Research Catalyst Grantee
Utah Valley University
Impact of Phragmites australis control on Utah Lake water quality
The introduction of the invasive perennial grass Phragmites australis in the 1980s has dramatically impacted the ecosystem of Utah Lake. This invasive species has choked out native plants, reducing biodiversity and decreasing the aesthetic value of the lake. State legislators have thus allocated significant funding for its elimination. The current method of removal involves aerial application of glyphosate-based herbicides followed by mowing, leaving the roots in the sediment. However, studies have shown that Phragmites plants sequester trace metals in their roots. Thus, management in this fashion only recycles the contaminants into the lake, even potentially worsening the water quality by introducing herbicides to the system. While it is important to control proliferation of P. australis for ecosystem stability, its removal must be done holistically and thoughtfully. This field study evaluates the impact of Phragmites spp. destruction by herbicide (with glyphosate) followed by mowing on water quality. Five replicate core sediment samples (0-90 cm depth) will be collected in 3 locations where Aqua Neat herbicide has been applied and plant smashing has occurred using a pre-washed stainless steel core sampler, placed in Ziploc bags and iced. Also, water samples will be obtained at a depth of 6-12 inches above the sediment core samples at the same locations. Additional samples including plants will be collected in three separate sites where the herbicide has not been applied to serve as controls. Samples will be collected in late spring, one month prior to aerial treatment to determine trace metal (As, Cd, Zn, Cr, Ni, Pb and Cu) concentration and Aqua Neat pesticide (glyphosate) levels. Within two days following aerial treatment, samples will be collected to determine actual concentration of the pesticide applied. Thereafter, samples will be randomly collected once each month for 5 consecutive months to ascertain changes in trace metal concentration, rate of metal release and rate of herbicide degradation. In the lab, samples will be prepped for acid microwave digestion, filtered and analyzed for trace metal content using the ICP-OES. Samples will be sent to the Utility Testing Lab in Salt Lake City for herbicide concentration determination. We hypothesize that trace metal concentration in sediment and water in locations where herbicide has been applied will be increasingly higher with time due to the slow decomposition of plant biomass relative to locations where Aqua Neat has not been applied, thereby reducing water quality.This work will use an interdisciplinary approach in the investigation of this environmental issue and will be performed by students (at least 4) under the supervision of scientists in different discipline.
Steven Emerman, Utah Valley University
Weihong Wang, Utah Valley University