Threats of Reefs By mariah, sara and emma

What are reefs?

Coral Reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral Reefs are built by colonies of tiny animals found in marine waters that contain few nutrients.

This photo shows 2 scuba divers, surrounded by the gorgeous coral reefs and the beautiful inhabitants.


Global Warming on the coral reefs is quite clear and undisputed scientifically. With a mere 1 to 2 degree rise in temperatures, the colourful plant part gets booted out, leaving the coral appearing bleached. The animal part is then left to starve to death if the heat persists. Exactly why this breakdown happens is a mystery that science is trying to solve.

Even in normal conditions, coral lives on the edge. Under still conditions with no currents and cloudless skies, the algae start to get stressed if they sit for even a few weeks in water that is 1 to 2 degrees above average. The algae's ability to process sunlight into nutrients is impaired. The alliance gets tense and the algae are ejected. It is not clear how the polyp ejects the algae.

Over time even human interruptions can impact the reefs immensely, climate change, rubbish and infrastructure hinder the growth and development of coral reefs. Even others like; Shipping accidents, oil spills and tourist visits.

This is a heavy oil spill off an Australian Coast.


Coral reefs are dying around the world. Human impact on coral reefs is significant. Coral reefs are dying around the world. In particular, coral mining, pollution (organic and non-organic), over fishing, blast fishing and the digging of canals and access into islands and bays are serious threats to these ecosystems.

Coral bleaching across the oceans.

The devastating thing about the coral dying is simply, that fish will also start dying also. The corals are habitats for millions of different species of not only fish but crabs and even small sharks.


Heron Island is a coral cay located near the Tropic of Capricorn in the southern Great Barrier Reef, 80 km north-east of Gladstone, Queensland, Australia, and 460 km north-north-west of the state capital Brisbane.

Situated on the island is a research center and a 5 star resort. The building of these structures would have harmed land species and even the coral reefs surrounding the island. Pollution in the building of these structures would have intensely risen, over the years, and polluted the air, harming the corals, through the temperature rise of the water.

The building structures of Heron Island nearly inhabited the complete island

The living organisms in the ocean, such as coral reefs survive and thrive using the food web.

The main producer of the ocean is the Algae, making the chain for the survival of the fittest make its way to the highest in the chain, the consumers, like Whales and sharks.


When the food chain is disrupted or disturbed the chain could possibly and completely fall apart. When the population of coral reefs and plankton start to die and the numbers will drop. Causing population drops of all species of consumers will have less food to consume, collapsing the food web entirely.


Coral colonies grow in shallow water and are often heavily branched. In contrast, deeper water corals often grow in sheets or plates. These flattened forms allow for more efficient use of lower light intensities in deeper waters. The growth rate of corals and coral reefs depends on factors such as light intensity, water temperature, salinity, turbidity, food availability, competition of space and predator access.

Diagram and colour description of coral growth

Coral Reproduction

Corals reproduce sexually by either internal or external fertilization. The reproductive cells are borne on membranes, that radiate inward from the layer of tissue that lines the stomach cavity.

Internally fertilized eggs are brooded by the polyp from days to weeks. Free swimming larvae are released into the water and settled within hours.

Externally fertilized eggs are developed while adrift. After a few days, fertilized eggs develop into free swimming larvae. Larvae settles within hours to days.

Reproduction process.


Created with images by Pexels - "water corals underwater" • lpittman - "divers underwater ocean"

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