coral reefs group 8

CORAL REEFSJulia Zapanta

Greg Saplagio III

CORAL REEFSOften called “rainforests of the sea”, they are one of the most diverse ecosystems on Earth. They occupy less than 0.1% (around 284,300 km2) of the world's ocean surface,

yet provide a home for 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, and other cnidarians.

They are most commonly found at shallow depths in tropical waters. Coral colonies thrive at 21-29OC, saline

environments, and clear waters.

LOCATION

Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and the Pacific) account for 91.9%.

CORAL TRIANGLEPHILIPPINES

TYPES OF CORAL REEFS

A fringing reef can take ten thousand years to form, and an atoll can take up to 30 million

years.

STRUCTURECorals are modular animals, anemone-like cylindrical polyps with prey-

capturing tentacles surrounding the opening or mouth. Most form sessile colonies supported on the tops of dead colonies and cease growth when

they reach the surface of the water

Coralline algae are important contributors to reef structure in those parts of the reef

subjected to the greatest forces by waves. These algae strengthen the reef structure by depositing limestone in sheets over the reef

surface.

ZONATIONGeneral abiotic conditions: Shallow waters, Temperature 21-29 C, Clear

low-nutrient waters, salinity 30-40 ppt.However, the coral reef can be divided into different zones with varying

abiotic characteristics and consequently different biological communities. The environmental factors responsible for these differences are wave action,

current direction and intensity, light intensity, etc.

Light sets the depth at which zooxanthellae can survive. Diversity is lowest at the crest near the surface, where only species such as massive pillar-shaped corals tolerant of intense or frequent disturbance of waves can

survive. Diversity increases with depth to a maximum of about 20 m. Then it decreases as light attenuates, eliminating shade-intolerant species.

Branching corals occur along the reef crest where abundant light drives photosynthesis needed to support rapid growth. Vigorous

wave energy clears sediment from the branching species that have no

biological means of sediment removal.

Further down the reef front, slower-growing hemispherical

corals (Mixed/Massive) are better suited for removing sediment

coming down the slope. In even deeper water, platelike colonies respond to continually

decreasing light levels. This shape places all the polyps on upward-facing surfaces, optimizing the

colony's ability to gather light—much like solar panels.

Adding to the productivity of the coral reefs are crustose, coralline algae, turf algae, macroalgae, sea grass, sponges, phytoplankton, and a large bacterial population. Coral reefs are among the most highly productive

ecosystems on earth.

This productivity and the varied habitats within the reef support a high diversity of life –thousands of kinds of invertebrates (some of which, such as sea urchins, feed on coral animals and algae), many kinds of

herbivorous fish that graze on algae, and hundreds of predatory species. Some of these predators such as the puffers and filefish, are corallivores, feeding on coral polyps. Others lie in ambush for prey in

coralline caverns. In addition, there is a wide array of symbionts such as cleaning fish and crustaceans that pick parasites and detritus from

larger fish and invertebrates.

SPECIES BIODIVERSITY

SOME ADAPTATIONS

SOME ADAPTATIONS

Threats to Coral Reefs

Natural and Human

REEFS WORLDWIDE ARE THREATENED

• 11% of reefs have been lost

• 16% of reefs severely damaged

• ~60% of studied reefs threatened by human activities

• No pristine reefs left

Threats to coral and coral reefs:• 1) Natural • 2) Anthropogenic –of human origin

Natural disturbances that affect corals and coral reefs?

• Hurricanes• Tsunamis• Volcanoes• Earthquakes• Predators &

competitors• Bleaching• Pathogens

Hurricanes

• Physical damage

• Destruction of other ecosystems upon which coral reefs depend

• Freshwater poisoning

• Smothering

Tsunamis

• Physical damage

• Possible disruption of reproduction and recruitment

• Erosion

Volcanoes

• Depends upon where volcano occurs

• Smothering and sedimentation

• Heat

Earthquakes

• Little direct impact

-coastal landslides

• Indirect impacts

-triggers tsunamis

Predators

• crown of thorns starfish

• snails• parrotfish• butterflyfish

Crown of Thorns Starfish

Coral-eating Snails

Competitors

• algae

• Loss of zooxanthellae

• causes – higher than usual

ocean temperature

– sharp changes in salinity

– heavy UV light exposure

Pathogens

• Diseases on the rise– new pathogens

(8+)– land pathogens

(Aspergillus)– occurring at all

depths–More

susceptible when stressed

Threats from Nature

• Unusually strong waves such as those from a hurricane

• Water temperature changes• Dramatic changes in saltiness of water• Predators, such as snails and crown of thorns

starfish• Overgrowth of algae

Threats to coral and coral reefs:• 1) Natural • 2) Anthropogenic –of human origin

Anthropogenic threats to coral

reefs:• Overfishing• Development• Mining and dredging• Recreation

Overfishing

• Ecological imbalance

Overfishing

• Ecological imbalance

Overfishing• Destructive fishing practices

Development

• Sediment smothering• Freshwater input• Pollutants & nutrients

(sewage, pesticides, fertilizer, heavy metals, pathogens)

Development

Development

Pollution

Power Plants

Mining for construction materials and dredging

• Destruction of reef structure• Stirs up sediment

Recreation

Anchors, boats, flippers, hands, feet•Kill animal tissue •Skeleton breakage

Threats from Humans

• Pollution– Sediments block light from zooxanthellae– Chemicals either poison corals or allow too much

algae to grow• Power plants– Filter water and kill fish and plankton– Releasing hot water kills organisms

More Threats from Humans

• Deforestation– Causes erosion which clouds the water– Burning of trees could be a factor in climate change

• Destructive fishing– Blasting with dynamite– Cyanide poison– Boats running aground, anchors– Overfishing

• interaction of natural changes & human activity

• multiple insults

Synergistic effects

Global climate change

• Reduced reef building• Increase in frequency and

intensity of hurricanes• Increases in bleaching• Increased in disease

A New Home

• Corals now have a choice of where to live

• Corals are very sensitive and are rapidly dying

• People are trying to help by creating artificial reefs

Arguments for Artificial Reefs• It can help

build or rebuild a reef

• It will increase fish populations by making new habitats

Arguments Against Artificial Reefs

• Moveable• Chemical leaking and

leaching into the ocean

• It does not increase fish populations but rather moves them to one location away from their natural habitat which makes them easier to catch

The Great Barrier Reef

Tubbataha Reef

It’s up to Us to Save Coral Reefs

           Be Responsible.