Blue-green algae: Can’t live with (too much of) it; can’t live without (enough of) it

Posted 4/24/19

Want to know what the world would be like without “blue-green algae”?

Hold your breath for five minutes.

Now make that 10 minutes.

Now make that forever.

Before cyanobacteria, there …

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Blue-green algae: Can’t live with (too much of) it; can’t live without (enough of) it


Want to know what the world would be like without “blue-green algae”?

Hold your breath for five minutes.

Now make that 10 minutes.

Now make that forever.

Before cyanobacteria, there was no breathable oxygen on the planet.

According to “the Rise of Oxygen,” published in 2003 by Astrobiology Magazine, “Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago.”

Cyanobacteria — the scientific name for what we call “blue-green algae” — is the oldest known life form on the planet. It produced the oxygen that allowed oxygen-breathing life forms to evolve on planet Earth.

Without the cyanobacteria there would have been no dinosaurs, let alone humans.

According to, algae and cyanobacteria produce 70 to 80 percent of the oxygen in the atmosphere today. That makes sense when you think about it. Water covers three-quarters of the Earth. Cyanobacteria and algae are in the water.

The “cyan” in the name refers to the color blue. Cyanobacteria is not actually algae. Cyanobacteria are prokaryotes. Algae are eukaryotes. What’s the difference? Simply put, eukaryotic cells have a nucleus containing their DNA; prokaryotic cells do not have a nucleus.

So why do we call it “blue-green algae”?

It’s really tiny — microscopic. It’s only visible to the unaided human eye when it reproduces rapidly into a “bloom” — that’s a lot of cyanobacteria in one place. And when it does that, it looks a lot like actual algae. You can’t tell the difference just by looking at it.

Where does it come from? Everywhere.

Remember, it’s the oldest life form on the planet. Over billions of years, cyanobacteria has gotten very good at adapting to changing conditions. Cyanobacteria has mutated, and continues to mutate to keep adapting. Cyanobacteria can be found in freshwater, salt water and brackish water. Cynaobacteria has been found in the desert and in the arctic.

How does it move around? Cyanobacteria usually relies on water currents to move around. But it can move up and down in the water column by inflating or deflating gas vesicles — like tiny balloons inside a single cyanobacterium. That is why, on a NOAA satellite image, it might look like it is “covering” Lake Okeechobee, but when fishermen go out on the lake, they do not see anything but water, fish, birds and alligators. Also the NOAA images aren’t regular photographs. They are computer-generated images that predict the presence of cyanobacteria. The NOAA images can’t tell what kind of algae or cyanobacteria are present, they predict percentages based on estimated chlorophyll levels .

Cyanobacteria is also carried from place to place by things n the water — boats, wading boots, fish, birds, otters, manatees, alligators … anything that moves through or in the water could carry cyanobacteria. It’s microscopic. It could be on your boat and you might not even see it.

Some researchers believe that cyanobacteria might even travel through the air. Remember, after billions of years on the planet, it’s very good at adapting and surviving.

There are thousands of species of cyanobacteria. Scientists do not even agree on just how many thousands of species there are. Estimates range from 2,000 to 8,000 species of cyanobacteria on the planet. Let’s just say “a LOT.”

And here’s the scary part: Some — not all — species of cyanobacteria can release toxins that are harmful to humans.

Note: Just because a species of cyanobacteria can release toxins does not mean it will. Whether or not toxins will be produced and how concentrated the toxins will be depend on other factors. What all of those factors might be and how combinations of different factors affect the cyanobacteria is the tricky part because scientists are still working on those questions. Scientists have theories, but we don’t know for sure. And what we don’t know, can hurt us.

So … why are we seeing so much toxic algae in recent years, not just in Florida but worldwide?

A major factor scientists do agree on: We’re feeding it too much.

Cyanobacteria has simple needs. To reproduce, it needs heat, nitrogen and phosphorus. Freshwater blue-green algae also needs low salinity, but remember, cyanobacteria is also present in brackish water and salt water. The sun provides the heat. Nitrogen and phosphorus can come from natural sources. For example, phosphorus is readily available in the soil in Florida. Decomposing plants can release nutrients into the water. Rains can wash nutrients into the water. Some cyanobacteria can use nitrogen from the air (an example at how good cyanobacteria is at adapting and surviving.)

The more phosphorus and nitrogen the cyanobacteria has available to consume, the more rapidly it reproduces.

There was plenty of phosphorus and nitrogen in the ecosystem for the cyanobacteria before humans moved onto the Florida peninsula. Human action has increased the nutrient load. Which means in some waterways close to heavily populated areas, the cyanobacteria now has a virtual all-they-can-eat buffet, contributing to rapid reproduction into blooms.

Unfortunately for humans, rapid reproduction into blooms is one of the things that appears to cause it to release toxins. And when it is in an enclosed canal, the blooms are more confined and that also apparently is a factor that causes the cyanobacteria to release more toxins. Changes in salinity as the cyanobacteria moves from the freshwater lake to the coastal estuaries can cause the cyanobacteria to die — and when it dies it might (doesn’t always, but might) release toxins.

In the open lake, fishermen report cyanobacteria blooms are feathery and ephemeral. They come and go, either pushed about by wind or disappearing into the water column. Florida Department of Environmental Protection tests also show that toxin levels in the big lake are usually low, even when NOAA shows cyanobacteria present in much of the lake.

In the canals and marinas, cyanobacteria grows into thick mats, which makes it (you guessed it) more likely to release toxins.

How can we help?

• Support state and federal programs to reduce nutrient load into waterways. Some programs are already in place, such as the FDEP Dairy Rule which requires dairies to control the run off from their farms. They use berms, retention ponds and sprayfields to recycle the nutrients in the waste from the dairy cows. More programs are needed to control all sources of nutrient load into the waterways.

• Support stricter water quality standards and stricter enforcement of the standards on the state and federal level.

• If your home has a septic tank, make sure it is pumped out regularly (at least once every five years, more often if you have a large family) and that the drain field is inspected to make sure it is functioning properly. All septic tanks leak into the drain field — it is what they are designed to do — but a malfunctioning septic system can pollute the groundwater and/or result in runoff that is high in nitrogen.

• Switch from septic to sewer if your neighborhood has the option of a sewer lines.

• Support stricter environmental standards for sewer and septic systems throughout the state.

• Plant “Florida Friendly” grass and landscape plants that are adapted to the local climate and soil and, after they are established, will not need as much fertilizing or watering. Vegetation can also help filter any runoff that leaves your property. Learn more about Florida Friendly plants at, or contact your local county extension office.

• Before you apply fertilizer to your yard or garden, have the soil tested to find out if you need to add fertilizer, and if so, how much. Over fertilizing wastes money and contributes to nutrient load in the runoff.

• Do not put grass clippings or other yard waste in canals. Decomposing vegetation releases nutrients into the water.

• Don’t litter! Trash and debris that is left along roadways can wind up in canals.

• If you live on a canal or waterway, plant deep-rooted plants along the shoreline to filter runoff and help prevent soil erosion.

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