January 12, 2023 — It is the “smell of decay and death”, says Beth Stauffer, from the University of Louisiana. “It has a physical presence. This layer of very striking greens and blueish greens…when you put your paddle in it, you can feel it.”
She’s describing the harmful algal blooms (HABs) that used to be more associated with marine environments. But in recent years they’ve been moving further inland and affecting freshwater systems, too. And scientists such as Stauffer are trying to find out why.
HABs occur when certain kinds of algae grow very quickly due to increased nutrients in the water – typically when artificial nitrogen and phosphorus applied to farmers’ fields wash out in the rain and enter waterways. The algae receive a meal on a scale they would never get naturally, and a bloom is formed. Sometimes this is harmless. But at scale, many types of algae can turn toxic and harmful to humans and animals. And this scale can be extraordinary.
The explosive growth of algal blooms is linked to rising temperatures and rising pollution. These green waves are both a warning sign and a symptom of a changing climate. As farming fertiliser and a tsunami of human sewage hit our warming waterways, we are in danger of turning our very drinking water toxic.