What is Diver Assisted Suction Harvesting (DASH)?
For the first time in the Adirondack Park's history, the Adirondack Park Agency (APA) has approved the use of diver assisted suction harvesting (DASH) as a control method for Eurasian Watermilfoil (EWM). A jurisdictional determination of approval was provided to Aqualogic Inc. (Aqualogic); a company based out of Gilford, New Hampshire that focuses on integrated management techniques for aquatic invasive plants. During DASH divers swim along the lake bottom to hand harvest target plant species. A key difference between DASH and more traditional hand harvesting methods is that divers don't have to come to the surface as often to dispose of harvested plants. Instead, divers carefully feed the aquatic vegetation into the intake of a submerged suction hose that transports water and the plant material to the surface and into a boat's bagging station. This means divers spend less time at the water's surface and more time at the bottom, harvesting plants.
What is Eurasian watermilfoil (EWM)?
Of all the aquatic invasive plant species in the Adirondacks, Eurasian watermilfoil (Myriophyllum spicatum) is one of the most well-known and widespread. This submerged aquatic invasive plant is well adapted to the region's climate and often thrives in lakes and ponds when introduced. Approximately 60 Adirondack lakes and ponds currently have infestations of EWM. Due to factors such as a lack of natural predators and the plant's ability to monopolize resources, EWM can quickly proliferate in a waterbody. Dense mats of EWM eventually form that outcompete native aquatic plant species, impede recreational boating and swimming, and reduce shoreline property values.
In early May I was fortunate to join the Adirondack Park Agency's Freshwater Analyst, Leigh Walrath, on a trip to Minerva Lake where the lake association and town have been combating an aggressive infestation of EWM. The town had recently decided to pursue DASH with Aqualogic after failed attempts to maintain the infestation, over previous years, with traditional hand harvesting techniques. My goal for the day was to shadow the Aqualogic team as they worked and gain a better understanding of the DASH method and its effectiveness. We first arrived at Minerva Beach and started the half mile paddle north towards the EWM harvesting area. As we glided into a hidden bay, the Aqualogic team temporarily halted operations to welcome us aboard their barge.
After brief introductions, John Jude, President of Aqualogic Inc., and his son Dominic started the DASH unit while another diver waited in the water. Cold, clear water quickly began to rush out of a long suction hose and over a sorting tray within the boat. Looking over the port side of the harvester, I could see the large, black suction hose move through the water as the diver slowly made his way along the bottom of the lake. It wasn't long before a large EWM plant shot out of the hose and fell into the sorting tray. Dominic quickly grabbed the sample to demonstrate how the entire plant had been harvested including roots, stem, and leaves. He then placed the plant in a porous bag, suspended at the end of the sorting tray, for disposal. The DASH system is meant to completely remove aquatic vegetation while not suctioning or dredging lake bottom sediments. Aqualogic's DASH unit also has a triple filtration system that filters harvest water extensively before it is allowed to reenter the lake.
With so much EWM being harvested from Minerva Lake this season I began to wonder what happened to all that harvested plant material. I was pleased to hear from Dominic that the vegetation is composted and given to a local garden club for use as fertilizer. Aqualogic still has a significant amount of harvesting ahead of them, but preliminary results may indicate that Minerva Lake is back on track in its DASH for sustained EWM control.