By Graham Freeman, Idaho DEQ
Harmful Algae Blooms (HABs) seem to be making all of the news these days, from newspapers to national television, from Florida to Washington and most places in between. So what exactly are Harmful Algal Blooms and why are they such a hot subject right now? Let’s dive in, or maybe we should observe from the shore…
Cyanobacteria, also known as blue-green algae, are single celled, prokaryotes that have been around for billions of years. Similar to green algae (eukaryotes), cyanobacteria uses photosynthesis to create sugars and releases oxygen as a byproduct of this chemical reaction. Cyanobacteria are often credited for oxygenating the atmosphere billions of years ago. When cyanobacteria rapidly reproduce in aquatic environments they create blooms with hundreds of millions of cyanobacteria cells.
We often refer to cyanobacteria blooms as Harmful Algae Blooms for several different reasons. First and most obvious, cyanobacteria blooms are often smelly and unsightly. Not many people want to swim or fish in waterbodies that look akin to slime you might see in an episode of the Simpsons. Secondly, algae cells from any type of bloom, harmful or otherwise, eventually die off. Once the cells die off, decomposition sets in and scavenger bacteria consume the dissolved oxygen from the water. If the rate of cell death is rapid enough or large enough, dissolved oxygen concentrations can drop low enough to stress or kill fish and other aquatic organisms. Finally, certain taxa of cyanobacteria are known producers of toxins, which are potentially toxic to humans, pets, livestock, and other wildlife.
Cyanotoxins are toxins produced by cyanobacteria and are considered some of the most poisonous naturally occurring substances. Cyanotoxins generally fall into a couple of different chemical classes that are known to damage to the liver, interfere with the nervous system, cause cancer, irritate the skin, and new research is showing that some cyanotoxins may play a role in neuro-degenerative conditions such as ALS and Alzheimer’s. More info on cyanotoxins can be found here on Environmental Protection Agency’s website. While there are thousands of different cyanobacteria species, remember that most cyanobacteria do not produce cyanotoxins. Additionally, some species of known toxin producing cyanobacteria may not produce cyanotoxins one day and begin to produce toxins the next day. Most people will assume that cyanotoxins are produced to stop planktovors (animals that eat plankton) from eating the cyanobacteria. However, it appears that this isn’t necessarily the case. Research indicates that cyanotoxins may be used by cyanobacteria in their normal metabolic processes, for nutrient uptake, for example.
If you follow the news closely, you’ve probably heard about HABs or at least some of the problems associated with cyanobacteria blooms. In 2014, a HAB contaminated a drinking water source leaving hundreds of thousands of people without water in Ohio. Just this year, 32 cattle were killed by a Harmful Algae Bloom in Oregon. In 2016, 11 confirmed HABs were reported on Idaho’s lake and rivers. During the first half of the summer of 2017, there have already been seven confirmed HABs.
Anecdotally, it appears that HABs are increasing in frequency and intensity across the nation. This could be a product of the public being more informed and therefore reporting more blooms or it could be a product of poor water quality. In the United States there are over 100,000 miles of rivers and streams, 2.5 million acres of lakes, reservoirs, and ponds, and more than 800 square miles of bays and estuaries that have poor water quality due to excess nutrients (nitrogen and phosphorus). Cyanobacteria are commonly associated with nutrient, specifically phosphorus, enriched waters. Additionally, at warmer water temperatures cyanobacteria reproduce more quickly and can out-compete nontoxic green algae. If the average global temperature continues to rise, we may see many more HABs on nutrient enriched waterbodies.
Now that you all know a little about cyanobacteria, cyanotoxins, and HABs – let’s talk about identifying and avoiding the blooms. Cyanobacteria blooms can take on many different colors and structure depending on the composition of the bloom. Often times cyanobacteria blooms cause surface scum that looks like spilled paint, with blue, green, and white colors. Some blooms will cause the water to look like pea soup. Because of wind and wave action, HABs are known to accumulate around shores of lakes and reservoirs, which can be particularly dangerous to animals looking for a drink. It is difficult to visually confirm a HAB and it is impossible to tell if a bloom is toxic through visual observation. Because HABs are difficult to identify, we encourage people to avoid contact with all suspicious looking water and report suspected blooms to the local Public Health District, waterbody manager, or the Department of Environmental Quality. If you are in doubt of the condition or safety of the water, stay out of the water. When in doubt, stay out!
The majority of the cyanobacteria exist in aquatic ecosystems without causing any problems. When conditions get just right, cyanobacteria begins to multiply and can create HABs, which are potentially toxic to humans, livestock, and other wildlife. Right now, there are not many short term solutions to reducing or eliminating HABs. Efforts to reduce HABs should focus on improving water quality, specifically reducing the inputs of nutrients to waterbodies. Reducing fertilizer inputs on agricultural fields, reducing erosion, and improving wastewater treatment processes are ways to limit phosphorus load to waterbodies. Additionally, we can all do our part by limiting fertilizer applications on residential lawns and cleaning up pet waste.
For more information on HABs and current water quality advisories in Idaho, please visit this website.