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TOXIC RUNOFF

Tropical Storm Barry could make a bad algae bloom worse

AP Photo/Lynne Sladky
Algae blooms are increasing nationally.
  • Zoë Schlanger
By Zoë Schlanger

Environment reporter

Published

The Gulf of Mexico has an algae bloom problem—and Tropical Storm Barry is poised to make it worse.

The New Orleans area is preparing for dramatic flooding over the weekend, generated by the combination of storm surges and historically high water levels in the Mississippi River. But the region is threatened by yet another global warming-driven feedback loop. Algae blooms thrive in the warming waters of the Gulf. And with heavier rainfall due to climate change, spillways must be opened for longer, sending agricultural runoff—algae food—into the basin. It’s a one-two punch of extreme rain and heat.

Algae blooms, like the kind proliferating in Lake Pontchartrain in Louisiana and off the Gulf coast of Mississippi, are typically caused when nitrogen and phosphorus from agricultural fertilizer and animal manure runs off land and into water. “When you’re seeing more rain, you’re getting more algae blooms,” says Anne Weir Schechinger, a senior economic analyst for the Environmental Working Group.

Meanwhile, the Bonnet Carre spillway on the Mississippi River in Louisiana has been nearly perpetually open since February, with just one month of respite in the spring. It was opened to prevent dangerous land flooding as rainfall swelled the Mississippi River. That additional water is pushing even more freshwater—along with the fertilizers in it—directly into the Gulf, where it is likely contributing to the algae bloom.

Already, Mississippi has had to close all 25 of its beaches due to toxic blue-green algae blooms. Businesses in the beach towns, which depend almost entirely on tourism, told the New York Times that the economic hit of the blooms is akin to what they experienced in 2010, during the Deepwater Horizon oil spill.

The situation is likely to worsen when Tropical Storm Barry touches down on Saturday, bringing even more rain to the already-flooded region. There is also a slim chance the storm surge could wash away some of the algae farther out into the Gulf, temporarily relieving beach communities. But Weir Schechinger says it’s unlikely. “People had hoped last year that the storms in Florida would get rid of the red tide. They didn’t,” she said. Still, “it could happen.”

EWG

Across the US, the algae bloom problem seems to be increasing each year. There have been 140 reported algae blooms in US waters so far this year, according to a report compiled by the Environmental Working Group. At the same time last year, there were 119.

In 2018, 255 toxic algae blooms were reported in 38 states, according to the report, a major uptick from 2010, which saw three blooms in three states.

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