Sutherland JW, Turcotte RJ, Molden E, Moriarty V, Kelly M, Aubel M, Foss A. 2021. The detection of airborne anatoxin-a (ATX) on glass fiber filters during a harmful algal bloom. Lake Reserv Manage. XX:XX-XX.Anatoxin-a (ATX) is a neurotoxic alkaloid produced by certain cyanobacteria genera that can occur during harmful algal blooms (HABs). This study is the first to report airborne ATX collected outside an aquatic ecosystem. ATX was captured on glass fiber filters using a field-deployed air sampler during an active 2019 HAB at Capaum Pond on Nantucket Island, Massachusetts (USA). These findings indicate that emission of ATX molecules, or cyanobacteria containing ATX, during HABs presents a potential human health exposure not previously examined.