13 December 2012

Rainy day check on seagrasses at Changi

Who is this hiding in the sand? We met this little creature and many others on a rainy day check on seagrasses at Changi this afternoon.
I was worried about the seagrasses as they seemed to be buried in sand during my last trip here in August and in May.

The shy little guy is a Pebble crab (Family Leucosiidae)! It does indeed look like a pebble and it can rapidly burrow into the sand, leaving only its tiny eyes peeping out. We also saw lots of little Flower crabs (Portunus pelagicus) with some moults of larger ones, many Spotted moon crabs (Ashtoret lunaris) and one colourful Flower moon crab (Matuta planipes). Rick also spotted an Elbow crab (Family Parthenopidae).
While I didn't see any living Baler snails (Melo melo) I did see only medium sized shell occupied by a Striped hermit crab (Clibanarius infraspinatus). There were many of these hermit crabs on the shore.
There were many hermit crabs on the shore. A shell occupied by a hermit crab is usually also occupied by all kinds of other animals such as Slipper snails. Here are two different kinds of Slipper snails, the Flat slipper snail (Crepidula walshi) on the inside of the shell, and Conical slipper snail (Calyptraea extinctorium) on the lip of the shell. The smaller slipper snails are males stuck on top of the bigger females!
In the murky water, a flash of a tiny flatfish: it looks like a Tongue sole (Family Cynoglossidae).
Among some seaweeds was a bright orange Volvotella slug (Volvatella vigourouxi), the only slug of the day. Other colourful creatures in the seagrasses include many Pink warty sea cucumber (Cercodemas anceps) and the Thorny sea cucumber (Colochirus quadrangularis). There were also many empty shells of Window pane clams (Placuna sp.), a dead Hammer oysters (Malleus sp.). Also a few large White sea urchins (Salmacis sp.).
In the sand, we found Cake sand dollars (Arachnoides placenta), Plain sand stars (Astropecten sp.), Painted sand stars (Astropecten sp.), a few Sea pencils, a Ball sea cucumber (Phyllophorus sp.), Smooth sea cucumbers and two Notable sea cucumbers (Holothuria notabilis).
Thankfully, there was still lots of seagrasses on the mid-water shoreline.
Here's another look at the seagrasses from one of the small narrow sandbars that stick out seaward.
I tried to have a look at the seagrass situation in deeper water, but it was too murky to see. Rick spotted a furrow that looked like a dugong feeding trail!
I saw all the three species of seagrasses found here: Needle seagrass (Halodule sp.), Spoon seagrasses (Halophila ovalis) and Fern seagrasses (Halophila spinulosa). They were healthy and lush, with fresh clean blades. Although there were patches with exposed rhizomes and bases of leaf blades, I didn't come across any bleaching blades.
There also a bloom of Scalpel feathery seaweeds (Caulerpa scalpelliformis). Easy to mistake for seagrasses, these are green seaweeds.
Rick noticed a layer of grey sand under the brown sand. Hmm? Is it because there is a fresh layer of sand washing down from the artificial beach on the high shore?
Just before we left, Rick spotted this wriggling worm. It looks like a Solitary tubeworm (Diopatra sp.)out of its tube, a rare sight! The beautiful iridescent worm has tentacles on its head and feathery stuff on the side of the body.
Despite the rain, we still managed to see some interesting marine life! But soon we had to leave as the rain got heavier. Hopefully, I'll get a chance to have a better look at the seagrasses on Changi on another low tide.

Tomorrow, we will be making our annual trip to the mysterious and special Lost Coast at Changi East.

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