Filed evaluation of EarthTec ZM for zebra mussel (Dreissena polymorpha) control. M.F. Albright 1 INTRODUCTION

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1 Filed evaluation of EarthTec ZM for zebra mussel (Dreissena polymorpha) control M.F. Albright 1 INTRODUCTION Zebra mussels (Dreissena polymorpha) native to Eurasia, were first documented in North America in 1986 in Lake Erie (Carlton 2008) and were first seen in Otsego lake in 2007 (Waterfield 2009). They are prolific spawners, the veliger (larval) stage lasting days, after which settling occurs (Mackie and Claudi 2010). Juvenile mussels anchor themselves to the substrate using byssal threads. As such, they often thrive growing attached to the inside of intake pipe, where flowing water provides ample dissolved oxygen and a steady food supple (Connelly et al. 2007). The Village of Cooperstown, Otsego County, NY, uses Otsego Lake as its water supply. A 14 (0.35 m) pipe extends approximately 1,300 m from the treatment facility to the intake, which is about 1 m off bottom at 14 m depth (Elliot 2017) (see Figure 2). Following the establishment of zebra mussels, efforts to prevent plugging to the intake pipe have relied primarily on using a pig, or a semi-flexible plug that is forced through the pipe using back pressure from stored water. The potential of this plug from lodging in the pipe is of considerable concern. From , potassium permanganate, an oxidizing agent, was injected into the opening of the pipe, partly as a disinfectant and partly in an attempt to control mussels. This was accomplished by feeding the chemical through a small pipe attached to the underside of the intake line and through injectors at the mouth. Given the limited contact time for water to flow through the line (about 1 hour) and a limited rate of injection, a dose/duration rate was insufficient to control the mussels. That adult mussels were dislodged during pigging implied that continual flow of permanganate through the pipe was not effective at preventing mussel growth. Beginning in summer 2017, arrangements were made to use EarthTec as a control agent. This is a formulation of copper sulfate pentahydrate with a base blend, the active form of copper being the cupric ion form (Watters et al. 2013). It was initially intended as an algaecide targeting cyanobacteria, but has since been recognized to control dreissenid mussels and has been labeled as such (EarthTec QZ). Constant use of EarthTec QZ at the Cooperstown Treatment Plant had commenced by mid-august and it was used through October at a tartgeted rate of 1-2 mg/l (= mg/l copper). 1 CLM. SUNY Oneonta Biological Field Station.

2 This study was an abbreviated field component that followed a more rigorous laboratory evaluation of concentration/duration combinations of EarthTec QZ necessary to kill adult and veliger zebra mussels (Iwanyckyj et al. 2018). METHODS The chambers used in the mortality tests, or bioboxes, were provided by RNT Consulting, Inc. The bioboxes were modified 60 l Coleman coolers (Figure 1).The inflow and outflow were both oriented upward near the top of the unit. Three plates were inserted inside the box, the first and third being held about 6 cm off the bottom, the second being tight to the bottom. This configuration promoted mixing and circulation through the unit. Figure 1. A biobox, used in adult zebra mussel mortality field experiments.

3 Two bioboxes were employed. The experimental unit was maintained at the Cooperstown Water Treatment Plant. It was plumbed in to the water system immediately where treated water returns to the plant, and as such represented EarthTec QZ concentrations as introduced at the end of the intake pipe. The control biobox was maintained at the Biological Field Station. It was fed with raw lake water drawn from Otsego Lake at a depth of about 5 m, about 0.5 m off bottom, in Rat Cove (Figure 2). Three Mile Point Control withdraw Experimental withdraw Figure 2. Map of Otsego Lake, showing locations of water withdraw for experimental and control biobox experiments and Three Mile Point, where mussels were collected for the experiments.

4 Adult zebra mussels were collected from the substrate off Three Mile Point (see Figure 2) the day before being introduced into the bioboxes. They were rinsed well in a flow through tank overnight, after which fifty mussels were added to each of four mesh bags (Doc Foster CE ). Bags were paired, with draw strings tied together, and were draped over the central plate (see Figure 1). Flow through both bioboxes was adjusted to about 3 gallons (12 l) per minute (Hammond 2017). Both experiments were initiated on 11 September By 19 September, most mussels in the experimental biobox were dead, so two more bags of mussels were added to this unit on 20 September. Mortality was evaluated at both the control and the experiment on 19, 22 and 28 September and 5 and 12 October Mussel s valves were gently probed; those remaining tightly closed were considered living, while those not reacting or those gaping were considered dead. At the end of each evaluation, dead mussels were removed and those living were returned to the bags and to the appropriate biobox. Also at the time of each evaluation, physical water quality parameters were accessed to ensure conditions between the bioboxes were similar and that conditions were favorable for mussel survival. Temperature, ph, specific conductance and dissolved oxygen were measured with a 6820V2-M YSI multiparameter water quality sonde. Free copper concentrations were measured daily at the Water Treatment Plant using a Hach copper colorimeter. These concentrations were spot-checked on samples measured at the Biological Field Station using the bathocuproine method (3500-Cu C) (APHA 2012) as a measure of quality assurance. RESULTS AND DISCUSION Temperature (mean o C, SD= 0.81), specific conductance (mean mmho/cm, SD= 0.005), ph (mean 8.08, SD= 0.13) and dissolved oxygen (mean 8.05 mg/l, SD= 0.31) did not differ between the control and experimental bioboxes. All parameters fell within the range considered suitable for zebra mussels (Mackie and Claudi 2010, Claudi et al. 2012). Over the course of the study, free copper concentrations in the water flowing through the experimental tank averaged 0.092mg/l (SD= 0.47), representing a mean concentration of EarthTec QZ of 1.53 mg/l. Figure 3 plots mortality over time for zebra mussels in both the control (n=100) and experimental (EarthTec QZ-dosed) (n= 200) bioboxes. Over the course of the experiment, 3/100 of the control mussels died. For the experimental mussels, about 50% mortality was achieved in about 5 days and all were dead by the end of the experiment. The efficacy of EarthTec QZ in these trials surpassed concurrent time/dose studies conducted in the laboratory (Iwanyckyj et al. 2018), where copper concentrations of 0.1 mg/l

5 Mortality (similar to that evaluated here) achieved only about 30% mortality over the course of 7 days. This would imply that chronic exposure to lower concentrations is an effective strategy to controlling these organisms, as newly attached mussels would be in constant contact with a fresh solution of this copper source Experimental Control Day Figure 3. Mortality of zebra mussels in the experimental bioboxes, exposed to ~1.5 mg/l EarthTec ZM (= 0.09 mg/l free copper) vs that in the control biobox. REFERENCES APHA, AWWA, WPCF Standard methods for the examination of water and wastewater, 17 th ed. American Public Health Association. Washington, DC. Carlton J.T The zebra mussel Dreissena polymorpha found in North America in 1986 and Journal of Great Lakes Research 34: Claudi, R. A. Graves, A.C. Tarborelli, R.J. Prescott and S.E. Mastitsky Impacts of ph on survival and settlement of dreissenid mussels. Aquatic Invasions 7: Connelly N, C. O'Neill, B. Knuth and T. Brown Economic impacts of zebra mussels on drinking water treatment and electric power generation facilities. Elliot, D Personal communication. Cooperstown, NY. Hammond, D Personal communication. Earth Science labs, Inc. Bentonville, AR.

6 Iwanyckyj, E., M. Albright and D. Stich Effectiveness of molluscicide EarthTec QZ on adult and veliger zebra mussel (Dreissena polymorpha) mortality. In 50 th Ann. Rept. (2017). SUNY Oneonta Biol. Fld. Sta., SUNY Oneonta. Macki, G.L. and R. Claudi Monitoring and control of macrofouling mollusks in fresh water systems. CRC Press. Boca Raton, Fl. Waterfield, H.A Update on zebra mussel (Dreissena polymorpha) invasion and establishment in Otsego Lake, In 41 st Ann. Rept. (2008). SUNY Oneonta Biol. Fld. Sta., SUNY Oneonta. Watters, A., S.L. Gerstenberger and W.H. Wong Effectiveness of EarthTec for killing invasive quagga mussels (Dreissena rostriformis bugensis) and preventing their colonization in the western United States. Biofouling: The Journal of Bioadhesion and Biofilm Research, 29:1,