26 December 2011

Terumbu Semakau with scary anemone and scarce seagrasses

This scary looking anemone is seldom seen, but I suspect has a nasty sting! So it was with much trepidation that I tried to photograph it in murky water. Trying to get a good shot without getting too close!
Sadly, the seagrasses here seem almost gone! Terumbu Semakau had lush meadows on our previous trips, probably the best growths after Cyrene Reef.

Here's another look at the Haekel's anemone (Actinostephanus haekeli). Those I've seen in the past were all black. My first time seeing one expanded that had brownish tentacles.
The tide was higher than predicted again! But this didn't stop us from landing on the reef. Another problem was a massive bloom of Sargassum seaweed (Sargassum sp.), normal for this time of the year. It makes it tricky to walk through as we don't want to kill marine life or step on Mr Stonefish! On the plus side, it didn't rain!
Fortunately, the Sargassum zone is limited to the edges of the reef, and we could walk more safely beyond it. But the water is rather murky, so it was a challenge to take photos even underwater. The strong breeze rippled the water so it was impossible to shoot from above water. Sigh.
The reef is vast and as the tide finally fell a little, we can see the extent of it. Here with Pulau Jong on the left (and a tiny shore explorer in our orange life vest) and Semakau Landfill on the right.
Terumbu Semakau is a submerged reef that lies just off the Semakau Landfill and some parts of the original Pulau Semakau.
The reef lies near Pulau Bukom, on the horizon. And yet, it has lots of marine life!
I couldn't go to the reef edge where most of the spectacular corals grow, but in the shallower middle of the reef, there were some small colonies, mostly Favid corals (Family Faviidae). With a few Pore corals (Porites sp.). Most of them were not bleached.
There were still some very large colonies of hard corals here. I'm relieved to see these made it through the coral bleaching that badly affected the corals here in 2010.
I saw two small colonies of this Acropora corals (Acropora sp.).
This is what I saw of these corals on our first trip to Terumbu Semakau in May 2010. There were lots more of the corals, the water was clear even though we also arrived at high tide.
Acropora hard coral (Acropora sp.)
I was quite shocked to see how little seagrass there was on Terumbu Semakau. The Tape seagrass (Enhalus acoroides) were all short and cropped. I saw several small patches like this. There were a few patches with sparse but long blades, mostly in the Sargassum zone.
I came across a small patch of Serrated ribbon seagrass (Cymodocea serrulata). I saw several patches of Spoon seagrass (Halophila ovalis). I didn't come across any Noodle seagrass (Syringodium isoetifolium) which we have seen here in the past.
The seagrass meadows were already sparse when we visited in March 2011. At that time, most of the Tape seagrass (Enhalus acoroides) were short and 'chopped'. But all the previously recorded species were seen: including the rare Noodle seagrass (Syringodium isoetifolium), Serrated ribbon seagrass (Cymodocea serrulata) and lots of Spoon seagrass (Halophila ovalis). .
Here's what the seagrass meadows looked like when we visited in June 2010.
And the lush growths seen on our first visit to Terumbu Semakau in May 2010. TeamSeagrass monitors seagrass health on nearby Pulau Semakau and similar habitats like Cyrene Reef. Hopefully, this data will help us better understand what is happening to seagrasses on all our shores.
Even in the high murky water, I could still see interesting marine life. Here's a little Spotted top shell snail (Trochus maculatus). It was clinging fiercely to the rock. Perhaps laying eggs?
I came across a half shell of what seems to be a Hammer oyster (Malleus sp.). Interesting internal structure!
All of us encountered small Noble volutes (Cymbiola nobilis). I saw two of them (about 8cm long).
This sponge had slits all over it. From Swee Cheng's Guide to Sponges of Singapore, think it's the Spongia sponge which has a close relationship with clams (Vulsella sp.) that lives only in sponges. The slits are the opening of the clam's shell while the little holes are part of the sponge structure.
I took a closer look at this Prickly yellow sponge (Pseudoceratina purpurea) and realised it too may have clams embedded in the branches. Some of the bumps were flattish with a slit around the edges. When I touched them, the slits closed up!
There were all kinds of different colourful sponges on the reef too!
The only nudibranch I saw was the common Jorunna funebris. Even Chay Hoon couldn't find any special nudis. The tide was just too high. But Russel spotted some squids! And James got good shots of a flatworm possibly eating an ascidian.
I saw a few individuals of some common marine life such as leathery soft corals (Family Alcyoniidae), flowery soft corals (Family Nephtheidae), Frilly sea anemones (Phymanthus sp.), two Giant sea anemones (Stichodactyla gigantea). I saw several Hairy crabs (Family Pilumnidae), a Red egg crab (Atergatis integerrimus), many swimming crabs (Family Portunidae). Also one fan worm (Family Sabellidae).
Common encrusting animals like zoanthids (Order Zoanthidae) and ascidians give a touch of colour on coral rubble.
As we wandered in the high water, Andy headed right to the reef edge to try to remove a long stick that seems to be used to lay out driftnets. Near him was a sampan with some people. On our trip here in June 2011, we did come across a very long driftnet laid across the reef. Driftnets not only kill fish but also rip up corals and other immobile marine life. Fortunately, on this trip, we didn't see any nets. There was one old broken fish trap which we flattened.
The reef was rather quiet today. It was hard to do a thorough check in the high murky water. Hopefully all is well in the deeper waters. We can only hope for the best, and go back to check on the reef some other time.

Others who posted about this trip
  • James with flatworm possibly eating an ascidian!

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