All 21 of Mississippi’s beaches are closed for swimming, due to a blue-green harmful algal bloom (HAB). The Mississippi Department of Environmental Quality (MDEQ) has shut down all the site’s beaches because of the HAB. It was reportedly at least partly caused by the opening of the Bonnet Carre Spillway, which controls flooding in Louisiana and has been open for an historically long period of time this year due to flooding of the Mississippi River. The freshwater has flooded the Mississippi Sound with pollutants that have killed wildlife. The algae can also cause rashes, nausea, diarrhea, and vomiting. Experts say the algal bloom won’t go away until the Spillway closes, which is scheduled to happen in mid-July. Beachgoers can still visit the sand, but both pets and people are advised to stay out of the water. Mississippi also closed all its beaches in December 2015 due to an algal bloom. HABs aren’t rare, but experts say they are occurring more frequently due to climate change.