A discovery into dolphin genetics may have brought research scientists one step closer to finding out the source of a mysterious animal die-off last year in the troubled Indian River Lagoon.
“Now, I gotta good one for you: if you’re swimming in the water and a fin comes up right by you, how can you tell instantly whether it’s a shark’s fin or a dolphin’s fin,” asked Barry Legé.
The answer? A shark fin is more straight, while a dolphin’s fin is more curved.
And, those are just some of the tidbits of information that Legé more widely known as Captain Chop shares on the Wildlife Lagoon Tour of the Indian River Lagoon—all while several passengers aboard his boat, including myself, were waiting to see a small pod of dolphins.
But, he says around this same time last year, dolphin sightings was practically non-existent, and he blames the polluted discharges from Lake Okeechobee into the 156-mile estuary.
“Record rainfall we were having last year, and they happened to release so much fresh water into the estuary and it really caused me alarm and caused some problems,” he added. It was first time the dolphin sort of like disappeared for a very long period of time. And, we kept wondering, ’Jesus, where are they?’ And, occasionally we’d see one, but it wasn’t the pods. And, soon as the water started clearing up, the bait fish started coming back and the dolphins started coming back.”
Last year, the Indian River Lagoon was also the location of a massive die-off of not only bottlenose dolphins, but also pelicans and manatees. There have been many theories as to the cause, including nutrients from septic tanks and fertilizer causing toxic algae blooms to form in the lagoon, wiping out 47,000 of acres of sea grass—a feeding ground to many of the lagoon’s wildlife.
Still, there have been no concrete answers, especially since it’s been hard pinpointing what could have caused the unusual amount of fatalities in three different species—some of which don’t even share the same diet.
For bottlenose dolphins alone, close to 80 were victims of the die off. To put it in perspective, around this same time last year, 7 dolphin deaths have occurred—according to the Hubbs-SeaWorld Research Institute—tasked with investigating the dolphin deaths.
But, using what’s called a molecular toolkit, researchers at Florida Atlantic University's Harbor Branch Oceanographic Institute say they may be close to finding an answer into the mysterious dolphin deaths using their genes.
The institute’s principal investigator Dr. Greg O’Corry-Crowe says it has three major aspects: how the genes reflect on the behavior and social structure of the dolphin, tracking dolphins’ innate ability to respond to environmental changes, and if a new group of genes can metabolize a toxin in response.
“So, in combination, if we can detect differences in the ability in different individual dolphins or populations of dolphins, for example, to mount an effective immune response to metabolize toxins effectively. This might help us understand more about things, such as these unusual mortality events, such as mass die-offs, you know, where they occur, why they occur, and when they occur,” he said.
This project is a four-year study started in 2009 that spans about a decade of samples dating back to the mid-90s that have been collected from the Jupiter Inlet in the south all the way north of the Indian River Lagoon to New Smyrna Beach. That’s a third of Florida’s east coast, which is not only within the lagoon system, but also along the Atlantic in that same area.
“And, I think you know that temporal perspective is really important as we move forward dealing with the current unusual mortality event, and other issues that will crop up. We now have this baseline and this sort of temporal continuity that makes it very powerful,” O’Corry-Crowe added.
That’s about 600 samples that researchers collected over the last 10 years from capturing and releasing live dolphins, or already dead dolphins as a result of strandings and beached events.
And, under the guidance of O’Corry-Crowe, the study was conducted by FAU Harbor Branch research biologist Sarah Rodgers.
“And, this is important because currently, previous to my research, these populations were deemed separated from the two. And, 40 years of previous research has been based on that theory,” said Rodgers.
By studying dolphins from the Atlantic and dolphins in the Indian River Lagoon, Rodgers says her findings disproved a widely thought assumption throughout the research community: that the Indian River Lagoon dolphin population was closed off from interaction with other dolphin populations, like the Atlantic.
“These animals are interacting together, and we can see that through their genetic signals. So, although there is an Atlantic coastal population that is separate from somewhat of the Indian River Lagoon population of dolphins. There are emigrants in each of those populations. So, there are Atlantic dolphins that are in the Indian River Lagoon, and there are Indian River Lagoon dolphins in the Atlantic. And, we’re able to detect the differences in those using genetics,” she added.
So, what’s their next step moving forward?
“See if there’s some differences. See if there’s some changes between this pre-mortality event and post afterwards…see if there’s changes between these two different genetic populations of dolphins and how they have responded to this die off, how genetically they're able and capable of dealing with it,” continued Rodgers.
Rodgers says they’ll also be continuing researching the DNA of dolphins on another part of the lagoon called the Mosquito Lagoon, where they’ve seen an anomaly that Atlantic and Indian River Lagoon dolphins are interacting with each other over a series of years, but not breeding.
Meanwhile, as they look to find those answers, the Harbor Branch recently received $2 million in this year’s budget to track pollution in the troubled lagoon.
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