The federal government's effort to avoid a flood disaster in New Orleans had catastrophic consequences of its own, causing massive fish kills and habitat destruction along the Gulf Coast, according to the governors of Louisiana, Mississippi and Alabama.

The governors say the Army Corps of Engineers' diversion of trillions of gallons of water from the swollen Mississippi River into the Gulf of Mexico killed fish, shrimp, oysters and crab and forced the extended closure of beaches. Dolphins have suffered high death and infection rates, researchers say.

The diversion ran for a record 123 days between late February and late July to prevent the Mississippi from flooding New Orleans the way it flooded communities across the Midwest this past winter and spring.

But diverting the nutrient-loaded fresh water into the saltwater Gulf of Mexico reduced the Gulf's salinity to dangerously low levels for sea creatures and created toxic algal blooms that made the water harmful to humans.

Some oyster habitats have been wiped out entirely, according to a report Friday by the Louisiana Department of Wildlife and Fisheries. Shrimp hauls are down by up to 44%, blue crab is down by as much as 84%, and certain fish catches are also far below recent average hauls, the report says.

"They're not capable of living in the lower salinity," said Nancy Rabalais, chairwoman of Louisiana State University's Department of Oceanography and Coastal Sciences.

"I don't think all negative economic impacts have been documented," Rabalais added. "Farmers couldn't farm. Tourism took a hit in Mississippi because people couldn't go to the beach."

Since late June, the Mississippi Department of Environmental Quality has directed people and pets to avoid contact with the Gulf of Mexico waters at most beaches in the state, effectively closing 25 beaches. The algal blooms can cause rashes, stomach cramps, nausea, diarrhea and vomiting.

"This is man-made by the Corps of Engineers," said Benedict Posadas, an economics professor at Mississippi State University who is tracking the impact of the diversion.

Posadas' analysis shows that the value of the shrimp haul in Mississippi in July was 60% below its typical average value in July and that the state's oyster harvest is almost entirely gone. The declining haul is damaging related industries such as processing, distribution, and retail and restaurant sales.

"Charter boats have been affected. Restaurants are saying they have reduced sales. Some hotels are saying the same thing," Posadas said in an interview.

The Army Corps has defended its decision to divert the Mississippi. The diversion involved opening the massive Bonnet Carré Spillway 33 miles upriver from New Orleans and sending as much as 1.5 million gallons per second of water into Lake Pontchartrain in New Orleans and the Mississippi Sound along the coast.

The Army Corps acknowledged that the "vast input of fresh water into these brackish and saline lakes has an immediate, short-term, adverse environmental effect."

But the long-range effect is "extremely favorable because it simulates the natural flooding cycle of the river and provides a replenishment of valuable nutrients to the ecosystem," the Army Corps added. "Spillway openings are strongly associated with increased oyster, crab and other fisheries production in Lake Pontchartrain and Lake Borgne for several years after the flood events."

Opening the Bonnet Carré also deposits millions of cubic yards of sediment in the Mississippi River floodway. The silts and sand are a "valuable local resource" that contractors and local governments use as fill material in residential and industrial projects, the Army Corps said.

Rabalais of LSU questioned the Army Corps' assertion that the freshwater diversion would benefit fisheries production.

"A correlation would be very hard to pull together. Fisheries data are quite variable. Other things might be affecting it," Rabalais said.

The Army Corps diverted 10 trillion gallons of water from the Mississippi River during the 123 days it opened the spillway this year, according to an E&E News estimate based on Army Corps data showing the daily discharge rate. The spillway, built after the Great Flood of 1927, has been opened only 14 times in its 88-year history. Until this year, the record for the number of days of openings in one year was 75, during the massive flooding of 1973.

The governors of Alabama, Louisiana and Mississippi have asked the Commerce Department to declare fisheries disasters in their states. The requests are under review.

Gov. Kay Ivey of Alabama said in her July 10 request that state officials are monitoring the impact of the freshwater intrusion. "Extremely low salinities for long periods generally have an adverse effect on the production and harvest of oysters, blue crash and white, brown and pink shrimp," Ivey, a Republican, wrote.

Democratic Gov. John Bel Edwards of Louisiana said in his June 13 request that "millions of baby oysters" being grown at a nursery in marshes east of New Orleans "have been lost due to low salinity."

The Army Corps' diversion also has drawn attention to how it decides whether to open the Bonnet Carré spillway.

Mississippi Attorney General Jim Hood asked Congress in a July 15 letter to amend the Mississippi River Commission to include one "permanent civilian employee" from Mississippi. The commission is an arm of the Army Corps that manages the Mississippi River and makes decisions on opening and closing dams and spillways.

Hood, a Democrat running for governor, threatened to sue the Army Corps in June to extract damages and reparations, according to local news reports.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news