Data Required for Assessment
63
tamination present, which is used as an estimate of the expected environmental concentration; and (2) the extent of fish and wildlife exposure to potentially toxic selenium concentrations. Exposure can be
difficult to characterize precisely. However, the data set required for
the Protocol helps with this problem because it specifies the use of egg
selenium concentrations. This focuses the assessment on the reproductive cycle, which is the critical period of exposure necessary for toxic
impacts. Hazard is maximized when the degree of contamination is
high and exposure occurs during the breeding season.
Five categories of hazard are recognized in the Protocol based on
the potential for reproductive impairment in fish and aquatic birds.
High hazard denotes a toxic threat sufficient to cause complete or nearly
complete reproductive failure in sensitive species of fish and aquatic
birds (eg, sunfish, family Centrarchidae; trout, family Salmonidae;
ducks, family Anatidae; stilts, family Recurvirostridae). Moderate hazard indicates a toxic threat of sufficient magnitude to substantially impair
but not eliminate reproductive success; some species will be severely
affected while others will be relatively unaffected. Low hazard denotes a toxic threat that could marginally affect the reproductive success of some sensitive species but leave most species unaffected.
Minimal hazard indicates that no imminent toxic threat is identified,
but concentrations of selenium are slightly elevated in one or more
ecosystem components (water, sediment, benthic invertebrates, fish,
birds) as compared to uncontaminated reference sites; continued comprehensive environmental monitoring is recommended. No hazard
indicates that no toxic threat is identified, and selenium concentrations are not elevated in any ecosystem component; periodic baseline
reconnaissance monitoring is recommended.
Data Required for Assessment
The Protocol requires a set of data for selenium concentrations measured in 5 ecosystem components: water (0.45 J..lm filtered samples),
sediments, benthic macroinvertebrates, fish eggs, and aquatic bird eggs.
Incomplete data sets, that is, sets in which one ecosystem component
is missing, will weaken the predictive power of the assessment, but it
can still be performed. Depending on species and time of year, bird
eggs and gravid fish ovaries may be very difficult or even impossible to
obtain. In that case, selenium can be measured in bird livers and wholebody samples of fish, and the results converted to approximate egg
concentrations using the following conversion factors: bird egg selenium = bird liver selenium x 0.33; fish egg selenium = fish wholebody selenium x 3.3 (Lemly and Smith 1987; Skorupa et al. 1996).
63
tamination present, which is used as an estimate of the expected environmental concentration; and (2) the extent of fish and wildlife exposure to potentially toxic selenium concentrations. Exposure can be
difficult to characterize precisely. However, the data set required for
the Protocol helps with this problem because it specifies the use of egg
selenium concentrations. This focuses the assessment on the reproductive cycle, which is the critical period of exposure necessary for toxic
impacts. Hazard is maximized when the degree of contamination is
high and exposure occurs during the breeding season.
Five categories of hazard are recognized in the Protocol based on
the potential for reproductive impairment in fish and aquatic birds.
High hazard denotes a toxic threat sufficient to cause complete or nearly
complete reproductive failure in sensitive species of fish and aquatic
birds (eg, sunfish, family Centrarchidae; trout, family Salmonidae;
ducks, family Anatidae; stilts, family Recurvirostridae). Moderate hazard indicates a toxic threat of sufficient magnitude to substantially impair
but not eliminate reproductive success; some species will be severely
affected while others will be relatively unaffected. Low hazard denotes a toxic threat that could marginally affect the reproductive success of some sensitive species but leave most species unaffected.
Minimal hazard indicates that no imminent toxic threat is identified,
but concentrations of selenium are slightly elevated in one or more
ecosystem components (water, sediment, benthic invertebrates, fish,
birds) as compared to uncontaminated reference sites; continued comprehensive environmental monitoring is recommended. No hazard
indicates that no toxic threat is identified, and selenium concentrations are not elevated in any ecosystem component; periodic baseline
reconnaissance monitoring is recommended.
Data Required for Assessment
The Protocol requires a set of data for selenium concentrations measured in 5 ecosystem components: water (0.45 J..lm filtered samples),
sediments, benthic macroinvertebrates, fish eggs, and aquatic bird eggs.
Incomplete data sets, that is, sets in which one ecosystem component
is missing, will weaken the predictive power of the assessment, but it
can still be performed. Depending on species and time of year, bird
eggs and gravid fish ovaries may be very difficult or even impossible to
obtain. In that case, selenium can be measured in bird livers and wholebody samples of fish, and the results converted to approximate egg
concentrations using the following conversion factors: bird egg selenium = bird liver selenium x 0.33; fish egg selenium = fish wholebody selenium x 3.3 (Lemly and Smith 1987; Skorupa et al. 1996).