Coastal Everglades, deprived of fresh water, near unhealthy ‘tipping point’

At the bottom of the Everglades along the mouth of the Shark River, a towering mangrove forest stands in a place few people outside anglers and researchers ever see: at the edge of a vast shallow bay where the salty sea and freshwater marshes conspired to erect a cathedral of trees.

In the current fight over restoration, this isolated region often gets overlooked. While Lake Okeechobee pollution to the north grabs headlines and gets the attention of Florida lawmakers, it’s actually here where damage may be most profound.

For the last 16 years, nearly 80 scientists and their students from 29 organizations — including all the state’s major universities, the National Park Service and the South Florida Water Management District — have embarked on one of the longest and largest studies ever conducted on South Florida’s coastal Everglades. They now fear the system may be at what lead investigator Evelyn Gaiser calls a “tipping point,” where change is happening faster than scientists expected and spinning into a self-perpetuating cycle of decline.

The mangroves ringing the coast are moving inland, overtaking vital freshwater marshes. Growing swathes of peat, the rich mucky soil that formed over a few thousand years, are collapsing. And periphyton, the spongy brown mats of native algae that form the foundation of the food chain, is shrinking.

Aside from losing one of the planet’s rarest ecosystems, changes happening in the system could also have global consequences, damaging one of the region’s main defenses against climate change fueled by greenhouse gases.

“The threat here is we’re changing the system from one that is very good at sucking carbon dioxide out of the atmosphere,” said Gaiser, a Florida International University aquatic ecologist, “to one that’s very rapidly losing it.”

Two forces are likely driving the change in the southern Glades: decades of flood control that altered historic water flow and rising sea levels. Both cause different problems, but can be partly solved in the short-term with a fairly straight-forward solution: more freshwater flowing south.

“The pace at which we accelerate freshwater restoration is going to matter to the future of being able to do anything with restoration,” Gaiser said.

The research effort now includes dissecting the entire ecosystem to look for signs of trouble, but it started with the long-running battle over setting phosphorus pollution levels in the Everglades. The nutrient, a primary ingredient in fertilizer, is blamed for the pollution in Lake Okeechobee that this past year stained both coasts and left the Treasure Coast coated with toxic algae.

In 1997, Gaiser was a post-doc student hired to help a team of scientists led by Ron Jones, a then-little known FIU microbiologist who discovered that the marshes could not withstand phosphorus at levels above 10 parts per billion. That amount is an incredibly low threshold that remains the bane of farmers who for decades relied on phosphorus-rich fertilizer to enhance crops — including a half million acres of sugarcane fields.

Lake Okeechobee, which once supplied a steady flow of clean water to the marshes, also has phosphorous concentrations too high for the system, thanks to now prohibited back-pumping from the sugar fields and runoff from suburbs, pastures and farms to its north. When the lake gets too full, much of that water is now sent down the Caloosahatchee and St. Lucie Rivers to the west and east, where it has repeatedly triggered stinky algae blooms that kill fish.

To help pin down the delicate balance of phosphorous in the Glades, Gaiser spent nearly every day in the field over five years, monitoring 325-foot long plastic and Styrofoam flumes built in the marshes.

When the the study ended in 2000, researchers realized they had another question to answer: if the marshes thrived on such a tiny amount of phosphorus, then what was fueling such an enormous mangrove forest along the coast of the Everglades — an ecosystem that rivals the Amazon in its ability to recycle and maintain itself in healthy conditions. It turns out the forest is the start of one of the planet’s rarest phenomenons: an upside down estuary. In a healthy Everglades, the phosphorus in the ocean fuels the mangrove growth, so as the saltwater turns brackish and then fresh, the mangrove trees themselves shrink and give way to the sweeping marshes that once dominated much of the Everglades.

As rising sea levels push deeper up creeks and rivers and freshwater flow from the north slows, the marshes that once made up much of the southern Glades have collapsed — at increasing speed.

Because those coastal marshes were so vulnerable, scientists also realized they cried for ongoing monitoring, so they applied to include the Everglades in the National Science Foundation’s Long Term Ecological Research Program. Gaiser said they never expected to be accepted. The highly competitive network has included only 25 such sights across the planet in its 37-year history.

So many studies occur in the Everglades it can be hard to keep track. But the Everglades LTE stands out because the enormity of its scale matches the pace of research with the pace of change.

The research findings could also stand as a bulwark against shifting politics that might disregard science. In the current debate over building a giant reservoir south of the lake, for instance, farmers, Big Sugar, and politicians have focused on whether and how much a reservoir will help stem the flow of polluted lake water in he Caloosahatchee and St. Lucie rivers. Critics call it a bad solution based on faulty science that will kill agriculture jobs.

But the LTE research shows that failure to get more water flowing south could strangle the southern Glades, continuing the decline of fresh water marshes and too-salty Florida Bay, which also has been hammered by seagrass-killing algae blooms.

The impact on Everglades peat has already been profound. Peat is a wetlands version of soil, the muck created in the soggy marshes that supports its unique plants. It needs to stay submerged to accumulate, but too much saltwater can cause it to collapse. In the 1990s, University of Miami professor Hal Wanless noticed large areas of peat were beginning to collapse. When the LTE began looking into it, they realized the pace was much faster than expected.

“You can see them from satellite imagery,” Gaiser said. “There are areas many square meters wide if not bigger.”

At first, they suspected the collapse was a normal process, the reason big, open water lakes suddenly appear in the Everglades, she said. They now fear the collapse is accelerating at a faster rate as sea water inches inland, threatening to turn much larger areas into big expanses of dark open water.

“Once you lose that soil, it’s gone,” she said. “You create a place where nothing can effectively grow. We’re not even sure mangroves can grow there.”

Further up the system, the team has also documented the disappearance of periphyton mats that over thousands of years have survived in an environment with hardly any phosphorus. It was here that scientists first realized how sensitive the Everglades are. When they started measuring phosphorus, they looked at what was in the water. But the FIU scientists led by Jones figured out that the true measure was in the periphyton, which soaked up what little was in the water.

“You could take a water sample and it doesn’t show anything,” she said. Meanwhile “the whole community is changing.”

While between 700 and 800 different kinds of algae exist in the wider Everglades, the periphyton mats contain just 10 to 15 hardy enough to survive the harsh conditions. The balance between the diatoms — the single-celled algae — that are among the oldest living things on the planet and the bacteria and other micro-organisms inhabiting the mats is so sensitive, that the tiniest amount of nutrient can make a difference.

In one of Gaiser’s projects, scientists are literally tracking a single molecule of water as it moves down the system, measuring how it changes when hammered by the forces of man and nature.

“They are the backbone of the Everglades ecosystem,” she said. “They also engineer the chemistry and even sometimes the physics and gas exchange of the water because they are full of these little microorganisms that are depending on phosphorus for growth.”

With too much phosphorus, bacteria in the algae mats seize control, consuming them from the inside out. In the place of the periphyton, other things can move in and dominate — for instance, expanses of less biologically diverse cattails that grow in the most phosphorus-tainted boundaries of the Everglades.

“A cattail lives anywhere in the world. Same thing happens in the little microbial community,” Gaiser said. “Weedy things come in that you could find in any lake or reservoir.”

What researchers haven’t been able to nail down yet is exactly how much this happened in the past.

Core samples taken in Florida Bay and the mangrove forests provide a record they think reflects what happens in certain conditions. But they haven’t been able to get samples in the places most likely to provide answers now: the upper Everglades where soils are badly preserved or shallow lakes where soils are constantly stirred up.

What they do know is the Everglades needs more water, from Biscayne Bay to the east — where a coastal restoration project slated for 2021 will clear the way for more water even if no reservoir exists to provide it — to Florida Bay.

In the next six-year phase of research, they’re also hoping to solve another riddle: projecting the “differential vulnerabilities” of the Everglades various parts to determine which are in most urgent need of fixing.

“It is amazing how just a couple of parts per thousand of salinity can really affect a sawgrass marsh,” Gaiser said. “With the phosphorus, we know any extra molecule has an effect.”