A plan to divert fresh water and sediment from the Mississippi River to the Barataria Basin could virtually wipe out bottlenose dolphins in that area over the next few decades, though state officials plan to spend $60 million to protect some of the mammals.
The $2 billion Mid-Barataria Sediment Diversion project, which could be built near Myrtle Grove in Plaquemines Parish beginning next year if permits are approved, is aimed at restoring and maintaining wetlands lost to sea level rise, subsidence and other factors. But sending fresh water to the basin and nearby bay, a brackish water environment, spells out trouble for the 2,000 dolphins that call the Barataria Bay home.
To preserve as many of the animals’ lives as possible, the state Coastal Protection and Restoration Authority and the National Marine Fisheries Service are working on a mitigation plan. The draft plan would see Louisiana spend:
- $20 million on a marine mammal intervention program that would help the dolphins, which could develop lesions and even die after exposure to fresh water, nutrients and sediment.
- $20 million to monitor the bay’s dolphin population before and after the diversion begins operations.
- $20 million on dolphin stewardship measures, including a network aimed at nursing wounded dolphins back to health; public education and other measures to reduce threats from fishers and dolphin hunters; and a contingency fund to address possible mass dolphin deaths.
This slide presented during a March 2021 meeting of the federal Marine Mammal Commission shows skin lesions caused by exposure to freshwater c…
Coastal authority chairman Chip Kline said the authority recognizes the threat the diversion may pose to the cetaceans and other wildlife. Officials expect to release a final version of their plans to mitigate that harm in late June.
“We’ve used this information and all the data available to us to develop measures that put us in the best position to minimize negative impacts to the dolphin population to the extent possible. Further, we do not believe that the statewide measures will increase the survival of dolphin stocks across Louisiana,” Kline said.
Still, some researchers remain unconvinced that those efforts will protect a dolphin population still recovering from the effects of the 2010 BP oil spill.
A new study, commissioned by the federal Marine Mammal Commission and published in the scientific journal Marine Mammal Science in March, predicts that 97% of the bay’s dolphins will be dead in 50 years, and the few that remain will only be found near Grand Isle , where the water is more saline.
This map shows how many bottlenose dolphins were located in various parts of Barataria Bay during a 2019 survey by biologists with the Nationa…
“The declines are predicted to be greater than those caused by the Deepwater Horizon oil spill and would take place just as the population is starting to recover from the spill,” the report said.
Dolphins have called basin home for decades
The Barataria Basin, the broad area of freshwater marshes and brackish wetlands that includes the bay and is bordered by the Mississippi River and Bayou Lafourche, is home to one of the 31 groups of dolphins that call the Gulf of Mexico home. Other dolphin groups are found in Breton Sound, the Mississippi Sound and elsewhere around the Gulf Coast.
Dolphins have populated Barataria since the start of the 20th century, when wetlands erosion provided them with enough space behind the coast’s barrier islands to forage for food.
Their potential deaths have been one of two major facing the state authority and the Louisiana Trustees Implementation Group, which is made up of the state and federal agencies overseeing the spending of $5 billion BP paid to restore natural resources in the aftermath of the Deepwater Horizon oil spill.
The other major issue will be changes in the types of commercial fish that can survive in the bay after the diversion is opened. The diversion is expected to make most existing oyster beds unusable, to reduce catches of more saline and brackish water fish species, and to delay the growth of some shrimp species.
Still, state officials believe the project is the state’s best shot at providing enough sediment to build an estimated 27 square miles of wetlands over 50 years.
Modeling conducted for the state indicates the Mid-Barataria Sediment Diversion will build more new wetlands than if no project is built. Thes…
While bottlenose dolphins are protected under the federal Marine Mammal Protection Act, Louisiana’s congressional delegation inserted a provision in the Bipartisan Budget Act of 2018 requiring the National Marine Fisheries Service to allow the state to deviate from rules prohibiting “takings” of mammals — that actions would harm or kill the dolphins.
The waiver language also required state and federal officials to “consult” on ways to reduce threats to the dolphins, though the language does not say whether or how many of the dolphins are required to be saved.
However, as part of an environmental assessment required by the Army Corps of Engineers, officials must also determine whether the diversion violates broader environmental requirements under the federal National Environmental Policy Act. The trustees group also must consider whether appropriate stewardship measures are being developed per the federal Oil Pollution Act, which governs the spending of the natural resource money.
The study at issue measures the effects of the diversion in decadelong increments over the first 50 years of its operation. It is an update to a 2021 study, also sponsored by the Marine Mammal Commission, that predicted an 85% decline in the dolphins after the diversion is built, said study author Lori Schwacke, a marine biologist with the National Marine Mammal Foundation.
The draft version of the Corps’ environmental impact statement, also released last year, predicted that as many as 30% of the area’s dolphins could be in any given year of diversion operations.
This map shows the areas in western, central and eastern Barataria Bay where bottlenose dolphins were counted during a 2019 survey by National…
‘We need to be prepared to do something’
To reduce the harm done, the state intends to monitor the dolphin population before and after the diversion comes online, Kline said. To better protect the animals, officials might shift when and for how long the diversion is operated, or limit the amount of fresh water that flows through it.
The state also intends to pump more money into a stranding network that has long worked to rehabilitate wounded dolphins, whales and manatees. That extra money will be provided in 2026, when the network’s existing funding is set to expire. The network’s expansion should reduce the time an individual dolphin is stranded, and potentially increase animal survival rates, Kline said.
Separately, an “unusual mortality event” contingency fund will cover staffing costs, should there be mass dolphin deaths. There have been several such events in Louisiana and Mississippi coastal waters dating back to just before the BP spill in April 2010, with the latest occurring in 2019 after an extremely lengthy Mississippi River high water period.
Though just what those staffers would do has yet to be decided, they could be tasked with moving or rehabilitating wounded dolphins, Kline said.
But the sickly animals might not survive the transport or adapt well to their new location, Schwacke said. There’s also no guarantee the dolphins won’t immediately swim back to Barataria once they are released.
“Plus, can you imagine trying to relocate 2,000 or so dolphins?” Schwacke added. “I’m not saying that it’s not worth a try. I think we need to be prepared to do something, even if it only saves a few dolphins from a slow, painful death.”