Abstract
Monitoring indicator species is a pragmatic approach to natural resource assessments, especially when the link between the indicator species and ecosystem state is well justified. However, conducting ecosystem assessments over representative spatial scales that are insensitive to local heterogeneity is challenging. We examine the link between polychlorinated biphenyl (PCB) contamination and population density of an aquatic habitat specialist over a large spatial scale using non-invasive genetic spatial capture-recapture. Using American mink (Neovison vison), a predatory mammal and an indicator of aquatic ecosystems, we compared estimates of density in two major river systems, one with extremely high levels of PCB contamination (Hudson River), and a hydrologically independent river with lower PCB levels (Mohawk River). Our work supports the hypothesis that mink densities are substantially (1.64–1.67 times) lower in the contaminated river system. We demonstrate the value of coupling the indicator species concept with well-conceived and spatially representative monitoring protocols. PCBs have demonstrable detrimental effects on aquatic ecosystems, including mink, and these effects are likely to be profound and long-lasting, manifesting as population-level impacts. Through integrating non-invasive data collection, genetic analysis, and spatial capture-recapture methods, we present a monitoring framework for generating robust density estimates across large spatial scales.
Highlights
Monitoring indicator species is a pragmatic approach to natural resource assessments, especially when the link between the indicator species and ecosystem state is well justified
The U.S Environmental Protection Agency (EPA) has estimated that the two General Electric Company (GE) manufacturing facilities located in Fort Edward and Hudson Falls, New York, discharged up to 1.3 million pounds of polychlorinated biphenyl (PCB) into the river[7], but the actual amount of PCBs discharged to the river, while unknown, could be significantly higher
Our results provide compelling evidence that the density of American mink is significantly lower in the Hudson River than in the Mohawk River in both years (Fig. 2)
Summary
Monitoring indicator species is a pragmatic approach to natural resource assessments, especially when the link between the indicator species and ecosystem state is well justified. The U.S Environmental Protection Agency (EPA) has estimated that the two General Electric Company (GE) manufacturing facilities located in Fort Edward and Hudson Falls, New York, discharged up to 1.3 million pounds of PCBs into the river[7], but the actual amount of PCBs discharged to the river, while unknown, could be significantly higher These unprecedented levels of discharge, and the subsequent releases from fractured bedrock, and erosion of contaminated soils and sediments have contaminated the riparian habitats including the river water, sediments, flood plains, and biota[8], with the potential to influence the ecology of fish and wildlife that inhabit these systems. In the Hudson River Valley, PCB burdens found in mink are positively associated with local environmental contamination levels[18,19] and in known contaminated areas, these burdens were 2.8 times the levels responsible for reproductive impairment[20], and 6.6 times the levels that can lead to potential health impairment[21], whereas in uncontaminated or less contaminated areas, burdens were generally below the levels that induce adverse toxicological effects[21]
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