All public beaches along Mississippi’s Gulf Coast have been ordered closed for swimming and fishing amid a sweeping bloom of harmful blue-green algae that authorities warn can sicken people and animals upon contact.
The order imposed Sunday by the state Department of Environmental Quality affects a total of 21 public beaches.
The blue-green algae, actually a bacteria called cyanobacteria, grows on the surface of water and can cause rashes, stomach cramps, nausea, diarrhea and vomiting in humans. The effects are even more serious for other animals, and infection can turn fatal within hours or days, according to the Centers for Disease Control and Prevention.
Health officials warn against swimming, wading or fishing in the water until further notice. The sand portions of the beaches remain open.
Harmful algal blooms, or HABs, have been reported in every U.S. coastal state, though less than 1% of algal blooms produce toxins. Still, HABs can be harmful to the environment in other ways, including depleting water of oxygen and sunlight, according to the National Ocean Service.
The current Mississippi bloom is linked to freshwater entering the gulf shoreline through the Bonnet Carre spillway. The spillway has been opened twice this year to relieve flooding along the Mississippi River following an extremely wet winter, the Clarion-Ledger reported.
The spillway was opened in February and in May to protect New Orleans from flooding ― the first time in its 90-year history that it has been opened more than once in a year.
Once the spillway closes, likely in mid-July, experts predict the algae bloom will dissipate.
The U.S. Army Corps of Engineers, which oversees the spillway, has acknowledged that flooding the shoreline with freshwater has an immediate adverse environmental effect. But the corps asserts that the harm is temporary, and that long-term benefits include the spreading of valuable sediment and nutrients.
In addition to fueling cyanobacteria, the surge of freshwater has been blamed for the deaths of at least 48 dolphins between May 22 and June 7 due to low salinity levels. This is more than half of the number of dolphins killed by the BP oil blowout during all of 2010, the Clarion-Ledger reported.
“During the BP oil spill we had 91 dolphins the entire year,” Moby Solangi, president and executive director of the Institute for Marine Mammal Studies, told the local paper. “So, that’s a considerable increase and the year isn’t over yet. Ecologically, we’re seeing a lot more sustained damage than the BP oil spill.”
The release of freshwater has also harmed oyster harvesting areas in Lousiana, the Times-Picayune reported.
Last month, scientists warned that the Gulf of Mexico would experience one of the largest “dead zones” in recorded history because of unusually heavy rainfall and pollution from agricultural runoff that feeds massive phytoplankton blooms, which destroy the water’s oxygen supply.
This oxygen-starved area is expected to grow to roughly the size of Massachusetts, or approximately 7,829 square miles, the National Oceanic and Atmospheric Administration said.
The Gulf Coast is particularly vulnerable to such dead zones because 41% of the U.S. drains into the Mississippi River, whose watershed is largely composed of farmland, according to the Environmental Protection Agency.