12 June 2010

How's Changi doing after the oil spill?

Early this morning, a small team when to check up on how this Changi shore is doing after it was hit by the oil spill on 28 May.
Although Sam checked up on this shore on 29 May and reported that all was well here, we worry about long-term effects of the oil spill and dispersants used. So it was a relief to see that the shore is still very much alive today! There were lots of tiny biscuit sea stars!

We love this Changi shore for the wonderful variety of echinoderms that are commonly seen here. These include sea stars, sea cucumbers, sand dollars, sea urchins and brittle stars. And all our favourite echinoderms seemed happy and healthy on this shore today.

There were lots of busy Plain sand stars (Astropecten sp.) on the clean sand. And I saw one Painted sand star (Astropecten sp.). Mei Lin and Chay Hoon each found baby Knobbly sea stars (Protoreaster nodosus) too! While Kok Sheng found a baby Cake sea star (Anthenea aspera). Check out the blogs by the team for more photos and stories.
Wee Hock also found a brittle star!

Today we saw all our favourite sea cucumbers: there were many Thorny sea cucumbers (Colochirus quadrangularis), some Pink warty sea cucumber (Cercodemas anceps).
Several small and large 'Garlic bread' sea cucumbers (Holothuria scabra), and Kok Sheng found this small strange transparent sea cucumber which is probably the See-through sea cucumber (Paracaudina australis). We also saw many Smooth sea cucumbers, and Ball sea cucumbers (Phyllophorus sp.). Chay Hoon also saw one Big synaptid sea cucumber (Family Synaptidae) not sighted previously on this shore.

We also saw several of the special Remarkable sea cucumbers (Holothuria notabilis) identified by Robin and which we have so far also seen only on Chek Jawa and Cyrene Reef.
Also seen, several of these Orange sea cucumbers with blue lines (may be faint or dark). These are not often seen on this part of Changi.
But today I didn't see any Beige sea cucumbers or Polka-dotted sea cucumbers (Holothuria ocellata) that are sometimes common here. Perhaps it's just not the season for them today.

All the commonly seen sea urchins on this shore were present today: many Black sea urchins (Temnopleurus sp.) with short spines, many small White sea urchins (Salmacis sp.). Also very abundant today were pink Thorny sea urchins (Prionocidaris sp.).
Both the white and black sea urchins 'carry' things on themselves. From small bits of debris to seaweeds and seagrasses. This white urchin (see yellow arrow) seems to have carried not only a small Window pane shell and an ascidian, but also a bit of debris to which a pink Thorny sea urchin was clinging!
We saw many Pink sand dollars (Peronella lesueuri) today. Sam also experienced this when he visited after the oil hit this shore. Chay Hoon found the first one, and many more too. I only saw this one (below), which was on the sand surface but 'carrying' sand so it was well camouflaged. The sighting of many Pink sand dollars is unusual as we have not seen them in numbers on Changi before.
The shore also had many healthy and large Cake sand dollars (Arachnoides placenta). I'm glad I didn't see any heart urchins today. At Tanah Merah just after the oil spill hit it, we saw several Oval Maretia heart urchins (Maretia ovata) on the surface. These burrowing creatures were probably distressed by chemicals in the ground.

This Changi shore is often teeming with flatfishes. And this morning, it remains so. In the outgoing tide, I saw this flatfish swimming away into deeper water. It appears to be a Tongue -sole (Family Cynoglossidae).
Tang Ling and I saw this stranded Peacock sole (Pardachirus pavonina). We carefully brought it back to the water whereupon it immediately disappeared. The fish produces a mucus that appears to have shark-repellent properties! Its bold patterns may serve to warn of its unpleasant nature.
Chay Hoon found this special flatfish that we have not seen before! It sure looks like a Zebra sole (Zebrias zebra). It has spiny things where its pectoral fins should be. Wow. Here's more about the fish on the Guide to Common Marine Fishes of Singapore. I shall have to do a fact sheet on this fish soon. Although we visit our shores so frequently, we still often see something totally new!
This is a strange fish that I don't recall seeing before. Is it a kind of flathead (Family Platycephalidae)?
We saw several small pipefishes that we commonly see among seagrasses. This one was found by Stephen.
There were lots of other fishes too. Familiar favourites of this shore that I saw today include many small White-spotted rabbitfishes (Siganus canaliculatus) swimming in the pools, and one that was stranded but alive. It swam off when I put it back into the water. Other common fishes include the Trumpeter perch (Pelates quadrilineatus).
There were also MANY Longspined scorpionfishes (Paracentropogon longispinis) and they were much larger than usual for this shore. Also abundant were these boldly barred flatheads (Family Platycephalidae). There were also many small Whitings (Family Sillaginidae).

Sadly, we couldn't find a single Estuarine seahorse (Hippocampus kuda) that are sometimes seen here. We hope they have simply moved into deeper water and that we will see them another time. Other than this, the fishes we saw seemed to be the ones we usually see on our trips.

Thank goodness the Gong gong conch snails (Strombus canarium) here were all very much alive. On Tanah Merah after the oil spill, many Gong gong snails were dead or dying. There were many living juvenile Gong-gong on Changi today, with thinner shells. Also in this photo, a tiny hermit crab, and a Plain sand star!
The burrowing snails at Changi today seemed happy and healthy. I saw one Pink moon snail, and one Lined moon snail (Natica lineata). Also several white Ball moon snails (Polinices didyma) busily burrowing in the clean sand.
Also abundant were many whelks (Family Nassaridae). But molluscs we sometimes see on this shore which we missed today include 'sotong' or cuttlefishes. We also didn't see any octopus. Also missing were living Button snails (Umbonium vestiarum) but these have been 'missing' for some time already.

The only nudibranch found were tiny black Gymnodoris nudibranchs (Gymnodoris sp.), of course sighted by Chay Hoon. And Mei Lin saw some Geographic seahares (Syphonota geographica). I did see some eggstrings of seahares among the seagrasses.

Among the seagrasses, were many many living Window pane shells (Placuna sp.) from small to very large ones. Also still seen on the shore, many living Fan shells (Family Pinnidae).
How reassuring to see many active Spotted moon crabs (Ashtoret lunaris) paddling about in the waves. I saw lots of small and large ones. When we visited Tanah Merah the day after the oil spill hit, lots of the moon crabs were dead or dying. Changi's shores were also teeming with small crabs of all kinds, and lots of small Flower crabs (Portunus pelagicus).
How nice to see lots of wriggly lively shrimps of all kinds on Changi today: the prawns (Family Penaeidae) that grow up to be our seafood, and many small snapping shrimps (Family Alpheidae). At Tanah Merah, many dead shrimps were seen after the oil spill hit that shore.
There were many large and happy orange Striped hermit crabs (Clibanarius sp.). And lots of smaller drab Tidal hermit crabs (Diogenes sp.).
I saw one Spearer mantis shrimp (Harpiosquilla sp.), very much alive and often seen here. On Tanah Merah, I saw a pair of banded mantis shrimp, unfortunately they were dead. James saw it also on Changi last year. Hopefully they are happily alive and hidden away on Changi today.
Burrowing creatures are among those expected to be affected by the dispersants used in the oil spill. So it was a relief to see many living burrowing Sea pencils today. These white tubular animals are sea pens (Order Pennatulacea), a colony of many tiny white polyps. So far, I've only seen Sea pencils in large numbers on Changi shores.
With a narrow white tubular body column, the Peachia anemone (Peachia sp.) does look like a Sea pencil but sea anemones are in a different Order Actiniaria. I also saw a small Swimming anemone (Boloceroides mcmurrichi), which doesn't burrow but has a short body column and clings to seagrasses.

There were several healthy looking Haddon's carpet anemones (Stichodactyla haddoni) also none of them had shrimps. And several Tiny carpet anemones (Stichodactyla tapetum). The rest of the team, however, saw some stressed out anemones.
I only saw two peacock anemones today. Both of them seem to be the kind that is dusky with more elegant tentacles. I didn't see any common peacock anemones.
The seagrasses were doing fine. They were lush and green (not bleached). In the photo below are Needle seagrass (Halodule sp.). There were also lots of Spoon seagrasses (Halophila ovalis) and some Fern seagrasses (Halophila spinulosa). Today, there didn't seem to be much seaweeds on the shores.
It was good to see several signs of living Acorn worms (above). The tubeworms were well in their tubes and much alive. Only showing the tippy tips of their tentacles, as they ought to (below). And none of us saw any peanut worms. Thank goodness, as the sight of countless dead or dying peanut worms on oil-slicked shores at Tanah Merah was quite painful.
Today on the shore, there was no smell of petrol. I didn't see any signs of oil stains even on the litter (sadly still common on the shore). Although there was this suspicious brown patch floating on the water on the high shore. But it could just be the usual scum that forms now and then on our shores (alas, our shores do have to put up with small 'slicks' every now and then).
On the very high shore were many empty shells of the Big brown clam (Mactra mera) which is quite a usual sight for me. There were no dead fishes on the shore, and most of the 'dead' crabs were moults.
Changi seems as lively as we usually see it on our previous trips. Let's hope this means there are no permanent long-term effects of the oil spill on this shore. As with our other shores, Changi remains on our regular schedule of checks and we will return again later on in the year.

After a lovely breakfast (thanks Tang Ling and Wee Hock!) we had a quick look at the mangroves at Changi Creek to look for signs of pollution.

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