Big-Fish-Vegetation-Report 2015 from July 27, 2015
About Eurasian Milfoil
A picture of Eurasion Milfoil:
What’s growing in our lake?
By Mary Schramel
The DNR completed an extensive study of the aquatic vegetation of Big Fish Lake in August of 1999. The list includes aquatic, emergent, and shoreline plants. Of the 35 species observed, 12 were varieties of pondweed. We have one that is of great concern to us, the Curled Pondweed. Curled Pondweed (Potamogeton crispus) is considered an exotic invader. Before these plants die out in June, they produce a seed pod which is used for propagating the next years growth.
A second species of concern is the Northern Milfoil (Myiophyllum sibiricum). Both of these plants can generate very dense weed beds which results in a lack of fish habitat, source of additional phosphorus and a decrease in the oxygen of the lake. Reed Canary grass, Cattail, Wild Celery and Arrowhead are a few of the more desirable plants in our lake. We do not have Eurasian Milfoil.
There are several plants in our lake that are non-rooted. Two that are abundant are Coontail and Chara. Chara is actually a form of algae. While many algal are microscopic, Chara is macroscopic. It has a grayish-green appearance, coated with lime and smells like skunk. Chara also forms a very dense, snarled mass. There are a few varieties of algal populations in our lake that are beneficial. The ones that we need to be concerned about are the blue-green. Anny, Fanny, and Mike are shortened names for some very harmful algal populations. Most of us remember the dog days of summer bringing the algal blooms in late-September. This bloom has been arriving earlier and earlier every year. Many of the lake residents were shocked to find it blooming by Memorial Day this year. What does this mean for the lake?
Cyanobacteria, often called blue-green algae, are messengers. They are telling us that the lake is nutrient rich. In order to prevent continual degradation of our lake it is important to go to the source of the nutrients and cut it off. We need to revegetate our shore land wetlands. There are many varieties of weed control available but first we have to stop feeding the weeds or we are throwing our money away.
Some additional concerns about the abundance of weeds we are witnessing in our lake are that if weed beds are too numerous the pan fish may become stunted. We will also see a decline in our game fish population because the decaying plant material in our lake is using oxygen to decompose. This decrease in oxygen levels is evidenced by a 1997 DNR report showing 5.5 ppm of oxygen at 30 feet in depth. Currently the oxygen level at 30 feet is less than 1 ppm and no oxygen at 36 feet. Game fish require 5 ppm of oxygen for survival. Carp and rough fish require less dissolved oxygen to thrive.