by Ian Rogers
Every day, swimmers pass unobtrusively over the George’s Mills benthic barriers that prevent variable milfoil from spreading across Sunapee; boaters receive quick courtesy inspections from blue-shirted Lake Hosts checking for invasive plants; and volunteer weed watchers pull out their Viewscopes or snorkels as they prepare to scour the shorelines for anything suspicious. The measures taken to protect Sunapee from invasive plants have become as familiar to residents as the “Mind if I check your boat for milfoil?” request uttered by the Lake Hosts—but what happens when the rules about invasive species change?
On June 25th, fishermen in the upper Connecticut River near Bloomfield, Vermont discovered a rough white algae clinging to the rocks and reported it to environmental services, who later confirmed it to be the invasive species Didymosphenia geminata. It is commonly referred to as didymo, but can best be visualized by its colorful nickname: Rock Snot.
Didymo is a rapidly reproducing variety of algae that clings to rocks, driftwood, plants, and anything else it comes in contact with. Because it has no natural predators in this part of the world, didymo can quickly blanket an entire riverbed where native plants would otherwise grow. Aquatic insects and other organisms also have difficulty surviving in didymo-infested waters, and a combination of the loss of food and plant cover causes a decline in a river’s fish population. Though didymo poses no threat to humans, its thick, gooey blooms are an eyesore and unpleasant to touch or recreate in—didymo blooms feel like rough tissue paper and turn brown as sediment becomes trapped in them. New Zealand has experienced the worst infestations with didymo appearing in over fifty of its rivers and streams; while in North America didymo has become a problem in Quebec, the Rocky Mountains, and the Tennessee River Valley. This is the first time that it has been spotted in the Northeast.
Didymo, like milfoil, spread to these areas through human activity. The algae can stick to almost anything: boat hulls, kayaks, life jackets, bathing suits, wading boots, fishing tackle, even a dog’s fur; and can live for several days if kept damp. When the surface carrying didymo enters a new waterbody, the algae can then break off and form a new colony. That it only takes a single microscopic cell to infect a river or lake is what makes didymo so difficult to control.
To prevent didymo infestations, the New Zealand Department of Environmental Services and Fish and Game Departments recommend a Check, Clean, and Dry system that is easy to remember:
Check: Before leaving a river, especially one known to have didymo, visually inspect your boat and anything else that has been in the water. Remove any suspicious clumps or bits of sediment and leave them at the river’s edge.
Clean: Wash all surfaces with hot water, or preferably a solution of either 5% dishwashing detergent or 2% bleach, and soak all items for at least one minute. Let felt waders or any neoprene items soak for at least a half hour for a full clean. For boats, a thorough power-wash is adequate.
Dry: If you find yourself unable to wash, let the surface dry in direct sunlight for at least 48 hours before putting it back in the water. Didymo requires moisture to survive, and cannot live for long under dry conditions.
To inform the public of this new threat, articles on didymo appeared in newspapers throughout northern New England, and NHPR featured didymo in a program on invasive species. Environmental officials from New Hampshire and Vermont are also working together on a public awareness campaign that includes posting signs on rivers known to contain didymo, which now includes Vermont’s White River in addition to the Connecticut.
Though didymo thrives best in the cool currents of fast-flowing streams, its appearance close by could have dire consequences for Sunapee. Data collected by Lake Hosts shows that many boaters frequent both Sunapee and the Connecticut River, so the possibility of infestation remains great. Little is known about how well didymo might fare if introduced into a lake, but the algae has been found to thrive around the major inlets and outlets of New Zealand’s Lake Manapouri. All three of Sunapee’s main boat launch ramps are also located near flowing water, which makes them prime candidates for infestation.
This news made everyone at the LSPA nervous, especially since a microscopic didymo cell could be missed by even the most vigilant of Lake Hosts. Briefly, there was talk of mandatory boat washes and equipment checks, or restricted access for boats coming from infected areas. However, such measures would go against the relaxed, free spirit of Sunapee and do more to evoke the draconian restrictions of a George Orwell novel than anything that would actually protect the lake from didymo. Instead, Lake Hosts have begun educating boaters on this new threat, and offer boat washes to anyone coming from the Connecticut River as word of the problem continues to spread
I am continually amazed at how successfully people in the Sunapee area have become informed about variable milfoil and how to prevent it from entering the lake, especially when compared to residents statewide who seem relatively unaware of the problem. I hope that it will not take the appearance of didymo in Sunapee to provoke a similar understanding of this new menace; for it is only by remaining aware of such threats and how to protect against them can we hope to keep our lake free of invasive species.
Date published on web site:
09-06-2007
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