Blue-green algae is lingering in Coast waters far longer than expected after closure of the Bonnet Carré Spillway.
When will it go away?
Local scientists are now saying the Mississippi Sound will have to cool off before the algae dies, which means it could be around for another month or so.
The water no longer looks green because the algae, a cynobacteria called mycrocystis, is not as concentrated.
The algae put a damper on tourist season, costing hotels operators, restaurant owners and beach vendors. The kind of national publicity that tourism areas hope to avoid has accompanied the algae blooms, which has kept beachfront waterways closed since late June from state line to state line.
The opening of the Bonnet Carré Spillway ushered in the algae blooms that normally thrive in fresh water. Salinity levels in the Mississippi Sound dropped to zero in the western Sound closest to Lake Ponchartrain, where the Bonnet Carré emptied trillions of gallons of Mississippi River water over 123 days — the longest opening in the spillway’s 88-year history.
Fertilizer in the river water, especially phosphates, feed the algae. Toxins it releases can cause skin rashes, while ingesting the water can lead to gastrointestinal problems and serious illness.
The Mississippi departments of Environmental Quality and Marine Resources have tag-teamed testing of waterways for the algae’s presence. DEQ samples for algae at beach stations it established to monitor bacteria levels along the shoreline, while DMR tests further offshore, checking water and fish for toxicity.
“We think the opening of the Bonnet Carré not only provided a pathway for (algae) to get to our warm water but allowed them to bloom in numbers that are not impacted by the higher salinity water,” said Joe Jewell, DMR director of fisheries. “We agree the only thing that will disperse them is the cold water.”
Advisories DEQ issued to avoid contact with the water also initially said people should not eat fish caught in areas with algae. However, DMR has been testing fish, shrimp, crabs and oysters for toxins.
“I feel very comfortable in saying that all the tests we have run on seafood show it is safe for consumption,” Jewell told the Sun Herald on Friday.
Toxicity levels in the water have also been below what the Environmental Protection Agency considers dangerous. The toxicity tests provide only a snapshot in time and might have missed unsafe levels, said Gary Rikard, executive director at MDEQ.
Mississippi has taken the safest approach in issuing its beach advisories, Rikard said.
“We’ve taken the position that if algae is present, we’re going to issue the warning — at any level, based on whether the algae is present, not whether the toxins are present,” Rikard said.
Consideration is being given to refining the system, he said, as some states do for their lakes where algae grow, by issuing warnings only when toxins released by blooming algae reach set levels.
He said DEQ is studying the issue, but has to take into account the differences between lakes, where algae is more stagnant, and a marine environment such as the Mississippi Sound where it tends to be disperse.
“At the end of the day,” he said, “we want to ensure the public is safe but we want to be reasonable.”
Moby Solangi, a biologist who heads the Institute for Marine Mammal Studies, believes it will take some time for the estuarine environment to stabilize from the Bonnet Carré opening.
“We are going to still see it’s after effects, maybe not as acute, until all that water is gone and mixed up,” he said.