Overview

Did you ever try to eat an entire apple pie chased with a quart of milk? If so, you how too much of a good thing can create problems. It’s the same with algae.

In many lakes and oceans, algae is an important part of the base of the entire food pyramid in naturally balanced ecosystems. But when algae is artificially over-fertilized in an unbalanced ecosystem, it can create waaaay too much of a good thing. And that can make things go horribly wrong.

AlgaePhotoTake Tainter Lake for instance. It’s located in northwestern Wisconsin and was once a pristine home to a number of bird, fish, reptile, and amphibian species. But nowadays, an organism known as blue-green algae typically forms a slimy mat over the lake during the summer. It not only stinks and prevents people from recreating on the lake, the toxic algae reportedly causes health problems for the lakeside residents. So what’s happening here?

As you’ll see in the video, our eco-investigator, Caroline, met with residents and scientists to discover how blue-green algae forms cyanobacteria each summer, which in turn, produce toxins. These toxins have caused health problems, such as lupus-like symptoms and hives for some residents.

To understand the causes of this environmental problem, we need to look at the basic chemistry and biology of plant and algae growth. Farmers put un-natural amounts of phosphorous (P) and nitrogen (N) on their fields to grow maximum crop yields. Those plant nutrients are often a combination of commercial fertilizers and animal manure. Unfortunately, rains wash off some of those fertilizers from the landscape and the mix ends up in rivers and lakes.

So the main cause for this toxic algal growth at Tainter Lake is the increasing concentration of “plant nutrients” getting washed into the lake. Phosphorous is one of the biggies, that’s contained in the fertilizers that modern farmers apply on their fields, and is a major chemical component of cow manure. Depending on a number of variables such as slope, rainfall, runoff, concentration, soil attachment, and erosion, both sources of phosphorous and nitrogen can get flushed off fields, into streams, and ultimately into lakes such as Tainter. So these forms of fertilizer that cause field crops to grow also functions the same way in the lake, except that it can cause a massive undesired algal bloom. Though not technically a plant, algae uses the same plant-like process of photosynthesis to grow and thrive. And when all that algae begins to die off, it causes depletion of the oxygen content in the water that can kill off aquatic life, creating a “dead zone”. To learn more about how nutrient-induced algae causes hypoxic zones, check out the NOAA link below.

CornHarvestSo what’s to be done? Society needs farmers to grow crops, right? Well, for starters farmers can limit how much phosphorous and nitrogen gets washed off their fields in a couple of ways. One is by limiting the amount of fertilizers they use on their crops. This is done through what is called “nutrient management planning”. In short, they only apply what the crops can absorb and use to grow. As you might imagine that depends on a number of technical things and the forces of Mother Nature. Another way to limit phosphorous and nitrogen runoff is by using improved farming techniques that help prevent excess nutrients from leaving the soils and landscape. To learn more how this is done, take a moment and watch the video.

To really “plow into” the science and environmental implications of all this, and ignite the chemistry and biology parts of your brain:

  • Explore the extended learning section below by clicking on the “Learn More” tab below.
  • Or better yet, ask your teacher to download the lessons below so your entire classroom can share in peer-driven learning. Now we’re talkin’ serious fun.

Also, find out more about what you can do to keep your local waters healthy and clean by checking out the website of our educational partner, Wisconsin Land+Water.

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