Algae: The Double-Edged Sword

Mark Rasmussen | Leopold Center for Sustainable Agriculture Director

We humans seem to have an affection and fascination with the color green—the green of money, the green grass of spring after a long winter, the green of a Christmas tree or the expanse of leaves in a deciduous forest.

Photo credit: Iowa Department of Natural Resources Beach Monitoring Program

But there are some forms of green that we look upon with suspicion or have grown to dislike—the green water of an algae bloom or the pond scum that covers the surface of our favorite beach.  We tend to lump different forms of life under the general term “algae” (including cyanobacteria, also referred to as blue-green algae, which are technically not algae at all!), so our relationship with algae can be confusing and somewhat complicated.

As photosynthetic organisms, algae use energy from sunlight to produce oxygen.  Over many eons of time, they are responsible for much of the oxygen in the atmosphere, and they are the original source of fossil carbon transformed deep in the earth into crude oil and natural gas. Algae are also the basis of many food chains in aquatic environments.

We look upon algae with favor when they are used to produce biofuels and nutrient rich dietary supplements. But then there are the “other” algae that are more suspect—blue-green algae.  (Remember, the blue-green algae are technically not algae at all, but early taxonomists used the term and it stuck.)  We especially need to be concerned with the blue-green algae that produce toxins as we enter another growing season here in Iowa.

Cyanobacteria, or blue-green algae, tend to do well in warm, slow-flowing, or stagnant water when both nitrogen and phosphorus are abundant and available. These nutrients, along with sunlight and temperature are the primary drivers of their growth. Some species can grow very rapidly in what is called a bloom.  In a pond they can be part of the natural process of turning a water body eutrophic when dense growth can cause a reduction in animal life due to the absence or limitation of oxygen.  In our agricultural world, blue-green algae growth can be the result of poor nutrient management when high levels of nutrients get into surface waters and stimulate growth.

Along with rapid growth, the production of harmful toxins from certain species of blue-green algae is of great concern. Children and small pets with less body mass are highly susceptible.  The toxins can also impact wildlife when they drink contaminated water.  Dried biomass on shore can also be toxic if inhaled as dust. Research has discovered that people who live or spend a lot of time near contaminated water have a greater risk of health effects just from being near this kind of water.

Toxin production in critical species is also stimulated by increased water temperature.  Therefore, we see more problems later in the summer as bodies of water warm.  Iowa began testing surface water in 2000, and every summer, beach closings and alerts are issued for water that has elevated levels of algae toxins. Climate change and hot summers which warm the water faster also stimulate toxin production and can be expected to increase the problem. 

It is difficult and expensive to purify water for drinking when water sources are contaminated, and most water treatment plants do not have that kind of purification capacity.  Last year the water in the Des Moines River in central Iowa was not useable for many weeks as a primary source due to the high level of toxins contained in the water.  Once contaminated, dilution with cleaner water is about the only solution. 

Given that we can expect this problem to get worse, we must redouble our effort to keep nutrients out of the water.  We can’t control the water temperature nor the hours of sunlight, but we can do something about the nutrient loading in our surface waters.  Unless we do more, we can expect there to be more problems with water quality in Iowa.

Mark Rasmussen

Harmful algal blooms connect the heartland to the coast

clgheaderEmily Heaton | Assistant Professor of Agronomy, Iowa State University | in conservation with Alina Corcoran | Research Scientist, New Mexico Consortium

Why should people on the coast care what happens in the heartland? I was recently asked this question by the producer of a major network TV show, and struggled to think of an answer. Our conversation went something like this:

TV producer: “Everyone cares about the place that raises their food! The Midwest produces the food I eat, right?”

Me (Emily Heaton): “That depends; do you eat meat?”

TV producer: “No.”

Me: “Hmm. Then no, we don’t produce the food you eat. How about your car? You probably drive a car that uses ethanol that we produce in the Midwest!”

TV producer: “I live in New York City and don’t own a car.”

Me: “Well, we mainly raise grain that goes to feed animals or ethanol plants”.

TV producer: “Ok, then. Other than the Iowa caucus, I am not sure why anyone on the coast should care what happens in the heartland”.

And this explains network news coverage of the “heartland”.

But then I saw a presentation about Harmful Algal Blooms (HABs) by Dr. Alina Corcoran of the New Mexico Consortium. Alina is a biologist who studies the algae – good and bad – that grow in our lakes, rivers, and oceans.  This is what she had to say about blooms.

Algae-oxygen-bubbles_Wikimedia CommonsMe: I didn’t know algae were such a threat to our health, environment, and economy.  Can you tell me more about blooms?

Alina: Actually, not all algae are bad.  Take two deep breaths.

Me: (breathing, deeply)

Alina: You can thank algae for one of those breaths.  They produce half of the oxygen on our planet.  But you are right that sometimes their growth can get out of control.  We call that uncontrolled growth a Harmful Algal Boom or HAB for short.

Me: What causes HABs?

Alina: Different kinds of microscopic algae and cyanobacteria cause HABs.  Some organisms live in glass houses.  Some have flagella that allow them to swim.  Some form chains.  Each organism thrives under a  different set of environmental conditions.  For example, some blooms occur when water temperature increases or when water becomes stagnant.  Other blooms occur when there are favorable winds or currents.  But I think it is fair to say there is one commonality.

Me: What is that?

Mississippi River WatershedAlina: All algae need a source of nutrients, like nitrogen and phosphorus, to grow.  What that means is that we can overfeed algae with our waste and fertilizers. In some cases, man-made nutrient sources that feed blooms are quite close to where a bloom forms, like at a sewage outfall. In other cases, the nutrient source can be a thousand miles away. The best example of that comes from the Mississippi-Atchafalaya River Watershed (pictured).  That watershed drains over 40% of the US – transporting nutrients from the heartland to the Gulf of Mexico, where they feed blooms and the dead zone.

Me: You talked about toxic algae in your presentation.  Are all blooms toxic?

Alina: No, we tend to divide HABs into two categories: nuisance blooms and toxic blooms.  Nuisance blooms can discolor the water and deplete oxygen, causing fish kills.  But there is a handful of algae species that produce toxins that can harm people and other animals.  Do you remember the Toledo water crisis?

Me: I do.  That was about five years ago, right?  Residents of Toledo could not use their water!

algalbloom_Erie 2017_NOAA

Image of the Sept. 23, 2017, bloom. Source: NOAA derived from Copernicus Sentinel-3a data from EUMETSAT

Alina: Right. There was an extensive HAB in Lake Erie caused by toxic cyanobacteria. Cyanobacteria are also called blue-green algae, even though they are not true algae. Cyanobacteria tend to bloom in freshwater systems that are polluted with nutrients from agricultural runoff. People, pets, livestock, and wildlife can be exposed to the toxins when they swim, drink the water, or breath bloom aerosols.  Cyanotoxins (like microcystin) can cause gastrointestinal symptoms like vomiting and diarrhea or neurological symptoms. There are also toxic blooms in estuaries and in the ocean.  In 2017, residents of Florida experienced a particularly damaging bloom caused by another type of algae, a dinoflagellate. The bloom, which lasted over a year, caused respiratory irritation in people, fish kills, and manatee deaths.  Blooms like that also have devastating effects on tourism and the shellfish industry.

Me: Because the shellfish die?

Alina: No. Actually, most shellfish survive toxic HABs but can accumulate the toxins in their tissue.  If we eat contaminated shellfish or seafood, we can become sick.  There are different poisoning syndromes that generate different symptoms. To protect human health, shellfish harvesting areas are closed when shellfish become toxic.  Unfortunately, this is a huge hit to shellfish farmers and their families.

Me: So what can we do about blooms?  You talked about prevention and control in your talk, but you didn’t really mention talking with farmers and land managers about nutrient loss.

Alina: Farmers and land managers are definitely part of the solution. There are a few notable success stories, like the Iowa Great Lakes, where blooms have been reduced or eliminated when communities have made an effort to reduce runoff and point sources of nutrients.


Alina: It is important for everyone to think about the downstream effects of their practices.  Fertilizer applied to a farm or lawn is not contained — ultimately unused nutrients make their way to water bodies.  There have been strong efforts to monitor blooms and protect public health, but there is definitely work to be done to both prevent and control blooms.

Me: Thanks for the work you do, Alina. We are all in this together.

Emily Heaton

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