The relentless heavy rains in the Midwest continue to cause damage, this time in the form of vast, harmful algae blooms off the gulf coast that have forced Mississippi to close all of its beaches.

The increased flow of freshwater into the Gulf of Mexico has fed the thick blue-green algae, which can cause rashes, stomach cramps, nausea, diarrhea and vomiting in people and animals. It has already killed off the state’s oyster beds, which could take years to recover, officials said.

Local tourism businesses, which were counting on a lucrative Fourth of July weekend, are comparing the economic hit to that of the Deepwater Horizon oil spill in 2010.

James Barney Foster, the owner of Life’s a Beach water sports equipment rentals on the Mississippi coast, had prepared for a busy summer season this year by buying dozens of new Jet Skis.