Stories about the demise of the world’s coral reefs are becoming all-too-commonplace, unfortunately. We’ve all heard the sad descriptions of Australia’s Great Barrier Reef, for example. Hundreds of miles of its most pristine northern sector are dead, with overheated seawater reported as the culprit. A researcher at the Harbor Branch of Florida Atlantic University, Brian Lapointe, PhD, has a slightly different take on the global coral problem, however. With a career spent studying nutrients, algal growth, and eutropication, Lapointe has analyzed water quality and living coral cover in the Florida Keys over the last 4 decades. While many scientists attribute coral demise to sea-surface temperatures associated with climate change, Dr. Lapointe’s findings about Florida’s coral reefs show otherwise.
Instead, increasing nutrient pollution from septic tanks, combined with new policies to “send water south” from Lake Okeechobee, have increase nitrogen concentrations and phytoplankton biomass at Looe Key, his study site. Sewage discharge makes it difficult for coral to thrive and damages the complex relationships that exist among the plants, coral, and other animals that are part of the reef ecosystem.
What we’re seeing, Lapointe outlines, is destruction of the coral reefs due to nutrient dominance. As the nitrogen-phosphorous balance in the ocean gets out of balance, certain membranes in the coral start to break down. The coral can’t get enough phosphorous, which leads to what Lapointe calls “phosphorous limitation and eventual starvation.”
“It degrades the ability of these organisms to survive high light and high temperatures,” Lapointe explains. “This is real, ladies and gentlemen. We are changing the chemistry of the planet.”
Florida Atlantic University, Harbor Branch Ocean Science Lecture Series
Nearly every Wednesday during the southern high season of January through March, the Harbor Branch of the Florida Atlantic University opens its door for a free lecture. The intent is to share with the public the research that usually takes place behind closed doors in laboratories. In this week’s session, Dr. Brian Lapointe talked about “Chasing Nutrients and Coral Reef Decline at Looe Key, Florida Keys: A Four Decade Quest.”
As the audience entered, a short film played on the overhead screens. Virtually, we swam along the reef with divers. Only the sounds of the scuba diver’s breathing were evident as we floated by schools of black and blue fish, coral with tree-like branches, and white chrinolated coral. We came to realize that we were watching a chronological unveiling of the life of a reef over a series of decades. The colors slowly weakened and bleached and became covered by meadows of brown algae in what we later learned in the lecture is a “coral algae shift.”
The Looe Key reef has evolved from being dominated by branching coral with schools of fish living in a 3-dimensional space to a loss of habitat so that, by 2018, much of the coral was white — ghost white. Why? Increasing nutrient inputs elevate the nitrogen to phosphorus (N:P) ratio in reef macroalgae, a condition known to cause metabolic stress in coral. That stress makes them more susceptible to coral diseases and bleaching.
Looe Key: 4 Decades of Analyzing the Coral Reef
Named after the 1743 British warship “Looe,” the Key was a problem for schooners who were circumnavigating the world for commerce. Louis Agassi was asked in 1851 about the ways to reduce the prominence of “unfavorable” reefs for the safety of navigation. “I do not see the possibility of eliminating in any way,” he mused, the growth of the coral reefs.
Little did Agassi know about the problem that would become anthropogenic-caused (human-caused) algae.
“Nutrient pollution is pushing Florida’s refs beyond their capacity to survive,” Lapointe wrote back in 1990. So what did the Florida cognoscenti do then? They let water out of Lake Okeechobee so it would cleanse the Keys, interpreting the reef change problem as a shortage of fresh water.
Such misinformed decision-making pushed more nutrients toward the Florida Keys and led them to be declared a dead zone in 2003.
Many people have argued that overfishing is the cause of the reef decline. Lapointe’s perspective is different, however. He says that the nitrogen content is a significant contributing factor to Florida coral reef loss. Mass tourism and agriculture change the reef due to nitrogen increases, which inspire algae blooms. Formerly “gin clear” water is now emerald green, due to a cyano bacterial bloom. Coral has been overgrown by algae — and not reduced grazing fish, Lapointe indicates, as his data indicates that grazing fish actually seem to be increasing over time.
Algae has replaced corals at Looe Key. High N:P ratios reduce resistance, and the reefs become susceptible to diseases. The result? Coral bleaching.
Poop is the Problem & It’s Expensive to Fix
The primary culprit is septic systems. “Do you know how many toilets are flushing in Orlando? We need to do more up there,” he says. He allows that agriculture, too, has a role to play. “Even with the cattle farms — we can do a lot more to treat the systems. A lot of people think that the problem is sugar cane, but their water goes south, into the Everglades. 95% or more of the water in Lake Okeechobee comes from its north, and nitrogen can move a mile a day.”
The release of water from Lake Okeechobee filled with nitrogen creates levels that starve the reefs of phosphorus and photo-oxydated stress. Lake Okechobee releases 120 million metric tons of reactive N per year. “We’re at a level that is double of a Woods Hole peak level warning from the late 20th century,” according to Lapointe.
“Lake Okeechobee calls for treatment and storage,” he continued. “Money is always the problem in getting these problems fixed.” He discussed how a major problem is septic system “infrastructure that’s at the end of its life cycle, which would cost an estimated $18 billion to fix. That’s just getting infrastructure that’s already in place up to grade. It’s not going to be cheap.”
Although the Environmental Protection Agency might once have been a partner in such septic system infrastructure upgrading, the “EPA isn’t looking so good with the cuts” to its funding, Lapointe reminded the audience.
Solutions are Possible to Restore Florida’s Coral Reefs
An emphasis of Lapointe’s work has been the role of land-based nutrient pollution in supporting harmful algal blooms and degrading coral reef and seagrass ecosystems. He tries to educate the public, business community, and policymakers regarding the need for improved wastewater and stormwater infrastructure to mitigate the harmful algal blooms and help secure Florida’s water future.
Lapointe’s findings suggest that local and regional actions to moderate anthropogenic nitrogen loading can increase the resilience of coral reefs under the current temperature stress.
“There is some hope. Bonair is one of the last beautiful reefs in the Caribbean,” he described. Government officials “got scared, and the Dutch government helped fund the central sewer construction. It was reported 2 years ago that, after the plant went online, corals are starting to grow again.”
“We, too, can make a difference. I’m just hoping that this sad story of the Florida Keys will resonate around the world,” Lapointe emphasized. A plan to treat the water north of Lake Okeechobee is necessary to solve the Florida Keys reef problems, Lapointe argues. “By these small island states taking action, they can make a change. We need to bring our wastewater upgrades up to par, I think, with what we’re spending on Everglades restoration.”
Other solutions can help the coral to revive, too, at least in part. “Denitrification can remove some of the nitrogen that we’ve been seeing,” he answered in response to an audience member’s question. “It takes nitrogen. Bacteria break it down and release it to the atmosphere, taking it from the reactive form.”
Looe Key and Rock Pile videos are available on YouTube. More information about Dr. Lapointe’s work can be found at Lapointe HAB Lab.
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