15 June 2010

Extensive coral bleaching at Tuas

Today a small team joined TeamSeagrass at Tuas, for monitoring done by the volunteers of Schering Plough.
As soon as we hit the shore, the weather turned ominous. And more ominous sights awaited us at the Merawang beacon (in the distance on the horizon) where many wonderful corals can be found.

Even before I reached the beacon, I could see many white patches in the water. This was in the last of the sunlight before the clouds closed in and it started to rain.
And more white patches as I got closer to the beacon.
The little fluffy white patches were Flowery soft corals (Family Nephtheidae). It seemed to me that most of them were bleaching. Most of the Flowery disk corals (Turbinaria sp.) were bleaching too!
Almost all the Pore corals (Porites sp.), small and large, that I saw were bleached.
Some of the bleaching colonies are very large!
A closer look at the large bleaching Flowery disk coral (Turbinaria sp.).
Bleaching happens when corals (and other cnidarians) lose the symbiotic algae in their bodies which help produce nutrients. It is the algae that give the animals their colour. Here's a comparison of a bleached Flowery disk coral (left photo) and one that is normal (right photo). Read more about bleaching on Bleach Watch Singapore.
But not every single hard and soft coral was bleached. There were a few Flowery soft corals that were still pink.
Some hard corals were also still alright. This large Thin disk coral (Turbinaria sp.) has its normal colours.
Colonial anemones or zoanthids (Order Zoanthidea) of all kinds seemed normal, and sponges continue to add a dash of colour to the shore.
More colourful sponges near bleached soft corals.I saw a Snaky sea anemone (Macrodactyla doreensis). Its tentacles seem more white than usual, but its oral disk is still brown.
The Haddon's carpet anemones (Stichodactyla haddoni) were still plentiful near the mid-shore among the seagrasses and in their normal colours. I didn't see any that were bleaching.
The shallow lagoon is carpeted with these muffin-shaped soft corals with tiny star-shaped polyps (Family Alcyoniidae). They are still mostly dark, as they usually are.
Other cnidarians on this shore do not seem to be affected by bleaching. The peacock anemones seemed normal, with their usual colours.
It's my first time seeing the Sea pencil on Tuas! This colony of tiny polyps is normally white so I don't think it is bleaching. Mei Lin also found a Spiky sea pen (Scytallium sp.).
Sea fans (Order Gorgonacea) are also cnidarians and there are many beautiful specimens here! Hoong Wei has come specially to have a look for the little snails, Ovulids (Family Ovulidae) that live only on sea fans. He found many different kinds of sea fans here and they seemed free of bleaching.
Other sea creatures on the shore seemed normal. I saw very many Thorny sea cucumbers (Colochirus quadrangularis) and many Orange sea cucumbers.
Mei Lin also found what looks like a Coral ghost shrimp (Glypturus sp.), my first time seeing one on Tuas.
We had to cut our trip short due to the lightning, but are glad we managed to come a little earlier so that we could check up on the corals at Merawang beacon. Thanks to Sheryl and Helen for arranging for us to come earlier.

The Tuas shore is home to a wonderful variety of marine life! Let's hope it will recover from this bleaching event.
More photos of Tuas on wildsingapore flickr.

More about coral bleaching on Bleach Watch Singapore.

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