Decaying Aquatic Vegetation:
a. Adds the nutrients to the substrate that support plant growth.
b. Absorbs oxygen from the water leaving an oxygen depleted layer.
c. Releases methane to the atmosphere (a far more effective atmospheric blanket that CO2).
Even with no other objections, the above resultants on the aquatic environment of decaying aquatic vegetation call into question the propriety of alternatives 1, 2, 3, 4, 5,
 Some weeds reproduce by seeds, others by segmentation and still others by their tubers. No type of harvester will interfere with the weed proliferation. Harvesting actually has the effect of spreading the exotic weeds such as Eurasian Milfoil when segments escape the harvester's maw.
Pulling the weeds does the job if the removed weeds are adequately disposed of and the roots are completely removed. On a cash basis this alternative is the cheapest if done by the property owner but relativity expensive if scuba divers are required - it takes a lot of time. |
Lowering the lake to dry and freeze the weeds, in my experience accelerates the take over of the lake by the exotics; while freezing may cut down the population of some native weeds, it does not stop the exotics. It can only be tried where there is a lake lowering capability and where hard freezing occurs in the winter months.
In the case of most lakes sunlight adequate to support the growth of weeds does not get to depths in excess of 15 feet; so, deepening the lake is an attractive alternative, except for its cost and problems with regulators. Dyes can restrict sunlight intrusion but are only practical for small ponds where the water flow is minimal; they should be inserted in early Spring and the level maintained thru June.
Installation of the weed eating fish seems like a good alternative with the following limitations (1) a sufficient number are required to do the job; (2) they don't like Eurasian Milfoil and eat it only as a last resort; (3) they grow fast and in time there may not be enough vegetation to support them; (4) they must be contained in the lake because the down stream neighbor may not want them; and (5) they likely will eat the vegetation that other fish require for reproduction, shelter and food.
http://plants.ifas.ufl.edu/guide/grasscarp.html
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There are many benthic barriers; installed properly they all will kill aquatic weeds; their install and maintenance costs are high primarily because scuba divers are needed to do the install job for most benthic barriers. Additionally, a benthic barrier isolates the benthos (Lake Bottom) from the aquatic environment and results not only in the demise of the flora (Plant life) but also the fauna (Marine life) living on the benthos.
There are several devises available that are used to massage the lake bottom not allowing the substrate to generate any growth. In some cases this can work great, like a sandy even lake bottom, but it does have its limitations; a) total area that it can cover. b) uneven and rocky lake bottoms may be a problem. c) in most cases needs electricity available where its being used.
The Lake Bottom Blanket is different.
It's a sunlight blocker that is positioned above the substrate; therefore it has no detrimental effects on the fauna (Marine life) inhabiting the benthos. It is relatively inexpensive and, being light weight, is easy to install and maintain. Put down before the weeds start growing in the early Spring, the problems reviewed above from rotting aquatic vegetation are avoided - Same for the effects of the dead vegetation of previous seasons. It does not encourage segmentation and by eliminating the exotic weeds it encourages the growth of the native weeds that reproduce from seeds. Additionally, the quonset hut formations between the hold down ribs provide shelter for small fish and the Lake Bottom Blanket only needs to be in the water for about a month to kill the targeted weeds.
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Another weed eater is the Milfoil Weevil, a very small Beetle that only eats Milfoil, which is a exotic weed that can choke a lake in only a few years. The weevil hollows out the stem of the plant leaving it limp and falling to the lake bottom. It is a relatively new weed control method and has worked in some cases and not in others. It seems to be costly at an annually cost from $150.00 - $2000.00 per Acre.