When Hurricane Harvey landed on the Texas coast in August, researchers feared that colorful coral colonies would be destroyed 100 miles south of the Texas-Louisiana border.
The corals of the National Marine Sanctuary of Flower Garden Banks were the first documented in 1936. But scientists believe that young corals carried by currents from Mexico formed on the salt flats there 10,000 to 15,000 years ago.
No other tropical reef system can be found so far north in the continental United States. The nearest reefs are located 400 miles south off the coast of Tampico, Mexico, according to the National Oceanic and Atmospheric Administration.
NOAA published its annual update of coral garden corals last month. From October 201
In the year before Hurricane Harvey, the flower garden coral corals were hit twice: once with a rush of freshwater from Texas and then extreme sea surface temperatures that led to one of the worst coral bleaching events on record.
In April 2016, heavy rains in the Houston region quenched fresh water in the Gulf of Mexico. The massive runoff could be seen in satellite imagery.
Coastal runoff does not usually go far enough to reach the reefs, said Michelle Johnston, a marine biologist with the Flower Garden Banks National Marine Reserve. But the wind has slowly driven it there. An expedition to the site confirmed that the freshwater had killed coral in the eastern part of the sanctuary.
Months later, the corals were hit again, this time with a rise in sea surface temperatures, said George "G.P." Schmahl, the head of the sanctuary. Research estimated that nearly 50 percent of the coral colonies in a study site in the eastern part of the sanctuary were bleached or in the process of bleaching.
Coral bleaching refers to the process by which corals expel the algae that live in their tissues. The corals provide these algae with the protection and compounds they need for photosynthesis. The algae return the favor by producing oxygen for the coral and helping to remove waste. The algae also give the coral its color. When the corals are stressed, they kick the algae out of their tissues and give the reef a white appearance.
The events of 2016 worried the scientists that the reef would get another hit by Hurricane Harvey. Record rain in Texas could once again find its way to the reef, they feared. But the currents and winds were different and took the coastal drain east and not so far off the coast. "We were lucky because the fresh water did not get into the flower garden benches," Schmahl said.
"But climate change is likely to increase the threat to the reef in the future," said Schmahl. As the surface air temperatures rise, the atmosphere can hold more water vapor. Rainfall is expected to increase due to major storms. It is also expected that the increase in global temperature will further increase sea surface temperatures, possibly leading to more coral bleaching events.
The loss of the flower garden The corals would put a huge strain on fishing in the Gulf of Mexico, said Schmahl] "Coral reefs are extremely important as breeding grounds for many fish species," he said. "They are just an incredible ecological system and, I would say, one of the most beautiful."