ORIGINAL PAPER Vacuolar myelinopathy: waterbird risk on a southeastern impoundment co-infested with Hydrilla verticillata and Aetokthonos hydrillicola Brigette N. Haram . Susan B. Wilde . Michael J. Chamberlain . Kenneth H. Boyd Received: 5 July 2017 / Accepted: 4 May 2020 / Published online: 21 May 2020 Ó Springer Nature Switzerland AG 2020 Abstract Invasive aquatic plants such as hydrilla (Hydrilla verticillata) are spreading through North America, impeding navigation and hydropower facil- ities, reducing macrophyte biodiversity, and affecting wildlife health. Managing invasive plants is challeng- ing, especially when the scope of effects to aquatic ecosystems is not fully understood. Hydrilla supports a novel epiphytic cyanobacterium (Aetokthonos hydrillicola) which is implicated in vacuolar myelinopathy (VM) disease. Ingestion of aquatic plants with A. hydrillicola causes often fatal neuro- logical impairment to waterbirds and is transferred from herbivore to predator. We investigated potential VM risk to wildlife species using hydrilla infested sites at a southeastern reservoir and developed a qualitative risk assessment for waterbird species that inhabited the reservoir during fall and early winter. We found that all avian species we observed on the reservoir used hydrilla beds to forage. Seasonal diets of these species exposed them to A. hydrillicola toxin either directly through herbivory, or indirectly through prey with dietary links to hydrilla and the cyanobac- teria. Avian and mammalian scavengers are also exposed to the toxin through waterbird carcasses. We present evidence that the current list of species affected by VM is not complete, and further studies are needed to determine the full scope of species vulnerable to VM in lakes and reservoirs with hydrilla and A. hydrillicola. Keywords Vacuolar myelinopathy Á Avian vacuolar myelinopathy Á Hydrilla Á Cyanobacteria Á Aetokthonos hydrillicola Á Neurotoxin Á Invasive aquatic plants Á Risk assessment Á Wildlife disease Introduction A better understanding of the ecological impacts of invasive species is crucial for prioritizing management efforts. Invasive species influence multiple trophic levels and detrimental effects of invasions are not always immediately clear, especially with invasive plants (Parker et al. 1999; Santos et al. 2011). Resource managers must consider ecological and economic factors when developing management strategies, and these decisions are complicated when information on the effects of invasive plants is conflicting or incomplete. In aquatic systems, sub- merged aquatic vegetation (SAV) can provide ecosys- tem services such as improving water clarity and B. N. Haram (&) Á S. B. Wilde Á M. J. Chamberlain Warnell School of Forestry and Natural Resources, The University of Georgia, 180 E. Green St, Athens, GA 30602, USA e-mail: bnharam@gmail.com K. H. Boyd US Army Corps of Engineers, J. Strom Thurmond Project, 510 Clarks Hill Highway, Clarks Hill, SC 29821, USA 123 Biol Invasions (2020) 22:2651–2660 https://doi.org/10.1007/s10530-020-02282-w