This green gunk is alive and dangerous. In July 2016, Utah Lake was struck by an algal bloom, affecting more than 384km2 of fresh surface water.
The cyanobacteria releases toxins such as microcystin, which can cause vomiting, diarrhoea, skin rashes and even liver damage. Utah Lake was closed for 13 days, with a period of "caution" for swimmers after that.
Utah's was only the latest bloom to hit American waters. According to 2015 UNESCO estimates, countering the phenomenon now costs the US more than $4 billion (£3bn) annually.
"Globally, there has been an increase in the incidence of harmful algal blooms," says Anna Michalak, a researcher at Stanford's Department of Global Ecology. "But there are factors in the US making waters more prone to this problem."
The blame is often pinned on phosphorus use in farming, which feeds the algae when it percolates to the water. Yet Michalak explains that it is difficult to find a single cause: "What's going on is an interplay between what we're doing on the land locally and what's happening with the climate globally," she says, as warmer temperatures provide the micro-organism with a cosier habitat, and heavier rains boost farm run-offs.
"Changing weather patterns are compounding the impact of the extra phosphorus reaching the water. It's the perfect storm."
This article was originally published by WIRED UK
