Toxic Algal Bloom Covering Florida Lake So Big It Is Visible From Space

A toxic bloom of blue-green algae is blossoming across Lake Okeechobee in Florida, leading to health warnings and the closure of parts of a local marina.

The bloom was thought to have spread across 380 square miles of the lake as of June 12. It is Florida's largest freshwater lake, and the 10th-largest natural freshwater lake in the U.S.

This algal bloom equated to an area of more than half the lake's 734-square-mile surface. It can be seen from space as pictures taken by NASA's Operational Land Imager-2 on the Landsat 9 satellite demonstrate.

The bloom had grown further to cover 420 square miles by July 4, and 440 square miles by July 15, covering nearly 60 percent of the lake's surface.

Lake Okeechobee's bloom has been growing since May, when the Palm Beach County Health Department issued health warnings after toxins from the algae were detected in the its water. The agency urged people to avoid swimming in or drinking from the lake.

It has had past issues with harmful algal blooms, with 45 percent of the lake being covered by the algae in July last year, and up to 90 percent of the its surface being coated in 2018, triggering a state of emergency across seven Florida counties.

Algal blooms are excessive growths of micro-organisms called cyanobacteria, which grow and reproduce rapidly when water is warm and abundant in the chemicals they need, like phosphorus and nitrogen. The algae can grow in large, odorous mats, and produce toxins, including those that target the liver (hepatotoxins) or toxins that target the nervous system (neurotoxins).

One of these toxins is microcystin, which was found in water samples taken from the lake on June 17. This toxin was found in 39 percent of lakes sampled by the U.S. Environmental Protection Agency in 2017.

These can be harmful to people that consume the water, causing flu-like nausea, vomiting and diarrhea, according to the Centers for Disease Control and Prevention, as well as throat or eye irritation, allergic reactions and respiratory issues.

Algal toxins can also harm, or even kill, pets and other animals.

"Owners can protect their pets by keeping their dogs away from bodies of water, such as lakes, ponds and rivers that you suspect may contain blue-green algae—this includes not letting them swim in or drink from the water, but also well away from the banks and surrounding areas," a spokesperson for the Kennel Club—a U.K.-based charity devoted to dog health and welfare—previously told Newsweek.

"Pay attention to any signage that may indicate if there is any nearby, but bear in mind that this may not be in place.

"If you suspect your dog has come into contact with blue-green algae, take them to your vet urgently—if possible, call ahead to let them know you are on your way as cases of blue-green algae poisoning often need rapid treatment."

Animals may also suffer neurological damage as a result of algal toxins, which can cause behavioral changes and uncharacteristic aggression, as has been suspected to have happened in cape fur seals in South Africa.

Do you have an animal or nature story to share with Newsweek? Do you have a question about algae blooms? Let us know via nature@newsweek.com.