Introduction

Coral reefs are beautiful marine ecosystems formed in the sea from the remains of tiny marine invertebrates called coral. These reefs provide habitats for a diverse range of species. The formation of coral reefs is influenced by various biotic and abiotic factors. Abiotic factors, such as water temperature and quality, play a significant role in the development of coral reefs. In this section, we are going to discuss the abiotic factors for coral reefs.

Corals are marine animals that belong to the cnidaria phylum’s anthozoa class. They are related to sea cucumbers and stay immobilized on solid surfaces on the ocean floor when they reach adulthood. Each coral polyp secretes calcium carbonate to build a hard exoskeleton around its body, creating a beautiful rocky shell. Corals are crucial to marine ecosystems’ health and beauty, enhancing the sea floor’s aesthetic appeal (1).

What is a coral reef?

Coral reefs are basically dead coral formations that are typically found in warm tropical oceans. They thrive in water temperatures ranging from 22°C to 28°C, which are common in shallow areas between 11 meters and 40 meters deep. These temperatures promote the growth of phytoplankton, which are microscopic plants that support the marine ecosystem. Zooplankton, a microscopic animal that feeds on phytoplankton, is an essential source of food for the coral. Therefore, coral reefs are abundant in areas where phytoplankton and zooplankton are thriving (5).

Definition

Elongated or ring-shaped marine landforms formed by the accumulation of green, yellow, pink, white, etc. colored corals on the shallow sea platform in the warm marine areas of the world are called coral reefs (1).

Example

The Great Barrier Reef of Australia and the Lakshadweep of India are examples of coral reefs.

Formation of coral reef

Coral reefs are special marine landforms that form on shallow ocean platforms in tropical regions. This coral reef is formed by accumulating the calcareous remains of a type of small worm called coral.

The coral worm colonizes a favorable marine environment by adopting a submerged island or a submerged volcanic cone or any other undersea platform and eventually dies there.

Then the calcareous structure of their skeletons is recolonized by coral worms and dies. Thus, over millions of years of continuous colonization and die-off, as well as layer upon layer of coral calcareous remains, coral reefs are formed (2) & (3).

Biotic factors for a coral reef

Biotic factors of coral reefs are many species of fish, turtles, mollusks, sea snakes, sponges, and polyps. The plants are algae, anemones, sea grass, and sea lilies. Living things are the most important biotic factors in a coral reef.

Plant

There are various types of plants found in coral reefs. These are green algae (chlorophyte), red algae (Rhodophyta), brown algae, seagrass, sea lettuce, seaweed, Neptune grass, eelgrass, coralline algae, etc. These plants give food and oxygen to the reef’s animals. Plants absorb sunlight which is the main energy source for coral reef animals. They are called phytoplankton. Different types of algae and other plants are converted into chemical energy through the photosynthesis process. When reef animals ingest these plants as food, the energy is transferred to their bodies. In this way, a food chain is created and maintained. Seagrasses play a great role. They provide shelter for reef animals like conch and lobster.

Animal

Sea urchins, sponges, sea stars, fish, sharks, rays, lobster, octopus, snails, and many types of other animals are found in coral reefs. They are the consumers of this coral reef. Animals in the coral reef act together. They are called coral polyps. Clownfish, sea anemones, stony corals, sea turtles, dugongs, starfish, lionfish, giant clams, brain coral, coral reef snakes, etc. are also found here.

Microorganisms

Microorganisms are mainly present in the form of decomposers. Certain types of bacteria, archaea, viruses, endolithic algae, Protista, and fungi are integrated with these coral reefs (2) & (4).

Abiotic factors for a coral reef

A coral reef is a special marine landform formed on a shallow sea platform in a tropical warm marine area. This coral reef is formed by the accumulation of the calcareous remains of a type of marine animal called coral. Depending on several favorable conditions, coral grows and forms colonies. Below is a discussion of abiotic factors for a coral reef.

1.Sea water temperature

Coral cannot tolerate extreme heat and extreme cold. Therefore, most corals grow and breed in moderately warm seawater, i.e. 18°C- 30°C. Because of this, coral reefs are formed in tropical seas.

2. Depth of seawater

Coral reefs cannot be developed at a depth of more than 60- 75 meters from the sea surface, because at higher depths coral do not get the sunlight and oxygen required for their activity and growth.

3. Salinity of seawater

The main food of coral is calcium carbonate. As the salinity of the seawater increases, the amount of calcium carbonate in the seawater decreases. Therefore, lack of food inhibits the growth of coral. Generally, seas with a salinity of 27% to 40% are ideal for coral reef growth. Because the salinity seawater continues to supply calcium carbonate, the main food of coral.

4. Effects of freshwater

Fresh water is unfavorable for the growth and reproduction of coral. Because exposure to fresh water is likely to kill coral. Therefore, far away from rivers, coral grows, form colonies, and build coral reefs in areas free from the effects of fresh water.

5. Sediment-free water

Coral requires clear water free of sediment to grow. Because when sediment particles accumulate in the mouth of coral, they cannot receive oxygen. As a result, they die without being able to digest. In addition, because sediment in water creates a barrier to sunlight, coral reefs are formed in clear water free of sediment away from the mouth of the river.

6. Ocean currents and ocean waves

Ocean currents and ocean waves are ideal for coral reefs to grow. Because these ocean currents and ocean waves continue to supply the necessary food and oxygen to the coral in the seawater. Therefore, open seas have coral reefs instead of lagoons or enclosed seas.

7. Submarine stage location

Coral reefs in the shallow seas required a submarine platform location. The location of the submarine platform, formed of continental hard rock at a depth of 100 m along the shelf, helps establish a strong foundation for coral reefs. Submerged islands act as undersea platforms in this case (1) & (2).

Q&A

1. What are the 5 abiotic factors in a coral reef?

Sunlight, depth of the ocean, water temperature, salinity, Sediment-free water, and ocean waves are the abiotic factors.

2. What are the abiotic and biotic features of coral reefs?

Abiotic features

Sea water temperature, ocean currents, ocean waves, submarine stage location, sediment-free water, effects of fresh water, the salinity of seawater, and depth of the water are the abiotic features.

Biotic features

Plants, coral, fish, and crabs are the biotic features of coral reefs.

Written By: Manisha Bharati