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Did you know how the wonderful symbiotic relationship between coral and algae is formed?
In the coral reef ecosystems of tropical seas, corals are known for their colorful and diverse biological communities. However, these beautiful ecosystems are facing unprecedented threats, especially the increasing impact of coral bleaching. Coral bleaching, simply put, is the process by which corals turn white due to the loss of symbiotic algae (organic, single-celled algae) that inhabit their tissues. This removes the coral's vivid color, revealing its white skeleton composed of calcium carbonate.
The relationship between coral and its symbiotic algae is one of interdependence, with the coral providing shelter to the algae, and the algae providing most of the energy to the coral through photosynthesis.
This symbiotic relationship has allowed corals to survive in nutrient-poor environments for more than 200 million years. When sea temperatures rise, this fragile relationship can be disrupted, causing corals to expel algae, and the result is coral bleaching. According to a report by the United Nations Environment Program, the frequency and intensity of coral bleaching events worldwide have increased dramatically since the 1980s. Unfortunately, this phenomenon is largely driven by climate change.
Corals usually need a stable environment to stay healthy, but when faced with various stresses caused by climate change (such as rising water temperatures, excessive sunlight, and changes in water quality), their living space will be threatened. They not only have to resist the influence of these external factors, but also face threats from pathogens. The spread of certain pathogens, such as the species Vibrio shiloi, which attacks psoriasis corals, further weakening their genetic resistance, is suggested by comprehensive research.
If environmental conditions are too harsh, corals may feed their symbiotic algae, leading to deep nutrient deficiencies and, in extreme cases, death.
As temperatures continue to rise, it becomes increasingly difficult to restore these symbiotic relationships, and coral reef systems in many areas are in danger of exhaustion. Especially between 2014 and 2017, the persistence and prevalence of global coral bleaching events reached unprecedented levels, with coral cover declining to crisis levels in many areas.
Triggers of coral bleaching
The availability of corals in the world is closely related to their environmental conditions. Extreme environmental changes, especially emergency heat waves caused by global climate change, have rendered large numbers of corals unable to survive. The U.S. National Oceanic and Atmospheric Administration (NOAA) monitors these bleaching "hotspots," areas where sea surface temperatures are 1°C above climatic average, typically marking the onset of coral bleaching.
The impact of bleaching events is not limited to the coral itself. When coral dies, many marine organisms that depend on it also suffer. The loss of these organisms not only changes the structure of the ecosystem but also has an economic impact, especially on local fishing communities that rely on coral reefs as a food source.
Thinking about the future
Facing the future, global alertness and action on climate change are particularly important. If we fail to respond appropriately to climate change, the relationship between corals and their symbiotic algae will face greater threats, which will eventually lead to the loss of ecological diversity. Humans are not immune to this process because our survival also depends on the health and stability of these ecosystems.
The defense of corals is not only a matter of protecting marine life, but also an important link in maintaining the relationship between humans and nature.
As we face the challenges of the current environmental crisis, how can we ensure the sustainable development of modern civilization while protecting coral ecosystems?
