Coral Bleaching

Corals are a type of animal in the phylum cnidaria. They live in colonies, building calcium carbonate skeletons around them that over time create the huge reefs that host a huge range of other creatures. They are sessile, meaning they live fixed in one place for their entire lives. Corals live in nutrient poor waters, which may initially seem counterintuitive. How does such a diverse ecosystem survive on nothing? They subsist through a symbiotic relationship with coral and a type of algae, known as zooxanthallae.The zooxanthallae live in the tissue of the coral. They provide energy for the coral through photosynthesis, giving their excess energy to the coral, and the coral provide protection to the zooxanthallae. The nutrient poor waters do not allow other types of algae to grow, keeping the water clear and allowing for high efficiency in the coral. Corals provide structure and energy for 25% of the earth’s ocean life, while covering less than 1% of the ocean floor. They also support almost a billion people through fishing and other industries, around ⅛ of the entire earth’s human population.

That said, coral reefs are very close to being destroyed forever. Already, 50% of corals have died. Why are they dying? Climate change is warming the oceans, and the heat is causing something called coral bleaching. Coral bleaching is when the coral turns white. When ocean temperatures rise too much, even a very small amount like a couple degrees celsius, the algae in the coral polyps start to produce toxins. The coral have to eject the algae or they will die from the toxins, and since the algae provide the coloration and a large part of the coral’s food, the corals turn white and start to die. They do not die immediately, because they can filter small amounts of food from the water, but they cannot survive long in this state. When a coral does die, strands of algae start to grow on it. When the corals die, every other organism in the reef is affected. Creatures lose their shelter as the coral decay, and they lose their food source as many creatures rely on coral and close associates for food.The accelerated global warming of the last half century is making it plainly obvious the effects climate change has on coral reefs. Before 1998, bleaching was rare and a result of special circumstances. 1998 saw the first global bleaching event in recorded history, and they have only been growing more common since then. Since 1998, there have been events in 2010, 2016-2017, 2023, 2024, and 2025. Notice the time in between each event as we grow closer to the present.They didn’t happen at all until 1998, and then 20 years passed until the next one, and then one happened 5 years after that, and now they are happening almost every year. In short, it sucks to be a coral(or one of the nearly billion people who depend on them). Bleaching events put immense strain on coral reefs. A reef may survive one bleaching event, but they will still take time to recover. Multiple bleaching events kill them off before they have time to regain their strength. It’s also not just bleaching that endangers corals. Increased carbon dioxide levels causes ocean acidification, which dissolves the calcium carbonate skeletons of the coral and kills them. Pollution can cause the water to be dangerous for coral or can stimulate algae growth too much and create a dead zone, where extremely low oxygen levels kill everything in the area. Over exploitation of reefs for commercial fishing purposes is also very harmful, because when a species is overfished the food web collapses and predators of harmful algae die off and the algae stifles coral. Normally coral polyps are robust creatures and can regenerate lost body parts with ease, but without the ability to produce food this adaptability is useless. They cannot take advantage of their undifferentiated cells, because there is no energy for this process to run on.

Some people and organizations are using a variety of strategies to try to save coral reefs. One method is to breed coral to be more resistant to changes. This is simply an example of evolution, just controlled by humans to take place faster instead of the natural environment. Another is making more comprehensive regulations for tourism and commercial fishing. But the main root of the problem, climate change, soldiers on unassailable. It doesn’t matter if coral can be made more heat-resistant if it keeps getting hotter, because coral will never be able to catch up with their slow reproduction and growth. Climate change continues to be a problem because a lot of people are confused and think that there is nothing they can do about it or that it is not as dangerous as everyone thinks it is. If everyone can understand the problem, it will be a much simpler matter to find a solution.

Some people and organizations are using a variety of strategies to try to save coral reefs. One method is to breed coral to be more resistant to changes. Another is making more comprehensive regulations for tourism and commercial fishing. But the main root of the problem, climate change, soldiers on unassailable. Climate change continues to be a problem because a lot of people are confused and think that there is nothing they can do about it or that it is not as dangerous as everyone thinks it is. If everyone can understand the problem, it will be a much simpler matter to find a solution.