Biology & STATUS oF CoRAl REEFS

SUBMITTED TO:DR. S.K.ROUT DEPT. OF AEM

SUBMITTED BY:

ASIK IKBAL

B.F.SC 2ND YEAR

FS-06/13

AEM-216

What is a “coral reef” ?Biological (“coral community”)

Organic, BiogenicCoral and Algal communitiesMostly “hermatypic” corals, algae, and other

sessile animalsGeological features (“reef”)

CarbonateIn situ build-upTopographic reliefWave resistantCemented, consolidated

Corals Class Cnidaria Hermatypic (hard)

corals contain symbiotic algae

Up to 500 spp. at some sites.Individual animals are called polyps

Several polyps make up a colony

Corals are closely related to jellyfish and sea anemones—they all contain stinging cells called nematocysts.

Darwin’s theory starts with a volcanic island which becomes extinct.

As the island and ocean floor subside, coral growth builds a fringing reef, often including a shallow lagoon between the land and the main reef. 

As the subsidence continues, the fringing reef becomes a larger barrier reef further from the shore with a bigger and deeper lagoon inside.

Ultimately, the island sinks below the sea, and the barrier reef becomes an atoll enclosing an open lagoon.

Darwin’s Theory of corals formation

Coral reproduction Corals are capable of both sexual and asexual reproduction. In addition to

the splitting of individual polyps, coral colonies can reproduce asexually by fragmentation. This usually occurs as a result of storm damage, when coral colonies can be broken into pieces and the pieces may be scattered. If the coral pieces do not become covered with sand, they may be able to resume growth and form a new colony. This is most common in the branching corals like elkhorn and staghorn corals.

All corals are capable of sexual reproduction, although the reproductive strategy varies with species. Some corals are hermaphroditic, where individual polyps contain both male and female reproductive organs. Others are gonochoric, where polyps are either male or female. Some corals release eggs and sperm into the water column and the eggs are fertilized externally—this is called BROADCAST SPAWNING. Other corals keep the eggs inside the polyps and they are fertilized internally and develop into larvae inside the mother polyp. This strategy is referred to as BROODING.

BROADCAST SPAWNING

BROODING

Building the reefCaCo3 addition - CaCo3 loss = AccumulationReef-building corals require clear, warm water

Shallow areasMost reefs are between 26° N and S latitude

There are corals found off Alaska and other cold waters, but they grow very slowly and do not form reefs.Environmental requirements: Physical environment

Temperature of 25-31oC (limited Northwards by the 18oC minimum isotherm)

Salinity of 34-37 ppt Biological environment

Oligotrophic, highly stratified water column

Types of Coral Reefs

Atoll Reef- extends all around a lagoon without a central island.* when an island sinks below the ocean’s surface.

Fringing Reef- directly attached to shore.* grow up to the edge of the shore.

Barrier Reef- separated from mainland by lagoon.* only grow when there is a change of sea level on the coast adjacent from it.* grow where land is sinking faster in the water.

A small atoll in the Maldives

Inhabited cay in the Maldives

This map shows areas of upwelling in red. Coral reefs are not found in

coastal areas where colder and nutrient-rich upwellings occur.

Boundary for 20 °C isotherms. Most corals live within this boundary. Note the cooler

waters caused by upwelling on the southwest coast of Africa

and off the coast of Peru.

Coral reef distribution

Location of Coral reef

Examples The Great Barrier Reef- Queensland,

Australia; the largest coral reef system

The Belize Barrier Reef- along the coast of Belize down to the Bay Islands of Honduras; second largest coral reef system

The Red Sea Coral Reef- coast of Egypt and Saudi Arabia

Pulley Ridge- Florida; deepest photosynthetic coral reef

The New Caledonia Barrier Reef- length of about 1500km

The Great Barrier Reef is on the northeastern coat of Australia

The Belize Barrier Reef

Coral diversity patterns

Threats to coral reef systems

OverpopulationBioerosionUnsustainable

fisheriesCoastal

developmentGlobal climate

change

Ecosystem effects of fisheries

Removal of predatorsRemoval of algal grazersChange in dominance

Californian Sea OttersUrchinsCrown of Thorns starfish “COTS”

(Acanthaster planci)Changes in size frequency of animals

Terrestrial impacts

PollutionSewageAgricultureAquacultureRubbish

SedimentationEutrophication

Construction on reef flats

Coral miningMangrove

destruction

Impacts of tourismTerrestrial developmentLand reclamation and creation of

beachesMangrove removalSand on reef flat

BoatsAnchorsDiver/snorkeller impacts and fish feedingSewageHarbour dredging

Human impacts on coral reefs

OverfishingSedimentationNutrient enrichmentChemicals/oilPhysical damage

(anchors, fishing, groundings)

ConclusionCoral reefs form some of the world's most productive ecosystems, providing complex and varied marine habitats that support a wide range of other organisms. Coral reefs deliver ecosystem services to tourism, fisheries and coastline protection. Coral reefs protect shorelines by absorbing wave energy, and many small islands would not exist without their reefs to protect them. So in this time the protection of coral reefs is highly importance. Biosphere reserve, marine park, national monument and world heritage status can protect reefs.

References

www.google.com/wikipediawww.slideshare.net

THANK YOU