10 July 2010

Sisters Island: bleaching not so bad

An enthusiastic team headed out for Big Sisters Island not too long after midnight. Among the highlights, an encounter with a sea turtle sleeping in the lagoon!
But first the bad news: it was disturbing to see several large colonies of Pore hard corals (Porites sp.) that had a ring of bluish stuff near the top.

The colonies were not bleaching as the lower portions are still brown, but many had this bluish band. In addition, this colony was producing a layer of mucus (the whitish patch on the brown parts).
Another colony with large areas that was bluish.
Here's a closer look at the bluish portion. These seem to be dead and decaying parts of the colony. Is this some kind of disease affecting the Pore hard corals? Oh dear.
As expected, we saw bleached hard corals too. But the bleaching is not so bad: probably about 20%. Does it mean the bleaching event is ending? Or did Sisters Island escape being heavily impacted?

Most hard corals that were completely white were Favid corals (Family Faviidae). I also saw only one bleached Cauliflower coral (Pocillopora sp.).
We also saw a gathering of many bleached Circular mushroom corals (Family Fungiidae). Later on, Sam shared that he saw some that were not bleached.
While most of the leathery soft corals (Family Alcyoniidae) that I saw were bleached, I did see one that seemed alright.
There was one large Lettuce coral (Pavona sp.) that was partially bleaching.
The Brain corals (Family Mussidae) did not look healthy.
Some of the Favid corals had odd, bright colours or were very yellowish.
The Anemone corals (Goniopora sp.) and Montipora corals (Montipora sp.) seemed alright.
I came across this Carnation coral (Pectinia sp.) with tentacles! A first for me! Looking more closely at the photos, I realise the polyps are on the sides of the 'walls' and the long tentacles seem to 'pool' in the area between the walls rather than extending away from the colony.
I did not see any Anchor corals (Family Euphyllidae).

Most of the corallimorphs (Order Corallimorpharia) were not bleached.
All the Frilly sea anemones (Phymanthus sp.) that I saw were bleached.
There were several Giant carpet anemones (Stichodactyla gigantea). While I didn't see any anemonefishes in them, Sam saw some fishes in one. I also only saw one Haddon's carpet anemone (Stichodactyla haddoni). None of these large anemones were bleached.
I saw a little sea anemone with balls on the tips of its tentacles. So far, I've only seen this on our Northern shores.
As the tide turned, I checked the high sandy shore and suddenly, there were several of these odd blobs that turned out to be sea anemones. And many Peachia anemones (Peachia sp.) also emerged from the sand.
The big lagoon remains very shallow with lots more sand in it compared to our visits many years ago. Many of the hard corals seem to be getting buried in sand.

The shore was rather quiet today. There was hardly any seaweeds and the ground rather bare. There weren't as many octopuses out on the shore today. And those I saw were small.
But there were lots of fishes in the lagoon. I saw several of these fishes lying quietly on the bottom. I still have no idea what it is.
More fishes I saw that I haven't identified.
As usual, I'm not very good at spotting little creepy crawlies and only saw these two flatworms which are very commonly seen on our reefs: the tiny Blue-lined flatworm (Pseudoceros sp.) and the large Spotted black flatworm (Acanthozoon sp.).
I head out to the other side of Big Sisters Island to try to find the missing giant clam. In the smaller lagoon, there were lots of VERY large Common sea stars (Archaster typicus). Earlier on, I also saw the Pink spotted sea cucumber that has just been identified as Holothuria fuscocinerea and is a new record for Singapore. There were also a few Black long sea cucumbers (Holothuria leucospilota).
There are only small patches of Spoon seagrass (Halophila ovalis) here and they were heavily covered in epiphytes today. The small cluster of Tape seagrass (Enhalus acoroides) is still there.
And I saw this coastal plant in flower. But I have no idea what it is. Alas, I couldn't find the giant clam as the tide wasn't really low enough.
While I was away, Ivan came across a sea turtle that was sleeping in the lagoon! The rest of the team also saw a seahorse and other exciting finds. They promised to blog about their finds. I'll update this post with links to theirs.

The tide turned well before sunrise and we only enjoyed this spectacular show on the way home!
It's a relief to know that bleaching at Big Sisters is not extensive!

Other posts about this trip:

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