The mysterious die-offs of marine life in parts of the 156-mile Indian River Lagoon have perplexed scientists, alarmed environmentalists, and angered local citizens. Over the past year, record numbers of dolphins, manatees and pelicans have been found dead in the estuary that runs along Florida’s Atlantic Coast. The lagoon is a unique subtropical ecosystem that is home to 4,300 species of wildlife, including more than 40 threatened or endangered species. The interconnected lacelike system of rivers, wetlands, and coastal marshes stretches south along the Atlantic from Volusia County to Martin County, passing Cape Canaveral midway.
photo by Howcheng, U.S. Fish and Wildlife Service
This narrow, shallow waterway has been deteriorating for decades, according to many citizens and environmentalists. Suspected causes for the lagoon’s decline include nutrient runoff from agricultural lands, overuse of residential fertilizers, and release of water from Lake Okeechobee, the largest freshwater lake in Florida. Experts are still trying to solve the mystery of the recurring algal blooms and the animal die-offs.
The current series of unexplained deaths in the northern area of the lagoon began in early 2013. This and previous die-offs have been designated “unusual mortality events,” or UMEs by the National Oceanic and Atmospheric Agency (NOAA). Between January and August, 62 dolphins died in the lagoon – about double what might be normally expected, according to NOAA. The deceased dolphins appear emaciated, as did pelicans that died by the hundreds between February and April of this year.
Although some people initially thought the dolphin die-offs in the lagoon might have been related to the large multi-state die-off of bottlenose dolphins along the Atlantic seaboard, from New York to North Carolina that began in July, this is not the case. The Atlantic Coast dolphins are succumbing to a type of Morbillivirus virus, a measles-like disease among cetaceans, which experts say must run its course as it did during a similar 1987–1988 outbreak when nearly 900 dolphins died.
The Indian River Lagoon dolphins are not as susceptible to the Morbivillvirus, says Blair Mase, coordinator for NOAA’s marine stranding program in the Southeast US. The Atlantic dolphins migrate up and down the coast and easily spread the disease. The Indian River Lagoon dolphins are residents and highly studied, so if they had the virus, it would have been noted, she says.
Dolphins and pelicans are not the only casualties in Indian River Lagoon. In Brevard County alone, 112 of the 274 manatees deaths recorded since July 2012 seem to be related to the UME, according to a spokesperson for the Florida Fish and Wildlife Conservation Commission. Manatees die from various causes throughout the year in Florida, including natural and human-related (for example, from being locked in flood gates or canals). However, the massive die-off in the lagoon is unusual, enough to earn it a UME designation as well.
While the dead dolphins and pelicans were emaciated, the manatees appeared well-nourished. Biologists have noted a change in the manatees’ diet, though it’s not clear if that’s the cause of mortality. The marine mammal normally consumes a variety of seagrasses, including shoal grass, manatee grass, and turtle grass. In the northern portion of the lagoon, an area called Banana River, where most of the manatees have died, more than 22,000 acres of seagrasses were decimated following a severe and prolonged algal bloom. As a result the manatees have been resorting to a diet of reddish brown macroalgae (seaweed) called Gracilaria.
An early, erroneous media account pointed to natural toxins on the Gracilaria as probable cause of the deaths. But NOAA communications director Ben Sherman says no definitive results have been found yet connecting the manatee deaths to their changed diet.
“At this point, there are zero linkages between the macroalgae and the deaths,” he says. To date, NOAA has not examined of any marine mammals (dolphins or manatees) for exposure to the possible toxins in question; however, tests are ongoing at the NOAA Hollings Marine Laboratory in Charleston, South Carolina.
The different species that are dying in the lagoon adds to the challenge of determining the cause of the die-offs. Manatees are vegetarians and mammals. Dolphins and pelicans, while in different zoological families, both consume fish. Meanwhile, other estuary birds as well as marine animals like sea turtles (that eat seaweed) seem fine. Tests on fish haven’t provided any clues for researchers yet.
Various species of algae, which grow out of control when too many nutrients are released into the estuaries, have plagued the Indian River Lagoon for decades. For instance, a species of reddish brown algae, Pyrodinium bahamense, can be toxic for humans and animals and has previously produced saxitoxin that has poisoned fish.
Dolphins have experienced two previous UMEs in Indian River Lagoon, in 2001 and 2008, and in both events the animal carcasses were emaciated and had empty stomachs. Researchers were not able to determine the cause in either case, although in the 2001 case, they suspected but never proved, saxitoxin as the cause.
The latest outbreak of unexplained dolphin deaths had slowed down by late September – with area of the most deaths, Volusia County, reporting only three. Unexplained pelican deaths have not been reported since the spring, according to state fish and wildlife officials.
Many environmentalists and Florida citizens are now pointing to the continued deterioration of the estuary as the general cause for the mysterious deaths.
Indian River Lagoon as has been determined an “estuary in distress” by the St. Johns River Water Management District. The Florida agency reports that the lagoon supports an economy of about $3.7 billion, providing more than 15,000 jobs, and offering recreational and vacation opportunities to more than 11 million people. The impact of so many nearby residents and visitors to the lagoon is causing some of the problems the water body is now facing, says Troy Rice, director of the Indian River Lagoon National Estuary Program. In some ways, the very things that make the lagoon famous – its extraordinary biological productivity and the threatened and endangered species (including the manatee) that call it home – have led to its decline, he says.
The widespread use of fertilizers and chemicals on lawns, as well as nutrient run-off from interior Florida agricultural lands that drain into the lagoon have led to its degradation. Increased levels of nitrogen and other nutrients from fertilizers and manure, and sewage from old or poorly maintained septic tanks are the major causes of algal blooms, continue to be a problem in various Florida waterways.
While there is no current scientific evidence to link the marine deaths and the declining health of the lagoon, toxic algal blooms have been an ecological hazard here since 2011 and may be contributing to the collapse of the ecosystem, Rice says.
The environmental law firm Earthjustice has collected hundreds of photos from coastal residents clearly demonstrating the invasion of toxic green slime in the area waterways. Earthjustice had filed suit against the US Environmental Protection Agency in 2008, on behalf of several Florida conservation organizations, to force the agency to establish Clean Water Act limitations on pollutants. The EPA agreed in 2009 to set numeric limits to sewage, manure, and fertilizer runoffs in Florida. However, the EPA is now seeking to modify the agreement, so as to allow continued pollution of Florida waters, says David Guest, managing attorney for Earthjustice in Florida.
“The slug of pollution has killed large numbers of dolphins, manatees, and sea birds. It is destroying the local economy. That’s why people are rallying against it by the thousands.” Guest says. The answer, he suggested, is not to move the polluted water around, as some have suggested, but rather to “clean it up at the source.”
Some of South Florida’s nutrient pollution issues have been caused by the release of billions of gallons of water from Lake Okeechobee since May by the US Army Corps of Engineers. The Corps regularly releases water to prevent damage to the 70-year-old dike surrounding the 730-square mile lake during high rainfall events. Florida experienced an exceptionally wet summer – the wettest start to a rainy season in 45 years, according to the South Florida Water Management District.
The freshwater and sediment that is discharged into canals from Lake Okeechobee makes its way to coastal estuaries (east and west) where the freshwater creates an imbalance in saline content of the fragile brackish water ecosystems. In addition, the nutrient-rich water is contaminated with runoff from agricultural lands, which stimulates the overgrowth of algae. And if that is not enough, stormwater runoff into the rivers carries fecal pollution from pets, wildlife and human sewage, which elevates bacterial levels in the waterways.
At the beginning of August, Martin County residents were cautioned not to swim in the algae-ridden waters of St. Lucie River that flows into the southern portion of the Indian River. Residents complained of burning sensations and rashes, and health officials continue to warn against swimming in certain parts of the river.
As the hundreds of photos submitted to Earthjustice indicate, local citizens have had enough. Late last month, more than 5,000 people gathered in eight cities along the Indian River Lagoon to call attention to ongoing environmental disaster.
At the north end in Volusia County, 250 people turned out in “brutal thunderstorms” to hold hands along one of the bridges that span the Halifax River. Farther south, 2,000 people rallied along the Melbourne Causeway and 1,000 people attended the event in Stuart, near the St. Lucie River, where residents are frustrated by the unremitting algae blooms.
Scheduled to coincide with the National Estuaries Week, the coordinated regional “Hands Across the Lagoon” events sought to raise awareness about the deterioration of Florida’s waterways. Ongoing campaigns and educational forums seek to gather support for increased restoration and protection of Florida’s wetland ecosystems, says Annie Morgan, of the Marine Discovery Center in New Smyrna Beach.