92
5. Teratogenic Deformity Index for Fish
surement of tissue concentrations is essential, it is not necessary to
conduct extensive surveys on hundreds of fish. Analysis of 6 samples
per fish species (eg, 6 adults or juveniles with teratogenic deformities
or 6 composites for teratogenic larvae/fry) is sufficient to reveal the
range of concentrations likely to be encountered (Lemly 1993, 1997).
Terata-Mortality Relationships
A considerable amount of data is available for assessing or predicting
the impact of selenium-induced teratogenesis on fish populations. Laboratory studies provide important information on the relationships
among egg concentrations of selenium, prevalence of teratogenic deformities in larvae, and associated mortality. These studies are of three
types; (1) those in which captive adult fish were fed selenium-laden
diets or exposed to high-selenium water and then allowed to spawn in
indoor tanks (Bryson et a1. 1984, 1985a, 1985b; Woock et a1. 1987;
Pyron and Beitinger 1989); (2) those in which outdoor artificial streams
were dosed with waterborne selenium, providing for exposure of adult
fish to natural food-chain selenium prior to spawning (Schultz and
Hermanutz 1990; Hermanutz 1992; Hermanutz et a1. 1992); and (3)
those in which adult fish were taken from selenium-contaminated
aquatic habitats and spawned artificially (ie, eggs and milt were removed and mixed) and the resultant hatch was monitored (Gillespie
and Baumann 1986).
The field data come from Belews Lake, NC, in the United States. This
lake was impounded in the early 1970s to serve as a cooling reservoir for
a large coal-fired electric generating station (2250 megawatt generating
capacity). Fly ash produced by the power plant was disposed in a settling
basin from which effluent containing 100 to 200
SelL (about 80%
selenite) was released in return flows to the lake. This selenium
bioaccumulated in aquatic food chains, and within two years, the fishery
of Belews Lake began to decline. Of the 20 species of fish originally present
in the reservoir, 19 were eliminated due to dietary toxicity and reproductive failure. This pattern of selenium contamination from the power plant
and resultant poisoning of fish persisted from 1974 to 1986 (Lemly 1985,
1997). In late 1986, the power company changed operations for fly-ash
disposal, and selenium-laden effluent no longer entered the lake. In the
following years, selenium levels fell substantially, and the fishery began
to recover (augmented by artificial stocking), but sediments and associated benthic-detrital food chains remained moderately contaminated, and
there were residual effects on the fishery, including persistent teratogenic
deformities.
Teratogenic assessment was used to evaluate the reproductive success of fish and determine the degree of impact in Belews Lake in
5. Teratogenic Deformity Index for Fish
surement of tissue concentrations is essential, it is not necessary to
conduct extensive surveys on hundreds of fish. Analysis of 6 samples
per fish species (eg, 6 adults or juveniles with teratogenic deformities
or 6 composites for teratogenic larvae/fry) is sufficient to reveal the
range of concentrations likely to be encountered (Lemly 1993, 1997).
Terata-Mortality Relationships
A considerable amount of data is available for assessing or predicting
the impact of selenium-induced teratogenesis on fish populations. Laboratory studies provide important information on the relationships
among egg concentrations of selenium, prevalence of teratogenic deformities in larvae, and associated mortality. These studies are of three
types; (1) those in which captive adult fish were fed selenium-laden
diets or exposed to high-selenium water and then allowed to spawn in
indoor tanks (Bryson et a1. 1984, 1985a, 1985b; Woock et a1. 1987;
Pyron and Beitinger 1989); (2) those in which outdoor artificial streams
were dosed with waterborne selenium, providing for exposure of adult
fish to natural food-chain selenium prior to spawning (Schultz and
Hermanutz 1990; Hermanutz 1992; Hermanutz et a1. 1992); and (3)
those in which adult fish were taken from selenium-contaminated
aquatic habitats and spawned artificially (ie, eggs and milt were removed and mixed) and the resultant hatch was monitored (Gillespie
and Baumann 1986).
The field data come from Belews Lake, NC, in the United States. This
lake was impounded in the early 1970s to serve as a cooling reservoir for
a large coal-fired electric generating station (2250 megawatt generating
capacity). Fly ash produced by the power plant was disposed in a settling
basin from which effluent containing 100 to 200
SelL (about 80%
selenite) was released in return flows to the lake. This selenium
bioaccumulated in aquatic food chains, and within two years, the fishery
of Belews Lake began to decline. Of the 20 species of fish originally present
in the reservoir, 19 were eliminated due to dietary toxicity and reproductive failure. This pattern of selenium contamination from the power plant
and resultant poisoning of fish persisted from 1974 to 1986 (Lemly 1985,
1997). In late 1986, the power company changed operations for fly-ash
disposal, and selenium-laden effluent no longer entered the lake. In the
following years, selenium levels fell substantially, and the fishery began
to recover (augmented by artificial stocking), but sediments and associated benthic-detrital food chains remained moderately contaminated, and
there were residual effects on the fishery, including persistent teratogenic
deformities.
Teratogenic assessment was used to evaluate the reproductive success of fish and determine the degree of impact in Belews Lake in