UME Florida: Unlocking Mysterious Marine Mammal Deaths
By: Kristin Harrison
When one animal of one species dies, it’s often the result of a life’s natural end. But when hundreds of animals, sometimes of different species, start dying, it’s a medical mystery demanding to be unraveled.
In July 2005, eight bottlenose dolphins stranded along Southwest Florida’s shores. The stranding numbers increased steadily each month: 13 in August, 16 in September, 22 in October — a month when an average of just three dolphins strand. Dolphins weren’t the only local species suffering: 107 sea turtles had stranded or died and more than 80 manatees would be dead by the end of the year. Scientists wanted to find the killer.
The multi-species deaths sparked a federally mandated investigation led by NOAA Fisheries’ Marine Mammal Health and Stranding Response Program and its Working Group on Marine Mammal Unusual Mortality Events. Composed of 12 experts with diverse marine science backgrounds — veterinarians, pathologists, biologists — the Working Group was codified by Congress in 1992 after the late 1980s deaths of more than 700 bottlenose dolphins along the U.S. eastern seaboard and subsequent large scale mortalities of bottlenose dolphins in the Gulf of Mexico. Since formed, the volunteer advisory group has overseen 36 Unusual Mortality Event, or UME, investigations that have involved thousands of animals, from sea otters to humpback whales, and have been caused by factors including infections, human interactions and biotoxins.
Functioning somewhat like the CDC during a health crisis, the Working Group analyzes initial event data and compares it to historical statistics and population trends to determine, within 24 hours by majority vote, if the situation meets at least one of seven criteria necessary to declare a UME. “We tackle these events like a forensics case,” says Trevor Spradlin, executive secretary of the Working Group and a NOAA marine mammalogist.
Once a UME becomes official, the Working Group serves as a resource for the local investigative team that is led by an appointed onsite coordinator. In the 2005/2006 west Florida event, marine mammalogist Melody Baran, contracted by the National Marine Fisheries Service, helped coordinate the dolphin data collection and analysis efforts of NOAA, 48 experts and five stranding response organizations. The group collected as many clues as possible from 130 stranded and dead dolphins, including tissue samples and carcass measurements, to determine the cause of the UME — the first to be declared in the area since 1991.
“One of the things that fascinates me during these events is watching scientists from different backgrounds go through a logical process and use their expertise to figure out a puzzle,” says Dr. Randall Wells, chairman of the Working Group and head of the world’s longest-running wild dolphin study, the Sarasota Dolphin Research Program based at Mote Marine Laboratory. “These investigators are doing highly-detailed detective work.”
Mote played an integral role in the recent Southwest Florida UME: Its Stranding Investigations Program provided first response and collected much of the carcass data and samples; lab scientists shared cutting-edge research on dolphins, red tide and other ecological aspects that “proved vital to the investigation,” says Baran. And Mote’s Dolphin and Whale Hospital successfully treated a live stranded dolphin from the UME and released her back into Tampa Bay, where the Sarasota Dolphin Research Program tracked her through her first month back in the bay.
Although still preliminary, conclusions for the cause of this UME point toward red tide, a dinoflagellate bloom that produces nerve toxins known as brevetoxins. A well-documented fish killer, red tide has gained recent notoriety in the dolphin world. Since 1999, scientists believe three UMEs in the Florida Panhandle affecting more than 200 dolphins were caused by brevetoxins. What Spradlin calls the “$64-million-dollar question”: Why are dolphins in the Panhandle dying in large numbers from red tide regularly when those in other regions with more frequent and more toxic blooms are not?
Similarly, during the west Florida event, Wells says the group of dolphins he studies in Sarasota Bay did not suffer the same high mortality rate as those in nearby Gulf waters. “What made our resident animals OK and not others?” he wonders. “The answer must lie in multiple factors. It’s not a simple situation.”
Understanding the cause of a UME can be just one of many challenges involved in the process. Depending on the location and the number and species of animals, expenses can be exorbitant, and “many facilities involved don’t always have tools or finances at their disposal to respond,” says Spradlin.
The Congressionally-appropriated Marine Mammal Unusual Mortality Event Fund provides some financial assistance for data analysis, equipment purchases or relief staff. “It’s a very helpful resource, but it’s finite,”says Spradlin. “We desperately need to grow the amount.”
Beyond the cost, each UME poses logistical challenges, from finding carcasses fresh enough to yield analyzable samples to performing necropsies on floating animals more than 100 miles offshore, as was the case of a 2003 UME involving humpback whales. But the time-consuming, labor-intensive investigations are critical, says Spradlin, because they provide a “much better understanding of ocean health.”
They may also help determine the impact humans are making on marine ecosystems. “Dolphins breathe the air we do, swim through the same waters we like to swim through, eat the same fish,” says Wells. “You have to wonder whether continuing changes to the coastal ecosystem are going to play out as more large-scale mortality events over time.”
Conversely, says Spradlin, “We all do this type of work because we care very passionately about marine mammals. But even if you’re not interested in marine mammals, they still serve an important function: They’re like canaries in the coal mine. If something is happening to dolphins or manatees, there could be significant impacts on human health as well.”
Funding for Unusual Mortality Event Investigations is provided by the National Marine Fisheries Service through the Marine Mammal Health and Stranding Response Program.
Learn more about: Stranding Investigation
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Mote Marine Laboratory has been a leader in marine research since it was founded in 1955. Today, we incorporate public outreach as a key part of our mission. Mote is an independent nonprofit organization and has seven centers for marine research, the public Mote Aquarium and an Education Division specializing in public programs for all ages.
