Linking Selenium Sources to Ecosystems: Local and Global Perspectives

Introduction

Modeling

Irrigation

Refining

Mining

Library/Links

Selenium is recognized as an important contaminant in aquatic environments because of its

ability to bioaccumulate through food webs. Selenium's role is well documented in local extin

of deformities of aquatic birds in affected habitats. Details of general ecotoxicological pathwa

of concern for selenium are shown in Figure 1.

Toxicity arises when dissolved selenium is transformed to organic-selenium by bacteria, alga

selenium-containing amino acids de novo) and then 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 hatching or proper development (teratogenesis or

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

1 of 7 4/20/2016 3:00 PM
Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

2 of 7 4/20/2016 3:00 PM
Details of 1) general ecotoxicological pathways of selenium for fish and birds; and 2) effects of concern for selenium

selenium taken up from diet distributes among tissues.

Specifically for selenium in aquatic ecosystems: (1) water-column selenium has proven to be

bioaccumulated in food webs because dietary selenium makes up 95% of tissue selenium in

biogeochemical transformation of dissolved selenium into particulate forms (algae, microbes

concentration of selenium available at the base of food webs; (3) a 38-fold variability in trop

to invertebrate species is mainly driven by physiological differences in assimilation efficiency

among invertebrates species; and (4) dietary transfer of invertebrate selenium to fish specie

median of approximately 1, which reflects preservation of selenium as it passes up food web

level below. Less information is available concerning dietary selenium biodynamics of aquatic

prey and the bioaccumulation kinetics of that prey are still fundamental to their exposure (as

differential response to selenium makes some predator species more vulnerable and, thus, m

collapse from moderately contaminated environments than others.

The main route of exposure for selenium is dietary, yet regulations lack biologically based pr

Ecosystem-scale selenium modeling conceptualizes and quantifies the variables that determi

through diet to predators (Figure 2). This approach uses biogeochemical and physiological fa

considers loading, speciation, transformation to particulate material, bioavailability, bioaccum

transfer to predators. Validation of the model is through data sets from 29 historic and recen

sites.

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

3 of 7 4/20/2016 3:00 PM
Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

4 of 7 4/20/2016 3:00 PM
Ecosystem-scale selenium modeling conceptualizes processes and parameters important for quantifying and unders

model can be applied to forecast exposure and to evaluate the implications of management or regulatory choices. K

factor between water and particulate 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 under different management or regulatory proposals or as a method

predator tissue) selenium concentration guideline to a dissolved selenium concentration. The

implementing a tissue criterion: 1) the choice of fish species determines the food web throug

the choice of food web is critical because the particulate material to prey kinetics of bioaccum

3) the characterization of the type and phase of particulate material is important to quantify

base of the food web, and 4) the metric describing partitioning between particulate material

allows determination of a site-specific dissolved selenium concentration that would be respon

specific environment.

The linked approach illustrates that environmentally safe dissolved selenium concentrations 

the ecological pathways and biogeochemical conditions in that system (Figure 3). Uncertaint

illustrated by varying exposure scenarios based on site-specific knowledge. The model can a

regulation and to present generic comparisons to illustrate limitations imposed by ecosystem

the model provides a tool for framing a site-specific ecological problem or occurrence of sele

that ecosystem, and narrow uncertainties about how to protect it by understanding the spec

biogeochemistry, and hydrology.

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

5 of 7 4/20/2016 3:00 PM
Linking Selenium Sources to Ecosystems - Modeling http://wwwrcamnl.wr.usgs.gov/Selenium/modeling.htm

6 of 7 4/20/2016 3:00 PM
Quantitative 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., invertebrate through fish to bird or to include forage fish to pr

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 ecosystem

Presser, T.S., 2013, Selenium in Ecosystems within the Mountaintop Coal Mining and ValleyAssessment 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, no

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 Administrativ

[Published 12/14/2010; released by USEPA (Region 9, San Francisco, California) 8/29/20

Presser, T.S., and Luoma, S.N., 2009, Modeling of selenium for the San Diego Creek watersh

Geological Survey Open-File 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

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

7 of 7 4/20/2016 3:00 PM