Autonomous suction harvesting as a novel approach to aquatic invasive plant control

In response to the mounting ecological and economic impacts of aquatic invasive plants, management actions now include a wide array of mechanical, physical, biological, and chemical control strategies. Diver-assisted suction harvesting (DASH) is a common physical approach but is well acknowledged to be labor intensive, costly, and to exert a high physical toll on divers. These limitations have sparked technological innovation in the form of prototyping a new methodology called autonomous suction harvesting (ASH) that replaces the diver with a remotely operated vehicle. The present study evaluated the efficiency, effectiveness, and unintended ecological effects of DASH and ASH when used to control nonnative Myriophyllum spicatum L. According to this field-based experiment conducted in Star Lake, Washington, USA, both suction harvesting methods suppressed the biomass of M. spicatum, but with some key differences. Harvest efficiency was 2× greater for DASH (10.3 kg/h) compared with ASH (5.0 kg/h), which was a result of additional time needed for the remotely operated vehicle to navigate submerged obstacles (e.g., logs) when abundant in the littoral zone. Suppression effectiveness of both approaches was similarly encouraging. Assessed 1 y after treatment, stands subject to either DASH or ASH methods had lower M. spicatum densities compared with control stands, which showed substantial natural increases over time. Stem fragmentation occurred during suction harvesting, and floating M. spicatum fragments not successfully removed averaged ∼20% (ASH) and ∼2% (DASH) of the total biomass harvested. Nontarget plants were also accidentally harvested during the treatments, with biomass ranging between 1 and 4× greater than M. spicatum biomass harvested. Macrophyte and epiphytic invertebrate community composition assessed 1 y after treatment showed no change when subject to either DASH or ASH. The present study offers an early proof-of-concept evaluation of ASH to suppress M. spicatum and highlights opportunities to improve the efficiency and effectiveness of this novel approach. Given that the growing challenges of aquatic invasive plants are outpacing current management strategies, developing innovative technological solutions provides an exciting research frontier in the freshwater sciences.