Cyanobacteria: What it is, why it matters

Wednesday, October 30

By Abby Phinney, Adrienne Funderburg and Jed Harvey, Lilly Center Staff | Part 1 | Part 2 | Part 3

What is cyanobacteria, more commonly known as blue-green algae? It was all over the news earlier this fall (herehere and here) for good reason. There’s a lot we don’t know about these organisms, although through our own original research and the research of others, the Lilly Center is steadily demystifying cyanobacteria’s growth patterns, habits and behaviors.

What’s the difference between “blue-green algae” and “cyanobacteria?”

Blue-green algae is not a “true” algae; its proper name is cyanobacteria. Cyanobacteria is a large group of bacteria which are photosynthetic (like plants) and are found all over the globe. Cyanobacteria are a natural part of all sorts of ecosystems, from the hot dry Sahara Desert to the frozen rocks of Antarctica, thriving in a variety of places including in water, in ice, in soil, in plant roots, on rocks, in lichen, and even in the fur of sloths. And in freshwater lakes!

When you hear about cyanobacteria in Kosciusko County, however, it’s frequently after the cyanobacteria begins to dominate a local lake ecosystem, often in the form of cyan or teal-colored particles or scum. These are blooms of aquatic cyanobacteria. Blue-green algae is a “catch-all” name for several types of cyanobacteria, including Microcystis, Anabaena, and Cylindrospermopsis. The Lilly Center currently focuses on the microcystin toxin, which can be produced by both Microcystis and Anabaena, among others.

Normally, cyanobacteria is hardly noticeable in the water, taking the form of tiny colonies or clumps of cells. When there’s a bloom, however, it is more obvious. Among other forms, blooms can have the consistency of spilled paint and can appear anywhere from green to blue-green (and occasionally red, as we observed during a winter bloom on Center Lake a few years back). The blooms are also notable for their unpleasant, boggy smell.

What does it do?

Cyanobacteria is a very interesting type of bacteria. Ecologically, it is a primary producer. It uses its pigments (chlorophyll and phycocyanin) to collect sunlight and turn the sunlight into energy.

Blue-green algae use gas-filled organelles to float up or down in the water depending on where the light and other conditions are just right. Interestingly, however, blue-green algae doesn’t constitute as food for the vast majority of microscopic and macroscopic organisms. Fish, mussels and other aquatic life (even a notorious invasive species, the zebra mussel) avoid it, likely because it can produce a harmful toxin.

The toxin, called “microcystin,” is a relatively large molecule that affects a few different parts of the body, causing rashes and liver damage at a high enough concentration. It can affect people and animals, and is especially harmful to pets such as dogs. When pets drink toxin-laden lake water or lick cyanobacterial cells off of their fur, it can be fatal.

The microcystin toxin is made inside the cyanobacterial cells and is released when the cells die. However, not every cyanobacterial bloom has toxins in it, and not every cell makes toxins. Why and when Microcystis and other cyanobacteria produce the namesake toxin are questions the Lilly Center is actively trying to answer.

Why does it bloom?

Right now, we know that blue-green algae blooms tend to happen when cyanobacteria get an advantage and are able to grow quickly, smothering other algae. It grows and multiplies until it uses up available resources, and then the bloom begins to die, releasing toxin if the cells contain it. Cyanobacteria are partial to warm water, so nutrient-rich lakes on warm summer days are particularly ripe for blooms.

Extra nutrients come from a variety of sources, such as storm water runoff, and decaying algae and other organisms. Some part of this nutrient influx can be mitigated by people. Excess lawn fertilizer, grass and leaves that get washed into a stream or storm drain, runoff from cattle lots or farms, and soil erosion are all major sources of nutrients that contribute to cyanobacterial blooms.


As with all of science, it’s difficult to replace a question mark with a period. There are many ways to study cyanobacteria, and all kinds of information to discover about them. Ultimately, studying cyanobacteria will help us avoid future blooms!

What else contributes to blue-green algae blooms? How can we prevent blooms, or at least prevent the toxin from being produced? These questions, and others, are ones the Lilly Center is working to answer. More on that soon!