Coral Reef

Known as “rainforests of the sea,” coral reefs cover less than 1% of the ocean but are home to almost 25% of all known marine species

Coral polyps are tiny, soft-bodied organisms related to sea anemones and jellyfish. At their base is a hard, protective limestone skeleton called a calicle, which forms the structure of coral reefs. Reefs begin when a polyp attaches itself to a rock on the sea floor, then divides, or buds, into thousands of clones. The polyp calicles connect to one another, creating a colony that acts as a single organism. As colonies grow over hundreds and thousands of years, they join with other colonies and become reefs. Some of the coral reefs on the planet today began growing over 50 million years ago.

Coral polyps are actually translucent animals. Reefs get their wild hues from the billions of colorful zooxanthellae algae they host. When stressed by such things as temperature change or pollution, corals will evict their boarders, causing coral bleaching that can kill the colony if the stress is not mitigated..

Coral reefs grow very slowly, at an average rate of just two centimeters per year

If you find a broken piece of coral on the beach, you can see its hard shell, which is actually an animal called a polyp. It is the cluster of these polyps growing together that gives coral reefs their shape

Coral reefs seem to grow best where there are stronger currents and wave patterns. Scientists believe that this is because stronger currents and waves deliver more food for the marine ecosystem.

Coral reefs help to improve the quality of the surrounding water. They do this by filtering out things floating in the ocean, which leads to cleaner water.

Coral reefs help stabilize the sea bed, helping seagrass, seaweed, and other marine plants to survive. These plants lessen the impact of storms and help prevent the ocean bed from being washed out. They also provide food and protection for a broad variety of marine animals. Fish, manatees, dugongs, and countless other species feed and raise their offspring there.

Though corals are animals, they do rely on photosynthesis to survive. But the coral polyps aren't doing the actual photosynthesizing. Microscopic algae, or zooxanthellae, live within the cells lining the digestive cavity of the polyp. As much as 90 percent of the energy a polyp needs comes from this symbiotic relationship. The other 10 percent comes from hunting the polyp does by extending its tentacles to catch prey.

Along many reefs, spawning occurs as a mass synchronized event, when all the coral species in an area release their eggs and sperm at about the same time. The timing of a broadcast spawning event is very important because males and female corals cannot move into reproductive contact with each other.

Scientists predict that we will lose 90 percent of coral reefs globally by the year 2050, due to global warming – even if we achieve the Paris Agreement targets.

In the last 30 years, we've lost 50 percent of corals globally.

Fifty percent of the Great Barrier Reef has died in the last two years alone, due to coral bleaching – in a trend mirrored by coral reefs around the world.

According to UNESCO, by 2050 warming will exceed the ability of coral reefs to survive at most World Heritage sites around the world.

The twin threats to coral reefs are coral bleaching, and ocean acidification - both are ultimately linked to anthropogenic (human-induced) high CO2 levels in the Earth’s atmosphere.

Feather stars, those 200-million-year-old creatures that look like something straight from the pages of a Dr. Seuss book, may be the next kings of the reef. The plant-like animals seem to be thriving, even as other reef dwellers, like corals, are dying from warmer waters linked to climate change.

Feather stars can purposely drop off an arm or two when threatened. The dropped arm may continue to wriggle to distract the predator while the brittle star escapes. The arm eventually re-grows, but it takes about a month before it is fully restored. Fishes are the main predators of feather stars.

Most of them don’t even bother to search for food, they simply wait until their feather star snags food particles on its sticky, Velcro-like arms and digests it.

We’re unsure about their lifespan, but I'm starting to think these animals are immortal. They can pretty much grow back to their full size as long as part of their centradorsal (the central disk where all arms radiate from) is intact

The ones that looks like a cheetos or twisties.

Fixed permanently to the seabed, a sea fan’s shape is based on the area they live. Fans will grow large and fan-like in shallow waters where currents are present as this shape allows the fan to flex with the current. However, in deeper, calmer waters sea fans grow taller, thinner and more rigid. Sea fans can reach over 1 meter high and wide, but it takes a while as they grow less than 1cm a year,

These soft corals do not have hard skeletons like the stony corals that build reefs, but instead have wood-like cores for support and fleshy rinds for protection

Sea fans are not a single animal. In fact, each fan is a colony of tiny coral polyps. These polyps are only millimetres in size and join together to form the delicate branching structures we all know and love. The polyps work together sharing nutrients to each other via their connecting tissue.

Each coral polyp that makes up a sea fan has eight stinging tentacles. Once night falls, each polyp spreads out these tentacles to catch plankton. This, coupled with the fans’ wide, branched shape, means this underwater marvel effectively becomes a giant net, ensnaring its prey as they sweep through on the current.

New colonies can also form if a fragment of an existing fan breaks off and manages to find a good place to secure itself.

Dolphins will rub themselves against the branches of a sea fan in order to take advantage of the antibacterial qualities of the chemicals that the fans produce. Marine scientists are researching these compounds as they may have medicinal use for humans.