Amid Dolphin Deaths, Study Finds Genetic Differences in Indian River Lagoon's Bottlenose Population

Bottlenose dolphins living in Florida's Indian River Lagoon belong to one of two, distinct genetic groups, according to the results of a decade-long, first-of-its-kind study from Nova Southeastern University. But the new research offers no new insights on why the lagoon's bottlenose dolphins are dying at unprecedented rates.

Though the lagoon's bottlenose dolphins all appear to be no different than bottlenose dolphins elsewhere, genetic analysis indicates the lagoon's dolphins are different from bottlenose dolphins that live offshore, in the northwest Atlantic Ocean, Gulf of Mexico and the Caribbean, the researchers said. What's more, there is a genetic split within the population of lagoon dolphins, with specimens living in the north of the lagoon having genetic dissimilarities compared to those living in the 156 mile-long lagoon's south.

"This study shows evidence that while it may appear that the bottlenose dolphins within the IRL look the same, from a genetic -- and geographic standpoint -- there are differences," said Jose Lopez, a professor at Nova Southeastern University's Oceanographic Center. "It's akin to the Hatfields and McCoys or Capulet/Montague stories, that is, different families that are unmistakably of the same species, but for whatever reason living apart. As we work to protect the IRL, this study provides baseline data moving forward as we continue to monitor and study the wildlife that call the area home."

Indian River Lagoon (IRL) has been in the news lately, but usually for more grim reasons. During summer the lagoon became a mysterious mass grave for hundreds of animals, including scores of bottlenoise dolphins. Since Jan. 1, at least 73 IRL dolphins have died mysteriously, Florida Today reported last month. Experts have said there have been more dolphin deaths in the lagoon this year than ever before.

"We're almost three times what we'd expect," Wendy Noke Durden, a researcher at Hubbs-SeaWorld Research Institute, told Florida Today.

The lagoon, which stretches across 40 percent of Florida's eastern coast, has reportedly long been polluted by nutrient and fertilizer runoff from lawns and farms, but in recent years the effects of the pollution may be coming to a tipping point. Florida does not have strict laws regulating the amounts of nutrients such as nitrogen and phosphorous allowed to run off the land into its surrounding waters.

"The lagoon is in a full collapse, it is ongoing," Marty Baum of the Indian Riverkeeper told Discovery News in June.

Since 2009 algae blooms have overtaken much of the lagoon, some of which have been identified as toxic. The toxins produced by the algae may have something to do with the death of the lagoon's marine life, but the blooms also affect the food chain.

Lately the lagoon's dolphins have been found with unusual amounts of shrimp in their stomachs. The crustaceans are not a preferred food of the dolphin, which indicates there may be a decline in seatrout and black drum, which the dolphins naturally prefer.