By Samhar Almomani, Publishing Associate: Researcher and Writer at Save the Water™ | July 7, 2025

Edited by Muhammad Afridi, Publishing Project Leader, at Save the Water™

Algal blooms are now believed to be the cause of the mysterious elephant deaths. This started in May 2020. Before collapsing, the elephants wandered aimlessly in circles, with some falling headfirst and dying where they stood. Furthermore, their carcasses were found near watering holes across the Okavango Delta, raising awareness among conservationists. By July, at least 350 elephants had died without explanation. In addition, in November 2024, scientists published a paper pointing to toxic water from an algal bloom as the likely culprit.

What is an Algal Bloom?

Algae are microscopic, plant-like organisms. They live in water and use sunlight to produce energy through photosynthesis. Their habitat includes aquatic environments, such as freshwater, saltwater, and brackish water—a combination of both.

Most algae are harmless and play an important role in aquatic ecosystems. However, some can produce harmful toxins under certain environmental conditions. Factors such as increased nutrients, changes in temperature, light, salinity, or pH levels can trigger toxin production. Furthermore, when these toxin-producing algae grow rapidly, they can form harmful algal blooms (HABs).

HABs can threaten the health of people, animals, fish, and the surrounding ecosystem. These blooms, sometimes visible, may appear green, blue-green, red, or brown, depending on the type of algae. However, not all blooms are easy to detect. Some grow below the surface or near the bottom of a body of water. As a result, you cannot always tell if water is affected by a harmful algal bloom simply by looking at it.

What Did the Researchers Find?

Researchers found that a sharp shift between dry and wet conditions in 2019 and 2020 created ideal conditions for cyanobacteria. As a result, cyanobacteria released toxins that were deadly to elephants. However, researchers were unable to draw firm conclusions because water samples were not collected quickly enough in 2020 due to the COVID-19 pandemic. Some blooms become dense enough to block sunlight from reaching key underwater habitats or release dangerous toxins. In addition, when large amounts of algae die, they consume oxygen in the water while decomposing. As a result, this creates “dead zones” where few fish can survive. “Dead zones” are areas in the water where oxygen levels drop so low that most aquatic life, like fish, can’t survive.

With rising global temperatures, harmful algal blooms are becoming more frequent and even appear now in the polar regions. These blooms are fueled by agricultural pollution, wastewater runoff, and warming temperatures.

Health Dangers of Algal Blooms

Harmful algal blooms can cause illnesses, from mild to severe. The symptoms vary based on the type of bloom and the way a person is exposed to it. These are some of the health effects caused by algal blooms:

• Contact with blue-green algae can result in skin rashes, stomach cramps, nausea, diarrhea, and vomiting.
• People who are highly sensitive to odors may experience respiratory irritation. 
• High levels of exposure to the toxin can impact the liver and nervous system.
• Blue-green algae can make pets ill, causing liver damage and death in severe cases

How to Protect Yourself?

There are several steps you can take to reduce the risk of getting sick from HABs. 

• Swimming: Avoid swimming in or coming into contact with water that seems to be discolored, has scum on the surface, or smells unpleasant.
• Pet Safety: Keep pets away from such water and areas as well.
• Local Advisories: Always check for and follow any local advisories related to swimming, fishing, or shellfish harvesting. If a HAB affects your drinking water supply, follow the guidance provided by local health or environmental officials.

Additionally, if you or your animal comes into contact with water affected by an algal bloom, rinse off immediately with clean tap water. If you develop symptoms that may be related to a harmful algal bloom, reach out to a healthcare provider or call the Poison Control hotline at 1-800-222-1222. Also, you can get help by calling the ASPCA Animal Poison Control Center for your pet in such situations.