Abstract
Aquatic invasive alien species (IAS) negatively impact freshwater ecosystems worldwide. As suppression and eradication of established invader populations are often complex, costly and resource-intensive, the prevention of further invader spread is considered a key aspect of proactive management measures. Although broad-spectrum aquatic disinfectants have been suggested as a suitable decontamination mechanism to enhance invader spread-prevention strategies, inconsistencies concerning their effectiveness are reported within the literature. Here, we examine the use of two aquatic disinfectants, which were developed to kill damaging microbes, to induce substantial degradation of the apical fragmentary propagules of five invasive macrophytes: Crassula helmsii (Kirk) Cockayne; Egeria densa Planchon; Elodea canadensis Michx; Hydrocotyle ranunculoides Linnaeus; Lagarosiphon major (Ridley) Moss. Apical fragments were exposed to 0% (0 g L-1), 2% (20 g L-1) or 4% (40 g L-1) solutions of Virkon® Aquatic and Virasure® Aquatic, for submergence treatments of five, fifteen, thirty or sixty minutes. After 28 days, degradation of treated fragments was significantly greater than that of control groups, particularly for 4% solutions and longer exposure times. Despite this, sustained viability in relation to shoot and/or root regrowth was exhibited by almost all plant species. However, new shoot growth rates were significantly reduced following exposure to all treatments. At matched concentrations, there was no significant difference between the two disinfectants. Overall, it appears that the examined aquatic disinfectants will not curtail the spread of these invasive macrophytes. Yet, longer submergence times, multiple applications and synergistic effects of different biosecurity treatments may enhance preventative measures against further spread and this requires investigation.
Highlights
Aquatic invasive alien species (IAS) have adversely altered the biodiversity, ecological functioning, and economic and social value of freshwater ecosystems (Ricciardi and MacIsaac 2010; Piria et al 2017)
All species were collected throughout Northern Ireland (NI) from a variety of sites, other than H. ranunculoides which was collected in Great Britain (Table 1)
Sustained viability, as evidenced by shoot or root regrowth, was demonstrated by C. helmsii, E. canadensis and L. major, scaled degradation significantly increased with treatment (χ2 = 163.53, df = 4, P < 0.001)
Summary
Aquatic invasive alien species (IAS) have adversely altered the biodiversity, ecological functioning, and economic and social value of freshwater ecosystems (Ricciardi and MacIsaac 2010; Piria et al 2017). Management options for effective suppression and eradication of established IAS populations are available, these are often complex, expensive and resource-intensive endeavours, which can be damaging to non-target species (Caffrey et al 2010; Hussner et al 2017; Coughlan et al 2018b, 2019b). Freshwater ecosystems are especially susceptible to the influx of damaging IAS due to the presence of numerous transport pathways and a plethora of associated vectors (Dudgeon et al 2006; Ricciardi and MacIsaac 2010; Coughlan et al 2017a). The concept of spread-prevention is integral to the Convention on Biological Diversity, and is strongly emphasised in national, e.g. EC (Birds and Natural Habitats) Regulations SI 477/2011, and international policy and legislation, such as EU Regulation 1143/2014, New Zealand Biosecurity Strategy, Great Britain Non-Native Species Strategy (EC 2011; EU 2014; GBNNSS 2015; PGNZ 2016)
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