Ecotoxicological and genetic effects of a mixture of heavy metals on selected aquatic macroinvertebrates (Colorado)

This research investigated the ecotoxicological and genetic effects of exposure to a mixture of heavy metals on selected aquatic macroinvertebrates. Studies centered on macroinvertebrates collected from, or concentrations found in, the upper Arkansas River. The upper Arkansas River receives wastes from mines and tailings piles in Leadville, Colorado and has been recognized as a site of poor water quality for many years.; To investigate the potential of sediments in the Arkansas River to act as a source of metals to benthic organisms, Chironomus tentans (Diptera: Chironomidae) were exposed to synthetic sediment spiked with a mixture of metals at concentrations similar to those found in the Arkansas River in a series of toxicity and bioaccumulation experiments. Results of these studies showed that a mixture of cadmium, copper, lead, and zinc readily accumulated in C. tentans, and were toxic at realistic concentrations measured in the field.; Because mining began in California Gulch 1859, it is likely that populations have been exposed to heavy metals for over 130 years. This site provided a unique opportunity to investigate both ecotoxicological and genetic effects of long-term exposure to heavy metals. Populations of the mayfly Baetis tricaudatus (Ephemeroptera: Baetidae) previously exposed to a mixture of metals in the field exhibited higher survival and growth, and bioaccumulated more cadmium than naive populations. In addition, previously exposed populations had significantly higher metallothionein concentrations. These findings suggest that long-term exposure to metals has resulted in tolerance, and that metallothionein may act as an underlying mechanism for this tolerance.; To determine if there were underlying genetic differences among these populations, a population genetic study was conducted. Mayflies were collected from seven sites on the Arkansas River at four different time points. A region of the ND1 mitochondrial DNA gene was amplified by polymerase chain reaction and analyzed by single strand conformation polymorphism analysis to determine haplotype. Haplotype diversity was generally lower immediately following spring runoff than in late summer, and generally lowest at the most contaminated site. Haplotype diversity was significantly correlated with concentrations of zinc in water, and copper and zinc in periphyton for one of the time points.