Coral encyclopaedia

28 Red Sea corals: hard and soft corals and anemones — symbiosis, bleaching science, and conservation

Source: Corals of the WorldTaxonomy: WoRMS / CoralBaseData: NOAA Coral Reef Watch

Coral is an animal, not a rock: each piece is a colony of thousands of polyps (1–3 mm) that secrete limestone. Zooxanthellae live with them in a complex mutualism. Dead coral is not “old stone” — it was breathing hours or years ago.

Filter:

Family Acroporidae

Acropora is the largest coral genus on Earth — more than 150 species. It is called a framework coral because it builds the main reef structure. It grows fastest among hard corals (3–15 cm/year) but is the most fragile in bleaching and crown-of-thorns outbreaks.

1 / 8

Jess · CC BY-NC 4.0

Florida Staghorn Coral

Acropora florida

NT — Near ThreatenedHard coral

Depth

1–25 m

Growth rate

5–15 cm/year

Range

Red Sea, Indian Ocean, western Pacific

Family

Acroporidae

English scientific description (Wikipedia)

The branch coral is a species of acroporid coral found in the southwest and northern Indian Ocean, the central Indo-Pacific, Australia, Southeast Asia, Japan and the East China Sea, Cook Islands and the oceanic west Pacific Ocean. It can be found in shallow reefs on the reef tops, walls and slopes to depths of 30 m.

Scientific notes (4)▼

1.Zooxanthellae — symbiotic algae in its tissues — supply about 90% of its food through photosynthesis
2.Bleaching is a heat signal — it expels zooxanthellae when temperature stays above 31°C for weeks
3.It is used in coral-gardening projects worldwide because it grows quickly
4.In major bleaching years (such as 1998 and 2016) 60–80% died in some areas

GBIF: 5184677

1 / 8

Robin White · CC BY-NC 4.0

Table Coral

Acropora cytherea

NT — Near ThreatenedHard coral

Depth

5–40 m

Growth rate

4–10 cm/year

Range

Widespread in the Indian Ocean, Pacific, and Red Sea

Family

Acroporidae

English scientific description (Wikipedia)

Acropora cytherea is a stony coral which forms horizontal table like structures. It occurs in the Indo-Pacific Ocean in areas with little wave action, favouring back reef environments from 3 to 20 m depth.

Scientific notes (4)▼

1.The table shape evolved to capture more sunlight in deeper water
2.A table colony can snap with a light touch — it looks sturdy but is brittle
3.They shelter dozens of small fish and crustacean species underneath
4.The largest recorded tables exceed 3 m across — often more than 50 years old

GBIF: 5184592

1 / 8

Sol Yoder · CC BY-NC 4.0

Pharaoh Coral

Acropora pharaonis

VU — VulnerableHard coral

Depth

2–20 m

Growth rate

4–8 cm/year

Range

Endemic to the Red Sea and Arabian Gulf

Family

Acroporidae

English scientific description (Wikipedia)

Acropora pharaonis is a species of acroporid coral that was first described by Milne-Edwards and Haime in 1860. Found in marine, tropical, reefs on slopes sheltered from wave action, it occurs at depths of between 5 and 25 m. It is classed as a vulnerable species on the IUCN Red List, and it has a decreasing population. It is common and found over a large area and is classified under CITES Appendix II.

Scientific notes (4)▼

1.A Red Sea endemic — it is not found in any other sea
2.It is a priority species in Saudi and Jordanian conservation programmes
3.Large colonies grow at 5–15 m on some of the finest reef slopes
4.Listed VU because of its small range plus rising heat stress

GBIF: 5184568

Family Merulinidae / Lobophylliidae (former Faviidae)

What was once Faviidae has been split into several families. These massive corals can live hundreds or thousands of years — a climate record carved into their skeletons.

1 / 8

Olivia Bañez · CC BY-NC 4.0

Maze Brain Coral

Platygyra daedalea

LC — Least ConcernHard coral

Depth

1–20 m

Growth rate

0.5–1.5 cm/year

Range

Red Sea, Indian Ocean, western Pacific

Family

Merulinidae

English scientific description (Wikipedia)

Platygyra daedalea, sometimes known as the lesser valley coral, is a colonial species of stony coral in the family Merulinidae. It occurs on reefs in shallow water in the Indo-Pacific region. It is a common species and the International Union for Conservation of Nature has assessed its conservation status as being of "least concern".

Scientific notes (4)▼

1.The maze surface area boosts zooxanthellae and photosynthetic efficiency
2.Some live more than 900 years — skeletons read like tree rings
3.More bleaching-resistant than Acropora — it can survive short heat events
4.It feeds at night when polyps emerge from the limestone to catch plankton

GBIF: 5184733

1 / 8

iNaturalist · CC BY 4.0

Star Coral

Favia stelligera

LC — Least ConcernHard coral

Depth

1–30 m

Growth rate

0.5–2 cm/year

Range

Widespread in the Red Sea, Indian Ocean, and Pacific

Family

Merulinidae

English scientific description (Wikipedia)

Goniastrea stelligera, commonly known as knob coral, is a species of stony coral in the family Merulinidae. It occurs in shallow water on the coast of East Africa and in the Indo-Pacific region. This is a common species of coral but it seems to be decreasing in abundance. The main threat it faces is from the destruction of its coral reef habitat, and it is also moderately susceptible to coral bleaching, so the International Union for Conservation of Nature has rated its conservation status as being "near threatened".

Scientific notes (4)▼

1.Each star on the surface is a polyp with its own mouth and tentacles
2.It spawns sexually in a synchronised night-time mass release of gametes
3.More tolerant of pollution and turbid water than delicate branching corals
4.Used as a water-quality indicator in environmental monitoring

GBIF: 2260124

Family Poritidae

The toughest and longest-lived corals. A single colony may live a thousand years or more. They form huge solid masses that are the backbone of many reefs.

1 / 8

iNaturalist · CC BY-NC 4.0

Massive Porites Coral

Porites lutea

LC — Least ConcernHard coral

Depth

0–25 m

Growth rate

0.8–1.2 cm/year

Range

Widespread across the Indian Ocean, Pacific, and Red Sea

Family

Poritidae

English scientific description (Wikipedia)

Porites lutea is a species of stony coral in the family Poritidae. It is found growing in very shallow water on reefs in the Indo-Pacific region. It sometimes forms "microatolls" in the intertidal zone and these massive structures have been used to study trends in sea levels and sea water temperature.

Scientific notes (4)▼

1.Colony age can be read by X-ray, like annual tree rings
2.Old masses hold a centuries-long record of climate, storms, and bleaching
3.Cliona sponges bore tiny holes in the surface — slow but lasting damage
4.Less heat-sensitive than many corals — a classic marker of old reef

GBIF: 5184758

1 / 8

Tom Heijnen · CC BY-NC 4.0

Column Porites

Porites columnaris

LC — Least ConcernHard coral

Depth

3–30 m

Growth rate

1–2 cm/year

Range

Red Sea, western Indian Ocean

Family

Poritidae

Clear columnar growth, sometimes a metre high, forming underwater stone thickets that shelter small reef fishes.

Scientific notes (3)▼

1.Tall columns mark low-current sites where corals compete upward for light
2.It bleaches in sequence — outer columns first, inner ones more sheltered
3.Dead old surfaces can be colonised by other coral species

GBIF: 5720616

Family Pocilloporidae

Branching corals with relatively fast growth. They shape shallow reef frameworks and host many larvae and small animals.

1 / 8

calebbergman · CC BY-NC 4.0

Cauliflower Coral

Pocillopora damicornis

NT — Near ThreatenedHard coral

Depth

0–25 m

Growth rate

2–8 cm/year

Range

Tropical worldwide — common in the Red Sea

Family

Pocilloporidae

English scientific description (Wikipedia)

Pocillopora damicornis is a widespread branching coral important for reef structure and coral reef ecology.

Scientific notes (3)▼

1.Often used in marine experiments on spawning and bleaching
2.Its larvae settle readily and help reconnect reef patches
3.It can take harsher conditions than Acropora, but it is not immune

GBIF: 2870930

1 / 8

ewoutknoester · CC BY-SA 4.0

Smooth Cauliflower Coral

Stylophora pistillata

NT — Near ThreatenedHard coral

Depth

0–40 m

Growth rate

2–6 cm/year

Range

Indian Ocean, Pacific, and Red Sea

Family

Pocilloporidae

English scientific description (Wikipedia)

Stylophora pistillata is a common branching coral in the Indo-Pacific, tolerant of a range of reef conditions.

Scientific notes (3)▼

1.It tolerates a wider temperature range than some Acropora species
2.Dense colonies shelter juvenile fishes
3.It is tracked in reef-health reports

GBIF: 2870939

Subclass Octocorallia

Unlike hard corals they do not make a solid limestone skeleton but flexible internal supports. They add colour and form to reefs. Each polyp has eight tentacles.

1 / 8

erinwoodward · CC BY-NC 4.0

Carnation Coral

Dendronephthya sp.

NE — Not EvaluatedSoft coral

Depth

5–60 m

Growth rate

Variable

Range

Red Sea, Indian Ocean, and Pacific

Family

Nephtheidae

Among the brightest reef animals — swollen trees in red, orange, purple, and pink. They inflate in current and shrink without it. No zooxanthellae; they filter plankton. They often cloak reef walls in vivid colonies.

Scientific notes (4)▼

1.They inflate and deflate with current — swell while feeding, shrink in slack water
2.They have no zooxanthellae — all food comes from filtering plankton
3.Bright colours come from pigments and defensive sclerites, not photosynthesis
4.Among the hardest aquarium species — they need strong, constant flow

GBIF: 2263423

1 / 8

Wikimedia Commons · CC BY-SA 3.0

Sea Fan / Gorgonian

Subergorgia mollis

LC — Least ConcernSoft coral

Depth

10–80 m

Growth rate

Variable

Range

Red Sea, Indian Ocean, and parts of the Pacific

Family

Subergorgiidae

English scientific description (Wikipedia)

Annella mollis is a species of soft corals belonging to the family Subergorgiidae. They live in areas in the Indo-West Pacific, around 12 to 18 meters deep, in lower reef slopes, on rocks and sand substrates.

Scientific notes (4)▼

1.A single network can span hundreds of square metres on reef walls
2.They host pygmy seahorses that camouflage in the branches
3.The flexible skeleton rides strong current — it sways instead of snapping
4.They grow slowly (2–3 cm/year) and take decades to reach full size

GBIF: 2262894

1 / 8

Wikimedia Commons · CC BY-SA 3.0

Leather Coral

Sarcophyton trocheliophorum

LC — Least ConcernSoft coral

Depth

1–20 m

Growth rate

Variable

Range

Widespread in the Red Sea, Indian Ocean, and western Pacific

Family

Alcyoniidae

English scientific description (Wikipedia)

Sarcophyton is a genus of soft corals in the family Alcyoniidae, commonly known as toadstool corals or mushroom soft corals. They are found in the Indo-Pacific region, including the Red Sea. Their distinctive toadstool or mushroom-like shape is formed by a stalk topped with a flat or wavy capitulum bearing polyps.

Scientific notes (4)▼

1.It secretes toxic terpenes that slow neighbouring hard coral and block settlement
2.It can drop polyps and resettle them — a defence and a way to spread
3.One of the easiest reef animals to culture — common in home coral tanks
4.Sarcophine compounds from it are studied for medical anti-cancer research

GBIF: 5185182

Order Actiniaria

Animals despite their plant-like look — they belong to the same group as corals (Cnidaria). Their tentacles sting passing fishes, yet they also host clownfish in a famous mutualism.

1 / 8

momaz · CC BY-NC 4.0

Bubble-tip Anemone

Entacmaea quadricolor

NE — Not Evaluated

Depth

1–40 m

Growth rate

Variable

Range

Wide range in the Red Sea, Indian Ocean, and western Pacific

Family

Actiniidae

English scientific description (Wikipedia)

Bubble-tip anemone is a species of sea anemone in the family Actiniidae. Like several anemone species, E. quadricolor can support several anemonefish species, and displays two growth types based on where they live in the water column, one of which gives it the common name, due to the bulbous tips on its tentacles.

Scientific notes (4)▼

1.Tentacles hold nematocysts that stun passing fishes at once
2.Clownfish mucus protects them from the sting — the mechanism is still not fully known
3.It can crawl centimetres a day toward better light or a better holdfast
4.One anemone can host several clownfish pairs in side groups

GBIF: 4339208

1 / 8

David Witherall · CC BY 4.0

Magnificent Sea Anemone

Heteractis magnifica

NE — Not Evaluated

Depth

1–20 m

Growth rate

Variable

Range

Red Sea, Indian Ocean, and western Pacific

Family

Stichodactylidae

English scientific description (Wikipedia)

Radianthus magnifica, also known as magnificent sea anemone or Ritteri anemone, is a species of sea anemone in the family Stichodactylidae that is native to the Hawaii, USA, Indo-Pacific.

Scientific notes (4)▼

1.They can live more than 100 years — among the longest-lived of these animals
2.They release holothurin-like toxins to deter predators
3.Prey is digested in the internal gastrovascular cavity
4.The partnership with Amphiprion goes back about 50 million years in the fossil record

GBIF: 5184183

Coral Bleaching: Science & Solutions

Bleaching is not instant death — it is a distress call. Coral expels its symbiotic zooxanthellae under heat or chemical stress and turns white. If stress ends within weeks, it can recover; if not, it starves.

Coral Bleaching Phenomenon

Symbiodiniaceae expulsion

NE — Not EvaluatedHard coral

Depth

all depths

Growth rate

Variable

Range

Worldwide — major events: 1998, 2010, 2015–2016, 2022–2023

Family

Marine ecology

Zooxanthellae (Symbiodinium and allies) are single-celled algae in coral tissue supplying 70–90% of its food. Above a heat threshold (often 1°C over the usual maximum) they harm the coral and are expelled. The white skeleton is limestone with no living tissue.

Scientific notes (5)▼

1.2016 saw the worst documented bleaching — more than 50% of Australia’s Great Barrier Reef bleached
2.The Red Sea resists bleaching better than most seas after millennia of heat selection
3.Coral-gardening projects try to restore reefs by planting fragments of resistant species
4.NOAA issues Coral Bleaching Watch alerts when sea temperature exceeds the threshold
5.Diver awareness: do not touch coral, stand on it, or dump sand over it

Coral safety rules for divers

⚠Do not touch any coral — one fingerprint can kill years of growth

⚠Do not stand on reefs — even if they look like dead rock

⚠Do not stir sand or silt over reefs — they smother underneath

⚠Do not use chemical sunscreen — oxybenzone is toxic to coral

⚠Stay at least 1.5 m above coral heads

⚠Report bleaching to the dive centre or the relevant environmental authority

Fish Invertebrates Sea conditions for diving Trainee reviews