Any change in normal conditions, like unusually warm water, can cause corals to release algae from their tissues. These algae give corals their color and provide their primary source of food.
“In about 15 - 20 years, we’ll see some parts of the Florida reef tract bleach annually,” says Ruben van Hooidonk, assistant scientist with NOAA's Atlantic Oceanographic and Meteorological Laboratory. That conclusion is based on water temperatures in the Gulf of Mexico and the Caribbean.
"Coral reefs are incredibly important for our economy; they bring in lots of tourism dollars. They also protect shorelines from erosion," van Hooidonk says. "They provide lots of fish for sometimes the poorest nations on Earth, and they’re incredibly beautiful ecosystems that deserve to be preserved for future generations."
Coral bleaching is supposed to happen only sometimes, not every year. “They’re an early indicator of problems because corals are so sensitive to these temperature changes," van Hooidonk says. "They are serving us as a warning for other dangerous things that could happen because of climate change.”
The study also found areas where bleaching will have less of an impact. Scientists say humans should reduce their footprint in those areas by minimizing reef damage caused by ships, pollution and over fishing.
"Those are all actions that we can take now," van Hooidonk says, "but without addressing climate change, those efforts will not be enough to save these reefs."