Are coral nurseries an effective way to restore dying corals?

By Vivek Saini

Hard corals that create habitat have been disappearing from coral reef ecosystems at an alarming rate in recent years. While passive habitat protection has traditionally been the primary goal of maritime conservation, interest in and needs for active habitat restoration have increased recently. In response to the threats to coral reefs in the Persian Gulf and the Gulf of Oman, the United Arab Emirates (UAE) is leading restoration efforts by establishing coral nurseries.

How is climate change becoming a threat to coral reefs?

A well-known occurrence that is raising concerns all around the world is the global decrease of coral reefs. Both local and international stressors cause these decreases, and even though significant efforts have been made to lessen local pressures, global impacts like human-induced climate change persist. Since the 1980s, coral bleaching—which results from expelling symbiotic algae under prolonged temperature stress—has caused widespread mass death.

Nearly every year since the early 1980s, one or more tropical or subtropical seas worldwide have experienced bouts of coral reef bleaching and death, mainly brought on by climate-induced ocean warming. Bleaching occurs in sporadic bursts, with the worst incidents frequently occurring in conjunction with related ocean-atmosphere processes like the El Nino-Southern Oscillation (ENSO), which causes sustained regional increases in ocean temperature.

Hard corals that create habitat have been disappearing from coral reef ecosystems at an alarming rate in recent decades. Reefs are impacted by a variety of acute and chronic anthropogenic disturbances, such as deteriorating water quality, destructive fishing methods, overfishing of reef species, and outbreaks of coral predators and coral diseases. However, over the past two decades, climate change has become the main threat to coral reefs. This was made clear during the recent global marine heatwave in 2016–17, which caused the most extensive coral bleaching event in recorded history, affecting distant and undeveloped reefs.

Although dynamic systems like coral reefs have an underlying potential for natural recovery, the frequency, intensity, and severity of mass coral bleaching and extreme weather events are rising, which shortens the period and capacity for healing between catastrophic occurrences. 

What is coral restoration, and why is it important? 

Restoration is “the process of aiding an ecosystem’s recovery after it has been degraded, damaged, or destroyed,” according to the Society for Ecological Restoration International Science & Policy Working Group. Furthermore, restoration attempts to return an ecosystem to its historical trajectory. The terms “restoration” and “rehabilitation” are currently used interchangeably when referring to coral reefs, with the latter emphasizing the reparation of ecosystem processes, productivity, and services, Without implying a return to pre-existing biotic conditions and frequently requiring some attendance. An ecosystem that has been restored contains sufficient biotic and abiotic resources to continue its development without further assistance or subsidy.

Global and local stressors are putting additional pressure on coral reefs, making reef restoration even more essential to protect marine resources and local economies. Coral restoration can be divided into two categories: active repair and passive restoration. Projects involving directly improving the coral reef’s health, abundance, or biodiversity are called “active coral restoration.” Coral reef resilience is made up of these three elements taken together. Resilient, or able to survive or rebound from disruptions, is a term used to describe a reef with many healthy corals comprising a variety of coral taxa.

Active restoration should ideally take place after passive restoration or after Marine Protected Areas (MPAs) have been established. The most frequent goals of functional restoration are to replace lost habitat and corals or to strengthen the reef’s resilience to lessen potential disturbances. Effective ecosystem restoration requires first reducing or eliminating the threat. However, there is little chance of preventing the conglomeration of imposing hazards from happening in many places today. To lessen the degree of damage and protect small reef patches from acting as “biodiversity banks,” repair to boost resilience must be implemented in these locations.

Coral Nurseries: A Glimmer of Hope for Coral Reefs

The Environment Agency Abu Dhabi (EAD) spearheads the battle by re-planting corals nurtured in specialised nurseries. In addition, Dubai has announced a bold plan to grow 1 billion corals along its coastline. “By 2040, EAD hopes to grow 1 billion artificial corals over a 200-square-kilometre (124-square-mile) area and 100 million mangrove trees along an 80-kilometre (50-mile) stretch of Dubai beaches.” These programmes try to replenish declining coral populations while protecting the fragile marine ecosystems that rely on them.

Marine biologist Hamad al-Jailani examines corals carefully collected from the reef nursery and immersed in a box of seawater in the crystal-clear seas near Abu Dhabi. Al-Jailani, an essential member of EAD’s coral restoration programme, discusses the nursery’s fostering procedure. Clear waters with strong currents and enough sunlight provide perfect conditions for coral recovery. He meticulously watches their growth, removes potentially dangerous seaweed and seagrass, and even permits fish to eat on the corals, cleaning them until their health and resilience return.

The coral rehabilitation and restoration activities were launched by EAD in 2021 in response to the UAE’s second coral bleaching incident in just five years. As a country frequently criticised for its large-scale developments and polluting businesses that destroy undersea habitats, the UAE’s public and private sectors have initiated several efforts to safeguard the reefs and the varied marine species they support. Despite improvement, researchers are concerned about the survival of these reefs on a warming planet.

Combating Bleaching and Other Issues

When corals lose the algae that give them their brilliant hues due to rising sea temperatures and stronger sunlight, they become pale and susceptible. Although corals can endure bleaching episodes, the ecosystems that rely on them are threatened by their reduced ability to harbour marine life. When sea temperatures reached a blistering 37 degrees Celsius (99 degrees Fahrenheit), according to EAD, the UAE saw a loss of coral of up to 70% in 2017. Al-Jailani, however, reports that 40–50% of the corals made it through the second bleaching episode in 2021.

“It did wipe out a good portion of our corals, but it also proved that the corals we have are resilient,” he says, highlighting the tenacity of the corals in the United Arab Emirates. These corals can endure these circumstances. Through programmes like coral nurseries and artificial coral cultivation, the United Arab Emirates is proactively rebuilding and maintaining its coral reefs.

The UAE is still dedicated to preserving and restoring these crucial marine ecosystems, despite the difficulties brought on by warming waters, bleaching incidents, and other human activities. Soon, ideas to lessen global warming and its effects will be discussed at the upcoming United Nations climate summit, which will be taking place in Dubai later this year.

References:

1. https://www.thehindu.com/sci-tech/energy-and-environment/to-restore-reefs-dying-in-warming-seas-uae-turns-to-coral-nurseries/article66949684.ece
2. https://www.sciencedirect.com/science/article/pii/S0925857418303094#b0005
3. https://www.sciencedirect.com/science/article/pii/S0925857418303094#b0010
4. https://www.sciencedirect.com/science/article/pii/S0272771408003405
5. https://www.science.org/doi/abs/10.1126/science.1086050
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1933595/
7. https://www.nature.com/articles/nature21707
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6408889/
9. https://www.nature.com/articles/s41586-018-0041-2
10. http://www.ser.org/
11. https://newheavenreefconservation.org/learning-resources/explore-topics/reef-restoration-methods
12. https://www.ead.gov.ae/en

Image source: https://www.pexels.com/photo/close-up-shot-of-corals-under-water-8395913/