Coral | Coral Reef | Coral Description, Types, and Facts

Coral | Coral Reef | Coral Description, Types, and Facts


Corals are marine invertebrates that are part of the Anthozoa class of the phylum Cnidaria. Typically, they form dense colonies that are made up of multiple, identical individual polyps. The coral species, which are essential for building reefs, are found in tropical oceans and exude calcium carbonate to form a stiff skeleton.

A coral "group" is a colony of many polyps that share a common genetic ancestor. Each polyp is a very little mammal that looks like a sac and is typically only a few millimetres in diameter and a few centimetres tall. A collection of tentacles around a central mouth opening. Near the base, each polyp excretes an exoskeleton. As a result, over many generations, the colony develops a skeleton that is distinctive to the species and can grow to be several metres long. Polyps' asexual reproduction helps each colony thrive. Corals can also reproduce sexually by spawning, in which gametes are concurrently released by polyps of the same species overnight, typically around a full moon. Planulae, a mobile early form of the coral polyp that settles to create a new colony, are created from fertilised eggs.

Coral | Coral Reef

Most corals get the majority of their energy and nutrition from photosynthetic unicellular dinoflagellates of the genus Symbiodinium that live within their tissues, while some corals can trap plankton and tiny fish utilising stinging cells on their tentacles. These, often referred to as zooxanthellae, are what give coral its colour. Such corals need sunshine to flourish, and they often thrive in shallow, clean waters that are no deeper than 60 metres (200 feet; 33 fathoms). Coral reefs that grow in tropical and subtropical waters, like the Great Barrier Reef off the coast of Australia, rely heavily on corals for their physical structure. As a result of stressors like high water temperatures or toxins, these corals are becoming more and more susceptible to bleaching events where polyps eject the zooxanthellae.

Other corals, such as the cold-water genus Lophelia, which can survive as deep as 3,300 metres, do not rely on zooxanthellae and can exist worldwide in much deeper water (10,800 feet; 1,800 fathoms). Others have been discovered off the coasts of Washington State and the Aleutian Islands, while some have been discovered as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland.

Coral Structure (Anatomy)

Corals are sessile creatures made up of colonies of genetically identical polyps over the most of their lives. Colonies can be created from millions of individual polyps, each of which can range in diameter from millimetres to centimetres. Stony coral polyps, commonly referred to as hard coral, create a calcium carbonate skeleton to fortify and shield the organism. The coenosarc, the living tissue that joins the polyps, and the polyps themselves deposit this. The polyps are located in corallites, which are cup-shaped depressions in the skeleton. A single species of stony coral may adopt an encrusting, plate-like, bushy, columnar, or huge solid structure in its colonies. The diverse morphologies are frequently linked to different types of habitat, with differences in light intensity and water circulation being significant.

The anatomy of the polyp's body can be roughly compared to that of a sac, whose wall is made up of two layers of cells. Technically speaking, the endoderm is the inner layer while the ectoderm is the outer layer. A supporting layer of gelatinous material known as mesoglea, secreted by the cell layers of the body wall, lies between the ectoderm and endoderm. Skeletal components produced from cells that migrated from the ectoderm may be present in the mesoglea.

The hard surface, which in the case of hard corals are cup-shaped depressions in the skeleton known as corallites, serves as the anchor for the sac-like body constructed in this manner. The solitary aperture, known as the mouth, is located in the centre of the upper end of the sac and is encircled by a circle of tentacles that resemble glove fingers. The tentacles are specialised organs used for both food capture and tactile sensing. Particularly at night, polyps extend their tentacles, which are frequently filled with coiling stinging cells (cnidocytes) that puncture, poison, and firmly grasp live prey, paralysing or killing them.

Plankton such as copepods and fish larvae make up the prey of polyps. Tentacles can contract to move food to the mouth thanks to longitudinal muscle fibres made from ectoderm cells. Similar to this, when muscles are tensed, circularly distributed endoderm-derived fibres allow tentacles to extend or thrust out. Stony corals rely on their hard skeleton and cnidocytes for defence, while soft corals can retract their polyps by contracting their muscle fibres. Terpenoid poisons are typically secreted by soft corals to fend off predators.

The tentacles of the majority of corals are retracted during the day and extend out at night to capture plankton and other tiny invertebrates. Soft and stony corals that live in shallow water can both be zooxanthellate species, which means they use these symbionts' photosynthetic products to supplement their plankton diet. A sophisticated system of gastrovascular canals connects the polyps, allowing for extensive interchange of nutrients and symbionts.

The polyp's outer shape varies widely. The column could be long and lean or it could be so short in the axial direction that its body takes on the appearance of a disc. It's possible for there to be hundreds, a small number, or even just one or two tentacles. They could have a feathery design or be plain and unbranched. The mouth may protrude and have a trumpet-like form, or it may be level with the peristome's surface.

blue coral
Blue Coral

Types of Coral

The two types of coral are:

Soft corals

Soft corals don't actually have a solid exoskeleton. However, these organisms' tissues are frequently strengthened by tiny calcium carbonate sclerites known as sclerites. The Octo in Octocorallia reflects the soft corals' eight-fold symmetry in their polyps.

Soft corals come in a wide range of shapes, and the majority are colonial. Only a small percentage of soft corals are stolonate, but the majority of them have tissue sheets termed coenosarc connecting their polyps. In certain species, these sheets are thick, and the polyps are deeply immersed within them. Some soft corals produce lobes or encrust other underwater objects. Others have a central axial skeleton inserted at their base in the matrix of the supporting branch and resemble trees or whips. These branches are made of a calcified substance or a fibrous protein known as gorgonin.

Stony corals

Stony coral polyps have a six-fold symmetry. The tentacles of stony corals are cylindrical and taper to a point, but those of soft corals are pinnate and have side branches called pinnules. These are reduced to mere stubs in some tropical species, and in others, they are merged to resemble paddles.

Calcium carbonate, either in the form of calcite or aragonite, makes up the biocomposites (mineral + organic) that make up coral skeletons. The "centres of calcification" and fibres in scleractinian corals are obviously different structures that differ in the shape and chemical makeup of the crystalline units. The proteins, sulphated sugars, and lipids found in the organic matrices isolated from various species are acidic and species-specific. Zooxanthellae and non-zooxanthellae specimens can be distinguished from one another because to the soluble organic matrices of the skeletons.

red coral
Red Coral

Coral Reef

Corals that build reefs define the underwater ecosystem known as a coral reef. Reefs are constructed by coral polyp colonies that are connected by calcium carbonate. Most coral reefs are composed of stony corals, whose polyps cluster.

Coral belongs to the class Anthozoa, while sea anemones and jellyfish are members of the biological group Cnidaria. Contrary to sea anemones, corals develop tough carbonate exoskeletons that serve as the coral's support and defence. Most reefs survive in water that is warm, shallow, clear, bright, and agitated. The microbial and sponge reefs of the Cambrian were replaced by the first coral reefs during the beginning of the Early Ordovician, 485 million years ago.

Some of the most diverse ecosystems on the planet can be found on shallow coral reefs, which are also known as underwater rainforests. At least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates, and other cnidarians, have their home there despite taking up less than 0.1% of the ocean's surface, or roughly half the area of France. In ocean conditions with few nutrients, coral reefs thrive. Coral reefs can be found on a smaller scale in deep water and cold water, but they are most frequently seen at shallow depths in tropical environments.

Coral Reef in Danger

Because they are susceptible to ocean conditions, coral reefs have fallen by 50% since 1950. Excessive nutrients (nitrogen and phosphorus) pose a concern, as do rising ocean temperatures and acidification, overfishing (from methods like blast fishing and spearfishing using cyanide), the use of sunscreen, and damaging land-use practises including runoff and leaks (e.g., from injection wells and cesspools).

Coral | Coral Reef

Coral Reef Formation

The majority of coral reefs were created following the Last Glacial Period, when rising sea levels from melting ice flooded continental shelves. The majority of coral reefs are under 10,000 years old. The reefs expanded higher as towns grew, keeping pace with the sea level rise. Reefs that climbed too slowly could drown if there wasn't enough light. Coral reefs can also be found in the deep ocean, next to oceanic islands and atolls, distant from continental shelves. Most of these islands were formed by volcanic eruption deposits. Others originated from plate m's tectonic movement.

Coral Reef Material

Coral skeletons from largely unbroken coral colonies make up coral reefs, as the name implies. Aragonite is created as additional chemical components found in corals are absorbed into the calcium carbonate deposits. But shell pieces and the skeletal remains of coralline algae, like the green-segmented genus Halimeda, can strengthen the reef's resistance to storm damage and other hazards. Structures like Eniwetok Atoll exhibit these mixes.

Types of Coral Reef

Since Darwin named the three traditional reef formations—a fringing reef encircling a volcanic island, a barrier reef, and finally an atoll—scientists have discovered more reef varieties. While some sources only list three, Thomas and Goudie list the fringing reef, barrier reef, atoll, and table reef as the four "principal large-scale coral reef types," and Spalding et al. list the same five "main types" as well: the fringing reef, barrier reef, atoll, "bank or platform reef," and patch reef. ovements raised the bottom of the deep ocean.

Location of Coral Reef

According to estimates, coral reefs occupy 284,300 km2 (109,800 sq mi), or less than 0.1% of the ocean's surface. 91.9% of this total comes from the Indo-Pacific region, which includes the Pacific, Red Sea, Indian Ocean, Southeast Asia, and the Indian Ocean. 32.3% of that amount comes from Southeast Asia, and 40.8% from the Pacific region, which includes Australia. Reefs in the Atlantic and Caribbean make up 7.6%.

Although corals can be found in both temperate and tropical environments, only a region between roughly 30° N to 30° S of the equator experiences the formation of shallow-water reefs. At depths more than 50 metres, tropical corals cannot grow (160 ft). Few coral reefs can survive in water below 18 °C (64 °F), but the majority of coral reefs thrive at a temperature of 26–27 °C (79–81 °F). But reefs in the Persian Gulf can withstand summer temperatures of 38 °C (100 °F) and winter temperatures of 13 °C (55 °F). This ecosystem is home to 37 different species of scleractinian corals near Larak Island.

What's the difference between SPS and LPS corals?

LPS and SPS kinds then further split hard corals. Small Polyp Stony is also known as LPS, which stands for Large Polyp Stony. Both "S"s may alternatively stand for Scleractinian. Large Polyp Large polyp stony corals have fleshy bodies that expand with water to conceal the skeleton beneath.

Coral beauty

The coral beauty is a variety of vibrant fish that has no connection to coral. The two-spined angelfish, often referred to as the dusky angelfish or coral beauty, is a type of marine fish with ray-finned fins that is a member of the Pomacanthidae family. In the Indo-Pacific, they can be found.

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