The stranding of more than 261 bottlenose dolphins along the Gulf Coast from Louisiana to the Florida Panhandle since Feb. 1, with 98 percent of the dolphins being found dead, prompted NOAA Fisheries to declare an “unusual mortality event” on Friday.
Scientists say many of the dolphins showed evidence of skin lesions likely caused by exposure to too much freshwater entering coastal bays, lakes and estuaries from both the unusually high Mississippi River and other rainfall flooding events along the coast.
But in a news release announcing the event, scientists said it was too early to determine the potential causes of the strandings and deaths.
“Many of the dolphins recovered are very decomposed, limiting the ability to collect samples to determine cause of illness or death,” the new release said. “In addition, a number of dolphins have stranded in remote locations, which limits the stranding network’s ability to examine or recover the carcass.
“Some of the stranded dolphins have had visible skin lesions that are consistent with freshwater exposure,” the release said.
But they also pointed to the potential continued health effects to dolphins and other marine mammals from the BP Deepwater Horizon oil spill. A separate unusual mortality event was declared for the spill that included the stranding of 1,141 cetaceans along the northern Gulf Coast, of which 85 percent were bottlenose dolphins.
The investigation for that event found adrenal and lung disease in dolphins, and linked the spill to both increased deaths and the loss of unborn and newborn dolphins within the oil spill area.
“Researchers saw evidence of chronic lung disease and adrenal impairment even four years after the … oil spill (in July 2014), and saw evidence of failed pregnancies in 2015,” said a question-and-answer sheet prepared by NOAA Fisheries about the new event.
In the question-and-answer document, officials pointed out that both high levels of rainfall along the Gulf Coast, combined with the opening of the Bonnet Carre Spillway and other spillways “have altered the flow of freshwater into some of the bays, sounds and estuaries of the northern Gulf affecting dolphin habitat." The spillway had been open a total of 79 days through Friday, and the river water has flowed through Lake Pontchartrain and Lake Borgne into both the Mississippi Sound and the area of the Gulf east of the river.
During a Friday news conference, NOAA Fisheries Southeast Region Marine Mammal Stranding Program Administrator Erin Fougères said the most strandings, 121, were recorded in Mississippi, with 89 in Louisiana, 32 in Alabama, and 37 in Florida.
She pointed out that the lower Mississippi Valley area has experienced the wettest year due to rainfall during the last 124 years, which has resulted in high freshwater levels in a variety of rivers and streams entering the Gulf, in addition to the use of the spillways for flood control purposes.
Because a mortality event has been declared, an onsite coordinator will be appointed to work with the Marine Mammal Stranding Network and NOAA to guide the response and help match resources to research needs, Fougères said.
Officials warned that other marine animals may also be suffering health problems this year, with increased strandings of sea turtles reported in Louisiana and Mississippi. Investigations into those strandings are under way.
“We do not suspect that the current sea turtle strandings are related to freshwater exposure – we do, however have concerns that decreased salinity will have longer term effects on sea turtle prey and habitat,” the question-and-answer publication said.
NOAA officials said stocks of dolphins that reside in 17 different locations along the coast tend to stay within those areas throughout their lives, and often don’t leave despite environmental threats such as too fresh water.
Bottlenose dolphins that live along the coast and in deeper oceanic waters are usually found in high salinity water, between 20 parts per thousand and 35 parts per thousand of salt. But in bays, sounds and estuaries, dolphins do periodically see lower salt levels, especially during spring and summer months, NOAA Fisheries officials said.
“Health impacts, such as kin lesions, abnormal blood chemistry, swelling of the cornea, and eventual death, can occur in dolphins due to low salinity exposure over a period of days to weeks,” said the question-and-answer document. “These health impacts can be exacerbated in dolphins with pre-existing conditions, such as injuries, infections, poor nutrition, or immune suppression.”
Officials asked the public to report any sightings of live dolphins in distress or stranded (floating or on the beach) by calling the 24/7 Southeast Marine Mammal Stranding Network at 877-WHALE HELP (877-942-5343). You can contact the U.S. Coast Guard on VHF Channel 16 or use our Dolphin and Whale 911 app on your smartphone. The stranding network will send out trained responders who will get to the scene quickly with appropriate equipment, officials said.
And they issued a series of dos and don’ts for those who come across a stranded live or dead dolphin:
· DON’T push the animal back out to sea! Stranded marine mammals may be sick or injured. Returning animals to sea delays examination and treatment and often results in the animal re-stranding in worse condition.
· If the animal returns to the water on its own, DON’T attempt to interact with it (swim with, ride, etc.).
· DO put human safety above animal safety. If conditions are dangerous, do not attempt to approach the animal.
· DO stay with the animal until rescuers arrive, but use caution. Marine mammals can be dangerous and/or carry disease. Keep a safe distance from the head and tail. Do not touch the animal and avoid inhaling the animal’s expired air.
· If the animal is alive, DO keep its skin moist and cool by splashing water over its body. Use wet towels to help keep the skin moist and prevent sunburn.
· If the animal is alive, DON’T cover or obstruct the blowhole. Try to keep sand and water away from the blowhole.
· DO keep crowds away and noise levels down to avoid causing further stress to the animal.
· DO report all dead marine mammals, even if they are decomposed.
· DO keep dogs/pets away from the live or dead marine mammal.
· DON’T collect any parts (tissues, teeth, bones, or gear, etc.) from dead animals. They are still covered by the Marine Mammal Protection Act.
Mark Schleifstein covers the environment and is a leader of the Louisiana Coastal Reporting Team for NOLA.com | The Times-Picayune. Email: mschleifstein@nola.com. Facebook: Mark Schleifstein and Louisiana Coastal Watch. Twitter: MSchleifstein.
