09 September 2010

Oil-spill check on Tanah Merah

It's been three months since the oil spill hit the reefs at Tanah Merah in late March. How are they doing today?
I was pleasantly surprised to see colourful hard and soft corals still alive on Tanah Merah's artificial seawalls.

First the good news. I saw some interesting corals including small colonies of a bright green Disk coral (Turbinaria sp.), a dark brown and unbleached branching Acropora coral (Acropora sp.) and a patch of purple Anemone coral (Goniopora sp.) which is a bit pale but not totally bleached.
There some large patches of corals.
Most of the large colonies of hard corals appear to be unbleached, although some were rather pastel in shade. Most were Favid corals (Family Faviidae) and Pore hard corals (Porites sp.)
And several small corals too, mostly Favid corals.
I saw one cluster of zoanthids (Zoanthus sp.) that looked alright.
I saw two small Haddon's carpet anemones (Stichodactyla haddoni). One was studded with stunned tiny baby fishes that blundered into their tentacles (like the baby fish to the left in the photo below). But the tiny transparent anemone shrimps (Periclimenes sp.) that live in the anemone were unharmed.
A tiny bobtail squid (Order Sepiolida) bobbed up near me then sank away into the murky water with paddles of its circular fins that reminds me of Dumbo the Flying Elephant!
Today, the water was much clearer. Unlike my trip to this shore about a month ago, the ground was no longer super soft with a slippery soft mush under the sand. It was much firmer, so I could walk without stirring up too much silt, and reach the seawall without slipping. Perhaps this is why I managed to get close enough to the seawall to see more corals, and also to see more fishes today. Also, it's the last predawn low tide, and the fishes are generally less shy at night.

Here's some of the fishes I saw today: Head-stripe goby (Amblygobious stethophthalmus), Common frill-fin goby (Bathygobius fuscus), Twig-like halfbeak (Family Hemiramphidae), a young Three-spot damselfish (Pomacentrus tripunctatus), Bengal sergeant (Abudefduf bengalensis), and unknown blue fish that we often see here, filefish (Family Monacanthidae), White-spotted rabbitfish (Siganus canaliculatus) and a small Painted scorpionfish (Parascorpaena picta).
There was a very small school of tiny Striped eeltail catfishes (Plotosus lineatus).
There were lots of little gobies that are very well camouflaged. They seem to be Ornate gobies (Istigobius ornatus).
Chay Hoon taught me to look for baby seahorses in the Sargassum seaweed (Sargassum sp.). I didn't find any today but I did see this tiny blenny (Family Blennidae) that looks just like the seaweed.
The fishes I saw today were more or less the usual that we might see on a typical trip before the oil spill. But I feel there were fewer fishes, and the fishes were smaller.

I saw one very small clump of Tape seagrass (Enhalus acoroides) and there were several filefishes (Family Monacanthidae) sheltering among the leaf blades. Even such a tiny clump of seagrass can make a difference for marine life!
Today I am struck by the large numbers of shrimps and prawns of all kinds on the shore. There were also a lot of tiny tiny baby fishes. In the photo below, there's a large prawn buried in the sand with its large eyes above ground, one very tiny shrimp swimming above it, and two tiny fishes at the bottom left.
I saw many busy small Penaeid prawns (Family Penaeidae) of various kinds.
There were several Ghost crabs (Ocypode cerathophthalmus) skittering about in the dark.Today I saw two dead hermit crabs. One was upside down in a crevice under a big rock, the other seems to be recently dead as a scavenging snail seems to be eating it.
There were also a lot of medium-sized swimming crabs (Family Portunidae) of all kinds including many small Flower crabs (Portunus pelagicus) and I also saw one Red egg crab (Atergatis integerrimus).
I didn't see many sponges. This was the nicest looking one. It's the Blue spatula sponge (Lamellodysidea herbacea).
Seaweeds seem to be starting to return to the shore. The most abundant seaweed I saw today were Knobbly agar-agar red seaweed (Soliera robusta), with some other kinds of Agar-agar seaweed (Gracilaria sp.), a few Spiny red seaweed (Acanthophora sp.), a few Mermaid's fan (Padina sp.) and very few clumps of Sargassum seaweed (Sargassum sp.).
I saw a few patches of Sea lettuce seaweed (Ulva sp.) among the more abundant red seaweeds.
Through the night in the darkness I could hear the calls of herons, and what seems to be migratory shore birds.

And thus ends the good news. Most of the rest of the shore is barren, and a very sad sight.

Vast areas of the shore were covered with clots of this brown scum. My first time seeing this after the oil spill.
The brown scum floats off in sheets.
The sheets slime everything on the shore.
Here's a closer look at the scum. I tried to feel it between my fingers. It was so fine that I couldn't actually feel anything.
One large colony of Pore coral (Porites sp.) seems to be shedding a white 'skin'. Corals can produce mucus to get rid of sediments and other unpleasant stuff that settle on them. But producing the mucus takes up energy and if the corals have to do it too often they can become weakened.
Large stretches of the shore at the mid-water mark were also covered with white and green scum.
Here's another look at brown floating scum and white scum.
Sadly, the mid-water mark is where most of the Common sea stars (Archaster typicus) are usually found. I still saw quite a number of these sea stars today, but I didn't obsessively count and photograph them as I did on my last trip.
Some of the sea stars were in mating position.
On some stretches, the streaming water reveals a dark layer under the sand.
On other stretches, there is less black stuff under the sand.
Even in at the mid water mark, there are still stretches of sand with crude under a thin top layer of sand.
I saw several living moon snails (Polinices didyma) burrowing in the sand. I didn't see any living Gong-gong snails (Strombus canarium) today.
I only came across a handful of these buried Acorn worms (Class Enteropneusta) creating their typical coiling casts on the surface. I scratched at the sand next to the piles and there seems to be no or little black stuff in the sand near these worms.
In some parts, a sheen of slick was still forming on the water surface.
On the high shore, there are still stretches of buried crude. I just scratched this with my foot and there is a thick layer of crude under a thin layer of sand. The crude is still sparkly and black.
An animal has just dug into the sand revealing the crude just beneath the surface.
All the large plastic bags on the high shore remain coated in crude, still brightly sparkling three months after it landed on the shore.
Today a pair of cheerful young men were energetically foraging along the sea wall with hand nets. They even said hello to me and asked if I found anything interesting before hurrying off. I noticed they didn't seem to have anything much in the sacks that they carried. In the past, we have encountered people gathering fishes that hide among the rocks with hand nets.

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

Tomorrow I shall be checking up the other stretch of Tanah Merah on the first evening low tide of the year.

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