Archive for ‘Ecological’

Surprise surprise

By , 20 June, 2014, No Comment

The other day, I was teaching an Advanced Open Water course and we had the pleasure of encountering a massive jellyfish.  We do see them on occasions here on Koh Tao, but they are relatively rare, so it’s always a treat.  Especially when we see the big ones.  It can be a little difficult to identify species of jellyfish, but I think it was a white-spotted jellyfish.

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They’re such strange animals that it made me wonder more about them.  Turns out they are not fish at all.  They don’t have specific organs for respiration, digestion or circulation.  In fact, they don’t even really have a central nervous system.  They just have nerves spread throughout their bodies.

 

Jellyfish bodies consist of about 95% water and their skin is so thin that they don’t really breathe, they just get their oxygen by diffusion.  They eat by stinging whatever they come across and jamming it into their bodies.  Because they are transparent, sometimes we see small crabs in their “stomachs”.

 

Always a pleasure to come across one of these strange beings.

 

Pete

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How to make a tropical beach…

By , 18 May, 2014, No Comment

Whilst sipping away on a Piña Colada, watching yet another glorious tropical sunset, have you ever stopped to think where your tropical beach comes from? Maybe this is far back in your mind, lazing away under a palm tree, but the answer may surprise you…

 

Those fine sandy beaches are not just created from millions of years of erosion as your high school Geography teacher may have you think. In fact, we can attribute entire tropical islands to a species of fish which is the bigger, uglier cousin (the cousin that you haven’t really met but you know served a couple of years in juvie for armed robbery) of Koh Tao’s very own Rainbow Parrotfish – the Green Humphead Parrot fish.

 

Both feast on the algae which grows on rocks and coral, problem is for a beast that can grow up to 1.3m is length is getting at it. The not so elegant solution nature came up with is that the combination of their razor sharp teeth, strong bite and incredible digestion system, mean that a school can devour entire coral reefs when coming to graze. They actually eat the rock and coral, process the algae for energy, and then excrete the unwanted rock in the form of fine sand. A single humphead can produce over two tons of sand a year, meaning that entire beaches and even islands are made up of the sand produced by this species.

 

Check this link out to see for yourselves…

 

http://www.youtube.com/watch?v=8T-gnZevlaY

 

rainbowparrot humphead

 

 

 

 

left: Koh Tao’s rainbow parrotfish; right: green humphead parrotfish

 

It’s Koh Tao cousin may not be big enough to be responsible for the formation of Koh Nang Yuen, but if your diving around Twins or White Rock, you’ll see these green and pink fish nibbling away on the rock, and then producing a cloud of sand when they finish digesting, go for a dive tomorrow and check it out for yourselves.

 

So there you have it. The Beach Creator. The Coral Destroyer. Don’t let this put you off your Piña Colada though… the sand still feels amazing between your toes.

 

By Chris Nuttall

 

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Lionfish the dangerous beauty

By , 15 April, 2014, No Comment

Petrois Volitans also known as the lionfish. The lionfish can live to around 16 years in the wild and lionfish often live longer if looked after well in captivity. There are around 8 different recognised species of lionfish that are found in the Pacific Ocean. The lionfish is natively found in coastal waters around rocky crevices and coral reefs where there are lots of smaller fish for the lionfish to eat and also places for the lionfish to hide.

Here on Koh Tao it is rare to find lionfish but there are a few places where you can see one or two of them such as the dive site junkyard an artificial reef just off the beach at Mae head, at the back of the site there is a table tipped over on its side with 3 benches around it here inside the table stand a baby lion fish stays and is almost always there either sleeping or just resting.

The largest of lionfish can grow to about 15 inches in length, but the average is closer to 1 foot. Lionfish prey on a wide variety of small fish and crustaceans that inhabit the tropical reefs. The lionfish is prey to few predators due to the large size of the lionfish and also the fact that the appearance of the lionfish is very intimating to other animals. The spikes that protrude from the body of the lionfish contain venom that the lionfish uses to defend itself if it is being pursued.

The lionfish although dangerous is a beautiful creature and is not inherently aggressive towards humans, this allows us to view it without much worry and admire just how stunning the lionfish really is. So come to Koh Tao request junkyard for your dive and go see the lionfish in all its glory

Nick Kelly

lionfish 1

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Stingrays

By , 2 March, 2014, No Comment

Let’s talk stingrays for a minute.

Stingrays are found quite frequently while diving here on Koh Tao.  There are two main types of stingrays that we see: The blue spotted ray and the Jenkin’s whipray.

The blue spotted ray is the more common stingray and its usually found subtly hiding under rocks during the day, although occasionally they’ll be just chilling out in the open almost as if they want divers to check them out.  They have very alien-looking eyes that protrude from their heads and spiracles behind their eyes to allow them to breathe.  The blue spots serve as a warning to other fish that they are poisonous and should not be messed with.  But no need to worry, they are not aggressive in the slightest and are perfectly safe.

The Jenkin’s whipray is rarer and although it doesn’t have any bright colors on it, it is a little more spectacular due to its larger size.  It’s quite a sight to behold.

Both rays are more active at night when they can be seen swimming around and hunting for mollusks by digging into the sand.  It’s one big attraction of doing the night adventure dive on your PADI Advanced Open Water course.

-Petestingray

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Nudibranches the superheros of the sea?

By , 20 February, 2014, No Comment

Nudibranches, or sometimes falsly known as sea slugs, are beautiful aquatic creatures. With their colourful skin, they attract every divers eye. But don’t let yourself trick from the beauty of those animals. As they don’t have a shell anymore they developed another defense system to protect themselves. One of their defense mechanism is their shape and appearance. Nudibranches camouflage themselves looking like their sorounding enviroment to avoid predators. As we know from other animals bright colofull bodies are always a warnign sign in nature. Another way is, they are feeding on hydrozoids, which are commonly known as stinging cells in the sea ( if you ever wondered why you should wear protection while diving, hydrozoids are one of the reasons) But hydrozoids won’t do any harm to the nudibranch, instead they take them into their cells to produce these hydrozoids on their own and use them on their outer skin to defense themselves. ( they have this amazing ability also with producing their own supply, after feeding on chloroplast, the part of the plant cell that is used for photosynthesis). Next time you come diving with us always watch out for those hidden superheros at the bottom of the ocean!

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