Coral is an animal that can reproduce in a number of different ways. Some ways are asexual. Corals can bud, dividing themselves into clones. They can also fragment, a natural process where pieces of coral break off and re-attach elsewhere to create new colonies. Most coral species are hermaphrodites, and many of them can reproduce sexually through broadcast spawning or brooding. Despite this reproductive versatility, less and less coral babies are actually being made.

According to Kimberly Stone, associate curator for fish and invertebrates at Georgia Aquarium, “Corals can adapt to climate change, but the amount of factors that are changing around them is so significant they can’t adapt fast enough.”

What are the factors working against the next coral generation? As carbon dioxide levels rise, the ocean becomes more acidic, making it harder for coral to build reefs. Coral is also being bleached by global warming and smothered by sewage and sediment runoff. Meanwhile, careless boaters, divers, snorkelers, fishers and souvenir hunters pose a constant threat.

The High Cost of Coral Loss

When coral reefs are destroyed, so is the marine life they support including about 4,000 species of fish. The destruction of these fish causes economic losses in the U.S. that can be in the tens of millions of dollars. In developing countries, the loss of fish means the loss of a critical food source for tens of millions of people.

In addition to serving as a valuable ecosystem often compared to rain forests in their diversity, coral reefs buffer shorelines from waves and help prevent erosion. They act as a natural home and life insurance policy along the coast, also protecting wetlands and harbors. Half a billion people around the world live and work within about 60 miles of a coral reef and reap its benefits.

How Reproductive Science Is Stepping In

The growth of coral is critical, yet it’s clearly challenged at every turn. Major research and conservation organizations are intervening with innovative methods to help coral reproduce where they have been unable to on their own. The non-profit Coral Restoration Foundation (CRF) pioneered the growth of coral fragments in an underwater nursery near Molasses Reef in the Florida Keys National Marine Sanctuary. Once viable, these fragments are transplanted to Molasses Reef and other affected reefs to spur growth of healthy corals and restore the breeding population. Georgia Aquarium staff and volunteers, with support from the UPS Foundation, have logged over 2,000 hours underwater assisting the CRF since 2010.

On a recent mission, Georgia Aquarium collaborated with several groups including the Florida Aquarium in Key Largo to support the annual three-day spawning event of staghorn coral. This endangered species, along with elkhorn coral, is a critical reef-builder that has experienced an 85% decline Caribbean-wide.

According to Stone, “The corals release gametes into the ocean, but because the numbers are declining, these gametes have a tough time finding each other and making connections to form embryos. We play the middle-man.”

Stone was a member of the team of 37, including four divers from Georgia Aquarium, that collected the gametes as they were released, brought them back to a lab setting for safe fertilization and outplanted them back to the reef to settle and grow.

“I remember the first time I saw a spawning event, other than on TV,” Stone said, “and it’s overwhelming. It’s pretty special to personally witness it and be able to help.”

This particular mission was considered a significant success as 520,000 gametes were collected, and 350,000 viable embryos were produced through the intervention.

In addition to the outplanting of the corals, some corals were kept in nursery and lab settings for further study of the optimal growth environment that corals need to reach adulthood and reproduce on their own. Helping corals become self-sustaining is the long-term goal of restoration efforts. These samples also serve as a bank of genetic material, in the case of extreme weather events like hurricanes that could wipe out both reefs and underwater nurseries.

To find out more about coral restoration, the Georgia Aquarium dive team and their recent underwater work, visit the Georgia Aquarium Blog.