Toxicity of Selenium to Salmonids. William Beckon, PhD, U. S. Fish and Wildlife Service, Sacramento, CA

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1 Toxicity of Selenium to Salmonids William Beckon, PhD, U. S. Fish and Wildlife Service, Sacramento, CA Presented at CalFed Science Conference, Sacramento, CA, October 24, 2008

2 EPA selenium criterion for the protection of aquatic life: 5 ppb (µg/l) in water since FR 60848

3 Most selenium-contaminated stretch of any major river in the Central Valley: San Joaquin River at Hills Ferry national criterion Jan-85 Jan-86 Jan-87 Jan-88 Jan-89 Jan-90 Jan-91 Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Selenium in water (ug/l) California Central Valley Selenium levels have been approaching compliance Data from Central Valley Regional Water Control Board

4 Is the 5 ppb national criterion protective of salmonids? Selenium in the water has little direct effect on fish. Toxicity is due to selenium accumulated in the tissue of fish from selenium in their diet. Most directly relevant: relationship of selenium in tissues to adverse effects.

5 Chronic Fish tissue-based criterion 7.91 µg/g (whole body, dry weight) LOAEC for juvenile mortality at 4 C. Bluegill sunfish (Lemly 1993), a warmwater fish

6 Aren t coldwater fish (salmonids) more sensitive? 190 chemicals (ECOTOX data) more sensitive rainbow trout less sensitive Teather K, Parrott J Assessing the chemical sensitivity of freshwater fish commonly used in toxicological studies. Water Qual Res J Canada 41:

7 Did EPA miss something? Data selection Model used for regression (monotonic) Criterion effect level (20%) If it kills 1/5 of the population, is it protective? Included in analysis: From EPA 2004

8 Included: selenium effect on salmon growth days EC20 = µg/g dry wt. EC20 = µg/g dry wt. Species Mean Chronic Value: SMCV = µg/g dry wt. EPA (Environmental Protection Agency) Draft Aquatic Life Water Quality Criteria for Selenium EPA-822-D

9 Excluded: selenium effect on salmon survival days same study Larval Chinook salmon from the Merced fish hatchery. Exposed to dietary selenium for 90 days. Log-logistic model. Survival 80% 60% 40% 20% 0% μg/g } } 10% 20% μg/g 7.91 μg/g 64.5% mortality due to selenium toxicity Selenium concentration in fish (μg/g whole body dry wt.) Hamilton, Steven J., K. J. Buhl, N. L. Faerber, R. H. Wiedmeyer, and F. A. Bullard Toxicity of organic selenium in the diet to chinook salmon. Environ. Toxicol. Chem. 9:

10 Stated reason for exclusion : unacceptable control mortality days But the control was in line with other treatments Survival 80% 60% 40% control } } 10% 20% 64.5% mortality due to selenium toxicity 20% μg/g μg/g 7.91 μg/g 0% Selenium concentration in fish (μg/g whole body dry wt.)

11 Selenium is essential as well as toxic so regression model should be biphasic Weight of whole fish (g) Rainbow trout Hilton et al Selenium concentration in diet (μg/g) Data: Hilton JW, Hodson PV, Slinger SJ The requirement and toxicity of selenium in rainbow trout (Salmo gairdneri). J Nutr 110: Regression: Beckon WN, Parkins C, Maximovich A, Beckon AV A general approach to modeling biphasic relationships. Environ Sci Technol 42:

12 Biphasic model applied to Hamilton et al Control is in good agreement with other data Optimum [Se]: about 1 µg/g LC10 = 1.84 µg/g Survival % control 1.84 μg/g Regression: y=1.71*x/(1+(0.80/x) ) n=11 R 2 = % mortality 2.49 μg/g 58% mortality due to selenium 7.91 μg/g Selenium concentration in fish (μg/g whole body dry wt) Brain P, Cousens R An equation to describe dose responses where there is stimulation of growth at low doses. Weed Res 29: Hamilton, Steven J., K. J. Buhl, N. L. Faerber, R. H. Wiedmeyer, and F. A. Bullard Toxicity of organic selenium in the diet to chinook salmon. Environ. Toxicol. Chem. 9:

13 Better biphasic model: same result Model of Beckon et al. (2008) * is more flexible but requires deficiency data. Additional data from Atlantic salmon Survival 90% Chinook salmon 90 days Atlantic salmon 42 days log-logistic model } 10% mortality due to Se Brain-Cousens model Beckon et al. model 10% mortality due to Se μg/g 1.85 μg/g } 0% Selenium concentration in fish (μg/g whole body dry wt.) *Beckon WN, Parkins C, Maximovich A, Beckon AV A general approach to modeling biphasic relationships. Environ Sci Technol 42: Poston HA, Combs GF, Leibovitz L Vitamin E and selenium interrelations in the diet of Atlantic salmon (Salmo salar): gross, histological and biochemical signs. Journal of Nutrition 106:

14 Salmon data is in good agreement with trout data Dietary selenium effect on rainbow trout fry growth: Dietary sodium selenite 140 days Optimum [Se]: about 1 µg/g EC10 = 1.89 µg/g Dietary Selenomethionine 90 days Geomean =1.70 µg/g Weight of whole fish (g) NOAEC Hilton et al data Brain-Cousens model Vidal et al data geomean of NOAEC and LOAEC: 1.70 μg/g }10% reduction in growth LOAEC EC10 = 1.92 μg/g Selenium concentration in fish (μg/g whole body dry wt.) Hilton JW, Hodson PV, Slinger SJ The requirement and toxicity of selenium in rainbow trout (Salmo gairdneri). J Nutr 110: Vidal D, Bay SM, Schlenk D Effects of dietary selenomethionine on larval rainbow trout (Oncorhynchus mykiss). Arch Environ Contam Toxicol 49: EPA MATC (maximum acceptable toxicant concentration)

15 Do young migrating salmon actually linger long enough in the contaminated portions of rivers to bioaccumulate selenium to levels of concern?

16 Selenium in juvenile salmon Saiki, Jennings, and Hamilton µg/g N=11? Stanislaus River µg/g Tuolumne River Merced River µg/g N=11 N=9 Subsurface drainage Low selenium Seepage Seepage and and storm storm flow flow µg/g N=2 San Joaquin River High selenium

17 What do these selenium levels 1 in fish mean? } } 25.6% 28.0% mortality due to selenium Survival μg/g 3.1μg/g 1 10 Mortality due to selenium 40% 30% 20% % Selenium concentration in fish (μg/g whole body dry wt) 0% mean range { Selenium in fish (μg/g whole body dry wt)

18 Selenium risk to juvenile salmon Mortality due to selenium Mortality due to selenium 40% 30% 20% 10% % µg/g 40% 30% N= % µg/g 10% N= Selenium in fish (μg/g whole body dry wt) 0% Selenium in fish (μg/g whole body dry wt) Stanislaus River Tuolumne River Merced River Subsurface drainage High selenium Mortality due to selenium Seepage Seepage and and storm storm flow flow 40% 30% 20% 10% 0% 1 Low selenium San Joaquin River µg/g N= Selenium in fish (μg/g whole body dry wt)

19 That was What about now? Agricultural drainage management has reduced selenium discharge to the SJ River.

20 Bioaccumulation: Relationship between selenium in fish tissue and selenium in water Selenium in fish tissue (µg/g whole body dry wt) NIWQP lentic: log 10 y= *log 10 x n=1007 R 2 =0.37 x NIWQP lotic: log 10 y= *log 10 x n=3171 R 2 =0.18 NIWQP rainbow trout: log 10 y= *log 10 x n=23 R 2 =0.10 Salt Slough sunfish: log 10 y= *log 10 x n=19 R 2 =0.69 Salt Slough mosquitofish: log 10 y= *log 10 x n=47 R 2 = % mortality in juvenile S. J. River Chinook salmon 1.84 µg/g X juvenile S. J. River Chinook salmon : log 10 y= *log 10 x n=11 R 2 = µg/l ppb Selenium in water (µg/l)

21 Selenium in the San Joaquin River remains above salmon effect levels 100 San Joaquin River at Hills Ferry % mortality national criterion 10% mortality 0.1 Jan-85 Jan-86 Jan-87 Jan-88 Jan-89 Jan-90 Jan-91 Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Selenium in water (ug/l)

22 Conclusion Selenium may have killed about a quarter of young salmon passing through this part of the San Joaquin River in the 1980s. Could kill >10% now.

23 unless selenium in the River is reduced or flows increased.

24 Thank you Mike Saiki Kevin Buhl Tom Maurer Ralph Seiler