coral reefs simplified

8/8/2019 CORAL REEFS SIMPLIFIED

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CORAL REEFSSIMPLIFIED

JAYACHANDRAN KS


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I am one of

the oldest

ecosystemson Earth !

though I look

young !!


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We occupy lessthan 1% of the

Earths surface,

but harbor 25% of

biodiversity !


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I am acoral reef

But first please

understand the

difference between

coral polyp, coral and

a coral reef !!


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Coral

polypcoral

Coral

reef


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an animal that belongs to the phylum cnidaria

radially symmetric, which means that they are

the same all the way around, 360 degrees!

built like sacs with a hole in one end that

is surrounded by stinging tentacles (stingingcells called nematocysts)

no skeleton inside the polyp

Coral

polyp


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Coral

polyp


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2 MAIN TYPES - different skeletal structures

the hard corals (stony corals, or scleractinians) -

rigid calcium carbonate skeletons

major reef-building species

cold water temperature - Caribbean species and Indo-Pacific

three types of growth forms:

massive forms such as brain corals

encrusting forms like the star corals

branching forms

growth forms represent adaptations to different

environmental conditions.

the soft corals (gorgonians or octocorals) - flexible

skeleton, made of a protein called gorgonin

coral


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simply a structure in the shallow parts of the ocean

that serves as a substrata to animals and plants.

a million of these individual coral polyp shells all

stuck one on top of the other

When coral polyps die, new ones land and grow right

on top

A coral reef


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EVOLUTION

PORIFERA -------- PLATYHELMINTHES

Middle triassic - Scleractarians appeared from some

unknown origin.

Late Triassic - Scleractarian had begun to contruct

reef systems in the nutrient poor zones.

Scleratarians were major reef builders for the rest of

Mesozoic and Cenozoic.

The evolutionary pattern amongst the corals have not

yet been established

since the differences in morphology have been a result

of environmental alteration


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Distribution

tropical and subtropical oceans

generally within 30 degrees N and 30 degrees S

latitudes

a. Western Atlantic reefs include these areas:

Bermuda, the Bahamas, the Caribbean Islands,

Belize, Florida, and the Gulf of Mexico

b. The Indo-Pacific ocean region extends from the

Red Sea and the Persian Gulf through the Indian

and Pacific oceans to the western coast of

Panama.


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Why these areas alone ?

1.Shallow waters (> 100m ) sunlight

penetration

2.Clear water

3.Low salinity

4.warm ocean temperatures western

sides of oceans (warm currents

5.strong wave action - waves carry

food, nutrients, and oxygen to the

reef; distribute coral larvae


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General shallowness

Lots of islands larger

continental shelf

Absence of large river mouths


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1. Gulf of Kutch

fringing typeextreme environmental conditions - a

large range in temperature and salinity-

the reefs are relatively less developed

and harbor a low biodiversity

high industrial development - large

scale of mortality

2. Lakshadweep Islands

Atollshealth of the reefs is excellent


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3. Gulf of MannarFringing reefs

northern and southern ends of the chain

are partially degraded due to human

activities

Gulf of Mannar Biosphere reserve

4. Andaman and Nicobar Islands

fringing reefs

healthy reefs with a large biodiversity.


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The Story of a Coral's Life Cycle

Reproduction asexual and sexual

Sexual maturity varies

Massive hard corals such as Brain corals - 8 years

Branching corals 5 years

Coral polyp male, female (gonochoric) or hermaphrodite

Coral colony - made up of many of these individual coralpolyps

sex of a coral - polyp and the colony level (gonochoric

or hermaphrodite)


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The Story of a Coral's Life Cycle

Two major contrasting modes of reproduction

Fertilization external or internal

broadcaster

A coral that releases all of its gametes into the water

AT SPECIFIC TIMES so that fertilization occurs

externally

co-ordinate this timing by the lunar (moon) cycle and by

the light-dark regime

brooder

Internal fertilization - mature sperm swim through the

water and find a polyp of the same species to fertilize

the eggs internally.


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Zygote development

broadcaster - zygote that is formed afterfertilization will develop into a larva which is

known as a planula inWATER

brooder - planula will developWITHIN THE

MATERNAL POLYP and will later be released intothe water column.

planulae

limited powers of locomotion and drift with the

plankton.

preyed upon by many reef invertebrates and by fish

survivors will settle on the bottom to become polyps

and start a new colony.

coral reefs simplified

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