What exactly is a Harmful Algal Bloom and what are its impacts? Here are some answers.

What is blue-green algae and what are the impacts?

SOUTH MISSISSIPPI (WLOX) - Toxic algae in the Mississippi Sound is causing concern for many people on the Gulf Coast as more signs go up announcing water closures at nearly a dozen beaches. But what exactly is a Harmful Algal Bloom and why is it so dangerous? WLOX First Alert Meteorologist Eric Jeansonne provides some answers to those questions.

The Bonnet Carre Spillway closing is good news but the problems aren’t going to go away anytime soon and one of the latest things we’re seeing now is the algal bloom. Photos from viewers show the blue-green color in the water in Bay St. Louis, Lake Borgne, and other sites around the coast.

This photo shows the blue-green algae in the Bay St. Louis Harbor.
This photo shows the blue-green algae in the Bay St. Louis Harbor. (Source: Melissa DeBardeleben)

This type of algae is actually a type of bacteria called cyanobacteria and it’s over 3.5 billion years old. It has plant-like characteristics that allows it to gain energy from the sun. This type of bacteria likes warm, fresh water. With the Sound’s salinity levels so low right now, that’s helping it to form and grow.

The algal bloom formed after the Bonnet Carre Spillway opened, spilling trillions of gallons of freshwater into the Mississippi Sound. In those trillions of gallons of water are a lot of fertilizer and nutrients. That caused a process called eutrophication, which is when the nutrient-rich water moves into an environment causing the plant-like cyanobacteria to bloom in large amounts across the area.

You can see the blue-green hue of the water here on Lake Borgne, a lake in southeastern Louisiana near the state line.
You can see the blue-green hue of the water here on Lake Borgne, a lake in southeastern Louisiana near the state line. (Source: Jason Hamilton)

The algae is harmful because it produces poisonous toxins that are harmful to humans and animals. Some of the symptoms exposure to the algae can cause include rashes, nausea and vomiting, skin and throat irritations, allergic reactions, breathing difficulties, and more.

Reduced oxygen levels are often a result of large algae blooms. This occurs because the algae is so thick, it blocks sunlight. This causes plants that need that sunlight and produce oxygen to die, resulting in lower oxygen levels in the water. In extreme cases, this can cause a dead zone. However, it’s too early to say if we’re going to see a dead zone in the Mississippi Sound.

A dead zone happens when all of the algae dies and the decomposition process of the algae takes all the oxygen out of the water with it. That oxygen-depleted water is harmful to animals and plants living it. Hopefully, a dead zone won’t form in the Mississippi Sound. It’s a situation that WLOX will continue to monitor.

The Mississippi Department of Environmental Quality advises that people and pets avoid contact with certain waterways that contain the blue-green algae, including swimming. Anyone who has been exposed to the water should wash with soap and water. There’s no time frame on when the beaches could reopen.

Click HERE to read more on cyanobacteria and its harmful effects from the World Health Organization.

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