16 December 2008

An 'improved' beach on Changi?

A stretch of Changi appears to recently suffered from 'beach improvement'. A small team visited it last evening.It was the school holidays and lots of people were out on the shores. The families and kids were obviously more interested in the muckier parts of the shore than the sandier areas.

Some explored the soft shore barefooted (which is dangerous as sharp objects may be buried under the soft silt). There was obviously some looking around with plastic containers, which were abandoned on the shore. This one still had a cowrie snail in it.Almost every stone had been overturned and most were not turned back. Including very large rocks like this one. Marine life find shelter under such stones and will die if the stone or rock is not replaced gently. We spent much of our time turning back the stones.Large oysters on the rocks which take a long time to grow to such a size were recently pried open as their empty shells have not yet been colonised by encrusting animals.In the shallow shores off the beach, several were fishing with cast nets.The rocky shores are very much alive. Some parts had lots of encrusting sponges and other animals.They come in all kinds of shapes and colours.Also coating the rocks is this very hardy hard coral, the Zebra hard coral (Oulastrea crispata). It has its common name because of its distinctive black-and-white skeleton.
Unfortunately, some of the sponges had discoloured tips. We're not really sure if this means they are diseased or affected by environmental conditions.On some parts of the rocky shore, stones were coated in what seems to be melted chocolate. These are probably the Melted chocolate ascidian.We also saw one tiny colony of Pink flowery soft coral (left photo) and a newly established sea fan with just one thin short branch (right photo).In deeper water, I saw a sea fan that appears to have been knocked over. It didn't seem to be doing very well.Sea fans are colonial animals made up of tiny polyps that look like small sea anemons with a tubular body column topped with a ring of tiny tentacles. In the photo on the right you can see the tiny yellow polyps of this sea fan. Sea fans are also homes to many small animals. This one had a few tiny colourful brittle stars wrapped around the 'branches'.Some parts of the rocky shores were carpeted with tiny zoanthids, which are also called colonial anemones.There were a few Ovum cowries (Cypraea ovum) on the rocky shores. These snails often envelope the shell with the fleshy mantle which has 'hairy' projections. So they are sometimes mistaken for slugs. Here's more on how to tell apart slugs and slug-look-alikes, and how to tell apart the Ovum cowrie from another similar cowrie found in the same habitat.
The rocky shores provide holes and hiding places for animals such as this octopus.
As well as a mantis shrimp (Order Stomatopoda). Despite its common name and appearance, this animal is not a shrimp and belongs to different group of crustaceans. They have sharp pincers to grab prey with as well as to pinch inquisitive fingers. So don't touch it!
There were a few medium sized carpet anemones (Stichodactyla sp.) on the rockier areas.
Those seen were spitting out a brownish liquid from their mouths. There were also a few swimming anemones (Boloceroides mcmurrichii) in the soft seagrass area. But sadly we did not see any other kinds of sea anemones. In the past, this shore was teeming with various kinds of sea anemones.There was also this purple sea cucumber that is sometimes seen on our rocky shores. Several ball sea cucumbers (Phyllophorus sp.) were also seen on the shores.Another surprise was this large Biscuit sea star (Goniodiscaster scaber).And a rather battered looking feather star (Class Crinoidea). These animals are relatives of sea stars and are sometimes seen on our northern shores.
The soft shores were covered with a bloom of Mexican green seaweed (Caulerpa mexicana) and some patches had good growths of Spoon seagrass (Halophila ovalis). Poking out from these growths were some peacock anemones (Order Ceriantharia), fan worms (Family Sabellidae) and thorny sea cucumbers (Colochirus quadrangularis).Some peacock anemones had phoronid worms (Phylum Phoronida) near them. This one is pinkish with black tips on the feathery tentacles.It's important to watch your step on all our shores. Even a dead leaf may shelter small animals such as this Porter crab (Family Dorripidea). This crab carries debris on its back with its special backward facing legs. It has another set of feathery legs which it uses to swim with.
A closer look among the seaweeds reveals a whole host of tiny crabs. These will grow up into Flower crabs (Portunus pelagicus) a favourite seafood item. Thus preserving seagrasses and weedy areas that may appear silty and rubbishy allows the fishermen on Changi to harvest these creatures when they grow up.Other animals include a tiny carpet anemone hardly bigger than a seagrass leaf, and a coil of eggs laid on a seagrass leaf.And a really tiny black sea urchin (Temnopleurus sp.).
And this tiny slug-like animal with a pair of tiny tentacles and what appears to be an internal shell. I have no idea what it is.Here's another look at it.

After exploring the shore, we realised it was a lot narrower than it used to be, even though last night was a very low tide. Also, many animals usually seen were missing (such as the seahorses, sea anemones and nudibranchs seen on past trips) or very much reduced in numbers. Ivan shares that he visited this shore about a month ago and he found much more life here.

It was then that we realised that a great deal more sand was on the beach. In fact, a finger of sterile sand stretched out in the middle of the shallow lagoon. Ivan said he did not see this sand bar during his last trip. All this sand is possibly the result of 'beach improvement'. Sadly, such works reduce the diversity of marine life, so that ironically, beach visitors have less of our marine heritage to enjoy.

This stretch of shore also faces regular dredging in the area.
Past visits to this shore on the wildfilms blog
  • In Jun 08 with frogfish, flatworms and sea anemones.
  • In Oct 07 with seahorse, brittle stars, sea stars and flatworms .
  • In Jul 07 with world sea anemone expert Dr Daphne to find special sea anemones.
  • In Jul 07 with sea anemones and nudibranchs.

2 comments:

  1. This is a very nice site for exploring but please be very careful. I have been stung by a small fish (about the size of my last finger) and the pain is horrendous. I suspect the fish in question belongs to the weaver family, I did not take any pictures but it's red in color and have a row of erected sharp spines at the top. I say again, be VERY careful!

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  2. Thanks for that warning Anonymous. Yes indeed, our shores can be hazardous. I agree with you that it is best not to touch unfamiliar animals.

    Often though, we hurt animals more than animals hurt us. So we should try to be gentle when we visit our shores.

    Thanks once again for the reminder!

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