

25 C

18 ppt

a

a

b

A

Dietary MeHg effects on green sturgeon predator

avoidance.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

Hg-0 ppm Hg-25 ppm

Hg dose (0 ppm)

qu

ad

ran

ts p

er

seco

nd

ambient

25 C

18 ppt

a

c

b

B

d

SeMet effects on simulated predator avoidance in white

sturgeon

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Se-0 ppm Se-20 ppm Se-40 ppm Se-80 ppm

Dietary dose SeMet (ppm)

qu

ad

ran

ts p

er

seco

nd

ambient

25 C

18 ppt

a

a a

b

cc

d

d

e

e

f

f

A

SeMet effects on green sturgeon simulated predator

avoidance

0.00

0.10

0.20

0.30

0.40

0.50

0.60

Se-0 ppm Se-20 ppm Se- 40 ppm Se-80 ppm

SeMet dietary dose (ppm)

qu

ad

ran

ts p

er

seco

nd

ambient

25 C

18 ppt

aa

a

b bbb bb

b b

B

b

Routine and ‘active’ metabolic rates determined using Blazka-type

respirometers after

the growth expt.

WS Routine & Active Metabolic Rate (MeHg)

0

100

200

300

400

500

600

hg-1 hg-2 hg-3 hg-1 hg-2 hg-1 hg-2 hg-3

Treatment Group

mg O

2/k

g/h

r

Ambient routine

Ambient active

25 C routine

25 C active

18 ppt routine

18 ppt active

A

GS Routine & Active Metabolic Rates

0

100

200

300

400

500

600

hg-1 hg-2 hg-1 hg-2 hg-1 hg-2

Treatment Group

mg

O2/k

g/h

r

Ambient routine

Ambient active

25 C routine

25 C active

18 ppt routine

18 ppt active

B

GS Metabolic Rates (SeMet)

0

100

200

300

400

500

600

700

Se

-1

Se

-2

Se

-3

Se

-4

Se

-1

Se

-2

Se

-3

Se

-4

Se

-1

Se

-2

Treatment Group

mg

O2

/kg

/hr

Ambient routine

Ambient active

25 C routine

25 C active

18 ppt routine

18 ppt active

B

WS Metabolic Rates (SeMet)

0

100

200

300

400

500

600

700

Se-1

Se-2

Se-3

Se-4

Se-1

Se-2

Se-3

Se-4

Se-1

Se-2

Se-3

Se-4

Treatment Group

mgO

2/k

g/h

r

Ambient routine

Ambient active

25 C routine

25 C active

18 ppt routine

18 ppt active

A

Dietary effects of MeHg on white sturgeon swimming

performance

0

20

40

60

80

100

120

MeHg-0 ppm MeHg-25 ppm MeHg-50 ppm

MeHg dietary dose (ppm)

cri

tical sw

mm

ing

velo

city (cm

/sec)

ambient

25 C

18 ppt

a

b

b

c

d

A

Dietary MeHg effects on green sturgeon swimming

performance

0

10

20

30

40

50

60

70

80

90

100

MeHg-0 ppm MeHg-25 ppm

Dietary dose MeHg (ppm)

critical sw

imin

g v

elo

city

(cm

/sec)

ambient

25 C

18 ppt

a

b

B

c

d

Dietary effects of SeMet on white sturgeon swimming

performance

0

20

40

60

80

100

120

SeMet- 0

ppm

SeMet-20

ppm

SeMet-40

ppm

SeMet-80

ppm

Dietary dose SeMet (ppm)

cri

tical sw

imm

ing

velo

cit

y

(cm

/sec)

ambient

25 C

18 ppt

a

b

c

d,f

e

A

Dietary effect of SeMet on green sturgeon

swimming performance

0

10

20

30

40

50

60

70

80

90

SeMet-0

ppm

SeMet- 20

ppm

SeMet-40

ppm

SeMet-80

ppm

SeMet dietary dose (ppm

cri

tical sw

imm

ing

velo

cit

y

(cm

/sec) ambient

25 C

18 ppt

a e g

b,cf

hb f

b,d

B

Conclusions

• Significant differences in ‘predator’ avoidance observed in both species with the most dramatic effect in GS

• Dietary SeMet treatments produced significant decreases in ‘active’ metabolism in WS at highest dose

• Dietary MeHg treatments produced significant decreases in bioenergetics albeit at very high doses

• Dietary SeMet resulted in significant declines in performance measures in both species with green sturgeon showing a greater sensitivity to this toxicant at all levels tested

• White sturgeon are not an appropriate surrogate for green sturgeon in determining the effects of these toxicants on sturgeon bioenergetics

Future Course

• Develop reliable source of green sturgeon larvae and juveniles for toxicity testing and tracking studies to determine habitat usage by green sturgeon juveniles, e.g., wild-caught broodstock

• Determine the NOEC of SeMet in green sturgeon juveniles

Related Posters

• Linares-Casenave, J., et al.............360

• Madison*, R.K., and D. Kueltz........368

• Doroshov, S.I., et al. ………………312

Acknowledgements

• We thank CALFED for providing the funding for this study as well as the efforts of Dr. Doroshov’s laboratory in development of a captive green sturgeon broodstock program which provided the larvae and juveniles for this study.