The understanding of plutonium ecotoxicity is limited by the number and types of studies conducted with the radionuclide. In aquatic systems, increased mortality and developmental effects in carp and fathead minnows occur at activity concentrations as low as 5.97 x 10 pBqmP1. In terrestrial systems, decreases in population density have been observed in earthworms, mites, and microar-thropods. Moreover, genotoxicity has been identified in terrestrial plants with effects to somatic cells. Plutonium toxicity at contaminated field sites is complicated by co-contaminants such as uranium-235 and -238 and other nonradioactive metals.
Alterations to organism development and decreases in survival because of plutonium toxicity have several potential repercussions from an ecological perspective. The removal of individuals from a population and the subsequent decline in population density can directly affect communities and ecosystems. This is particularly relevant when the reduction is large enough and the populations affected occupy low trophic levels or are otherwise integral components of the food web, or if they occupy an important ecological niche.
In the long term, developmental effects potentially alter population age structure and, as a consequence, the net reproductive rate. Although genotoxic and carcinogenic impacts may lead to the death of individuals, mortality may not occur until later in life, when the full reproductive potential of the organism has been realized. An even larger concern is mutations in germ cells, which may alter reproductive success if gametes are affected. A final consideration from an ecotoxicological perspective is the possibility for contaminant-induced evolution if mutations in germ cells are inherited by offspring.
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