The Mississippi Department of Environmental Quality has closed all 21 of the state’s beaches due to the presence of toxic blue-green algae.

Pascagoula Beach West and Pascagoula Beach East were closed Sunday, marking the shut down of the final two beaches open for swimmers. The sand portions of all of the beaches remain open but people are advised to stay out of the water and not eat fish or seafood from the affected areas.

The current Harmful Algal Bloom, or HAB, was at least partly caused by the opening of the Bonnet Carre spillway in Louisiana, which has triggered "excessive" freshwater to the coastline, the Jackson Clarion Ledger reported.

HABs occur when "colonies of algae -- simple plants that live in the sea and freshwater -- grow out of control and produce toxic or harmful effects on people" or wildlife, according to the National Oceanic and Atmospheric Administration.

“The human illnesses caused by HABs, though rare, can be debilitating or even fatal. HABs have been reported in every U.S. coastal state, and their occurrence may be on the rise. HABs are a national concern because they affect not only the health of people and marine ecosystems, but also the 'health' of local and regional economies,” NOAA said.

HAB can cause rashes, stomach cramps, nausea, diarrhea and vomiting.

People can get sick by eating shellfish containing toxins produced by the algae and airborne HAB toxins may also cause breathing problems and, in some cases, trigger asthma attacks in susceptible individuals.

A water contact advisory has also been issued for part of the Jourdan River in Hancock County from the Interstate 10 bridge to the mouth of the river at St. Louis Bay.

The closed beaches are: