Healthy corals in Florida surprise scientists

Research findings could help scientists develop new coral restoration strategies to replenish this key natural protection infrastructure for coastlines against erosion and storms.

MIAMI — During a scouting mission to check on coral colonies in inshore Biscayne Bay last year, Caroline Dennison and a few other marine biology graduate students found something astounding: healthy populations of brain corals.

There were no signs of white spots or bleaching and the vivid yellowish brown colors indicated that the corals were untouched by yet another mysterious disease that’s ravaging reefs along the Florida coast.

Even more extraordinary was that these corals were thriving in shallow and warm water right off the seawall at Bill Baggs Cape Florida State Park, near a bustling seaside metropolis.

“That was pretty amazing because you wouldn’t imagine that type of coral living successfully in a foot of water, at that location, considering all the issues affecting reefs in the area,” said Dennison, a coral researcher at the University of Miami Rosenstiel School of Marine and Atmospheric Science. “It was just astonishing, I couldn’t believe it.”

What’s protecting these corals? The discovery has opened up a world of research possibilities on what’s killing Florida reefs and the water quality problems making it harder for corals to survive in troubled Biscayne Bay.

Dennison is hoping the thriving colonies will shed some light on a myriad of threats to corals: from the impact of rising temperatures and nutrient pollution on reefs to the relationship between corals and the algae that live within them.

Findings could also help scientists develop new coral restoration strategies to replenish this key natural protection infrastructure for coastlines against erosion and storms.

The surprisingly good shape of the nearshore corals also highlighted Biscayne Bay’s diverse ecosystem, which has pockets of healthy habitats.

Not far from these corals, or an artificial reef right next to Port Miami, is the Coral City Camera, which livestreams a constant parade of colorful fish, manatees and sharks near a channel used by huge cruise ships.

Those areas with abundant marine life aren’t far from where a massive fish kill happened in August.

The sight of thousands of fish carcasses floating in the northern part of the bay and the algae blooms that followed alarmed residents and triggered a reckoning over critical issues plaguing Miami-Dade’s treasured turquoise waters:

Contamination from crumbling sewage pipes and failing septic tanks, stormwater runoff and a seagrass die-off that’s drastically reducing the bay’s ability to handle pollution and regenerate.

The Bay is very sensitive to nutrient pollution because historically it didn’t have that much phosphorus and nitrogen going into its waters.

The Everglades ecosystem filtered these nutrients before the water flowed to the coast. That means that plants and other bay organisms like corals grew slowly because of the nutrient limitation.

Once development and draining altered the flow of the Everglades and population growth led to a jump in nutrient pollution flowing to Florida’s coasts, life began to change in Biscayne Bay:

Slow-growing turtle grass, for example, with its long and broad blades, was replaced by microalgae which grows faster. The bay has lost over 20 square miles of seagrass over the past decade.

“If things grow faster they are competitively dominant; what we’ve seen over the past decades is a change in species composition from slow-growing things to fastgrowing things and now in the northern part of the bay we’ve gone over the edge,” said Jim Fourqurean, a professor of biology and director of the Center for Coastal Oceans Research at Florida International University.

Slower-growing corals like the brain species, which used to be common over the Florida reef tract, have also suffered because of the apparent shift in the bay to a nutrient-rich system, he said during a virtual town hall organized by

Commissioner Daniella Levine Cava earlier this week.

“We just gotta stop doing that, we have to stop putting nutrients into the bay so we can return to the system that we used to have,” Fourqurean added.

To be sure, nutrient pollution is just one stress factor affecting Florida’s coral reefs. A disease that was first observed in 2014 off Virginia Key has been destroying the soft tissue of many stony coral species, killing them within months of becoming infected.

Colonies in the U.S. Virgin Islands, the Bahamas, Puerto Rico and as far as Mexico have been affected, and the disease has advanced along the Florida Keys. The causal agent is still unknown.

Brain corals are particularly vulnerable, and that’s why Dennison was so ecstatic to find vigorous colonies just steps away from the hiking trail and fishing docks on the seawall at Bill Baggs park.