Elevated pH: An Effective, Economical and Safe Tool to Control Release of Invasive Species

Increased global human travel and commerce create substantial challenges for managers and regulators that seek to protect natural ecosystems from infestation by invasive aquatic species. We studied the efficacy of elevated pH (11.4 to 12) as a tool to treat and disinfect tanks, including ballast systems to prevent the transfer of aquatic invasive species. Our trials included small scale laboratory tests and scaled up shipboard field trials to illustrate the effectiveness of aqueous solutions of elevated pH as disinfectant. In laboratory trials we estimated the LT99 for several life stages of quagga mussels, New Zealand mudsnails, and Asian clams in static renewal tests. Trials aboard the National Park Service’s Ranger III evaluated the efficacy of sodium hydroxide at pH 11.6. We conducted two trials, each with replicated test and controls testing naturally occurring plankton from Portage Lake pumped though ballast pumps. Trials lasted 12 and 18 h including retention at target pH, neutralizing steps with an engineered carbonization/mixing system from the ship’s diesel engine. Tests were 100% effective in killing all zooplankton regardless of size. These results provide promising data to support elevated pH as a safe, economical and effective disinfection for applications in large or small scale systems.