CORAL REEFS SIMPLIFIED
JAYACHANDRAN KS
I am the largest living structure on the planet!
though I look little !!!
I am one of the oldest ecosystems on Earth !
though I look young !!
We are one of the most diverse and productive communities on Earth !
We occupy less than 1% of the Earth’s surface, but harbor 25% of biodiversity !
I am a coral reef
But first please understand the difference between coral polyp, coral and a coral reef !!
Coral polyp
Coral reef
coral
Coral polyp
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 (stinging cells called nematocysts) no skeleton inside the polyp
Coral polyp
coral
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 IndoPacific 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) skeleton, made of a protein called gorgonin
flexible
A coral reef
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
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
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.
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
General shallowness Lots of islands – larger continental shelf Absence of large river mouths
1. Gulf of Kutch fringing type extreme environmental conditions - a large range in temperature and salinitythe reefs are relatively less developed and harbor a low biodiversity high industrial development - large scale of mortality 2. Lakshadweep Islands Atolls health of the reefs is excellent
3. Gulf of Mannar Fringing 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.
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 coral polyps sex of a coral - polyp and the colony level (gonochoric or hermaphrodite)
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.
Zygote development broadcaster - zygote that is formed after fertilization will develop into a larva which is known as a planula in WATER brooder - planula will develop
MATERNAL POLYP
WITHIN THE
and will later be released into
the 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.