Coral reefs are essential ecosystems that are highly vulnerable to the effects of climate change. To commemorate World Oceans Day, we reflect on why the ocean is so important to all life on Earth and also how global warming threatens it. What is coral bleaching? we look at how MDPI researchers are working to restore coral reefs, which are essential to protecting marine life. The 1987 Brundtland Report emphasized that the ocean does not have a strong voice and is often marginalized in environmental debates. 

What is Coral Bleaching?

Even though oceans cover 70% of the planet, nations are reluctant to take responsibility for them. With this in mind, World Oceans Day was proposed at the Earth Summit in known 1992 and launched by the Ocean Project in 2002. In 2022, he worked with more than 10,000 organizations and companies and organized more than 150,000 events in more than 140 countries. In 2023, it will be held on the 8 June and also aims to raise awareness of how human activities affect the oceans and develop a global movement in response. Additionally, the initiative will promote the #30×30 petition campaign, which commits countries to protect 30% of the ocean by 2030.

Blue Planet 

The ocean plays a very important role in maintaining the climate, atmosphere, and ecological processes. The sun evaporates water, which condenses into clouds and releases moisture as rain. All life depends on this water cycle. Water absorbs and releases heat slowly, so it helps balance the Earth’s temperature by absorbing heat in the summer and releasing it into the atmosphere for circulation in the winter. 

At least 230,000 known species live here in diverse habitats, and almost half of the human population makes their living there. The ocean has also absorbed 30% of the carbon dioxide emitted by humans, helping to cushion the impact of climate change. However, this has a negative impact on the ocean, among other factors.

Climate Change 

Increasing amounts of carbon dioxide and also other greenhouse gases are preventing heat radiated from the Earth’s surface from reaching space. This warms the atmosphere and increases radiation on Earth. The ocean primarily absorbs this additional heat because of its large surface area. Also, water has a large heat capacity, so it absorbs a lot of heat before it reaches its temperature. Therefore, the oceans can help slow global warming by absorbing excess heat, but at the cost of absorbing carbon dioxide. The colder the ocean water, the greater its ability to dissolve carbon dioxide. 

As the oceans warm due to increased greenhouse gas emissions, less carbon dioxide can be stored in the oceans, creating conditions that can accelerate global warming. Ocean heatwaves are part of the natural variability of climate. However, “global warming is causing more frequent and extreme marine heatwave events.” This puts a huge strain on marine life, which already has to adapt to rising temperatures. In addition to rising temperatures, ocean acidity has increased by 30% in the past 50 years, oxygen depletion is creating lifeless dead zones across the ocean, and plastic pollution is increasing at a rate that would otherwise persist for hundreds of years.

Coral Reefs 

Coral reefs cover less than 1% of the ocean floor but are home to more than a quarter of all marine life. They form complex species ecosystems where species interact with each other and the environment. Coral reefs are made up of coral, a type of animal related to jellyfish and sea anemones. Stony corals have hard skeletons that form the basis of coral reefs and contain hundreds of thousands of polyps that extract calcium from seawater and harden into skeletal structures. Only the surface is alive; the mass underneath is a skeleton of calcium carbonate. 

Another coral is the august coral, which does not have a skeleton and forms succulent plants. Polyps contain microscopic algae called zooxanthellae. Corals provide habitat and algae provide food to corals through photosynthesis. Because of this process, corals live in clear, shallow waters to receive sunlight. Coral polyps are transparent. The color comes from algae.

Why Are They So Important?

Coral reefs “serve as centers of activity for marine life,” including many of the species of fish, sponges, and crabs. They provide habitat and food for over 1 million aquatic species. Their loss would trigger a domino effect with unpredictable consequences, dramatically changing the food chain and reducing fish populations that depend on corals. This will have a significant impact on commercially harvested fish stocks and thus coastal economies. According to the United Nations, around 1 billion people depend on coral reefs for food and livelihood. Additionally, they protect coastal infrastructure from storms and flooding by acting as wave buffers. Their losses will push coastal cities further inland and hurt the tourism industry.

Global Warming And Coral Bleaching 

When corals are stressed by fluctuations in temperature, light, and nutrients, they expel the algae that live in their tissues. This is called bleaching because the coral turns completely white. When this happens, they don’t die, but they become extremely vulnerable because they have lost their main food source while already under great stress. Once coral dies, “reefs rarely come back.” They are difficult to propagate and deteriorate quickly. The effects caused by global warming, such as warming oceans and increasingly intense and frequent heat waves, are causing “coral bleaching events to become more frequent around the world.

Coral Reef Conservation 

The current paradigm for combating coral reef loss is the 50 Coral Reef Initiative. This UN-backed approach involves the focusing on the 50 coral reefs most likely to survive into the future. This includes conservation efforts and the goal of repopulating nearby coral reefs over time. The MDPI article “Coral-focused climate change adaptation and recovery based on accelerating natural processes: Launching the “Reef of Hope” paradigm” takes a critical view of this approach. Author Austin Borden-Kirby argues that given our dire circumstances, we should challenge our current paradigms and help strengthen them. See how this author uses open access to share her suggestions for coral reef restoration. 

Serious Situation Borden-Kirby argues that this approach primarily “does not help protect the more stress-adapted corals, which are the best source of adaptability to future conditions. He emphasizes that traditional methods of restoring coral reefs are insufficient, as increased temperature stress must be accepted as inevitable. The number of corals that can survive in the highest temperatures has reached its limit. So if we lose them, we lose what is best suited to survive global warming and the changes that come with it. Coral reefs are often known to as the “rainforests of the sea,” so the authors base their approach on afforestation techniques.

Reef Of Hope 

Reforestation techniques focus on transplanting larger tree saplings into smaller areas. Large trees provide a recreational core, attracting life and promoting succession. This creates an attractive living space and promotes structural complexity. Rather than protecting trees, we help restore the ecosystems they support. In the coral bleaching phenomenon, “individual differences” are observed in which some corals die and others survive, so it is necessary to transplant the surviving large corals to a higher temperature environment. The priority is to move climate-adapted, bleach-resistant corals to cooler areas before they are eventually succumb to rising temperatures.