By Dave Sherwood and Alien Fernandez
CIENFUEGOS, Cuba (Reuters) -&nbsp;Cuban&nbsp;marine biologist Ariandy Gonzalez emerges uneasy from the sun-speckled Caribbean sea off a remote stretch of Cuba's south coast. Something is not right.
The sea floor, once a mosaic of colorful&nbsp;corals, is now marred by patchy white splotches. That is evidence of heat-related&nbsp;coral&nbsp;bleaching, where stressed&nbsp;corals expel their colorful algae symbionts, leaving them pale and vulnerable.
"I think this is the worst bleaching we've seen yet," Gonzalez told five fellow&nbsp;scientists, hoisting himself into a small diveboat that heaved in churning seas.
Gonzalez is among 18&nbsp;scientists&nbsp;and crew members who for nearly two months have circumnavigated Cuba in the M/V&nbsp;Oceans for Youth ship to&nbsp;hunt&nbsp;for&nbsp;clues&nbsp;that could help researchers across the globe protect&nbsp;reefs&nbsp;in the face of warming waters, over-fishing, pollution and other threats.
The ongoing "Bojeo a Cuba" study is a snapshot in time of the health of Cuba's reef, fish and sea life, the first of its kind across such a large area of the island's waters, said Dr. Fabian Pina, a&nbsp;Cuban&nbsp;marine biologist and expedition co-leader who initiated the project nearly two years ago.
The project has received funding from the&nbsp;Cuban&nbsp;government and international partners, Pina said.
Preliminary observations - the voyage is still about a week from completion - suggest both good and bad news, the&nbsp;scientists&nbsp;told Reuters in interviews at sea.
The water here, off the island's little developed south-central coast, is a sweltering 90F (32&deg;C), and elsewhere even warmer, the&nbsp;scientists&nbsp;said.
Sea surface&nbsp;temperatures&nbsp;globally have broken records this year. In Florida, just 90 miles (145 km) from Cuba,&nbsp;temperatures&nbsp;soared to hot tub levels, prompting U.S.&nbsp;scientists&nbsp;to warn of the potential for catastrophic bleaching.
Pina said the expedition's&nbsp;scientists&nbsp;were also disappointed to find few larger specimens of fish like grouper, snapper and sharks even on&nbsp;Cuban&nbsp;reefs&nbsp;that appeared otherwise healthy.
Communist-run Cuba, which faces ongoing food shortages, has struggled to regulate its fisheries, leading to declines in many species and the 2019 passage of a law to bring order to its fishing industry.
But Pina said there was plenty of good news, too.
"We are finding natural wonders almost everywhere we go," the biologist said, noting that many of Cuba's keys and mangrove forests are far more intact than in Florida and some Caribbean neighbors.
That could give Cuba's&nbsp;reefs, some of which are thought by&nbsp;scientists&nbsp;to be among the world's most pristine and resilient, an advantage in a changing climate.
"It's still an open question," Pina said. "But the expedition now provides a baseline, so we can come back and check on these&nbsp;reefs&nbsp;and see, for example, if they have recovered from the bleaching they are experiencing."
GLIMMERS OF HOPE
The team faced challenges - scarce internet, intense heat and a hurricane at sea - but also, glimmers of hope along the 3,541-mile (5,700 km) circumnavigation of the island.
Expedition divers observed an unusually large school of exotically-colored triggerfish in eastern Cuba, and a kaleidoscope of vibrant&nbsp;corals along the&nbsp;ocean&nbsp;floor near the densely-developed tourist destination of Varadero.
And off Guanahacabibes national park in far western Cuba,&nbsp;scientists&nbsp;used camera traps to photograph big,&nbsp;ocean-going sharks, mostly absent across hundreds of miles of coastline the team had already traveled, said Dorka Cobian, an expedition biologist and a researcher at the park.
Cobian said she held hope that the peninsula's&nbsp;reefs&nbsp;would bounce back from the recent bleaching, which she said had affected 60-80% of&nbsp;corals in the area.
"This reef is very resilient," she said. "We've suffered many bleaching events, and in general, they have recovered."
Expedition leader Pina said it was still too early to draw anything but preliminary conclusions from the reams of data, video footage and observations collected by the team.
But the biggest lesson was already lying in plain sight, he said.
"Our ecosystems are in general well conserved," he said, struggling to choose a favorite site among so much splendor. "We must find a way to take advantage of the enormous opportunity that provides."
&nbsp;
(Reporting by Dave Sherwood and Alien Fernandez, additional reporting by Mario Fuentes, Alexandre Meneghini; Editing by Rosalba O'Brien)

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