## Linking Selenium Sources to Ecosys tems: Local and Global Perspectives

Introduction Modeling Irrigation Refining Mining Library/Links Selenium is recognized as an important contam inant in aquatic environments because of its ability to bioaccumulate through food webs. Selenium's role is well documented in local exti n of deformities of aquatic birds in affected habitats. Details of general ecotoxicological pathw a of concern for selenium are shown in Figure 1

. Toxicity arises when dissolved selenium is tr ansformed to organic-selenium by bacteria, alg a selenium-containing amino acids de novo) and th en passed through food webs. It is general biochemically distinguish selenium from sulfur, and therefore excess selenium is substituted function. Other biochemical reactions also can determine and mediate toxicity. The effect of importantly in birds and fish, as failures in ha tching or proper development (teratogenesis o r toxicity endpoints include growth , winter survival, maintenance of body condition, reproduct 

### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

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### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

2 of 7 4/20/2016 3:00 PMDetails of 1) general ecotoxicological pa thways of selenium for fish and birds; and 2) effects of concern for seleniu m selenium taken up from diet distributes among tissues. Specifically for selenium in aquatic ecosystems : (1) water-column selenium has proven to b e bioaccumulated in food webs because dietary selenium makes up 95% of tissue selenium in biogeochemical transformation of dissolved se lenium into particulate forms (algae, microbes concentration of selenium available at the base of food webs; (3) a 38-fold variability in tro p to invertebrate species is mainly driven by physiological differences in assimilation efficiency among invertebrates species; and (4) dietary tran sfer of invertebrate selenium to fish speci e median of approximately 1, whic h reflects preservation of sele nium as it passes up food we b level below. Less information is available concerning dietary selenium biodynamics of aquati c prey and the bioaccumulation kinetics of that prey are still fundamental to their exposure (a s differential response to seleni um makes some predator specie s more vulnerable and, thus, m collapse from moderately contamin ated environments than others.

The main route of exposure for selenium is dietary, yet regulations lack biologically based p r Ecosystem-scale selenium modeling conceptualiz es and quantifies the variables that determ i through diet to predators ( Figure 2 ). This approach uses biogeo chemical and physiological f a considers loading, speciation, tran sformation to particulate material, bioavailability, bioaccu m transfer to predators. Validation of the model is through data sets from 29 historic and rece n sites. 

### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

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### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

4 of 7 4/20/2016 3:00 PMEcosystem-scale selenium modeling conceptualizes processes and parameters import ant for quantifying and under s model can be applied to forecast exposu re and to evaluate the implications of management or regulatory choices. K factor between water and part iculate material; TTF = biodynamic food-web transfer factor between an animal and i The model ( Figure 2 ) links selenium concentrations across media (water, particulate, tissue used to forecast toxicity underdifferent management or regulatory proposals or as a metho d predator tissue) selenium concentration guidel ine to a dissolved selenium concentration. Th e implementing a tissue criterion: 1) the choice of fish species determines the food web throu g the choice of food web is crit ical because the particulate material to prey kinetics of bioaccu m 3) the characterization of the type and phase of particulate material isimportant to quantify base of the food web, and 4) the metric desc ribing partitioning between particulate material allows determination of a site-specific dissolve d selenium concentration that would be respo n specific environment. The linked approach illustrates that environmen tally safe dissolved selenium concentrations the ecological pathways and biogeochemical conditions in that system ( Figure 3 ). Uncertain t illustrated by varying exposure scenarios base d on site-specific knowledge. The model can a regulation and to present gene ric comparisons to illustrate limitations imposed by ecosyste m the model provides a tool for fr aming a site-specific ecological problem or occurrence of sel e that ecosystem, and narrow uncertainties about how to protec t it by understanding the spe c biogeochemistry, and hydrology. 

### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

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### Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

6 of 7 4/20/2016 3:00 PMQuantitative outcomes from applying ecosystem-scale selenium modeling to various environmental exposure scena reservoir, mainstream river, backwater, saline lake, and a wetland. Food webs illustrate invertebrates as prey and f be added to illustrate more complex food webs (e.g., inverteb rate through fish to bird or to include forage fish to p r



### Links to the ecosystem-scale selenium modeling methodology: Luoma, S.N., and Presser, T.S., 2009, Emerging opportunities in management of selenium c Technology, v. 43, no. 22, p. 8483-8487. Presser, T.S., and Luoma, S.N., 2010, A Methodology for ecosystem-scale modeling of selen and Management, v. 6, no. 4, p. 685-710. 

### Links to in-depth publications for site-specific application of ecosyste m Presser, T.S., 2013, Selenium in Ecosystems within the Mountaintop Coal Mining and Valley

Assessment and Ecosystem-Scale Modeling , U.S. Geological Survey Professional Paper 1 Presser, T.S., and Luoma, S.N., 2013, Ecosystem-scale selenium model for the San Francisc Implementation Plan (DRERIP) : San Francisco Estuary and Watershed Science, v. 11, n o Presser, T.S., and Luoma, S.N., 2010, Ecosystem-scale selenium modeling in support of fish for the San Francisco Bay-Delta Estuary, California : U.S. Geological Survey Administrati v [Published 12/14/2010; released by USEPA (R egion 9, San Francisco, California) 8/29/2 0 Presser, T.S., and Luoma, S.N., 2009, Modeling of selenium for the San Diego Creek waters h Geological Survey Open-F ile Report 2009-1114, 48 p.
U.S. Department of the Interior| U.S. Geological Survey URL: http://wwwrcamnl.wr.usgs.gov/Selenium/guidelines.htm Page Contact Information: gs-w-camnl_webmaster@usgs.gov Page Last Modified: Wednesday, 09-Jun-2010 12:50:49 EDT 

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