Coral - what seascape would be complete without it? These tiny architects are best known for the reefs, beaches and atolls they create, but did you know they...
1. The Dwellers BeneathCorals are cylindrical creatures with a tentacle-ringed mouth, closely related to anemones and jellyfish. They are animals, but often have photosynthetic algae inside their cells that provide them with sugars. Many corals can be found in the shallower (and thus better lit) parts of the ocean, but a similar number of deep-water (and significantly more predatory) varieties exist. The most well known corals grow together and produce hard exoskeletons – given time, these can become a coral reef.
These tiny critters have a disproportionate effect on our oceans and coasts. The coral reefs that surround many tropical islands take the brunt of the oceans fury when a storm rolls in, while simultaneously providing a habitat for many marine creatures. Their ground-down exoskeletons produce the white sand of premium beaches, and some reefs are so big that they are visible from space. Finally, the filter-feeding of corals cleans the seawater as they eat.
You might be wondering why the coral would hurl away a food source - it's to do with the algae themselves. When exposed to warm temperatures and strong light, the photosynthetic algae go into overdrive. They produce a great deal of reactive oxygen, which causes oxidative stress in the coral. To put it another way, oxygen free-radicals start tearing the coral apart from inside.
Bleaching isn't necessarily a death sentence - throwing out the algae buys the coral some time. If conditions change and the algae slow down their rate of photosynthesis, the coral can stop ejecting them and allow their internal population to regrow.
While it is usually the result of warmed waters, anything that disrupts the symbiotic algae (i.e. cold water, pollutants etc.) can cause bleaching. This is due to the algae not growing rather than being thrown out!
Unfortunately, the plastic is not good for the hungry coral. Not only is it indigestible, it can become trapped inside the creature and potentially starve or poison it. Given the huge amount of plastic waste that ends up in the sea, this could be a real issue.
As to why the corals like raw plastic, researchers theorize that one of the chemicals used in the production of the plastic is attracting the attention of the polyps. Scientists hope that they can identify exactly which chemical the coral finds delicious, and maybe change the manufacturing of plastics to exclude it!
4. Pharmacy of the SeaMany prey animals are fast or camouflaged, able to evade predators and thus survive in a hungry world. Coral doesn’t really have that option, being both stationary and obvious. Instead, it relies on a battery of unique chemical defenses that range from deterrents to outright poisons. The fact that corals have survived since the era of the dinosaurs implies they are pretty good at what they do. In fact, one deep-water black coral (Leiopathes) colony was found to have been active for 4270 years.
The end result of all this is that coral reefs are ideal for “bio-prospecting.” By collecting various corals, researchers hope to find useful chemicals for medicine or industry that could be synthesized in the laboratory.
This may be surprising given their small size and immobility, but some corals are capable of capturing and devouring jellyfish. Despite being tiny by comparison to a free floating jelly (only a few millimeters in diameter) colonies of coral can work together to bring down much larger prey.
Colonies of Astroides calycularis can cover huge amounts of rock in shallow waters, favoring overhangs or verticals that a jellyfish might be washed into. When an an unfortunate jellyfish brushes against the reef, the polyps grab tentacles or anything they get a hold of. The struggles of the jelly slowly bring it into contact with more and more polyps, each of which grabs on. Once the jellyfish is well and truly trapped, the corals slowly nibble it to death!
There is another coral (Fungia scruposa) that feeds on jellyfish, but it takes a rather different approach. Unlike most corals it is solitary and quite large (reaching 30cm in diameter) whilst also being capable of limited movement. The exact mechanism used to capture large prey is unknown, but we know it can – the coral has been caught slurping up an unfortunate jellyfish!
- Have a huge impact on the ocean?
- Bleach themselves in an attempt to survive stress?
- Love the taste of plastic?
- Are prime targets for bio-prospecting?
- Can capture and eat jellyfish?
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| Corals are tiny animals related to anemones and jellyfish... (marcelokato) |
1. The Dwellers BeneathCorals are cylindrical creatures with a tentacle-ringed mouth, closely related to anemones and jellyfish. They are animals, but often have photosynthetic algae inside their cells that provide them with sugars. Many corals can be found in the shallower (and thus better lit) parts of the ocean, but a similar number of deep-water (and significantly more predatory) varieties exist. The most well known corals grow together and produce hard exoskeletons – given time, these can become a coral reef.
These tiny critters have a disproportionate effect on our oceans and coasts. The coral reefs that surround many tropical islands take the brunt of the oceans fury when a storm rolls in, while simultaneously providing a habitat for many marine creatures. Their ground-down exoskeletons produce the white sand of premium beaches, and some reefs are so big that they are visible from space. Finally, the filter-feeding of corals cleans the seawater as they eat.
2. Bleached Coral, Dying Coral
Unfortunately corals don't take well to stressful conditions - and the most obvious way this manifests is coral bleaching. When exposed increased temperatures, shallow-water coral may eject their algae. This turns the normally colorful coral white (i.e. bleaches it) and starts to starve the stressed animal.You might be wondering why the coral would hurl away a food source - it's to do with the algae themselves. When exposed to warm temperatures and strong light, the photosynthetic algae go into overdrive. They produce a great deal of reactive oxygen, which causes oxidative stress in the coral. To put it another way, oxygen free-radicals start tearing the coral apart from inside.
Bleaching isn't necessarily a death sentence - throwing out the algae buys the coral some time. If conditions change and the algae slow down their rate of photosynthesis, the coral can stop ejecting them and allow their internal population to regrow.
While it is usually the result of warmed waters, anything that disrupts the symbiotic algae (i.e. cold water, pollutants etc.) can cause bleaching. This is due to the algae not growing rather than being thrown out!
3. An Appetite for Trash
It turns out that coral polyps have something of a taste for plastic. Researchers at Duke University in America fed coral collected from the coast a variety of small objects, including raw and biofilm coated (i.e. covered in bacteria) plastic. Coral feeds on the bacteria and algae that form biofilms, so the researchers were surprised to find that coral preferentially consumed the raw plastic.Unfortunately, the plastic is not good for the hungry coral. Not only is it indigestible, it can become trapped inside the creature and potentially starve or poison it. Given the huge amount of plastic waste that ends up in the sea, this could be a real issue.
As to why the corals like raw plastic, researchers theorize that one of the chemicals used in the production of the plastic is attracting the attention of the polyps. Scientists hope that they can identify exactly which chemical the coral finds delicious, and maybe change the manufacturing of plastics to exclude it!
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| ...but groups of them can have a big impact! (CoffeewithMilk) |
4. Pharmacy of the SeaMany prey animals are fast or camouflaged, able to evade predators and thus survive in a hungry world. Coral doesn’t really have that option, being both stationary and obvious. Instead, it relies on a battery of unique chemical defenses that range from deterrents to outright poisons. The fact that corals have survived since the era of the dinosaurs implies they are pretty good at what they do. In fact, one deep-water black coral (Leiopathes) colony was found to have been active for 4270 years.
The end result of all this is that coral reefs are ideal for “bio-prospecting.” By collecting various corals, researchers hope to find useful chemicals for medicine or industry that could be synthesized in the laboratory.
5. Wall of Death
Predatory behavior shows up in all corals – especially those that live without light. Some live in the deepest depths whilst others live in caves surprisingly near the surface, but all of them need to get food somehow. Without access to light a coral can’t rely on symbiotic algae for energy – so it puts the ring of stinging tentacles around its mouth to use, capturing small organisms and plankton… normally.This may be surprising given their small size and immobility, but some corals are capable of capturing and devouring jellyfish. Despite being tiny by comparison to a free floating jelly (only a few millimeters in diameter) colonies of coral can work together to bring down much larger prey.
Colonies of Astroides calycularis can cover huge amounts of rock in shallow waters, favoring overhangs or verticals that a jellyfish might be washed into. When an an unfortunate jellyfish brushes against the reef, the polyps grab tentacles or anything they get a hold of. The struggles of the jelly slowly bring it into contact with more and more polyps, each of which grabs on. Once the jellyfish is well and truly trapped, the corals slowly nibble it to death!
There is another coral (Fungia scruposa) that feeds on jellyfish, but it takes a rather different approach. Unlike most corals it is solitary and quite large (reaching 30cm in diameter) whilst also being capable of limited movement. The exact mechanism used to capture large prey is unknown, but we know it can – the coral has been caught slurping up an unfortunate jellyfish!
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