We have long known that coral reefs are in trouble but it seemed like an insurmountable problem. The good news is that there is reason to be cautiously optimistic.
Most coral are tropical but some varieties live on the ocean bed off the coast of northern Europe. Cold water varieties have not been well studied because they live in a place that is inhospitable to us. When people talk about coral issues they are usually referring to the warm-water animals.
Reefs are vitally important. About 20% of all ocean fish spend their early childhood in a reef. Nooks and crannies are there to provide protection against predation and plankton is available for food. Without reefs, fish populations would decline significantly. Fewer fish would lead to wide spread hunger among humans. We need healthy reefs.
Dangers to reefs include fragmentation caused by collisions with fishing vessels and hurricane-strength storms, overfishing, ocean acidification caused by absorption of excess CO2 in the air, and increased water temperature.
Fragmentation: The treatment for fragmentation consists of cloning. The corals are broken into smaller pieces, if they aren’t already in small pieces. This stimulates the coral tissue to grow into clones at many times the normal growth rate. The fragments are then place in shallow, temperature-controlled tanks for about a year or so, until they are fully grown corals and ready to be planted back into the ocean. The National Oceanic and Atmospheric Administration (NOAA) has been using this method and has now successfully planted more than 20,000 corals onto depleted reefs in the Florida Keys.
Overfishing: Coral needs the attention of a variety of fish. Unsustainable fishing on coral reef areas can lead to the depletion of key species. These losses have an effect not on just the reefs, but also on local economies. Fishing plays a cultural role in many communities and is often an important source of food and income. Marine reserves, “No-Take” zones, can be located near to coral reefs and provide a haven for fish. Number of fish and the number of species will increase stocks in surrounding areas. Both large and small reserves have proven successful.
Acidification: Ocean acidification is caused by absorption of excess CO2 in the air. This makes it more difficult for corals to build their calcium carbonate skeletons. Coral needs the secure structure of their skeletons. Conservationists recommend increasing coral diversity on a reef. Some species are not as vulnerable as others. They also suggest planting seagrass beds nearby. Like other plants, seagrass sequesters CO2. Some of these remedies may be temporary because acidification is ongoing. Perhaps managing it is a work in progress.
Water warming: The most effective treatment for reef suffering from warmer water is to increase the diversity of coral on the reef. Some species seem to be able to adapt rather well. This can be done by tapping into the coral reproductive system.
Corals have multiple reproductive strategies. They can be male or female or both, and can reproduce either asexually or sexually. Asexual reproduction is important for increasing the size of the colony, and sexual reproduction increases genetic diversity and starts new colonies. In sexual reproduction, eggs are fertilized by sperm, usually from another colony, and develop into a free-swimming larva. Eggs and sperm are released in a spawning event and float up to the ocean surface.
Biologists can interrupt the process at this point by capturing eggs, sperm, and larva. As the eggs are fertilized, they are placed on small tiles. The tiles (with their cargo) are kept in a nursery, fed and protected from predation, for about two years. The tiles and resident coral are then transported to the reef and glued into place. This method has been quite successful. The immigrant coral grow, reproduce, and spread.
It might be necessary to do coral reef maintenance on a regular basis, during our lifetime at least. The good news is that we can make a difference.