A dolphin washed up on Coast beach. What she may reveal about Gulf ecosystems.
After she died, the dolphin bobbed on the surface of the Gulf of Mexico for days.
By early Thursday, her body had washed up onto the beach in Pass Christian. A beachgoer spotted her and called the hotline run by the Institute for Marine Mammal Studies, the Gulfport-based nonprofit that has cared for sick and injured dolphins, sea turtles and other animals since 1984.
The dolphin is the 66th stranded dolphin researchers have encountered this year, IMMS stranding coordinator Theresa Madrigal said.
They determined that she was an adult female Atlantic bottlenose dolphin, the most common dolphin type in the Gulf, and the state mammal of Mississippi.
Because the dolphin’s body was so decomposed by the time they arrived to collect samples, researchers may never determine exactly how she died. But the samples will be sent to a pathologist and a toxicologist and could show whether she was suffering from a particular disease.
And in any case, studying the dolphin will help researchers in their quest to identify patterns and warning signs among the Mississippi Sound’s dolphin population.
“This is just one data point,” said IMMS President Moby Solangi. “It’s used against the rest of the animals that we will be seeing, seeing if there’s a trend or some commonality.”
Largest U.S. dolphin population
The Mississippi Sound’s dolphin population is the largest in the United States. The area is also home to the world’s most endangered sea turtle species, the Kemp’s ridley.
Every year in February or March, the dolphins move toward the coast to give birth, and they stay in the area until around September, he said.
That period is also the peak for dolphin strandings, Madrigal said, but there are a few animals reported to the Institute every month.
As top predators, the health of dolphins provides an indication of the overall health of the ecosystem. Problems lower down in the food chain, such as with the shrimp population, will show up among dolphins and sea turtles.
“If they are dying, that means everything below it, from the very small algae, [and] shrimp to all these other [organisms] that form the links to the ecosystems, are being affected,” Solangi said.
Dolphins who strand, whether dead or alive, may be suffering from illness. Some die of natural causes, like old age or while giving birth. Others suffer from what the researchers call “human interaction,” for example becoming entangled with fishing lines or crab pots. Madrigal said she’s seen a few cases this year where it appeared humans played a role.
In recent years, Solangi said, the Institute has logged around 60 dolphin strandings per year, higher than the historic annual averages of 30 to 40.
Threat of freshwater diversion
In 2019, the U.S. Army Corps of Engineers opened the Bonnet Carre spillway for well over 100 days, diverting the Mississippi River to protect New Orleans from flooding. The massive influx of freshwater into the Mississippi Sound devastated fisheries and killed sea turtles, oysters, shrimp and dolphins.
That year, Solangi said, IMMS recorded 153 dolphin deaths.
Through sampling, they found about half of the dolphins were suffering from freshwater lesions, indicating they had suffered the consequences of the spillway opening.
“It’s like an aquatic hurricane that comes in and ravages all this stuff,” Solangi said of the spillway opening’s effects. “Just like on land, it takes years to rebuild, for the shrimp and the oysters and all the other long-lived species to come back online. So you have these long-term effects that we are trying to study.”
Now, the issue of freshwater diversions into the Mississippi Sound is back in the headlines. The U.S. Army Corps of Engineers is currently reviewing a Louisiana plan to divert Mississippi River water south of New Orleans. The idea is that the river sediments will help rebuild marshes.
Louisiana leaders have said they think it’s unlikely that their plan will lead to freshwater reaching the Mississippi Sound. But many Missisippians are skeptical, the Sun Herald reported on Thursday.
Solangi hopes their research will raise awareness about the potentially “catastrophic response” following freshwater diversions.
What to do if you find a dolphin
The Institute’s hotline for dead, injured and sick dolphins and sea turtles is staffed 24/7. You can call whenever you encounter an animal on a Mississippi beach.
Do not touch a stranded dolphin, whether you believe it to be alive or dead, unless directed to do so.
One person walking on the Pass Christian beach Thursday came across the dead dolphin and contacted the Sun Herald because of orange paint and what appeared to be burn marks on its body.
But Madrigal said the paint was the researchers’ tag to inform sand beach staff that they had already evaluated it, so they would know to dispose of the body.
And what appeared to be burn marks were most likely left by the sun while the dolphin was floating in the gulf after it died.
To contact the Institute for Marine Mammal Studies if you encounter a dead, sick or injured dolphin or sea turtle on a Mississippi beach, call their hotline: 1-888-SOS-DOLPHIN (1-888-767-3657)
