* By Justin Gillis

* Published Aug. 29, 2022

* Updated Aug. 30, 2022

Satellite images of Earth’s coastal waters have revealed a disturbing trend: Harmful algal blooms are becoming more frequent and larger.

The images, taken by NASA’s Aqua satellite, show that the total area covered by algal blooms increased by more than 50 percent between 2000 and 2019. The most dramatic increases were seen in the Gulf of Mexico, the North Sea and the Baltic Sea.

Algal blooms are caused by a rapid growth of algae, often fueled by excess nutrients from agricultural runoff, sewage and other sources. These blooms can produce toxins that are harmful to humans, animals and marine life.

The growth of algal blooms is contributing to a decline in water quality and the loss of marine habitats. They can also make swimming, fishing and other recreational activities unsafe.

In addition to the environmental impacts, algal blooms can also have a significant economic impact. In the United States, for example, algal blooms cost the economy an estimated $82 million a year in lost tourism revenue and damage to the seafood industry.

As the climate warms, the conditions that favor algal blooms — higher temperatures, increased rainfall and more nutrient pollution — are likely to become more prevalent. This could lead to even larger and more frequent algal blooms in the future.

The good news is that there are things we can do to reduce algal blooms. We can reduce nutrient pollution by improving wastewater treatment and reducing fertilizer use. We can also protect coastal habitats that help filter nutrients from the water.

By taking action to address algal blooms, we can protect our oceans and ensure a healthy future for marine life and human communities.