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In South Florida, where the Everglades meet the bays, environmental challenges abound. Sea level rise threatens homes and real estate. Invasive species imperil native plants and animals. Pesticides reduce the risk of mosquito-borne diseases, but at what cost? WLRN's award-winning environment reporting strives to capture the color and complexity of human interaction with one of the most biodiverse areas of the planet.

New Study Says Everglades Water Is Harming Keys Corals. Not Everyone Agrees

Shark River empties from the Everglades at Ponce De Leon Bay in Southwest Florida.

The Florida Everglades can be a contentious place. Politicians, conservationists and farmers never seem to agree on much.

Debate among scientists tends to be collegial. But a new study on coral and the Florida Keys that gained national headlines last week has reignited a decades-old dispute over pollution and the Everglades.


The study, published in the journal Marine Biology by Florida Atlantic University marine biologist Brian LaPointe, concludes that water from the southern Everglades is harming reefs near Looe Key. LaPointe said water sampling he conducted over 30 years showed that big pulses of water from the Everglades' Shark River preceded the Keys' mass bleaching events over the years. He says the remote river is polluted with nitrogen from farms and urban development, which can harm corals. 

"There is, you know, multiple lines of evidence showing that run-off from the Everglades is a contributing factor to algal blooms and nitrogen enrichment," LaPointe said.

But at least 16 scientists who work in the Everglades are raising questions. They say more widespread monitoring doesn't appear to support the findings of excess nitrogen. They're taking a closer look and plan to submit a formal rebuttal.

"That would be very surprising," said aquatic biologist Evelyn Gaiser, who leads a team of Everglades scientists as part of a longterm research project at Florida International University established by the National Science Foundation in 1980 and involving 29 institutions. None were asked to peer-review the article, she said.

"We have an incredible wealth of data that we can evaluate to help understand those trends and dynamics," she said. So far, they show nitrogen only spiking during natural events like tropical storms, cold freezes and hurricanes.

The South Florida Water Management District said in an email that its monitoring also failed to detect dangerous levels of nitrogen in Florida Bay outside severe storms. Spokesman Randy Smith said the agency was also reviewing the findings.

The editor of the journal article, Sandra Shumway, a Universitiy of Connecticut marine biologist who specializes in shellfish, said by email she was traveling and unavailable for an interview. 

Credit Jenny Staletovich/WLRN
Audubon Florida biologist Jerry Lorenz holds dead seagrass in Florida Bay from a 2016 die-off that followed a drought. The die-off eventually covered 60 square-miles in Florida Bay.

Part of the complexity is understanding the dynamic between nitrogen and phosphorus, the two chemicals at play in the ecosystem. Seagrass thrives on a ratio of high nitrogen and low phosphorus. Reefs, which are disappearing at an alarming rate and now in the midst of an unprecedented disease outbreak, are the opposite.

If LaPointe is correct, the consequences could be major. Everglades restoration is based largely on the premise that flood protection has cut off the southern Everglades from the water that naturally flowed out of Lake Okeechobee, down the river of grass and out marshes into the vast seagrass meadows in Florida Bay. The meadows help maintain the kind of gin-clear water that reefs need to thrive by stabilizing the muddy bottom. They also provide food and habitat for the rich mix of marine life that lives on reefs.

Over the years, too little water has made Florida Bay's seagrass vulnerable to drought. In droughts in 1987 and again in 2015, the bay became too salty and triggered major die-offs. More than 60 square-miles of seagrass died by 2016. The 1980s die-off set the stage for catastrophic algae blooms that caused the bay to crash.

The state of Florida has spent millions, including $880 million for filtering marshes, to clean water and get it back into the the southern Everglades. But it focuses on phosphorus, the chemical in fertilizer coming off sugar fields and in water out of Lake Okeechobee. Too much phosphorus can cause cattails and other plants to grow in the sparse marshes and interrupt the flow of water and over-stimulate seagrasses. The state does not focus on removing nitrogen.

In 1999, Everglades scientists published findings blaming the drought for the die-off, a finding largely accepted by South Florida's scientific circles.

But LaPointe has long argued that elevated nitrogen flowing from the southern marshes, not the dead seagrass, caused the blooms. Four years after the 1999 study, he published comments saying seagrass biologists Jay Zieman and Jim Fourqurean overstated the impact from the drought and called their findings "untenable."

Credit Florida Keys National Marine Sanctuary
Stony coral disease first appeared off Virginia Key in 2014 and has since spread up and down the Florida reef tract.

Zieman and Fourqurean fired back in a published response, saying LaPointe misinterpreted data from another scientist at Everglades National Park. They said his findings illustrated "a repeated lack of understanding of the geography and hydrology of the southen Everglades and Florida Bay."

The nutrient-starved Everglades remove most of the nitrogen from water flowing in to the bay, they said, and the Gulf of Mexico is likely a far larger source.

Scientists also say the data he relies on for this study measured Everglades nitrogen at the north end, near Tamiami Trail, not the mouth of the river.

LaPointe looked at nitrogen levels in water he sampled over 30 years at Looe Key, about 25 miles east of Key West. He also looked at chlorophyll-a to see what affect the nitrogen was having on water and at nitrogen levels in seaweed.

Leaky septic tanks and deadend canals have long been blamed for driving up nitrogen levels in water around the Keys. Monroe County has spent about $1 billion to convert the string of islands to a central sewer line. The county had planned to spend about another $700 million to clean up canalsbefore Irma hit.

LaPointe said while it's clear that local sources provide some nitrogen, his research found it's likely carried from the Everglades as well. He said water sampling from 2010 and 2011 showed elevated levels of nitrogen at Shark River. Drifter studies also prove water flowing from the mouth of the river can reach Looe Key.

"This has been covered, this concern, this back and forth has been published in the New York Times, Nature Magazine and others," he said. At the time, he said Everglades scientists were criticized for ignoring the role of nitrogen.

"I'm one of those scientists that was really never part of that Florida Bay club," he said.

LaPointe's critics say he's cherry-picking his information in this latest study and ignoring the bigger picture. He relies on his own sampling from a single reef and water collected at Shark River over just two years. They say a broader picture captured by longterm monitoring by the Florida Keys National Marine Sanctuary and the Everglades research project at Florida International University should have been considered.

Given what's at stake, Gaiser said scientsts would normally confer with one another if data suggest unexpected findings.

"The way that many of us would react to that is to reach out to colleagues and build as robust of an analysis as possible to figure out what's going on," she said. "You have a result that isn't what most scientists would anticipate, then you would want to dig in more deeply and see if there might be some other explanation."

The team is now reviewing LaPointe's study. Their rebuttal will undergo the same peer-review as LaPointe's paper.

Jenny Staletovich is WLRN's Environment Editor. She has been a journalist working in Florida for nearly 20 years. Contact Jenny at jstaletovich@wlrnnews.org
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