LOCALadk Magazine

16 Summer 2015 LOCALadk Magazine LOCALadk Ecosystems on separate continents have remained safe from one anoth- er for many eons thanks to the low likelihood of their interaction. Human activity in recent centuries has introduced these ecosystems to one an- other too quickly and at too great a scale for their own good. Species of all kinds have begun to emerge in places they would almost never be able to reach without our inadvertent help. Their emergence has often been disastrous. In North America, one such species is Eurasian watermilfoil, a submerged aquatic plant once loved for its beauty in aquariums. As its name implies Eurasian watermilfoil (hereafter milfoil) hails from Europe, Asia and North Africa. Its arrival date in North Ameri- ca is a guess of sometime between 1880 and 1940 and the vector for its invasion is un- known. Like any good invader it undoubted- ly used several, among them aquariums and ship's ballasts. Aquariums get dumped out and ships blow their ballast water and a wave of immigrant creatures arrive in the New World much like European humans several hundred years earlier. The invaders that thrive in our ecosystems of- ten do so because the factors that limit their growth in their homeland do not exist in ours. The most aggressive invaders have charac- teristics that promote their own spread. Milfoil thrives in the littoral zone, or the area in a lake shallow enough to support plant growth. In Adirondack lakes this zone can range from the surface down to 25 feet deep depending on water clarity. This invader's ability to self-propagate is incredible to see. The plant's stringy stems are fragile so that any phys- ical disturbance breaks them into fragments. These fragments are able to form new plants so long as they contain a bit of stem with a leaflet node. Later in the growing season the plants actually produce fragments with roots already extended to increase their success in uncolonized lake bottom. While the stems are busy feeding potential new plants into the water column the roots are growing laterally below the mud and creating new stem shoots around the original plant. In an area with a well-es- tablished bed of Eurasian milfoil the stems are densely crowded, loose fragments carpet the lake bottom in and around the bed and up high in the canopy more buoyant fragments break loose and float away in the surface or subsurface currents to form new beds elsewhere. As a result milfoil has quickly spread throughout North America. Global human activity brought milfoil to the Adirondacks and regional human activity helped it spread throughout them to the point where it is confirmed in nearly 60 Adirondack lakes according to the Adirondack Park Invasive Plant Program's 2014 data. Our love of recreational boating has served as an ideal vector allowing milfoil fragments to hitch rides from lake to lake on boat trailers, props and canoes and kayaks. There is prob- ably even some help from waterfowl as frag- ments likely get stuck in their plumage and land in new lakes and ponds with the birds. In the end our pleasure boats serve the same purpose as the aquarium trade and the ne- cessity of ship ballast, they help spread the invasion. Milfoil, thanks to its aggressive nature, grows unhindered in the right conditions. Fertile Adirondack lake bottom provides these con- ditions and milfoil beds rapidly appear. These dense stands of growth cause several problems simultaneously. They add excess nutrients to the water column in the form of decaying plant matter, they decrease oxygen levels in the water hindering fish and in- vertebrates, they impede boat travel and swimming with their thick mats of vegetation, they stagnate shallow areas promoting mosquito growth and reducing water flow and in the long run they convert a diverse and stable ecosystem into a monocultured, unstable one. It's an aquatic ver- sion of the industrial farming problem. Stop The Invasion! By Andrew Lewis

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