Die Hard: impact of aquatic disinfectants on the survival and viability of invasive Elodea nuttallii

Abstract

Aquatic invasive species (AIS) continue to adversely influence freshwater ecosystems worldwide. Management protocols designed to prevent further invader spread are essential, as control and eradication of established AIS populations are often complex, costly, resource-intensive, and can be relatively ineffective. Therefore, in-field biosecurity techniques designed to deliver effective decontamination of water users’ equipment, e.g. angler’s nets, footwear, and kayaks, are needed. Disinfection through brief submergence in chemical solutions may be beneficial. Although broad-spectrum, aquatic disinfectants have been recommended as suitable biosecurity agents, the ability of these chemicals to inhibit invader spread remains poorly understood. Here, we examined the effectiveness of two aquatic disinfectants, Virasure® Aquatic and Virkon® Aquatic, to reduce growth rates, induce biodegradation, and decrease shoot and root production at the fragmentary propagule stage of the prolific invasive macrophyte, Elodea nuttallii (Planchon) H. St. John, 1920. We examined the efficacy of both chemicals at submergence times of one, two and five minutes, using 0% (0 g L−1), 1% (10 g L−1) and 4% (40 g L−1) disinfectant solutions. Both apical and mid-stem fragmentary sections were examined separately. A biodegradation scale was applied to visually assess tissue degradation and/or resumption of growth. Although E. nuttallii displayed substantial and sustained degradation after all disinfection treatments, all fragments demonstrated viability through resumption of shoot or root growth over the observation period. Therefore, at the examined concentrations and exposure times, it appears that these broad-spectrum aquatic disinfectants are not capable of curtailing the spread of invasive E. nuttallii. However, longer submergence times, multiple applications and synergistic effects of different biosecurity treatments could potentially prevent further E. nuttallii spread and this requires investigation.