Rush Lake: An Aquatic Ecosystem in its Infancy

Rush Lake is a new (<5 style=""> Three houses now occupy the fairly steep sloping shoreline. Earlier this spring, we stocked the lake with Golden Shiners, the first fish ever to inhabit the lake. Currently the lake has no vascular aquatic plants and very little Chara. There is nothing to take up nutrients but ubiquitous filamentous algae. Most natural lakes in MI have had thousands of years to develop diverse and balanced ecosystems. As we have discussed at length, in-lake phosphorus concentrations above just 10 parts per billion can stimulate plant and algae growth. In a healthy diverse lake the native aquatic plants will quickly take up the small amount of natural nutrient inputs (terrestrial plant debris/leaves, suspended sediments from inlets…) with little to no visible changes to the plant/algae community. When I got a call to come out and check on Rush Lake last week, I was concerned. The last time I was out to look at Rush was a few weeks before. Before the prolonged and intense rains and sunshine that wash nutrients into a lake and give rise to algal blooms. What I observed when I arrived is detailed in the photos below.

A view of Rush Lake's East shoreline looking North.Filamentous algae is photosynthesizing, filling with gases and rising to the surface. Not exactly beautiful.

This I what I saw looking South along the East shore. More unsightly filamentous algae.

I noticed a tremendous amount of animal life using the algae as habitat as no other aquatic plants were available. Here we see an American Toad looking for love in the green slime.

I grabbed my handy dandy $3.99 rake and went to work. A half an hour later I had removed the vast majority of the algae from the East shore.

A view looking North after raking.

A view looking South after raking. This photo was taken on Friday the 26th. When I returned on Memorial Day the shore looked much like it did before I raked. Filamentous had begun to establish itself again. I had a feeling this would happen. By raking out the algae, I had removed the nutrients that stimulated its growth. The problem is more nutrients continue to enter the system to stimulate further algal growth.

The last thing I want to do is call out individual home owners. I grew up on Lake of the Clouds and I'm sure their is phosphorus in that lake with my name all over it. I have to use this photo to explain the predictable cause and effect occuring. Fine and course particulate organic matter (P) is entering the lake in large amounts from wind and rain activities. The phosphorus stimulates algal blooms as seen in the picture taken May 26. We can treat the algae with copper sulfate killing the algae and much of the animal life. The nutrients are released back into the water and a few days later we will have another bloom. Long-term, this path will lead to a degraded ecosystem, the opposite of what we want for Rush. The solution lies in vigilance in limiting nutrient inputs, once they are in, they are recycled year after year and nuisance plant and algae control becomes more and more difficult. Step two is to establish beneficial native aquatic vascular plants and colonial algae (Chara) to take up nutrients and provide food and cover for a developing ecosystem In the mean time we may have to be willing to do some raking. to remove the mats (which make great garden compost by the way).

Gross, What is that Slimy Stuff?

Green and stringy, on the surface when filled with gases from photosynthesis or covering the bottom after a rain event or cloudy days, this intimidating slimy and stringy mess is filamentous algae (mainly Spirogyra). It is one of the simplest forms of plant life in the aquatic world. It is ubiquitous, being found in essentially every natural lake in Michigan and the world beyond. Filamentous algae will “bloom” when solar radiation, temperature and nutrients allow. It is a very basic and predictable aquatic equation: heat + sunlight + nutrients (phosphorus) = algal bloom. No big deal until it comes to our expectations. To the vast majority of lake participants, these algal blooms are unsightly,
restricting and just plain freaky. To us as biologists, they signal an over abundance of available nutrients.

These filamentous algae blooms were observed back on May 4th. Interestingly, they were right on top of the natural artisian wells supplying the area with ground water and they were the only mats we saw on the lake at that time. Is it possible that this ground water is the same high nutrient ground water supplied from the deep wells?

What is Causing the Algal Blooms?

Remember the equation: sunlight + temp + nutrients = bloom. We have had a relatively mild spring in terms of solar radiation coming into the holiday weekend. I know this both from the meterological data and from the fact that I received dandy sunburn on my pale skin over the weekend. So, part one of the equation was definitely satisfied in the past few days. As for temp, water temps were in the mid 60’s all the way up to the holiday weekend. By Monday, water temps were over 80 F in the shallow bays. 15-20 degrees F in a matter of days is hard on almost everything in our lakes except for aquatic plants and algae. Lastly, we have nutrients. Over the past few seasons we have documented that as beneficial native aquatic plants wake up and start growing in the spring, there is a marked decrease of phosphorus concentrations in the water column. This is ideal and what we are trying to foster. If the nutrients are taken up by beneficial aquatic vascular plants, they will not be available to algae for blooming. This is nature’s form of algal control and in an intact and diverse aquatic ecosystem, it is very effective. But, every year there is more and more phosphorus entering our lakes. We have identified the major sources and the CLPOC has taken actions to minimize the gross inputs. Last year at this time we saw a similar effect with terrestrial inputs (grass clippings, Aspen and other tree pollen and “fuzz”, fertilizers, erosion…) are washed or blown into the lakes. They breakdown and can release a tremendous amount of nutrients. The nutrients are released at a rate that exceeds the rate native beneficial aquatic plants can take them in and lock them up and away from nuisance algae. This spring has been a banner year for flower, bloom, pollen production and much of it has ended up in the lakes. Looking out my window as I write this there is so much Cottonwood fuzz in the air that it looks like it is snowing and this has been going on for the past two weeks or longer.

The small cove behind Country Corners Plaza in East Lake is demonstrating the extreme influence tree debris has had on the lakes again this year. This photo was taken on May 26.

Why Not Prescribe a Lake Wide Copper Sulfate Application?

Copper sulfate is very effective at lysing algal cells, thereby dissolving the algal blooms and mats. It is commonly used by applicators (even when inappropriate) and often overused, as it is not selective in its cidal nature. Looking closely around the shoreline where these algal blooms tend to be blown and concentrate, one will notice schools of larval bass and other fish fry, insects, various amphibians, beneficial plants and so on that are working to diversify and stabilize the ecosystem. All of these organisms are affected by copper sulfate treatments either by direct death or indirectly by loss of habitat or food source. This destabilizes the ecosystem leaving it more vulnerable to expressions of imbalance like algal blooms. To prescribe copper sulfate at this time would be pushing the lake in the wrong direction. A healthy diverse aquatic ecosystem requires the least amount of effort and money to maintain as well as providing the pleasing aesthetics and experiences that result in property appreciation. Dependence on herbicides and algaecides will successfully create the short-term illusion of high water quality, but long-term the create dependency and instability. We have a lake wide general herbicide application scheduled for June 12-13. This treatment is a major shock to the lake system. The nutrients released by the dissolving treated aquatic plants are more than ample to stimulate significant algal blooms. We are hoping that with some rain and mild weather we can get by until late June before any copper sulfate algaecides are used. This is critical as not only are copper treatments ecologically costly but they are financially costly as well. If this summer proves to be as hot and sunny as last, we will need to spend every penny in our aquatic nuisance budget as wisely as possible.

If you look closely, you will see thousands of frog eggs in this photo of an algal mat taken May 26. Copper sulfate will kill these and any other eggs in the vicinity of the treatment. This is just one reason we aviod algacide treatments until after the general herbicide treatment has taken place in mid June if at all possible.

Though difficult to make out, this is a photo of an albino bluegill we observed in the marina in East Lake. This is the first time for both Tom and I that we have seen an albino fish in the wild, amazing!

Image showing the invasive Curlyleaf Pondweed on the left and beneficial native Illinois Pondweed on the right.