What is Coral Bleaching and What it means for the Corals

120th Discovery Posting

Recently, an probably alarming amount of coral bleaching has been sighted and reported in Singapore and around the region. I will give a short list of blog posts with reference to some of these sightings at the end of this posting.

Coral Bleaching might not ring a bell for some discoverers/readers (my own friends included), so I have decided to dedicate a post on this issue.

First off, if you have ever been to the shores or watched shows that features corals, you might have noticed that corals are brownish/greenish in colour (picture below).
However, it is important to note that the original colours of corals are not like that. Their original colour is more whitish or I could say white. Two main reasons for the colours would be coral fluoresence (a link will be provided at the end of this posting which will explain more about this) and the presence of zooxanthellae (a kind of algae) in the polyps of the corals.

Now it is important to note that the zooxanthellae and corals share an important relationship. The corals provide a place or home for the zooxanthellae to stay in while the zooxanthellae will give the extra food it makes during photosynthesis to the coral. So basically, it's a "you scratch my back, I scratch your back" or "I help you, you help me" relationship.

So what is coral bleaching?
Well, first, it has nothing to do with bleach or dyeing... =P
Let me try to make it simple for everyone.

Imagine you are the zooxanthellae living in a polyp of a coral colony and these past few days, the water has been really hot and you cannot stand it (and there is NO fan or air-conditioning in the polyp). So what would you do?

Would you leave the polyp and get out in the open water to 'cool' down?

Yes, that's what happens, NOT the 'cool' down part though, I think...hahaha

So when you and many of your neighbours, the zooxanthellae leaves the coral, the coral will lose the brownish colours and show their original colour, white.
Now here's another important point, you, the zooxanthellae, can provide up to 90% of the food that the coral needs. So what might happen if you and your neighbours leave the coral?

Yes, the corals might die!
Another thing to note is that sometimes, after you and your neighbours (you are still a zooxanthellae) leave the coral. Other people, I mean zooxanthellae which can tolerate heat better might move into the coral.

Okay, even if you are not interested in corals and coral bleaching, here's something to make you sit up. One main reason that corals bleach is due to the increase of water temperature. The impact of this is not only the death of corals and the other organisms it supports. The increase of water temperature in our seas/oceans also means the ice caps will melt faster which leads to the increase of sea levels. Sitting up now? =D

Before I end, I would like to highlight that the increase of water temperature is NOT the only reason for coral bleaching to occur. There are other factors as well, I will leave some links for your own reading if you are interested to find out more and read more in depth about coral bleaching.

Here's a video from youtube that explains coral bleaching.

Here are the links that explain coral bleaching:
1) http://en.wikipedia.org/wiki/Coral_bleaching
2) http://www.marinebiology.org/coralbleaching.htm
3) http://saltaquarium.about.com/od/aboutcoraldiseases/a/aacoralbleach.htm

Here's the link that explains coral fluoresence
1) http://mountain-n-sea.blogspot.com/2007/12/coral-flourescence-and-other-attributes.html

Blog Links that report Coral Bleaching
1) Wildshores
2) http://tidechaser.blogspot.com/2010/05/extensive-coral-bleaching-at-semakau.html
3) http://wondercreation.blogspot.com/2010/06/snorkeling-at-tioman.html

Inter Tidal Walk @ Semakau on 2 Jun 2010

119th Discovery Posting

Another late and over due posting about the inter tidal walk last week. On 2 Jun 2010, I was free to help do guiding for the Project Semakau. This time round, I was assigned to guide a group of students from Boon Lay Secondary School.

Our morning that day didn't start off well. This was not because of the students nor teachers in my group but the weather. It was drizzling quite heavily when we reached the island. Luckily, there was no lighting alert, therefore, the walk would continue. However, all the groups would have to walk under the drizzle to the inter-tidal area as the drivers had not arrived on the island yet.

Despite the rainy weather, spirits were still quite high. I reckon this had to do with the amount of high energy the participants had. Hahaha... Anyway, the day got better as it went on. The first of it was a rainbow that appeared as we approached the forest trail.The second great thing that happened was that the rain cleared as we started to walk onto the inter-tidal area. Here's the group photo at the seagrass meadows (picture below).I did not really take a lot of photos during this trip and some of them did not turn out well, so I'm only posting the ones which you could get a good look at.

First off is this juvenile cushion star, first 'discovery' (picture below).
I guess the most interesting thing to my group about sea stars would be that they have no brains... that's why Patrick in the Spongebox show is so err.. silly...hahaha.

The other organism I would like to feature in this short post would be the knobbly sea star (picture below).
And here's the group photo with the 'star' of the walk (picture below).I have to apologize for the late and short post as I was slacking for the past few days and right now I have to rush out some work matters with regards to a project I'm doing at my workplace. PS: I hope all my group participants, Coral Reefs, enjoyed themselves last week cause I did. Thanks for another great experience =D

Why are rainbows in an arc-shaped?

118th Discovery Posting

I am sure that many of you have seen a rainbow in the skies above you before. But have you ever wondered why are rainbows shaped in an arc? Personally, I am not sure of it myself and I was made curious about the answer by one of my participants in a recently guided inter tidal walk who asked his son this question when they saw a rainbow over at Big Sisters' island not long ago. As a result of this curiosity, I decided to do some simple research on the internet and do up this blog post.
The first thing to note is that rainbows are caused sunlight passing through raindrops and by refraction, which is the bending of light as it passes from one medium to another. I would not go through the exact science of how to explain this as I have found websites that does this explanation better than I can. You can find the websites below.

It is interesting to note that a rainbow is really circle in shape than the arc shaped or semi circle shape we usually see. The reason why we don't see the whole circle is because the earth blocks our view. And the closer the sun is to the horizon, the more of the circle we see. So this means that the best time to see a longest rainbow would be either during early morning after sunrise and evening time before sunset. =D
Great websites that explains how a rainbow is formed and why is it in a arc.
a) http://science.howstuffworks.com/rainbow.htm
b) http://www.scientificamerican.com/article.cfm?id=why-do-rainbows-form-inst

Side note:
Rainbow Connection by Kermit the Frog. Enjoy! =D

Inter Tidal walk @ Big Sister's Island on 30 May 2010

117th Discovery Posting

Personally, I have been to Big Sister's Island for less than the fingers on one hand. So it was a great chance to both visit and introduce other people to this small little island to the south of Singapore through a guided inter tidal trip.

Sidenote:
If you would like to read more about Big Sister's Island, you may visit http://www.wildsingapore.com/places/sisters.htm
I need to mention that this was also the first public guided trip on Big Sisters organised by RMBR and I was guiding a group of rather experienced participants as most of them have to been other shores with us.
To start off, the first 'discovery' is something which I really like, feather stars (picture below)!
As their name suggests, their arms are a little like feathers, handle with care as they may break easily. I have seen them in many different colours besides red. They include black, yellow, white, etc. They are also related to the sea stars being in the same echinoderm phylum.

As we moved towards the coral reefs, a participant spot this school of juvenile catfish, second 'discovery' (picture below).Like other fishes you may find in the sea, juvenile catfishes are often seen in a group or what we call as a school of fish. They do this as a predator will find it harder to pounce on a group for food than compared to an individual, this is otherwise known as safety in numbers. Interestingly, as the cattail grows bigger, their group gets smaller and they are usually found alone when they are adults. As they have poisonous spines, it is not advised to touch them. One reason, I guess, why they are called catfish is because of their whiskers, these are usually to help them find food in murky waters.

If in case you are wondering, a cat's whiskers help it to find its way and move around. A little similar to the function of the catfish's whiskers.

Now, it is to be noted that Big Sister's Island has one of the nicest looking coral reefs where one can come really close up into (picture below). And my group, coral reefs, did spent a certain amount of time admiring at it. As we moved on, we came across this leaf slug which our hunter seeker has found for us, third 'discovery' (picture below).The leaf slug is named so mainly because of its colour which resembles a leaf. I reckon another reason which it is named as such is because that it is able to retain the chloroplasts of the seaweed it eats. These chloroplasts which it manages to retain will continue to carry out photosynthesis inside the slug and provide it with extra nutrients. Cool, isn't it?

Just to sidetrack a bit, we had this little joke about if we could do the same, would we be green in colour as well...hahaha

Moving on, our hunter seekers also found us a flatworm, fourth 'discovery' (picture below). As their name suggest, flatworms are really flat. This can help them to squeeze or move into narrow and small spaces to find food and at the same time to hide from their predators. At the same time, being really flat means that their bodies are easily tore when handled, so please handle them with them or don't handle them at all. One really interesting thing about them is that flatworms are hermaphrodites. In really simple terms, this means that a flat worm is both a guy and gal. In specific terms, flatworms have both the male and female reproductive organs.

And the last organism I am going to feature is this bohol nudibranch, fifth 'discovery' (picture below).First off, they are sea slugs. They are called nudibranchs because they have naked gills. Notice the flowery like thing near the center of the picture? That's the gills for this nudibranch. They may look like easy prey, they are however not. They protect themselves in different ways like producing distasteful substances, toxins and even acids. It is important to take note that these protective methods vary from species to species. Some of them will advertise themselves to be 'not nice to eat' with their really colourful bodies while some, like this bohol nudibranch will try to camouflage themselves.

As we were still wondering around the shore to look for more things, dark clouds and strong winds came in quickly and threaten to drench us, so we had no choice but to end the walk prematurely and leave the shore quickly.
Luckily, it did not rain eventually and the visitors has some time to take a short picnic and relax on the island.
Before I sign off, I would like to say thanks to all Coral Reefs, my group for the day. I hope the 3 first timers enjoyed themselves as I did not really give much details about the things we've seen that day and of course not forgetting the rest of my group.

Last note:
As a result of the passing rain clouds, we caught sight of a really beautiful rainbow which I would blog about in the next post, so do come back soon to check that posting out. =D

Survey on another part of Semakau

116th Discovery Posting

Last Saturday, a small group of Project Semakau volunteers, including myself, went off in the early morning to do a survey on a different part of Semakau where we don't usually do our surveys.

In this blog posting, I will give a peek into the various organisms which we saw.

First 'discovery' would be a cryptic sea star (picture below).
Interestingly, this kind of sea star has not been seen on other places in Singapore other than Semakau. They are usually found under or on stones near the mid-water mark so sometimes we might have to turn stones over to find them. They are known to feed on algae and small animals found on the surfaces of stones.

Still in the area of the mid-water mark, the second 'discovery' would be this onch slug (picture below).
Compared to the cryptic sea star, the onch slug is much more common. The only reason why you might not see them as often is that they are pretty well camouflaged. They also feed on algae found on stones and unlike other sea slugs, the onch slug does not live underwater. Instead they are able to breathe air through their simple lungs and when the tide is high, they would burrow into mud or sand, trapping an air bubble to breathe in.

After suffering numerous sand fly bites near the rocks, we finally moved into the sandy parts of the area and we encounter this cute little spotted moon crab, third 'discovery' (picture below).
The moon crab is actually quite common on our shores. They however do hide buried in the sediments and are more active during the night thus you might not have seen them before. To help to bury themselves quickly into the sand, all ends of their legs (excluding the claws) are shaped like a paddle.

As you might have already read/know, we found a long drift net in the area and a number of things including three black tip reef sharks became victims of the net. Here's another victim, a big fish, I'm not good with the identification of fishes. And at the side was a red swimming crab trying to scavenge the dead fish (picture below).
As most of us had very little sleep the night before as we spent our night over on the island, the rising of the sun did provide us with some injection of energy into our lethargic bodies (picture below).
The last animal we encounter before we went to document the three dead black tip reef sharks was this dog faced water snake, fourth 'discovery' (picture below).The dog face water snake is another animal which is quite common to Singapore. They are usually seen in mangroves and sometimes the inter tidal area. They are much more active at night and spent the day mostly in hiding. Please do not try to handle this snake if you came into close contact with it as they are mildly venomous. You just need to move away and not disturb it and it would not attack you as it is mostly docile.

That about ends this blog posting and do come back in a few days as I still have back logged blog postings to make. =D