Coral

Biology Of ---

Submitted By – Puspendu Samanta M.F.Sc. 1st Year. 20013-14

Submitted To – Prof.S.K.Das.

Dept Of Fisheries Resource Management

FRM- 503

Introduction :-

• Corals are marine invertebrates in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps".

• The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

• The Muslim polymath Al -Biruni (d. 1048) classified sponges and corals as animals arguing that they respond to touch.

• Nevertheless, people believed coral to be a plant until the 18th century, when William Herschel used a microscope to establish that coral had the characteristic thin cell membranes of an animal .

What Is Polyp ?

• The coral head is the familiar visual form of a single organism, it is actually a group of many individual , yet genetically identical , multicellular organisms known as polyps.

• Polyps are usually a few millimeters in diameter, and are formed by a layer of outer epithelium and inner jellylike tissue known as the mesoglea.

• They are radially symmetrical , with tentacles surrounding a central mouth, the only opening to the stomach or coelenteron, through which food is ingested and waste expelled.

Anatomy of a coral polyp

Coral Polyp

Scientific Classification :-

Kingdom: Animalia. Phylum: Cnidaria. Class: Anthozoa. Subclasses: Alcyonaria ,Zoantharia. Orders: Alcyonacea ,Helioporacea , Antipatharia ,Corallimorpharia,

Scleractinia ,Zoanthidea. - Ehrenberg, 1831

Feed & Feeding :-

• Most reef-building corals have a mutually beneficial relationship with a microscopic unicellular algae called zooxanthellae (also known as Symbiodinium) that lives within the cells of the coral's gastrodermis.

• As much as 90 % of the organic material the algae manufacture photosynthetically is transferred to the host coral tissue.

• In addition to the symbiotic relationship with algae, most corals capture and consume live prey ranging from microscopic zooplankton to small fish, depending on coral size.

• Using its tentacles that extend outside it body, the coral with utilize it nematocysts, or stinging cells, to stun and kill its prey before passing it to its mouth. Once the food has been digested, the waste is expelled from the same opening.

Symbiotic relation between Corals and symbiodinium.

Light and confocal images ofSymbiodinium cells in hospite

(livingin a host cell).

Habit & Habitat :-

• Corals can be found throughout the oceans, from deep, cold waters to shallow, tropical waters.

• Shallow coral reefs have optimal growth rates in warm water ranging from 70–85° F (21–29° C).

• Coral reefs can be found at depths exceeding 91 m (300 ft), but reef-building corals generally grow best at depths shallower than 70 m (230 ft).

• The most prolific reefs occupy depths of 18–27 m (60–90 ft), though many of these shallow reefs have been degraded.

• Corals also need salt water to survive, so they also grow poorly near river openings with fresh water runoff.

• Other factors influencing coral distribution are availability of hard-bottom substrate, the availability of food such as plankton, and the presence of species that help control macro algae, like urchins and herbivorous fish.

Distribution :-

• The warm water corals are found in the tropics (between 30°N and 30°S) in areas where the water is clear and over 18°C. The maximum depth for warm water corals is generally around 60 meters. 

• Some species of coral are found in all oceans of the world. • Cold water corals have been found in places as Antarctica,

Australia, Canada, Ecuador, Japan, New Zealand, Europe and the United States.

Types of

Corals

Hermatypic Corals :-

• Hermatypic corals in the order Scleractinia are stony corals that build reefs.

• They mostly obtain their energy requirements from zooxanthella(Symbiodinium), symbiotic photosynthetic microalgae.

• They secrete calcium carbonate to form a hard skeleton.

• This group includes reef-building corals (scleractinians), sea anemones and zoanthids.

• Hermatypic genera include Scleractinia, Millepora, Tubipora and Heliopora.

• In the Caribbean alone, at least 50 species of uniquely structured hard coral exist. Well -known types include :-

Brain corals grow to 1.8 meters (6 ft) in width. Acropora and staghorn corals grow fast and large,

and are important reef-builders. Staghorn coral displays large, antler-like

branches, and grows in areas with strong surf. Pillar coral forms pillars which can grow to 3

meters (10 ft) in height. Leptopsammia, or rock coral , appears almost

everywhere in the Caribbean.

Pillar Coral

Ahermatypic Corals :-

• Ahermatypic corals have no zooxanthella (Symbiodinium).

• They include corals in subclass Alcyonaria, as well as some species in order Anthipatharia (black coral , Cirripathes, Antipathes).

• Ahermatypic corals, such as sea whips, sea feathers, and sea pens, are also known as soft corals.

• Unlike stony corals, they are flexible, undulating in the current, and often are perforated, with a lacy appearance.

• Their skeletons are proteinaceous, rather than calcareous.

• Soft corals are somewhat less plentiful (in the Caribbean, twenty species appear) than stony corals.

Fan Coral

Sea PenSea Feathers

Reproduction

• Corals can be both gonochoristic (unisexual ) and hermaphroditic, each of which can reproduce sexually and asexually.

• Reproduction also allows coral to settle in new areas.

Sexual

Corals predominantly reproduce sexually. About 25% of hermatypic corals (stony corals)

form single sex (gonochoristic) colonies, while the rest are hermaphroditic.

Sexual reproduction is the more common method and can be performed in two ways: 1. Broadcast spawning .

2. Brooding.

1.Broadcasters :-

About 75% of all hermatypic corals "broadcast spawn" by releasing gametes —eggs and sperm—into the water to spread offspring.

The gametes fuse during fertilization to form a microscopic larva called a planula, typically pink and elliptical in shape.

A typical coral colony forms several thousand larvae per year to overcome the odds against formation of a new colony.

2.Brooders :-

Brooding species are most often ahermatypic (not reef-building) in areas of high current or wave action.

Brooders release only sperm, which is negatively buoyant, sinking on to the waiting egg carriers who harbor unfertilized eggs for weeks.

After fertilization, the corals release planula that are ready to settle.

Asexual

• Within a coral head, the genetically identical polyps reproduce asexually, either via gemmation (budding) or by longitudinal or transversal division.

Budding :-

• It involves splitting a smaller polyp from an adult.• As the new polyp grows, it forms its body parts.

The distance between the new and adult polyps grows, and with it, the coenosarc (the common body of the colony).

• Budding can be: Intratentacular—from its oral discs, producing

same-sized polyps within the ring of tentacles.Extratentacular—from its base, producing a

smaller polyp.

Division :-

• Longitudinal division :– It begins when a polyp broadens and then divides its

coelenteron, analogous to splitting a log along its length. The mouth also divides and new tentacles form. The two "new" polyps then generate their missing body parts and exoskeleton.

• Transversal division :– Occurs when polyps and the exoskeleton divide

transversally into two parts. This means one has the basal disc (bottom) and the other has the oral disc (top), similar to cutting the end off a log. The new polyps must separately generate the missing pieces.

Colony Division :-

• Whole colonies can reproduce asexually, forming two colonies with the same genotype.

• Fission occurs in some corals, especially among the family Fungiidae, where the colony splits into two or more colonies during early developmental stages.

• Bailout occurs when a single polyp abandons the colony and settles on a different substrate to create a new colony.

• Fragmentation involves individuals broken from the colony during storms or other disruptions. The separated individuals can start new colonies.

Reefs

• The hermatypic, stony corals are often found in coral reefs, large calcium carbonate structures generally found in shallow, tropical water.

• Reefs are built up from coral skeletons, and are held together by layers of calcium carbonate produced by coralline algae.

• Reefs are extremely diverse marine ecosystems hosting over 4,000 species of fish, massive numbers of cnidaria, mollusks, crustacea, and many other animals.

Economic

Value

of

Corals

Jewelry

• Corals have many colors give it appeal for necklaces and other jewelry.

• Intensely red coral is prized as a gemstone.• Sometimes called fire coral , it is not the same as

fire coral .• Red coral is very rare because of overharvesting.

Red Coral

Reef of Red Coral

Red Coral jewelry

Medicine

• In medicine, chemical compounds from corals are used for cancer, AIDS, pain, and other uses.

• Coral skeletons, e.g. Isididae are also used for bone grafting in humans.

• Coral Calyx, known as Praval Bhasma in Sanskrit, is widely used in traditional system of Indian medicine as a supplement in the treatment of a variety of bone metabolic disorders associated with calcium deficiency.

These are all Coral Skeleton used in

medicinal purposes

Construction

• Coral reefs on land provide lime for use as building blocks ("coral rag").

• Coral rag is an important local building material in places such as the East African coast.

Coral rag Houses

Climate Research

• The annual growth bands in deep sea bamboo corals (Isididae) and others may be among the ocean's first organisms to display the effects of ocean acidification. They produce growth rings similar to those of trees, and can provide a view of changes in the condition in the deep sea over time.

• It underlie high-resolution records of past climatic and environmental changes using geochemical techniques.

• Certain species form communities called microatolls, which are colonies whose top is dead and mostly above the water line, but whose perimeter is mostly submerged and alive. Average tide level limits their height. By analyzing the various growth morphologies, microatolls offer a low resolution record of sea level change.

Aquaria

• The saltwater fishkeeping hobby has increasingly expanded, over recent years, to include reef tanks, fish tanks that include large amounts of live rock on which coral is allowed to grow and spread.

• The most popular kind of coral kept is soft coral , especial lyzoanthids and mushroom corals, which are especially easy to grow and propagate in a wide variety of conditions, because they originate in enclosed parts of reefs where water conditions vary and lighting may be less reliable and direct.

Coral Aquaria

Aquaculture

• Coral aquaculture, also known as coral farming or coral gardening, is the cultivation of corals for commercial purposes or coral reef restoration.

• Aquaculture is showing promise as a potentially effective tool for restoring coral reefs, which have been declining around the world.

• Coral seeds are grown in nurseries then replanted on the reef.

• Coral is farmed by coral farmers who live locally to the reefs and farm for reef conservation or for income.

• It is also farmed by scientists for research, by businesses for the supply of the live and ornamental coral trade and by private aquarium hobbyists.

Status &

Threats

• Coral reefs are under stress around the world.• In particular, coral mining, agricultural and

urban runoff, pollution (organic and inorganic), overfishing, blast fishing, disease, and the digging of canals and access into islands and bays are localized threats to coral ecosystems.

• Broader threats are sea temperature rise, sea level rise and pH changes from ocean acidification, all associated with greenhouse gas emissions.

• In 1998, 16% of the world's reefs died as a result of increased water temperature.

• General estimates show approximately 10% of the world's coral reefs are dead.

• About 60% of the world's reefs are at risk due to human-related activities.

• The threat to reef health is particularly strong in Southeast Asia, where 80% of reefs are endangered.

• Over 50% of the world's coral reefs may be destroyed by 2030; as a result, most nations protect them through environmental laws.

• In the Caribbean and tropical Pacific, direct contact between ~40–70% of common seaweeds and coral causes bleaching and death to the coral via transfer of lipid-soluble metabolites.

• Water temperature changes of more than 1–2 °C (1.8–3.6 °F) or salinity changes can kill some species of coral .

• Under such environmental stresses, corals expel their Symbiodinium; without them coral tissues reveal the white of their skeletons, an event known as coral bleaching.

Picture of Coral bleaching

Protection

& Suggestion

• Marine Protected Areas (MPAs), Biosphere reserves, marine parks, national monuments world heritage status, fishery management and habitat protection can protect reefs from anthropogenic damage.

• Many governments now prohibit removal of coral from reefs, and inform coastal residents about reef protection and ecology. While local action such as habitat restoration and herbivore protection can reduce local damage, the longer-term threats of acidification, temperature change and sea-level rise remain a challenge.

• To eliminate destruction of corals in their indigenous regions, projects have been started to grow corals in non-tropical countries.

Last Note • At last we can say that corals are now in great danger. If we don’t

take any management measures for it, in future they will be vanished surely.

• Marine protected areas may protect biodiversity and maintain fish stocks for protecting corals is also useful.

• Diversification of local economies may be effective in reducing pressures on coral reefs.

• Tourism brings new pressures which must also be managed.• Coral reefs contain diverse fish and invertebrate assemblages.

– This makes them valuable, but difficult to manage.• Coral reefs are mainly found in the poorest areas of the world.

– This makes them prone to over-exploitation.

Reference• Jones, O.A. and R. Endean. (1973). Biology and Geology of

Coral Reefs. New York, USA: Harcourt Brace Jovanovich. pp. 205–245. ISBN 0-12-389602-9.

• Squires, D.F. (1959). "Deep sea corals collected by the Lamont Geological Observatory. 1. Atlantic corals". American Museum Novitates 1965: 1–42.

• The Greenpeace Book of Coral Reefs.

• Veron, J.E.N. (2000). Corals of the World. Vol 3 (3rd ed.). Australia: Australian Institute of Marine Sciences and CRR Qld Pty Ltd. ISBN 0-642-32236-8.

• Gulko, David (1998). Hawaiian Coral Reef Ecology. Honolulu, Hawaii: Mutual Publishing. p. 10. ISBN 1-56647-221-0.

THANK

YOU- For your kind attention