16 July 2011

Rich reefs of Kusu Island

Kusu is ringed by thick growths of reefs and they seem to be doing well! Isn't it amazing to have such rich reefs just off our business district on the mainland!
The reefs seem to be doing better than our last visit in Sep 2010 just after the coral bleaching event.

With the outgoing super low tide, I rushed out to take a look at the corals at the mouth of the lagoon.
The reef edge stretched some way outside the seawall. On the horizon is the artificial shore created by burying the submerged reefs of Seringat and Kias. We visited this other shore with Dr Daphne recently.
The corals have also settled on the outside of the artificial seawalls!
The common corals here included Favid corals (Family Faviidae), Pore corals (Porites sp.), as well as many Blue corals (Heliopora coerulea). There were also many small colonies of leathery soft corals (Family Alcyoniidae) and of all kinds, as well as Asparagus flowery soft corals (Family Nephtheidae).
There were even some Circular mushroom corals (Family Fungidae)! It's the first time I've seen them on Kusu Island! They seemed alright although one was very pink.
Some parts of the reef were thick with delicate corals! It reminds me a bit of the thickly encrusted reefs at Raffles Lighthouse.
The delicate plates are mostly Montipora corals (Montipora sp.). Although there were also some Thin disk coral (Turbinaria sp.) and Flowery disk coral (Turbinaria sp.).
It was good to see several healthy Cauliflower corals (Pocillopora sp.) and Sandpaper coral (Psammocora sp.). These two species were badly affected by bleaching last year.
What a huge lilac-coloured coral colony! I was stumped by its identity.
A closer look reveal that this is probably a boulder shaped Horn coral (Hydnophora sp.). It is the largest colony of this kind of coral that I have seen!
I only saw two small colonies of Acropora coral (Acropora sp.).
I also came across some Brain corals (Family Mussidae).
I also saw some Lettuce coral (Pavona sp.).
I saw many healthy Galaxy corals (Galaxea sp.) today.
Here's a wider look at the reef at the mouth of the lagoon at sunrise, as the tide turned and the water started turning murky.
Corals have also crept inside the lagoon ringed by the artificial seawall. There are still many colourful colonies here.
Inside the lagoon, there are thick 'fields' of branching corals! These could be Pore corals (Porites sp.) or Montipora coral (Montipora sp.).
Some corals, however, were still showing signs of bleaching.
These were of various species. But I didn't notice many diseased corals on this trip.
There are lots and LOTS of Magnificent anemones (Heteractis magnifica) at Kusu! The cluster at the mouth of the lagoon has grown in number of individuals!
I learnt from Dr Daphne that Magnificent anemones can reproduce by division. This often results in a cluster of clones which look like one another. Indeed, at Kusu, some clusters had purplish body coloumns, while others had reddish body columns.
Aha, I finally get to have a look at this sea anemone that the others saw on our trip last year. At first glance I thought it was a Snaky sea anemone (Macrodactyla doreensis) especially when I saw the white radiating stripes on the oral disk.
But a closer look at the huge bumps on the body column, and the leathery tentacles with pink tips and indeed, the team did identify it correctly as a Leathery anemone (Heteractis crispa). It had a pair of Five-spot anemone shrimps (Periclimenes brevicarpalis) in it!
There were also many Giant carpet anemones (Stichodactyla gigantea), and one of them had a False clown anemonefish (Amphiprion ocellaris). Of course, there were many Frilly sea anemones (Phymanthus sp.) in the reefs.
I saw some interesting reef fishes today. I don't know what this one is.
Mystery fish no. 1
This looks like an Anchor tuskfish (Chaeorodon anchorago).
Other interesting fishes seen included a glimpse of an Eightband butterflyfish (Chaeotodon octofasciatus), and a hidden Yellow-banded damselfish (Dischistodus fasciatus). The two fishes on the lower row I'm not too sure of their identity.
Lower row, mystery fish no. 2 (left) and no. 3
Today, we saw many Saron shrimps (Family Hippolytidae)! Usually shy and lurking in crevices, this one was wandering out on the sand and was easy to photograph for a change! I also saw many swimming crabs (Family Portunidae) and a Sally-lightfoot crab (Grapsus albolineatus). When the tide turned, there were suddenly many Moon crabs (Ashtoret lunaris) in the water!
After the tide turned, we explored the lagoon. Here, there are some patches of tiny Spoon seagrass (Halophila ovalis). Among them were bazillions of Bazillion snails (Batillaria zonalis), and many Shadow gobies (Acentrogobius nebulosus). Also some tiny hermit crabs, but not a lot of other creatures.
Chay Hoon found this Remarkable sea cucumber (Holothuria notabilis) which we have been seeing on this shore. It's good to know that it's still there.
In one corner of the lagoon at the high water mark, there were patches of bright green seaweed, possibly Chaetomorpha sp.
Among the green seaweeds were other kinds of seaweeds. And many 'beads' which might be the egg mass of sea slugs. We didn't see any slugs in the seagrass or seaweeds, perhaps a new batch is just about to hatch?
In the sandy lagoon, there were some Cake sand dollars (Arachnoides placenta) and many Common sea stars (Archaster typicus).
We found that the lagoon seemed a lot sandier, and the level of sand in the reefier parts also seemed higher. I get the sense that there was a 'sand slide' from the high shore leading out to the mouth of the lagoon. We failed to find the Fire anemone (Actinodendron sp.) and Haddon's carpet anemones (Stichodactyla haddoni) that used to be here. Did they get buried? Where did the sand come from? Beach 'improvement' or due to the ongoing dredging near Kusu?

We should visit Kusu's lovely reefs more often, but there just aren't enough low tides! More about Kusu Island on wildsingapore.

After the trip, Andy and I dropped by to listen to Wei Ling's talk about Singapore's seagrasses.

Tomorrow another super early trip, to our now favourite submerged reef, Terumbu Bemban.

Posts by others on this trip
  • James with feather stars, razorfish and more.
  • Rene on facebook with anemone overdose and a heart urchin.
  • Russel on facebook with lots of colourful corals and more.
  • Jerome on facebook.

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