Corals, along with sponges, are members of the Phylum Porifera, which literally means ‘pore-bearing’. This name refers to the pores that allow gas exchange (similar to fish gills) and for the release of waste products.
Coral are omnivorous animals that play an important role in the food web of the reef ecosystem. They are secondary consumers, meaning that they eat animals but they also eat plants and detritus so they do contribute somewhat to the decomposition of organic matter in the oceans. They are not producers, but they do have an interesting relationship with algae!
Coral capture plankton like algae and microscopic animals as well as small particles of organic matter from the water by effectively filtering the water.
This diet helps them to supplement the nutrients they receive from their symbiotic dinoflagellate algae partners that also provide them with energy in exchange for giving the algae a place to live!
Like sponges and sea squirts, corals are colonial animals, often building massive structures, some of which are even visible above water, but they do need water to survive.
Structure and Diet of Corals
Corals are small, sessile, non-moving animals. They are colonies composed of individual polyps, which can reproduce asexually or sexually, depending upon species. Polyps are mobile and are responsible for capturing prey and secreting digestive enzymes, which break down the captured prey.
The digested food is then transported across the coral surface, where it can be efficiently captured by the gastrozooid, a gastropod-like opening that leads to the pharynx (feeding organ).
The pharynx then transfers the food through the food conduit, which delivers it to the stomach – yes corals have stomachs!
The stomach then secretes enzymes that further break down the food, which is finally passed into the intestine (food storage area), where the nutrients can be absorbed.
Corals have an important symbiotic relationship with algae called zooxanthellae. These are a type of dinoflagellates that are actually small photosynthetic animal-like protists! But they are not quite animals nor plants just like Euglena are.
The zooxanthellae live inside the coral tissue and provide the coral with nutrients through photosynthesis. And they also give the corals their beautiful colors!
In return, the coral provides the zooxanthellae with some nutrients, a safe place to live, and access to sunlight. This symbiotic relationship is essential for the survival of both species.
Why are corals important for the marine ecosystem?
Corals are important animals in the ecosystem because they provide a home for many other creatures, help to keep the water clean, and provide food for many other animals.
Coral reefs are some of the most diverse ecosystems in the world. They are home to thousands of different species of fish, invertebrates, and other marine life. Without coral, these animals would have nowhere to live and would eventually die off.
Corals also help to keep the water clean by filtering out harmful pollutants and providing a safe place for fish to lay their eggs. Many fish species depend on coral reefs for their survival.
Finally, corals provide food and hiding places for many other animals in the ecosystem. Herbivorous fish graze on algae that grow on the coral reefs, while carnivorous fish eat smaller fish that live among the corals.
If there were no coral in the ecosystem, these animals would not have anything to eat and would eventually starve to death.
Are Corals Carnivores, Herbivores or Omnivores?
Corals are omnivores. They eat both plants and animals. Corals are not considered herbivores because plant matter makes up a very small portion of their diet. Corals eat microscopic algae, plankton and planktonic invertebrates (animals).
Are Corals Producers, Consumers or Decomposers?
Although corals may look like plants, they are in fact animals and that makes them consumers because they eat other living organisms. Corals are omnivores, which means that they eat both plants and other animals.
Only plants as well as some bacteria and protozoa are producers.
What Type of Consumer is a Coral?
Corals are secondary consumers because some of the animals eaten by corals also eat animals! Generally, herbivores are primary consumers, omnivores secondary consumers and predators are tertiary consumers.
Are Corals Decomposers?
Corals are not considered decomposers because they do not eat a lot of dead or decaying matter.
However, they do occasionally filter out dead organic matter from the water, which means that they are helping the decomposition of organic matter and may be considered part-time detritivores!
Where are Corals in the Food Chain?
Corals are the second trophic level in the energy pyramid because they are secondary consumers.
They eat plants, algae, bacteria and some amounts of microscopic crustaceans (zooplankton) which places them at the 2nd and 3rd trophic levels.
Are Corals Autotrophs or Heterotrophs?
Corals are animals and are therefore heterotrophs because they eat or are dependent on other living organisms for their food. Practically no animals are autotrophic because animals do not get their energy directly from the sun as plants do.
However, corals are a bit different than most animals in this regard!
However, being in symbiosis with algae can make corals (almost) independent of other food sources. If you consider these algae part of the corals they are sort of semi-autotrophs!
What Animals Prey on Corals?
Corals are food for a variety of animals including fish, snails, crabs, barnacles, starfish and marine worms. However, hard corals have a skeleton made from calcium, are not so easy to eat!
Many animals also eat corals when they die. A dead coral will be eaten by small scavengers and bacteria in a matter of months. They also eat their skeleton as a source of minerals!
In this blog post I have looked at the diet of the coral as an animal that is rarely thought about on a day to day basis.
Some of the important take away learnings are:
A coral is actually a small animal living in large colonies that are a vital part of the ecosystem and is often used as a living reef in aquarium.
A coral is an important part of the food chain because it is a secondary consumer.
A coral is a filter feeder and it uses the food that it consumes to build itself and its structure.
A coral is a complex organism that may live in symbiosis with algae – a collaboration that is very interesting to observe.
Unfortunately, many corals are subjected to so-called bleaching, a stress situation that strips them of from their vital algae symbionts:
In this blog post I have looked into the diet of the coral as an animal that is rarely thought about on a day to day basis.
If you are interested in coral, you can find out more about it in my previous post here.