International Journal of Marine Science, 2024, Vol.14, No.1, 14-20 http://www.aquapublisher.com/index.php/ijms 16 (Zooxanthella). Symbiotic algae are a type of micro unicellular plants that live within the tissues of coral animals. They convert sunlight into energy through photosynthesis and produce organic matter, providing energy and nutrients for corals. At the same time, coral animals provide a suitable living environment and shelter for symbiotic algae, and this symbiotic relationship enables corals to survive and thrive in nutrient poor waters. In addition to coral animals (Figure 3) and symbiotic algae, coral reef ecosystems also include other rich and diverse biological populations. Fish, shellfish, sea anemones, sponges, and marine plants, along with coral animals and symbiotic algae, form a complex food web. Fish find refuge, breeding grounds, and food sources in coral reefs (Alissa and Laura, 2023), while also helping to remove algae from corals and maintain their healthy state. The presence of other biological populations enriches the biodiversity of coral reefs and promotes the stability and function of ecosystems. Figure 3 Underwater organisms on coral Non biological environmental factors play an important regulatory role in the development and maintenance of coral reef ecosystems. The temperature of seawater is a key factor, and an appropriate temperature is conducive to the growth and reproduction of corals. Excessive temperature can lead to the breakdown of the symbiotic relationship between coral animals and symbiotic algae, known as coral bleaching. In severe cases, it may lead to coral death. Light levels also have a significant impact on coral reef ecosystems. Insufficient light can affect the photosynthetic efficiency of symbiotic algae, affecting the growth and health of corals. Changes in salinity can also have an impact on the adaptability of coral and other biological populations. However, global climate change has led to increased seawater temperature and ocean acidification, posing pressure and death risks to corals and symbiotic algae (Li and Yi, 2021). Overfishing, pollutant emissions, and human activities have also had serious impacts on coral reefs. Overfishing has disrupted the food chain and ecological balance of coral reefs, leading to a decrease in fish and other biological populations. 1.2 Ecological roles and functions of coral reefs Coral reefs play an important role in marine ecosystems and provide multiple functions. Coral reefs are hotspots of biodiversity and treasure troves of species richness. They are home to numerous marine organisms, providing shelter and breeding grounds for various species, and are habitats for many organisms such as fish, shellfish, crustaceans, sea anemones, sponges, and marine plants. These organisms form complex food webs and ecosystem interactions in coral reefs (Michael and Philip, 2019), maintaining the stability and functionality of marine ecosystems. Coral reefs also provide a source of food for many species. Coral animals and symbiotic algae in coral reefs produce organic matter through photosynthesis and provide energy and nutrients. These organic substances become a food source for other organisms, including plankton, small fish, crustaceans, etc. Fish rely on plankton and other small organisms in coral reefs to feed, forming a complex food chain (Josefin et al., 2019). The food chain of coral reefs not only nourishes the organisms within the coral reef ecosystem, but also provides important fishing resources for nearby fisheries.
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