13 May 2012

Bleaching anemones, uprooted sea cucumbers on Chek Jawa

 I saw bleaching carpet anemones on Chek Jawa during TeamSeagrass monitoring today.
The last time we saw lots of bleaching carpet anemones, was during the mass deaths at Chek Jawa in 2007! There were also lots of Smooth sea cucumbers lying above ground today. These are usually well buried in the sand. What do these sightings mean?

Most of the Haddon's carpet anemones (Stichodactyla haddoni) I saw today were the usual healthy shades of bluish green, green or purple. A few were yellowish.
But on the Northern sand bar, I saw about 10 small and medium-sized Carpet anemones that were quite seriously bleaching. I didn't see this on my last trip to Chek Jawa in Apr 2012 or in Jan 2012.
During the mass deaths at Chek Jawa in 2007, Carpet anemones turned bright yellow or neon green, bloated up, exploded and died. More photos of this here.
20070120 d7636
However, I did see bleaching carpet anemones in 2004 and 2005 which did NOT end up in mass deaths. So let's hope for the best...

Another disconcerting observation: lots of Smooth sea cucumbers lying above ground everywhere. On the sand bar, in the seagrass meadows. Most of them seemed unharmed. Although some looked a little chewed up. During the 2007 mass deaths, many burrowing sea cucumbers emerged and died. But today, I saw no other burrowing sea cucumbers above ground, e.g.,Garlic sea cucumbers (Holothuria scabra) , Ball sea cucumbers (Phyllophorus sp.). This is the first time I've noticed this. I'm not sure whether something in the ground has annoyed just the Smooth sea cucumbers, and none of the other burrowing animals. Or is this something natural and nothing to be alarmed about, e.g., are the Smooth sea cucumbers emerging to mate? Another reason to regularly monitor Chek Jawa!
I saw several Thorny sea cucumbers (Colochirus quadrangularis) and also some Pink warty sea cucumbers (Cercodemas anceps). They seemed alright, only this one seemed a little 'damaged'.
I saw a few healthy looking cerianthids (Order Ceriantharia). Sometimes called peacock anemones because they come in such a wide variety of colours, they are not true sea anemones. They build tubes that they can retract into, and are thus sometimes also called tube anemones.
Today, Len and Rudi of international SeagrassWatch are with us and I took the opportunity to learn more from them. TeamSeagrass Site 1, which is closer to the boardwalk, is full of seagrasses. Except for the tips of transect 2 and 3 where the Southern sand bar seems to have moved inward and thus there is no seagrass. This is how long term monitoring like TeamSeagrass can provide valuable information about changes taking place on a shore.
Here, there is lots of Smooth ribbon seagrass (Cymodocea rotundata), much more than previously. Len explained to me that this species of seagrass likes sandy substrates. Another sign that Chek Jawa is changing and that the central lagoon is becoming more sandy. Most of the Smooth ribbon seagrasses are alright, although I came across a few patches with yellowing bases.
Len pointed out some dugong feeding trails near Site 1!
We then head out to Site 2 which is nearer the Northern sand bar. This sand bar has expanded so much that it has 'eaten' up almost all of Transect 1 and quite a bit of Transect 2. I still failed to find Sickle seagrass (Thalassia hemprichii) that used to grow here. These were probably buried by the expanding Northern sand bar.
Len spots more dugong feeding trails near Site 2. Later, I learnt from Len that we can't really tell much from dugong feeding trails (like how many dugongs or how big they are), aside from the fact that dugongs have come by to feed. He says that elsewhere there are seagrass meadows where there are known to be many dugongs, but few dugong feeding trails. Possibly because the dugongs just crop the seagrasses sticking out of the ground, without actually leaving a trail.
We had a quick look at the seaward side of the Northern sandbar and I noticed that the shallow intertidal portion has grown enormously. Today, the tide is not very low and  yet vast stretches are exposed.
Seagrasses are growing lushly here. There are lots of healthy looking carpet anemones here as well as various kinds of seagrasses.
Here, I saw lots of Spoon seagrass (Halophila ovalis) and Needle seagrass (Halodule sp.).
There are also Fern seagrass (Halophila spinulosa) here. And Rudi spotted dugong feeding trails here too.
There were still lots of Cake sand dollars (Arachnoides placenta) on the Northern sand bar. But I didn't come across the Button snails (Umbonium vestiarum), though we did see these in Mar 2012.
We then walked back south and along the Coastal Boardwalk so Len and Rudi could check out the seagrasses growing here. There's some colourful encrusting marine life growing on the 'legs' of the boardwalk! The ground here is still soft and silty (not so hard and sandy as from the pontoon to the Northern sand bar) and there's more Fern seagrass (Halophila spinulosa) growing near the low water mark. In the Southern lagoon, most of the Fern seagrasses are growing on the seaward side of the Southern sand bar.
I had a quick look under the stones on the rocky shore, and there's still quite a variety of animals there.
Len and Rudi then walked all the way to the seagrass meadows on the other side of House No. 1.
Where there are still some patches of the rare Beccari's seagrass (Halophila beccarii). In the past, there used to be larger stretches of this seagrass (seen in Apr 2008) but these seem to have been affected by large debris and some parts of the shore have been covered by sand.
These observations suggest that Chek Jawa is changing. While TeamSeagrass does help to monitor the health of seagrasses, it seems wider biodiversity monitoring as well as more data on changes in Chek Jawa's geography would be useful for a better understanding of what is going on.

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