Thursday, August 7, 2008

Threats to corals

Any animal in the wild surely faces numerous threats which can extinguish its existence like a candle flame in a hurricane. After all, mother nature is tough on her children. The threats get even more numerous if you are a sessile creature, unable to walk out of harms way. I.e., being firmly rooted to the middle of the road in the way of an oncoming SUV tearing along at 70mph. I hear voices of protest now, 'Surely corals do not have to content with crazy drivers underwater! Well, they have to put up with much worse.


That's what they get reduced into.

In the natural world, they have to deal with predators like crown of thorns and parrotfishes. Then of course, humans come along into the picture, and fish the corals out of the water for aquarium trade, or drag fishing nets all over them in trawling, blow them up with dynamite fishing or just destroy the ecosystem they are in by overfishing. Of course, the same humans then proceed to destroy other parts of the planet which also affects the corals such as polluting the waterways, land erosion, pesticide wastes and warm water outflows. Let's examine some interesting ones in depth.

Corals for aquariums
Some people who love exotic marine life but are hydrophobic. Corals are used in aquariums so that the underwater tank resembles an exotic coral reef. The concept is rather like a zoo: take the animal from it's homeland and chuck it in an enclosure somewhere. The market to keep these hydrophobes happy is on a global scale. The problem with it is that when you keep removing healthy individuals by the truckload from the reef, there won't be a reef to mimic in the first place. Irresponsible catching of organisms will bring instability to the fragile reef ecosystem.

Bottom trawling and dynamite fishing
Both trawling and dynamite fishing are non specific methods of fishing. You catch whatever you can. In bottom trawling, a net is dragged over the sea bed and everything in its path destroyed and hauled up. (This is how you get your cod, squid and halibut. Guilty?) In dynamite fishing, you throw an explosive into the water, kill all the marine life within a certain radius, collect whatever fish floats up and sell/eat them. Except corals don't float when they die, they aren't edible, and they are dead anyway.

Global warming
Ooh! Everyone knows this issue about global warming and how the polar caps are melting. There is a closer consequence anyway, one that's happening around the tropics rather than the arctic/antarctic circle. Zooxanthallae, the secret behind the success of corals, the wing beneath their wings, the wave beneath their tentacles, do not like heat. No sir, not one bit. A slight change in temperature (like a couple of degrees) is enough so make them go crazy, so crazy that they'd jump out of a building (figuratively). They'd leave their coral hosts and just float around in the ocean, leaving the corals behind without any photosynthetic partner, friend, colour and self-esteem.

Warm water outflows
Same as global warming, but more regional. Same effects as global warming (prelude of what is to come, eh?)

Land reclamation and land erosion
While these two seem to be opposing each other (reclamation = more land! erosion = less land!), they both do the same damage to corals. Land reclamation works and soil erosion causes large amounts of silt to be dumped into the water. If you were a coral you'd be freaking out. Imagine being stuck in a sandstorm while someone cemented your feet in a 10000kg stone slab. Corals get really stressed out when there's alot of muck and mud on them. They start producing massive amounts of mucus (think: what your nose does when you have the flu) to get rid of the dirt. Of course, when you waste all your energy making mucus, you don't really get to grow and do other things.

Sewage and pesticide wastes, industrial pollution and oil spills
All of these are like dumping rubbish into people's houses. Would you like someone dumping pesticides and sewage into your room? I had a neighbour who had a leak in his house, and he kept complaining to the management for weeks on end, telephone calls and letters and emails. Can you imagine each individual coral complaining to upper management? It's gonna be an administration nightmare. Sewage and pesticides are NOT part of ANY animals recommended diet.

Tourism
Tourists directly or indirectly destroy corals by pollution, bad diving practices and irresponsible docking of boats.

Ocean acidification
Think trees are the only things that remove carbon dioxide? Here’s what you should think, the ocean is the largest carbon sink on earth. The ocean is like a carbonated drink the only problem is that we can’t shake it. Continued release of carbon dioxide into the atmosphere means the largest of carbon sinks is getting larger. When carbon dioxide reacts with water carbonic acid is formed. pH changes are bad for coral and all life for that matter.

Coral disease
Like all living organisms coral can catch diseases too, from bacteria and fungi infections and from viruses. When someone is sick he shouldn’t be rolling around in dirt otherwise exacerbating his illness! Sadly corals don’t get breaks from a constant slew of environmental threats.

Crown of Thorns



Crown of thorns (COT) is a star fish. It is not cute at all. Believe it or not they are ferocious creatures. Two mechanisms ensure their survival. Puking mechanism enables throwing up of stomach to digest coral. Spiny mechanism deters predators. It is a lean mean eating machine. In normal quantities they improve reef biodiversity by controlling competition between coral species. Their larvae (babies) are predated upon. But over-fishing removes such predators and COT flourish.

Invasive species

Aliens are real. The introduction of foreign species will disrupt the ecosystem. Without any predators such aliens will multiply like the children of Abraham. An example would be the red-eared slider (terrapin) as they infest the waters of Singapore displacing the locals.

References:
http://www.iyor.org/reefs/status.asp
Photos by Jacque

Jacque and Theophilus finished work at 12:06 PM

______________________________

the marine junkies
Jacque and Theophilus
18071990 / 28081990
NUS High School
NUS Marine Biology Labs

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Nudibranchs drawn by Prof. Chou
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