Viability of Aquatic Plant Fragments following Desiccation

Abstract Desiccation following prolonged air exposure challenges survival of aquatic plants during droughts, water drawdowns, and overland dispersal. To improve predictions of plant response to air exposure, we observed the viability of vegetative fragments of 10 aquatic plant species (Cabomba caroliniana, Ceratophyllum demersum, Elodea canadensis, Egeria densa, Myriophyllum aquaticum, Myriophyllum heterophyllum, Myriophyllum spicatum, Potamogeton crispus, Potamogeton richardsonii, and Hydrilla verticillata) following desiccation. We recorded mass loss, desiccation rate, and plant fragment survival across a range of air exposures. Mass loss accurately predicted viability of aquatic plant fragments upon reintroduction to water. However, similar periods of air exposure differentially affected viability between species. Understanding viability following desiccation can contribute to predicting dispersal, improving eradication protocols, and disposing of aquatic plants following removal from invaded lakes or contaminated equipment. Nomenclature: Brazilian egeria, Egeria densa Planch., common elodea, Elodea canadensis Michx., coontail, Ceratophyllum demersum L., curlyleaf pondweed, Potamogeton crispus L., Eurasian watermilfoil, Myriophyllum spicatum L., fanwort, Cabomba caroliniana Gray, hydrilla, Hydrilla verticillata (L. f.) Royle, parrotfeather, Myriophyllum aquaticum (Vell.) Verdc., Richardson's pondweed, Potamogeton richardsonii (A. Bennett) Rydb., variable-leaf watermilfoil, Myriophyllum heterophyllum Michx Management Implications: A framework for assessing the vulnerability of ecosystems to invasion by aquatic weeds must consider many aspects of species invasions: which species will arrive, how will they get there, and will they establish and generate impacts following introduction. Knowledge about physiological responses to stressors provides critical input to such a framework. In our study, we compared the viability of vegetative fragments of 10 aquatic plant species following variable periods of desiccation. We found that while desiccation expectedly decreased plant viability, desiccation rates and tolerances differed significantly between plant species. The species-specific nature of desiccation warrants species-specific management actions. Our results suggest that boat launch inspection programs should be extra vigilant in their search for species that are relatively desiccation-resistant or –tolerant, such as emergent Myriophyllum aquaticum. On the other hand, our finding that some common invasive plants (Ceratophyllum demersum, Hydrilla verticillata) are comparatively intolerant to air exposure suggests that for these species, greater attention should be given to specific situations that promote insulation of vegetative material (e.g., entrainment in nets or anchor wells, burial in sediments), plant propagules that are more tolerant or resistant to desiccation (e.g., seeds or tubers), and alternative invasion pathways (e.g., water garden contaminants).