NOAA to investigate dolphin deaths in Indian River Lagoon
Published: Wednesday, July 24, 2013 at 1:28 p.m.
Last Modified: Wednesday, July 24, 2013 at 11:14 p.m.
Federal officials will launch a formal investigation into a dolphin die-off in the central and northern parts of the Indian River Lagoon as the number of dead dolphins creeps toward 10 percent of the lagoon’s entire dolphin population.
The National Oceanic and Atmospheric Administration said Wednesday it will create a task force to look into the dolphin deaths, which were formally declared an unusual mortality event this week under terms of the federal marine mammal protection act.
The task force will work separately from a task force already investigating more than 120 manatee deaths in the lagoon, but some of the same scientists may be working in both investigations and the two groups will communicate and coordinate closely, said Blair Mase, Southeast regional marine mammal stranding coordinator for NOAA Fisheries.
The dolphin and manatee deaths are just two of a number of unusual events occurring in the Indian River Lagoon system, which started after a long drought and several bouts of freezing temperatures in 2010 and 2011. A phytoplankton bloom covered much of the lagoon in the summer of 2011, then a brown tide algae bloomed in the summer of 2012 and this spring.
The lagoon is a system of estuaries and waterways that lie along Florida’s east coast, beginning at Ponce de Leon Inlet in Volusia County and stretching 156 miles south to Jupiter Inlet in Palm Beach County.
Scientists have not yet determined the cause of death for the manatees, dolphins or the more than 250 dead pelicans that have been discovered. While many people suspect poor water quality may be a factor, no definitive links have been established yet.
More than a dozen agencies and organizations are working together in the search for answers. A state Senate committee was created last week to look into lagoon issues and coordinate water management.
Since Jan. 1, 51 dolphins have been found dead in the northern Brevard County portion of the lagoon, nearly twice the normal number, said Erin Fougeres, a NOAA biologist and stranding program administrator for the Southeast.
“It’s a significant number,” said Megan Stolen, a biologist with Hubbs-SeaWorld Research Institute in Orlando. “We’re a little worried.
In aerial surveys of the entire lagoon system from Ponce Inlet to Jupiter Inlet in South Florida, Hubbs has estimated the dolphin population at about 700, Stolen said.
An independent panel of experts in marine mammal health and toxicology concluded this week that the dolphin deaths meet the criteria of an unusual mortality event, Fougeres said. That opens a formal investigative process and means additional resources will be available from a national contingency fund.
The manatee investigation was opened months ago. The two investigations will remain separate in part because the circumstances of the deaths are different.
“We definitely need to coordinate and communicate,” Mase said. “There may be similar factors impacting all of these species.”
The manatees appear to be dying quickly, while the dolphins are emaciated. But investigators have noticed apparent changes in the diets of both animals, with researchers finding macroalgal seaweed-type plants in the stomachs of the manatees and invertebrates rather than fish in the dolphins.
Manatees normally eat seagrass and dolphins typically eat fish associated with seagrasses in the lagoon. But tens of thousands of acres of seagrass have disappeared across the lagoon since the widespread algal blooms began occurring.
“There seems to be some sort of ecosystem thing going on,” Mase said, “and that’s what we’re going to be looking into, but we’re not ruling anything out at this point.”
Stolen said the dolphins seem to be “eating somewhat unusual items,” adding they still need to do “a lot more investigation to say that’s really an outcome or a contributing factor.”
While the dolphins in 2013 have been generally emaciated, a few factors are hampering the investigation, Stolen said.
The first is that many of the dolphins have been “scavenged by large sharks,” she said. “We all know there are sharks in the river, that’s a common finding, but in this case, it’s a bit extreme.”
That has prevented them from finding and keeping high quality samples for testing, in part because it speeds up decomposition.
“We don’t think the sharks are causing the die-off, but it’s causing a problem for the investigation,” she said.
Researchers also are concerned because dolphin calving season is approaching in August. Already in the past three weeks they’ve found three dead calves. Stolen said they don’t know if that’s because the calves have lost their mothers or if they are becoming part of the die-off. If it’s a dietary issue, the calves wouldn’t directly be affected, she said, because they’re still dependent on their moms for milk.
The investigations could take weeks, months or even years.
“It’s not going to be quick,” said Mase. “Analysis takes a lot of time, especially when you’re looking at a lot of factors, like seagrass, toxin anaylsis and water quality.”
Two mass stranding events have occurred among dolphins in the lagoon, one in 2001 and one in 2008. In both cases, investigators never determined a cause of death.