Coral Reefs

Coral reefs are often referr to as the ocean’s rainforests. This is owing to the fact that both ecosystems are wealthy, productive, and diversified. Coral reefs, on the other hand, are the most diversified ecosystem on the world at the phylum level, with 32 of the 34 animal phyla represented.

This variety includes a third of all marine fish species, with a total number of species estimated to be between 600,000 and 9 million.

This variety is a remarkable effort considering coral reefs only make up around 0.05 to 0.1 percent of the ocean floor. When looking at the global distribution of coral reefs, their minimal global coverage may be noted.

Due to their unique physical requirements, they restricted to a small area. Tropical waters with a temperature of 18-20 degrees Celsius are required for coral reefs. Light and salinity limit them, thus they can only found in shallow waters away from river mouths. This adds to their diversity, as this is an area of the ocean that isn’t known for being particularly fruitful. The corals themselves are, of course, one of the most distinguishing elements of coral reefs.


Corals belong to the Cnidarian phylum, which also contains jellyfish and anemones.

The class Anthozoan, which includes corals, included within this phylum. Polyps, which are soft-body, sessile animals clinging to the seafloor, are the adult stage of Anthozoans. There are many distinct varieties of corals among the Anthozoans, and they can be find all across the world’s waters, not just on reefs. The reef-building corals belong to the Scleractinia order, which belongs to the Hexacoralia subclass.

The stony corals are what they known for. Because the polyps secrete a calcium carbonate skeleton to protect their soft body, this is the case. While many Scleractinian species are solitary, many more are colonial, which means that a group of genetically identical polyps is linking together and acts as a single entity. When you think of large corals like brainy corals or large branching corals that dominate reefs, these are actually many identical individuals acting as one. These Scleractinian corals also serve as reef builders.

They collect calcium carbonate from the surrounding waters and secrete it as a skeleton, which later becomes the reef’s substrate.

Coral skeletons dissolve into sand, which accumulates in cracks and crevices on the reef as they die. This sand is them cemente by other critters into a hard limestone rock. Reef cementation is the term for this procedure. The reef expands and rises through time, allowing it to remain in the shallow water that many of its species require.

Because the substrate is biogenically generate, coral reefs are a one-of-a-kind environment.

This process also leads in a complex ecosystem with a wider range of habitats and species diversity. A symbiotic association between corals and a single-celled algae called zooxanthellae is one of the key reasons why coral reefs are so productive and diversified while also being so environmentally sensitive. When two species are mutually dependent on each other for survival, this is referr to as a symbiotic connection. Corals are heterotrophic, which means they require sustenance from outside sources.

Corals, for example, are predators that filter feed on zooplankton using their stinging nematocysts. Reef-building corals, on the other hand, exist in tropical waters where there are insufficient nutrients and food for the corals to survive.

This is when zooxanthellae’s symbiotic interaction with them comes into play. The zooxanthellae are find in the corals’ endodermis, or inner skin cells. Zooxanthellae are photosynthetic, which means they can produce their own food using solar energy.


This makes it possible to get nutrients from low-nutrient liquids. Zooxanthellae are so good at it that they can photosynthesize 10 to 100 times the amount of organic materials they require for their metabolic and development needs. They then feed the excess food to the corals, allowing them to grow and contribute more energy to the ecosystem as a whole. Because this is a symbiotic interaction, zooxanthellae benefit as well. As part of their respiratory and metabolic activities, corals produce waste carbon dioxide and ammonia, which the algae require.

The corals also shelter the zooxanthellae from grazers and provide an environment where they can photosynthesize near to the sun.

This relationship explains why reefs can teem with life despite the fact that the surrounding seas are comparably barren. Finally, corals are a diverse, dynamic, and intricate ecology. Because of how the ecosystem is produced and where the energy comes from. That’s it for today’s video, but when it comes to corals, this is just the top of the iceberg.

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