Lakes are experiencing worse algal blooms, global survey shows


In lakes all over the world, algal blooms are getting more severe. In a new global survey of large, freshwater lakes — the first of its kind — scientists found algal blooms have become more frequent and intense over the last 30 years.

Algal blooms can negatively affect humans and ecosystems by robbing freshwater of sufficient oxygen supplies and producing dangerous toxins.

“Toxic algal blooms affect drinking water supplies, agriculture, fishing, recreation, and tourism,” Jeff Ho, researcher at the Carnegie Institution for Science, said in a news release. “Studies indicate that just in the United States, freshwater blooms result in the loss of $4 billion each year.”

Most studies of algal growth have focused on specific bodies or water or regions, like the Great Lakes. For the new study, published this week in the journal Nature, researchers used images captured by the NASA’s Landsat 5 near-Earth satellite to analyze the size and growth patterns of algal blooms in 71 large lakes across 33 countries and six continents.

With the help of Google Earth Engine’s algorithms, scientists analyzed more than 72 million data points.

“We found that the peak intensity of summertime algal blooms increased in more than two-thirds of lakes but decreased in a statistically significant way in only six of the lakes,” said Carnegie scientist Anna Michalak. “This means that algal blooms really are getting more widespread and more intense, and it’s not just that we are paying more attention to them now than we were decades ago.”

Read more