05 April 2011

Nudibranch at Tanah Merah!

Hurray, it's the first time I've seen a nudibranch on Tanah Merah since the oil spill hit this shore slightly more than a year ago.
Dr Paul found this rather large Discodoris boholiensis crawling about on the rock wall. And this is also my first entry for Tanah Merah into the wild fact sheets. Wow.

I am out for an early morning trip with Dr Paul Erftemeijer. We arrived before dawn for a not-so-low tide. He is very tall, so the high water doesn't bother him much.
Another strange sighting this morning, this transparent creature which Dr Paul suggests is a kind of salp. Salps are free-swimming ascidians, often found in colonies of long rows of individuals.
Here's closer look at the innards of this transparent creature. It seems salps play an important role in sequestering carbon in the ocean! Dr Paul noticed many individuals of our usual sea squirts growing on the seawall.
Later, near some rocks, I saw this bunch of tiny transparent creatures also pulsating like the salp. I'm not sure what they are.
It's my first pre-dawn trip to Tanah Merah for the year! It's much easier shooting fishes in the dark as they are less shy. I saw many tiny Bengal sergeants (Abudefduf bengalensis) swimming in schools near the rocks.
There were a lot of cardinalfishes! I only know the top left which is the Chequered cardinalfish (Apogon margaritophorus). I'm not sure what the other cardinalfishes are. As usual, the most abundant small fish I saw are the Ornate gobies (Istigobius ornatus).
Mystery cardinalfishes
And here's some mystery fishes that we saw.
Mystery fish no. 1: An emperor (Family Lethrinidae)?
I often see this fish on Tanah Merah even after the oil spill, but they usually swim away very fast.
Mystery fish no. 2
Another strange fish with a mosaic like pattern. Some kind of grouper?
Mystery fish no. 3
I saw four medium-sized Painted scorpionfishes (Parascorpaena picta) and one False scorpionfish (Centrogenys vaigiensis) which is actually a grouper (photo on the right). Fortunately, we didn't encounter the Stonefish! Here's more on how to tell apart fishes that look like stones.
There were also many small White-spotted rabbitfishes (Siganus canaliculatus) in the seagrasses, seaweeds and out and about in small schools over the sand.
We came across several squids (Family Loliginidae)! They seemed rather nervous and scooted away from us rapidly. Here's the same squid changing patterns before squirting out a squid-shaped ink blob and zooming away.
Dr Paul also finds a living Ovum cowrie (Cypraea ovum)! I've seen a cowrie a few times on trips since the oil spill, but not often. The most abundant snail remains the Bazillion snails (Batillaria zonalis) which carpeted the sandy lagoon.
We saw six Common sea stars (Archaster typicus) spaced rather far apart. I didn't see any in mating position.
We saw several medium-sized Blue-tailed prawns (Family Penaeidae). They were behaving as usual, burrowing into the sand when threatened, leaving only their bulbous eyes sticking out on the surface.
We also came across two of these large Mud crabs (Scylla sp.). This one seems to be eating some kind of snail? During my trip in Oct 2010, I also encountered these crabs here. These crabs are usually only found in mangroves. They are also commonly released by people who do so for religious reasons. It's sad to see them here as they are not in their natural habitat and are unlikely to be able to find enough of the food that they are specialised to feed on. Animals release can harm the animals and the habitat. More about this issue.
I didn't see many small Flower crabs (Portunus pelagicus), but did see this pair that seems to be getting ready to mate. I did see several small to medium-sized Swimming crabs (Family Portunidae), and one small Stone crab (Myomenippe hardwicki).
The water was clear, but tended to form a weird blur in our footsteps (as if the water was boiling). I suspect it's some kind of sheen that gets into the water when we step on the sand.

I saw the usual hard corals growing on the seawall. All those I saw seemed unbleached. Most were Favid corals (Family Faviidae) with many small and large patches of Zebra coral (Oulastrea crispata) and a few Pore corals (Porites sp.). Dr Paul also pointed out some tiny colonies of Flowery disk coral (Turbinaria sp.). I saw one patch of Button zoanthids or colonial anemones (Zoanthus sp.).
The two patches of Smooth ribbon seagrass (Cymodocea rotundata) are still large and seem to be growing! The blades look well. Dr Paul says this seagrass is among the fastest growing pioneer species! Wow, I didn't know that.
In the seagrasses, were some tiny baby Barracudas (Family Sphyraenidae).
I saw one small Haddon's carpet anemone (Stichodactyla haddoni) among the seagrasses. Perhaps the others that I saw on my earlier trips have burrowed into the sand?
Dr Paul pointed out that the Tape seagrass (Enhalus acoroides) had bloomed recently. The blades looked well, and there were many white blobs on them. Eggs?
We missed checking on the patch of Sickle seagrass (Thalassia hemprichii)and we still didn't see any Spoon seagrass (Halophila ovalis) here. From what I saw, the most abundant seaweed on the shore were Mermaid's fan (Padina sp.) on the rocky seawall, with only a few strands of Sargassum seaweed (Sargassum sp.) here and there. Ropes were covered with Pom pom red seaweed and other kinds of seaweeds.

We saw a few happy and fluffy fan worms (Family Sabellidae), both the orange and the brown banded ones.
I saw one Peanut worm (Phylum Sipuncula). It was not distressed like the ones we saw when the oil spill first hit the shore. It was quite lively and burrowed rapidly back into the sand.
There is a sand bar in the middle of the lagoon that seems 'clean. It is teeming with burrowing sand bubbler crabs (Scopimera sp.), and has many signs of living Acorn worms (Class Enteropneusta). We also saw many shallow 'craters' on the sand bar, perhaps made by foraging stingrays?
All too soon, we enjoyed a splendid pink sunrise and the tide turned.
As the tide rose, Dr Paul noticed a pair of Striated herons feeding along the sand bar which was still exposed. A small flock of white egrets fly away. In the background is a large series of structures that are being built right next to this shore. They appear to be housing units, perhaps for foreign workers?
Alas, there are still 'pancakes' of crude on some parts of the shore. Although I feel there are much fewer than before.
Where the crude lies close to the surface, the area is tinged with sheen. But my sense is there was less sheen today on the lagoon water surface than on my trip here a month ago.
As we left, I saw 5 people fishing with rod and line on the seawall in the incoming tide. There was another group of three starting up to begin fishing on the mainland seawall.
Alas, though I tried very hard, I failed to find a seahorse for Dr Paul which he so very much wanted to see. I guess he just has to come back to visit our shores again, until we find him a seahorse!

More about the oil spill on this blog and on the Oil spill facebook page.


  1. Thank you for posting this.
    This post has really been helpful !
    The salp reminds me of something I have found on the sandy sea shore in the middle of the year of 2008. I found a small transparent square-shaped living thing with a black round nucleus inside the center, making it look like a unicellular organism. It has a pulse too, pulsating like a beating heart. They are surprisingly abundant, almost a thousands are washed up ashore, and there are many more floating in the waters, maybe millions ! The ones found ashore are usually the larger ones, maybe the fully grown ones, which can reach up to about 20mm. Most of the ones still floating in the waters are smaller ones and they are chained to each other forming a long line of them. Could it be some kind of salp too? I hope you can tell me what I may possibly witness. Thank you.

  2. Thanks for sharing this encounter. I'm not really sure whether what you described is a salp. But it sounds fascinating!



Related Posts with Thumbnails