Phragmites autralis control on Utah Lake water qualityDr. E. Cadet, Clayton Rawson, William Pacheco, Sophia Garrido, Carol Cardenas-Bejar

The introduction of the invasive perennial grass Phragmites autralis 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. autralis for ecosystem stability, its removal must be done holistically and thoughtfully. This study evaluates the impact of Phragmites spp. destruction by herbicide on water quality. Five replicate plant, water and sediment samples (0-45 cm depth) were collected near Lindon Harbor where Aqua Neat herbicide has been applied. Water samples were placed in polyethylene containers and core samples were collected using a pre-washed stainless steel core sampler, placed in Ziploc bags and iced. Samples were collected in June 2016, one month prior to aerial treatment to determine the initial concentrations of trace metals (As, Cd, Zn, Cr, Ni, Pb and Cu) and Aqua Neat pesticide (glyphosate) levels. Following treatment, samples will be collected at the same site once each month for 5 consecutive months to determine changes in trace metal concentration in plant, water and sediment. In the lab, sediment core samples were divided into 15 cm increments to determine the vertical migration of trace metals in the sediment. All samples will be acid digested, filtered and analyzed for trace metal content using the ICP-OES. To understand the behavior of trace element in each respective site, parameters such as temperature, pH, organic matter (OM), electrical conductivity, redox potential, dissolved oxygen, particle size distribution, total nitrogen, and total phosphate will be determined.

Over the past few decades anthropogenic activities have introduced significant amounts of pollutants into Utah Lake. When sufficiently elevated contaminants such as trace metals and polychlorinated biphenyl compounds accumulate in water bodies, they can cause harm to the ecosystem and disturb the biochemical equilibrium of the lake. Considering that this area has been populated since the mid-1800s, with a current population size of over 500,000 in Provo city alone, one would expect a tremendously high level of toxic trace elements in Utah Lake. However, there are several natural processes which serve as sinks whereby trace elements and other contaminants may be sequestered, reducing their bioavailability and concentrations in the lake. Important sinks in Utah Lake include sediment trapping and bioaccumulation of contaminants in fish as well as precipitation of contaminants as insoluble solids in the water column. However, an important sink which has been ignored in the current management of Utah Lake is that of the plant life, particularly Phragmites australis (Cav.) Trin. Ex. Steudel. Because of its invasive nature, this common reed has proliferated at an alarming rate since its discovery in the 1980s. It is perceived as a weed which is deteriorating the ecosystem by outcompeting the native plant species and decreasing the aesthetic value of the lake. For this reason, state legislators have allocated significant funding for the removal of P. australis. This removal process was initiated in 2008 without considering the beneficial role it may have in the ecosystem of the lake in its present condition. The Phragmites spp. removal program involves the scheduled indiscriminate aerial application of the herbicide Aqua Neat (with glyphosate) over sections of the lake containing patches of the Phragmitesplant three to four times a year followed by mowing with the purpose of its eventual eradication, leaving the roots in the sediment (Utah State, 2014). Studies have shown that Phragmites plants sequester trace metals in its roots (Weis, JS, and P Weis. 2004; Wu et al., 2013

Hypothesis

Methodology

Results

Conclusions

Site 1 Urban – TreatedSite 2 Industrial – TreatedSite 3 Municipal – UntreatedSite 4 Wildlife Refuge - UntreatedSite 5 Recreational - TreatedSite 6 Agriculture - UntreatedSite 7 Mining - TreatedSite 8 Urban – Treated

Soil

• Air Dry• Oven Dry• Grind• Sieve

• Pre-Digestion• Digestion• Filtration• ICP-OES

Water

• Filter

• Digest

• Filter

• ICP-OES

Plant

• Separate Root-Bound Soil

• Acid Wash• Oven Dry• Grind

• Pre-Digestion• Digestion• Filter

• ICP-OES

• Observation• Stunted plants• Altered plant life cycles• Changes in plant, insect and animal populations• Changes in soil odor and appearance• Possible plant hybrids• Increased algae and mosquitos• Phragmites roots in some cases can accumulate trace metal contaminants even during decomposition

(a unique characteristic of this plant, confirming the results of other authors. • Data

• Trace metal content changes in soil, water, and plants.• Slight change in pH and DO change

• There is a negative impact on Utah Lake water quality with regard to trace metal levels according to our preliminary. Onsite observations show that method of Phragmites australis removal is changing Utah Lake.

We hypothesize that the current method of removal of Phragmites australis may have an adverse impact on water quality in Utah Lake due to the release of trace metals from their roots and

rhizomes during decomposition

Site Two Phragmites autrali

Abstract

Project Summary

Brackish Water