Saturday, August 31, 2013

Reefy splendor of Northern Semakau

Five years on and I'm back to survey the reefs of Northern Semakau with the intrepid team on this last predawn intertidal survey of the year. The last time I had a good look at this stretch of shore was in May 2008.

Situated opposite Terumbu Raya (also known as the Great Reef), this stretch of reef at Northern Semakau is full of life with lots of corals, anemones, fish, sponges etc etc. It looks like an underwater garden from this shot through my underwater camera.

The extent of the corals is quite large which good growths such as the Ridged plate coral (Merulina sp.) shown in this underwater photo.

Above water and by the reef edge, one can also see that the shore is packed with corals and other marine life. It's amazing how all these coexist with the Semakau Landfill and Bukom oil refinery which are nearby.

Here's another shot of the surrounding with the oil refinery at Pulau Bukom at the background. This was taken right after we landed just before sunrise. There are lots of hard and soft corals!

Similar to Terumbu Raya, there are many Bubble tip sea anemone (Entacmea quadricolor) on the reef. Can you spot two of them in the above photo?

Some of them have tentacles with bulbous tips. There may be a white 'equator' or band around the bulbous portion.

While others have 'deflated' tentacle tips. Am not sure what causes the difference between the tips of their tentacles.

This anemone that look alike to the previous one is the Magnificent sea anemone (Heteractis magnifica). As the name suggests, it looks more magnificent in purple and is much larger!

This bushy creature that looks like soft coral is a menace if you touch it. From the name of the Fire's anemone (Actinodendron sp.), you can sort of guess how it would feel if you want to try the sensation.
There are some lovely echinoderms on the reef such as this gorgeous Feather star (Order Comatulida) perched on top of a plate-like hard coral.

This was how it looked it from far while I was documenting the reef edge.

And viola! Here's another three black feather stars on the huge plate-like hard corals. Can you spot the three of them? Only one is obvious in this photo.

How nice to find a large orange Cushion star (Culcita novaeguinea)! These huge and heavy sea stars are usually found on the reef edge. The younger ones are sometimes found on seagrass meadows.

Cushion stars have been known to feed on corals and I think I witnessed the process on this trip. When I turned this cushion star around, the external stomach retracted back and it sorts of reveals that some feeding could be going on. Interestingly, the coral looks half bleached as well. Could it be due to the cushion star?

Ria found a Tiger cowrie (Cypraea tigris)! This rare cowrie is sometimes seen on reefs around this area. My previous sightings were on Terumbu Raya and Terumbu Semakau which are nearby!

Ria also came across this special sea cucumber that probably could be a pale brown / beige version of the Herrmann's sea cucumber (Stichopus herrmanni). It's my first time seeing it!! Awesome!

This is the underside of the sea cucumber which has short tube feet. This sea cucumber is also called the Curryfish as it is among the sea cucumbers that are edible and harvested for the restaurant trade. I'm not sure how this relates to curry though!

Ria showed me this blade of the tape seagrass with two slugs! The one on the left is the Thuridilla slug (Thuridilla gracilis) and she later saw the Lined chromodoris nudibranch (Chromodoris lineolata).

As for me, I saw this white with orange Gymnodoris nudibranch (Gymnodoris rubropapulosa) and took a photo of it with my underwater camera. I only realized that I missed the Pimply phyllid nudibranch (Phyllidiella pustulosa) which was just right beside. 

I probably also missed many more slugs because of the fact that they are quite small and well camouflaged or that I'm kind of blind haha!

Looking alike to the Carpet eel blenny (Congrogadus subducens), I later realized that this slow-moving creature is actually the Banded file snake (Acrocordus granulatus) with algae-covered skin.

An interesting sighting would be this moment where a Saw-edged spooner crab (Etisus utilis) was eyeing two nearby prawns.

Here's a closer look at the eyeing crab with the prawn right in front of it. I didn't have the time to wait for the crab to take any possible actions but am still amused by this shot!

Shall end the post with a series of feature on hard corals just like how it started. The reefs of Northern Semakau is spectacular and is probably the thickest as compared to the other stretches that I've explored.

There are many Circular mushroom corals and some of them can be quite large!

The green hard coral in this photo is also another type of mushroom coral and is known as the Feather mushroom coral (Ctenactis sp.).

What is different about mushroom corals as compared to other types of hard corals would be that most mushroom corals are not attached to the ground as adults and most are giant solitary polyps (although some are colonial).

There were a number of "mushroom coral lookalikes" that puzzle me till now because they look like circular mushroom corals but looks rather similar to a boulder coral as it is raised. I should have checked if they are attached to the ground to confirm its identity.

This anemone-lookalike is actually a Sunflower mushroom hard coral (Heliofungia actiniformis) which are commonly seen at Pulau Hantu and Pulau Semakau.

There were many Fan worms (Family Sabellidae) found near and also on hard corals such as this particular one on the Castle coral (probably Pachyseris rugosa).

Seeing how rich the coral reef is at Palau Semakau comes as a form of nature therapy and also a relief that we still do have rich marine biodiversity in Singapore waters.

Here's a look at the same patch of hard corals jammed packed against each other with Terumbu Raya at the background.

Despite the respite from normal Singaporeans, Pulau Semakau still faces threats from fishermen and we encountered a rather fierce one on this trip. You may read more about this from Ria's account on her blog:

That's about all for now and I'll return to update on our latest adventures from the upcoming evening field trips which will only kick in much later as the peak season for field trips has ended.

I'll also take this break to blog some of the seriously-overdue blog posts of my previous trips over the next few weeks. Time to clear all backlogs!

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