G06: Ecosystem Problems & Solutions: Coral Reefs & bleaching

Tropical coral reefs are the most diverse marine ecosystems on earth, giving shelter to thousands of animal species. Many millions of people depend on fisheries, tourism and coastal protection provided by healthy coral reefs. Yet today, coral reefs are dying at an alarming rate all around the globe

Coral reefs are wondrous, diverse, productive, valuable ecosystems, upon which millions of people around the world depend. Despite their importance and value, reefs are severely threatened by both local and global threats, including climate change. This global profile provides an overview of why coral reefs are important, what threats they are facing, what makes them resilient and what we can do to save them.

A reef is a big group of rocks on the ocean floor, but did you know that a coral reef is actually alive and covered with very small animals called corals? These animals glue their tiny skeletons to rocks, so they end up staying in the same place their entire lives!

What is coral bleaching?
Coral bleaching happens when corals lose their vibrant colors and turn white. But there’s a lot more to it than that. Coral are bright and colorful because of microscopic algae called zooxanthellae. The zooxanthellae live within the coral in a mutually beneficial relationship, each helping the other survive. But when the ocean environment changes—if it gets too hot, for instance—the coral stresses out and expels the algae. As the algae leaves, the coral fades until it looks like it’s been bleached. If the temperature stays high, the coral won’t let the algae back, and the coral will die.

When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.

When corals are under stress, they expel the microscopic algae that live in their tissues. Without these algae, corals' tissues become transparent, exposing their white skeleton. This is called coral bleaching. Bleached corals are not dead, but are more at risk of starvation and disease.

As climate change continues threaten the planet, coral reefs — which cover less than 0.1 percent of the ocean’s surface and provide shelter to 25 percent of marine life – have been dying at shocking rates over the past few years. In 2016, the Great Barrier Reef in Australia suffered its worst-to-date die-off due to significant coral bleaching.

Coral reefs are in decline in the U.S. and around the world. Many scientists now believe the very existence of coral reefs may be in jeopardy unless we intensify our efforts to protect them (Frieler et al. 2013). Threats to coral reefs come from both local and global sources.

Taiwan is home to a diversified coral ecology that is rarely seen in other subtropical areas around the world. However, as the climate is getting hotter and breaking historical records, Taiwan begins seeing widespread coral bleaching in its oceans.

Coral bleaching happens when corals lose their vibrant colors and turn white. But there’s a lot more to it than that. Coral are bright and colorful because of microscopic algae called zooxanthellae. The zooxanthellae live within the coral in a mutually beneficial relationship, each helping the other survive. But when the ocean environment changes—if it gets too hot, for instance—the coral stresses out and expels the algae. As the algae leaves, the coral fades until it looks like it’s been bleached. If the temperature stays high, the coral won’t let the algae back, and the coral will die.

New research shows that, in a hotter climate, urgent action will be needed to prevent the vast majority of coral species from collapsing by the end of the century. Humans will have to limit emissions of heat-trapping gases, but that alone likely won't be enough. Reefs may also need a helping hand through efforts like restoration or coral breeding, which cultivates heat-resistant varieties.

The Great Barrier Reef in Australia is an area of outstanding natural beauty. More than 2000km long, it is home to sealife like rays, molluscs, dolphins, tropical fish, sea turtles, and more than 400 kinds of coral. At first glance coral looks like a plant, but it is actually a strange kind of animal that attaches itself to rocks. Stretching over huge areas, coral is an important part of Earth’s ecosystem.

With coral reefs in decline and NOAA calling for a larger protected area for reefs in the Gulf of Mexico, U.S. Geological Survey scientists are pointing out another strategy to save reefs: First save the mangroves.

There is a scientific laboratory at the top of the new Frost Museum of Science in Miami, Florida. The lab houses colonies of colorful corals, called staghorn corals. Corals are creatures that grow in oceans, often forming large structures called coral reefs.
Scientists at the lab have a strange job. They are purposely making the corals uncomfortable. The goal is bring them right up to the edge of death, but not past it.

The Persian Gulf's coral reefs only have 10 percent of the diversity of reefs in some other waters, and they are not quite as pretty to look at. But the waters off the United Arab Emirates (UAE) coast might contain something even more precious. Scientists think it might hold clues that could help other reefs survive the climate change that has caused ocean waters to become warmer.

Without these interventions, scientists say the Earth’s coral reefs as we know them could disappear before the next century.