NOAA's Reporter's Coral Reef Tip Sheet
September 1, 1997 - Week 35
Warm waters and unique weather patterns are beginning to take a toll on the planets coral reefs. Coral bleaching is being observed in a variety of coral species in the Florida Keys, across the Caribbean, and in other parts of the world. Some scientists are blaming this years bleaching event on the extreme weather patterns created by the El Niño now occurring in the Pacific. Bleached coral is currently being observed in the Florida Keys from Key Largo to the Dry Tortugas, both offshore at the reef tract and inshore.
"This years bleaching is beginning to look severe," said Florida Keys National Marine Sanctuary (FKNMS) Superintendent Billy Causey. "In some spots we have seen as much as 70 percent of an area affected. Another indicator of the severity is that bleaching is occurring in the nearshore waters in species that generally are more adept at adjusting to temperature fluctuations."
Sea surface temperature data indicate that water temperatures in the
Keys and Caribbean are higher than normal. As water temperatures rise,
corals become increasingly stressed. When stress levels get too high, corals
expel the symbiotic algae, or zooxanthellae (tiny one-celled plants), which
live within the thin layer of live coral tissue. Zooxanthellae are important
because they turn sunlight into food for their coral hosts. They also facilitate
the formation of the coral skeleton -- the main structural component of
coral reefs. Because zooxanthellae give corals their various rich colors,
a coral without zooxanthellae appears bleached. Corals can not thrive without
zooxanthellae and may become more vulnerable to the numerous coral diseases
that are ravaging coral reefs around the world.
"Temperatures of 86-87.8°F are common triggers," said Causey. "If these elevated temperatures continue for one to two months, the results can be lethal." Data collected this summer from the Florida Institute of Oceanographys C-MAN buoys, located strategically along the reef, show summer water temperatures ranging from 86°F to the extraordinarily high 91.4°F detected at the Long Key station.
This is not the first time that FKNMS waters have experienced the conditions that bring about coral bleaching. Warm waters also contributed to bleaching events in the Florida Keys in 1980, 1983, 1987, and 1990.
Although this severe natural stress is of concern, it is not necessarily the death knoll for corals. If water temperatures fall back to normal levels, bleached corals can rebuild their bonds with their algal partners. In the Florida Keys, scientists have been able to monitor water temperatures since the bleaching event of 1987. During that episode, sanctuary biologist Harold Hudson installed 27 thermographs along the length of the reef tract to better study the effects of temperature on coral and other organisms. In addition, the C-MAN buoys continually collect weather data that help alert scientists to coral-threatening trends. Much of these data are now available on the Internet.
By not compounding the stress on these delicate organisms, they may be able to survive this summer of bleaching. Scientists and resource managers encourage divers, snorkelers, and even fishermen to take extra care around coral. Touching or breaking off pieces of coral will only decrease their chance of recovering from this stressful period.
FOR MORE INFORMATION ABOUT THE INTERNATIONAL YEAR OF THE REEF , PLEASE CONTACT:
tel: (41 22) 999-0251
FOR MORE INFORMATION ON BLEACHING IN THE FLORIDA KEYS NATIONAL MARINE SANCTUARY, PLEASE CONTACT:
Florida Keys National Marine Sanctuary
216 Ann Street
Key West, FL 33040
tel: (305) 292-0311
fax: (305) 292-5065
FOR MORE INFORMATION ON SEA SURFACE TEMPERATURES, PLEASE CONTACT:
Alan E. Strong
NOAA/NESDIS/ORA/ORAD -- E/RA3
NOAA Science Center -- RM 711H
5200 Auth Road
Camp Springs, MD 20746
tel: (301) 763-8102
fax: (301) 763-8108
FOR TWICE-WEEKLY "HOT SPOTS" THAT ATTEMPT TO POINT TO POTENTIAL BLEACHING SITES
FOR MORE INFORMATION ON EL NIÑO, PLEASE CONTACT:
C. Mark Eakin
NOAA, Office of Global Programs
1100 Wayne Avenue, Suite 1210
Silver Spring, MD 20910-5603
tel: (301) 427-2089 x19
fax: (301) 427-2073
FOR A CLOSE LOOK AT THIS YEARS EL NIÑO, VISIT: