Lakes, Plants, Algae, and Wildlife

The first thing people say when they move to a lake is “It is so beautiful!”

Many times the second thing is (depending on the season) “Can we get rid of the weeds in the lake?”

The short answer is: No – It is a lake, not a pool. You should expect life — plant and animal — to thrive in a healthy ecosystem.

What happens when you get rid of all of the plants in a body of water? Other things start growing, primarily algae.

Why does this happen?

The plants grow by creating energy from sunlight by a process called photosynthesis. One of the byproducts of photosynthesis is oxygen. When the plant is in the water, this oxygen tends to stay in the water. That is good for fish since they breathe the oxygen through their gills. It is generally bad for algae (especially blue-green algae).

So when things are in balance, plants grow in the lake and algae growth is slowed by the presence of the plants (and eaten by the animals in the healthy lake).

But sometimes things get out of balance — the plants get too thick and weeds grow and interfere with residents enjoying the swimming, boating, and fishing on the lake.

What causes this? Nutrients (principally phosphorus and nitrogen) from the soil and surrounding houses. Sometimes it is fertilizer, sometimes it is a large storm that brings in grass clippings, leaf litter and soil. Sometimes it is a failing septic system.

So to help keep a balance for the lake life and the residents, we treat the lake with herbicide in the spring to get rid of some (but not all) of the weeds. The weeds get knocked to the bottom of the lake. If we overdid it on the herbicide or other factors combine (heat wave, drought, etc), algae growth can multiply.

Other factors include increased air and water temperatures leading to less dissolved oxygen – prime conditions for algae blooms. Less water circulation due to late summer mini-droughts can also be a factor (algae like still water). Usually it is a combination of factors making simple “just fix it” notions impossible.

Later in the summer we usually treat the lake with an algaecide to make the conditions less suitable for algae growth. By the time the algae cycle is over, it is usually near the end of the summer. The algae blooms are mitigated by the cooler nights and shorter days (less sunlight = less photosynthesis). Fall comes then plants and algae go dormant for the winter. In the spring the cycle starts again.

This is a very simplified view of life in the lake which considered only plant life. We also have amphibians (frogs, salamanders, newts), reptiles (turtles, snakes), birds (geese, heron, ducks, eagles, hawks, loons, a multitude of migratory birds, etc.), mammals (deer, muskrat, otter, fox, coyote, mice, voles, skunks, raccoons, weasels, mink, etc.), insects (too many to list), and of course fish (bass, perch, pike, etc.).

All of this can and does have an impact on the lake and the shoreline. And we can impact them. More on this in another article.

The key word is “Balance” – we need to avoid pushing too hard in any direction. And we need to be constantly vigilant and adapt as conditions change.

Bonus: Some tips on lawn maintenace for lake area homeowners

As homeowners, we can greatly impact the flow of nutrients into the lake by the type of shoreline we maintain. The ideal shoreline for protecting the lake has a shoreline buffer of plants to slow nutrient and water runoff into the lake. Most people would like access to the lake so you don’t usually see a complete vegetation buffer. But you can get the best of both worlds with a small access to the lake through the vegetation, oftentimes leading to a dock.

Minimizing the turf grass coverage of lakeside properties is also useful in many ways. To a Canadian Goose, a well manicured lawn is a tasty buffet. They find it irresistable. And with a clear path the the water they see little reason to leave and can stay for hours. Putting in a vegetation buffer at the water’s edge makes them fear for their escape route and they will not stay as long if they come ashore at all.