Episode Details

How Can Coral IVF Fight Coral Bleaching?

As ocean temperatures increase due to climate change, an emergent crisis known as coral bleaching is on the rise. Coral bleaching poses the largest threat to coral reefs, which are some of the most diverse ecosystems in the world. Coral reef habitats occupy less than one percent of the ocean floor, but constitute more than 25% of all marine life, providing habitats for a vast array of species from small organisms to large fish and sharks. Additionally, biodiverse reefs provide a variety of economic benefits, supporting jobs, tourism, and fisheries. Reefs also protect lives and property in coastal areas, absorbing 97% of a wave’s energy while buffering against currents, waves, and storms.

However, when ocean temperatures rise, corals become stressed and expel the marine algae living inside their tissues, known as zooxanthellae. Typically, coral live synergistically with zooxanthellae, meaning the algae provide food for the coral while the algae use the coral as shelter. Due to stress, corals expel zooxanthellae, causing them to become a white skeleton. If the temperatures remain high, the coral won’t allow the algae back and the coral will die. Once corals die, reefs rarely come back. As climate change progresses with its warming trend, corals endure greater stress, and experience longer and more intense bleaching events. Between 2014 and 2017, 30% of the world’s reefs experienced heat-stress leading to coral bleaching. In 2005, the US lost half of its coral reefs in the Caribbean in one year due to a massive bleaching event. Fortunately, marine biologists have been working on a new strategy to restore damaged coral reefs, known as Coral IVF (in vitro fertilization), which entails taking healthy coral eggs and sperm, crossing them in a supervised pool, and returning the mature coral to a damaged coral reef. Importantly, IVF coral are often bred to be resilient to heat-induced bleaching, making Coral IVF a successful strategy in fortifying reefs against bleaching.

What exactly is Coral IVF?

Coral IVF begins with biologists collecting spawn, or coral eggs and sperm, from heat-tolerant corals that have survived coral bleaching events. With these spawn, biologists can rear millions of baby corals in tanks and coral nursery pools before repopulating damaged reefs for restoration. So far, coral IVF has proven successful. The Great Barrier Reef (GBR) Foundation planted 22 large colonies of new baby corals off Heron Island in 2016. Four years later, the researchers found that the corals had survived a bleaching event and grown to maturity. The next year, the corals had reproduced and spawned babies of their own. 

In 2016, 81% of the northernmost section of the GBR was severely bleached, including mass bleaching in other sections. The GBR provides an estimated economic value of $56 billion, including 64,000 jobs stemming from the reef. Losing the reef would be a major eco