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Flower Garden Banks
National Marine Sanctuary

Sanctuary Researchers Monitor Reefs Following Natural Impacts

By Shelley Dupuy
Flower Garden Banks National Marine Sanctuary

Manta ray and two divers

Example of bleached corals when water temperaturs remain too warm for an extended period. (Photo: Emma Hickerson, Flower Garden Banks National Marine Sanctuary)

The Flower Garden Banks National Marine Sanctuary science team conducted several expeditions in 2006 to monitor the status and recovery of reefs that were hit hard by a series of impacts in 2005 including a disease outbreak, bleaching event and close encounter with a hurricane.

The trouble began in January 2005 with an outbreak of a plague-like coral disease that slowed down, fortunately, as the water warmed. “This was unusual in that coral disease outbreaks are normally associated with the warm water temperatures of summer” said G.P. Schmahl, Flower Garden Banks sanctuary superintendent.

The assault continued with a coral bleaching episode that began in August, when water temperatures were higher than average throughout the Gulf of Mexico. Then in September, Hurricane Rita tore through the Gulf of Mexico. The eye passed within 60 miles of the sanctuary, exposing the reefs to high wind and turbulent wave action.

“Our surveys in October 2005, documented damage on the coral reef from Hurricane Rita,” according to Emma Hickerson, sanctuary research coordinator. “Multiple large coral colonies had been plucked out and tossed across the reef. About one meter of sand was scoured from the sand flats and redeposited elsewhere around the reef. Several large barrel sponges had been ripped off at the base, topped, or filled with sand."  

Researchers also conducted surveys to quantify the coral bleaching event. They found that up to 45 percent of the coral colonies on the reef cap above 95 feet deep were affected to some degree by the bleaching event that was first documented in August, 2005. “It was the most severe bleaching event on record at the Flower Garden Banks,” said Hickerson. 

The team followed up with another expedition in March 2006. Those surveys revealed that the reefs were beginning to recover from the bleaching, with only a small percentage of the colonies at the banks still exhibiting signs of bleaching. Unfortunately, the surveys also revealed that the plague-like coral disease had returned. At least eight percent of the coral colonies at the East Flower Garden Bank and three percent of those at the West Flower Garden Bank were affected. At least seven species of corals were involved - almost one-third of the total species on the reef cap. 

Manta ray and two divers

Scientist collects tissue samples from a diseased coral colony. (Photo: Joyce and Frank Burek)

During the monitoring expedition in June 2006, the sanctuary team observed that the reef had recovered from the bleaching event. Researchers found that very few heads of star coral (Montastraea cavernosa) still showed minimal signs of bleaching. The plague-like disease event also appeared to have slowed its progress. Very few colonies exhibited active lesions.  Anecdotal observations indicated a loss of fire coral (Millipora alcicornis) due to bleaching and some overall cover loss due to disease in locally affected areas.  These anecdotal observations will be quantitatively documented during future annual long-term monitoring expeditions. 

The reefs appear to be recovering from the year and a half of intense pressure according to Hickerson. The sanctuary team is focusing its efforts on limiting human-induced pressures on the reefs to ensure that they continue to be resilient in the face of natural events. This high level of resilience was illustrated by the prolific coral spawning events that took place in August and September 2006. 

Manta ray and two divers

The U.S. Navy's research submarine NR-1 dockside in Groton, CT. (Photo: US Navy)

Sanctuary scientists are continuing their monitoring in 2007 that includes studying other areas in the northern Gulf of Mexico that may serve as critical habitat for the entire Gulf of Mexico ecosystem.  This included the Secrets of the Gulf Expedition in February 2007 that involved Dr. Robert Ballard and a world-class team of researchers, who used the Navy’s nuclear-powered research submarine NR-1 to explore the northwestern Gulf of Mexico. What the team learned will be used to help protect these resources for current and future generations.

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