摘要：Abstract Unlike ionic copper, chelated copper herbicides reduce fish toxicity by chaperoning copper. Application guidelines that were developed based on toxicity data from ionic copper may therefore be too strict for chelated copper herbicides, limiting their application to concentrations ineffective against target plants. Our goals were to examine the toxicity of the chelated copper herbicide NautiqueTM relative to other copper herbicides in laboratory and field trials. Our laboratory results showed that NautiqueTM was two orders of magnitude less toxic than CaptainTM and copper sulfate, indicating that it had a larger margin of safety for non-target fish. The results of our caged fish study in Greene County, NY, however, indicated that NautiqueTM can elevate fish mortality in field settings at concentrations much lower than those observed in the laboratory. Mortality risk for caged fish within the first 72 h after treatment was 2.3 times greater, on average, in the treatment sites than the reference sites. The elevated fish toxicity we observed in the field trials could have been affected by high water temperature. In our laboratory trials, a higher percentage of fathead minnows died at 28°C than at 22°C after NautiqueTM exposure. It is possible that the stress of the higher lake water temperatures (29–34°C), particularly for caged fish that could not descend to cooler waters, increased NautiqueTM toxicity. Although our laboratory results indicate that NautiqueTM may have fewer impacts on non-target fish than other copper formulations at concentrations effective for aquatic plant control, field trials indicate that the margin of safety of NautiqueTM may be lower for fish in warm lake waters. Warming climate trends may therefore increase and complicate the challenges of invasive macrophyte control.
