Survival of invasive aquatic plants after air exposure and implications for dispersal by recreational boats

Background/Question/Methods

Recreational boating is widely recognized as an important vector for overland transport of invasive aquatic plants. Since their dominant form of recruitment is vegetative reproduction, entangled fragments on boats and trailers can establish new populations. The effectiveness of recreational boats as a transport vector relies on the resistance of macrophytes to air exposure. During the summers of 2011 and 2012, we conducted nine field experiments in northern Wisconsin to assess air tolerance of Eurasian water-milfoil (Myriophyllum spicatum) and curly-leaf pondweed (Potamogeton crispus). We simulated conditions these plants would experience when ensnared on boats and trailers by testing both single stems and coiled plants. Each experiment involved hanging macrophytes to dry for varying amounts of time and assessing viability based on positive growth rates after rehydration.

Results/Conclusions

Single stems of M. spicatum and P. crispus were viable for up to 24h and 18h of air exposure, respectively. Coiling extended the viability of M. spicatum to 72h of air exposure. Vegetative propagules, such as the turions of P. crispus, may also be carried by boats. A preliminary experiment indicated turions can survive at least 2 weeks air exposure. The fact that boaters can easily travel among many lakes within a few days suggests that most lakes are susceptible to introduction of viable plants, and so management should continue to focus attention on boat cleaning, especially at lakes known to have populations of invasive species.