New Species of Black Corals

November 29, 2022

Syllabus: General Studies Paper 3

Scientists discover five new species of black corals living thousands of feet below the ocean surface near the Great Barrier Reef.

Australian scientists used the Schmidt Ocean Institute’s remotely operated vehicle – a submarine named SuBastian – to explore the Great Barrier Reef and Coral Sea.

About black corals:

Black corals can be found growing both in shallow waters and down to depths of over 26,000 feet (8,000 meters), and some individual corals can live for over 4,000 years.
Many of these corals are branched and look like feathers, fans or bushes, while others are straight like a whip.
Unlike their colourful, shallow-water cousins that rely on the sun and photosynthesis for energy, black corals are filter feeders and eat tiny zooplankton that are abundant in deep waters.
Black corals or antipatharians are colonial animals which are related to sea anemones and stony corals.
They are named for the colour of their stiff, black or brownish skeleton.
More than 150 species of black corals have been described. At least 14 species of black corals are currently known from Hawai’i.
Distribution: Black corals are found in all oceans, but are most common in deep water habitats of tropical and subtropical seas.
Black corals are carnivores.

Corals

Corals are marine invertebrates or animals not possessing a spine. Each coral is called a polyp and thousands of such polyps live together to form a colony, which grows when polyps multiply to make copies of themselves.

Types of corals: Hard coral and soft coral.

Hard corals, also called hermatypic or ‘reef building’ corals extract calcium carbonate (also found in limestone) from the seawater to build hard, white coral exoskeletons.
Soft coral polyps, however, borrow their appearance from plants, attach themselves to such skeletons and older skeletons built by their ancestors. Soft corals also add their own skeletons to the hard structure over the years and these growing multiplying structures gradually form coral reefs. They are the largest living structures on the planet.

The major types of coral reefs are:

Fringing Reefs: These are coral reefs that grow in shallow waters and in areas of low rainfall runoff, primarily on the leeward side. They closely border the coastline or are separated from it by a narrow stretch of water.
Barrier reefs: These grow parallel to the coast, but are separated from land by a lagoon. Example: Great Barrier reef, Queensland, Australia
Atolls: These grow surrounding (or partly surrounding) an island which then sinks relative to sea level. Example: Maldives consists of 26 atolls.

What is coral bleaching?

Bleaching happens when corals experience stress in their environment due to changes in temperature, pollution or high levels of ocean acidity.
Under stressed conditions, the zooxanthellae start producing reactive oxygen species, which are not beneficial to the corals. So, the corals expel the colour-giving zooxanthellae from their polyps, which exposes their pale white exoskeleton, giving the corals a bleached appearance. This also ends the symbiotic relationship that helps the corals to survive and grow.
Bleached corals can survive, depending on the levels of bleaching and the recovery of sea temperatures to normal levels.
But, severe bleaching and prolonged stress in the external environment can lead to coral death.

Threats

Coral Diversity

In the so-called true stony corals, which compose most tropical reefs, each polyp sits in a cup made of calcium carbonate.
Stony corals are the most important reef builders, but organ pipe corals, precious red corals, and blue corals also have stony skeletons.
There are also corals that use more flexible materials or tiny stiff rods to build their skeletons—the sea fans and sea rods, the rubbery soft corals, and the black corals.
The fire corals (named for their strong sting) are anthozoans, which are divided into two main groups.
The hexacorals have smooth tentacles, often in multiples of six, and the octocorals have eight tentacles, each of which has tiny branches running along the sides. All corals are in the phylum Cnidaria, the same as jellyfish.

Location of coral reefs:

Coral reefs are mainly found in tropical seas (30°N to 30°S )where the sea is shallow (less than 100m); and warm (usually between 25° and 29°C).
They are also found in cold waters (temperature as low as 4°C) at depths between 40m to 2000m.
Unlike tropical corals, they don’t need sunlight to survive and don’t have zooxanthellae living in their polyps.
They feed solely by capturing food particles from the surrounding water.
Example: They are found off the coast of Norway’s Røst Island,

In India, coral reefs are located in 7 regions:

Question: What are the corals? Highlights the physical conditions for their growth and also show the their location in India.