Those Devilish Interloper Aquatic Plants

Your Humble Editor, along with about 20 residents from sundry lakes in the area, attended the information session held by the Conseil regionale de l'environnement (CRE) on the subject of aquatic exotic invasive plants (AEIP) last Friday, July 7. And jolly interesting it was.

The session was given by Melissa Laniel, the Bleu Laurentides project manager, offering basic information on aquatic plants generally, how they live, what they do. She also briefed us on how to differentiate between algae and aquatic plants. She outline the process for surveying a lake's aquatic plants and for determining whether there are any AEIPs. Vanessa Nadeau, the project's liaison officer, gave us a short course on our native species.

Currently Quebec has detected six AEIP species in its waters, with a further seven species "at our doors" (which seems to be principally, Maine, where they are causing big problems).

Much attention is being paid to one AEIP in particular: the Eurasian water-milfoil. And I can tell you why.

Eurasian water-milfoil lives submersed in a lake's littoral zone (between shore and deep water). The distance it can grow from shore is determined by the amount of light penetration, so by the lake water's clarity and colour. Eurasion water-milfoil has no natural predators, so it will grow from the shore outwards in an uninterrupted blanket. One lake near Ste-Agathe has the plant on its entire periphery to a distance of seven metres (about 15 feet) from the shore, effectively precluding (or rendering very icky) swimming, boating and other water pleasures. Oh, and just hauling them out is a really bad idea as they are capable of spreading by "fragmentation", i.e., if a little broken bit floats free, it will settle on the bottom and start a whole new plant.

The best defense is a good...defense. Which is to say, prevention. This includes carefully cleaning and drying any equipment used in another lake that is brought to Lake Anne: canoes, boats and their trailers, scuba gear, fishing kit...and praying no float planes come in for a landing.

Quebec has a  number of indigenous milfoils which can be fairly easily distinguished from the bad guy. All milfoils have leaves made up of numerous paired leaflets arranged in a whorl of four around the central stem. In the Eurasian water-milfoil, each leaf has between 12 and 24 pairs of these fronds, while our native species have three to 14 pairs. Yes, even we learners noticed the overlap and were advised to take another sample if we met a plant with 13 pairs.

The other distinction is that the Eurasian water-milfoil's leaf whorls are spaced along the stem at distances of greater than one centimetre. Our native species have gaps of less than one centimetre.

To confound and confuse the issue further, there are a number of indigenous aquatic species that look a lot like milfoils, but aren't. Your basic bladderwort, for instance.

All of this and more will be explained by Vanessa Nadeau, who will begin with a training session when she comes to help us survey our plant species on July 24 and 26.

I just wrote "help us" because she can't do it on her own. Here's what she'll need:

Boats: preferably with small fishing motors, not too tippy as the plants are viewed through an "aquascope" held over the side of the vessel.

Skippers: one per boat, their job is to drive the boat, anchor (if necessary) and operate the GPS (to note the location of interesting or suspicious species for later collection).

Crew: two people, one to use the aquascope, one to take notes. (Vanessa will be a crew member on one boat).

With five volunteers (plus Vanessa), we can have two boats working and significantly reduce the time involved.

If you can lend a hand, or a boat, please let me know at lakeannenews@gmail.com