05 November 2009

Boom in the Bryopsis Bloom

When life gives you Bryopsis, you get a Bug Backache . . . a Bug-ache?
The thick tangle of Hairy green seaweed was teeming with teeny weeny critters!

Yesterday, the shores of Sentosa were smothered in a bloom of Hairy green seaweed (Bryopsis sp.).
In the water, it was like walking through a green bee hoon soup. Rolls of the seaweed accumulated on the high shore. But when we took a closer look, we saw a whole galaxy of marinelife!
Besides minute crabs, there were small Swimming crabs (Family Portunidae) in all sizes and colours and patterns.
Miniscule crabs of all kinds.
And the cutest, tiniest, littlest Hairy crab (Family Pilumnidae) that I've ever seen.
The most abundant crustaceans, however, were amphipods. Also known as beachfleas, these animals are not shrimps but belong to a different Order Amphipoda.
Many were busy in pairs. Hmmm. Probably making more amphipods.
There were also lots of worms of all kinds slithering among the strands of seaweed. Like these pretty glittering bristleworms (Class Polychaeta).
I even saw a tiny flatworm. It seemed to have a tail.
And strangely, we also saw many many peanut worms (Phylum Sipuncula)!
Processing the photos back home, I found yet more critters! A tiny brittle star (on the left) and possibly a sea spider (on the right).
But of course everyone just wants to see slugs. There were a few large Ornate leaf slugs (Elysia ornata) hidden among the seaweeds and very difficult to spot or take a good photo of.
Most of the slugs, however, were very tiny. There were lots and lots of Bryopsis slugs, which I think are Placida dendritica. These are not only small but also well camouflaged in the seaweed.
A little more obvious but still often overlooked as just a bit of fluff, is the Woolly elysia.
And what a surprise to see many of these tiny nudibranchs! They seem to be some sort of Gymnodoris.
While the previous slugs are vegetarians that just slurp up the sap of seaweeds, nudibranchs are carnivores. And some Gymnodoris nudibranchs even eat other nudibranchs. So the little Gymnodoris must be the Feared Predator that strikes terror among the tiny creatures of this miniature jungle.

Wow, it sure is surprising what we can find if we take the time to look. We should do this more often. Here's what I saw the last time I peered closely at a bunch of seaweeds. This was at Pasir Ris during a bloom of Sea lettuce (Ulva sp.).

This experience also emphasises why we should avoid stepping on seaweeds. One careless step can kill countless tiny creatures.

And all this stooping and peering is really hard on vertebrates, who unfortunately have (now aching) backbones.


  1. I think beachflea bites people. It did a few times when I walked on the shore.

  2. Oh dear. Thanks for the warning Murphy. Though I'm more afraid of sandflies! And so we usually go out to the shores well covered.



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