The voice of the woman on the other end of the phone was laden with concern.  She called to report a possible infestation of Eurasian watermilfoil in the outlet of Sacandaga Lake, just past the Route 8 bridge in Lake Pleasant.  I took down her contact information and told her I would check it out.

That evening, my husband and I loaded up his Carolina Skiff with a glass jar full of water to collect a plant sample, a cooler to keep the sample cold, and an aquatic plant identification book.  The sky was streaked with ominous clouds against a low, red sun, and the boat ride would have been enjoyable if I were not so anxious to get to the plant bed.  Images of benthic mats and hand harvesting SCUBA divers flashed before my eyes, and my thoughts turned to the expensive cost of milfoil management that could take years to successfully eradicate.  According to a 2003 study, New York State spends an estimated $500,000 to control Eurasian watermilfoil each year.

Matt slowed the motor and pulled up to the spot.  Starring into the water with polarized sunglasses, I breathed a sigh of relief.  “It’s not Eurasian watermilfoil,”  I hollered.  I crouched on the bow of the boat and dunked my hand into the water, grasping for a hunk of plant to get a closer look.  When I sat back down with the dripping specimen I explained to Matt that it was bladderwort, a carnivorous native plant with bladders that trap small, aquatic critters.  He turned us around, heading for home.

Eurasian watermilfoil is native to Asia and Europe, and was introduced to New York State possibly in 1940s through ship ballast water or an aquarium release.  Another invasive milfoil, variable-leaf milfoil, is native to some parts of the United States.  Due to its aggressive nature in some Adirondack lakes and other water bodies throughout New York State, the Adirondack Park Invasive Plant Program (APIPP) recently upgraded the plant from a species to watch to a full-on invader.  You can visit APIPP’s website for their locations around the Adirondacks.

Without the ecological checks and balances found on their home turf, and because they tolerate a wide variety of environmental conditions, these invasive milfoils can form dense populations.  Fragmentation is the main means of reproduction.  They hitchhike to new bodies of water on trailers, boats, motors, kayaks, canoes, deck rigging, pets, gear, seaplanes, and wildlife.

A number of adverse impacts can result from aquatic invasive plant infestations.  They can out-compete native plants for growing space, light, and nutrients, resulting in decreased biodiversity.  They can reduce valuable habitat for fish, waterfowl, and invertebrates, and congest waterways that make fishing, swimming, paddling and boating unenjoyable. They can devalue shoreline property and provide good mosquito breeding grounds.

Native and invasive milfoil can be difficult to distinguish, sometimes causing even expert botanists to fret over identification.  Eurasian watermilfoil, often confused with bladderwort and native milfoil, has blunt-tipped leaves with (usually) greater than 11 leaflets.  Leaves are whorled around the stem with large internodal spacing in between the whorls.  A reduced, emergent bract appears above the water surface, but this can be difficult to spot.  Bright red growing tips are another diagnostic characteristic.  If held upside down, the plant droops around the stem.

Variable leaf milfoil has a bottle-brush, bushy appearance.  Leaves are whorled around maroon stems that are thicker than Eurasian watermilfoil stems.  Leaves are composed of greater than 11 leaflets, and little internodal spacing occurs between whorls.  Surface spikes emerge above the water’s surface.

The day after our trip to investigate the outlet of Sacandaga Lake, I called the woman who reported the possible invasive to let her know the suspect she spotted was bladderwort, not Eurasian watermilfoil.  She was elated to hear the suspect was non-invasive and I thanked her for reporting the location.  Early detection of invasive species can result in a rapid response.  The sooner an infestation is confirmed, the less expensive it is to manage, and the greater the success in eradication.

I told her to keep those possible invasive species sightings rolling in.

Photos: From above, Eurasian watermilfoil on a boat prop;  Eurasian watermilfoil; variable leaf milfoil in Lake Durant in July 2012; and below, Bladderwort.