Answer:
Coral reefs are underwater structures formed by the accumulation and growth of coral organisms. Coral reefs are known for their high levels of biodiversity, with a vast array of organisms inhabiting the reefs, including fish, invertebrates, and algae. Coral reefs are found in warm, shallow waters, generally in tropical and subtropical regions.
The formation of coral reefs requires specific environmental conditions. Coral reefs typically require clear, warm waters with a temperature range of 20-30°C. These waters must also have a stable salinity and pH level. Coral reefs also require sunlight, which provides energy for photosynthesis, as well as a hard substrate on which to grow.
The relationship between coral and algae is essential for the formation and maintenance of coral reefs. Coral provides shelter and nutrients to the algae, while the algae provide the coral with food and oxygen through photosynthesis. This symbiotic relationship, known as mutualism, is critical to the growth and survival of coral reefs.
It is unlikely that a coral reef would form near the mouth of a major river. Rivers often carry large amounts of sediment and nutrients, which can reduce water clarity and quality. High levels of sediment can also smother and kill coral, while excessive nutrients can cause harmful algal blooms, leading to oxygen depletion and coral death. Additionally, the fluctuating salinity levels near the mouth of a river may not be conducive to the growth and survival of coral. Therefore, the conditions necessary for the formation of coral reefs are usually not present near the mouths of major rivers