A recent spike in bottlenose dolphin deaths is more than simply unusual.

During a Wednesday meeting concerning the state of the St. Johns River, a waterbody lately inundated with issues ranging from fish kills to foam, the University of North Florida scientist Radha Pyati remarked on just how unusual recently reported dolphin deaths are: “I think the average is only around one to three mortalities a year, and St. Johns has had at least 14 this summer.” Make that 19, in two months. According to the National Oceanic and Atmospheric Administration, 19 dolphin strandings have occurred from early June to mid-September — a striking leap from the average.

Erin Fougeres, a marine mammal biologist with NOAA, says that it’s likely not a mere coincidence that the dolphin strandings occurred in unison with a massive fish kill in the same area: ”There are a couple of things that could be happening. The strandings occurred around the same time as a fish kill, so they could be related, or it could be another factor. At this point, the strandings have tapered off, and we are just beginning our investigation.”

Because such events are so unusual, the dolphin strandings have now been officially deemed a “Marine Mammal Unusual Mortality Event.” Since 1991, there have been only 50 formally designated Unusual Mortality Events in the country; Florida is second only to California in claiming the most such events.

Marking the deaths as an unusual event means that Fougeres and her fellow scientists will receive additional funding to conduct a thorough investigation. They have also consulted with a working group of scientists, academics, and experts in marine mammal help: “Since it is an official UME [Unusual Mortality Event], we are now legally required to investigate the strandings and are now tasked with forming an investigative team.”

Fougeres says that they are still in the process of forming their team, and its first meeting will occur this week, but there are still hurdles to discovering the root cause of the mysterious dolphin deaths: “We need to look through samples and look through the environmental parameters of what was happening in the river at that time. Unfortunately, most of the carcasses were pretty decomposed by the time we received them, so we don’t have fresh tissue samples and we have limited samples, to begin with.”

Bottlenose dolphins are the species most commonly involved in Unusual Mortality Events. A similar spike in dolphin deaths occurred in the Florida Panhandle around the time of the gulf oil spill, though the cause was not determined. According to the NOAA website, “since 1996, UMEs associated with biotoxins from harmful algal blooms have become more prevalent.”

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