SJI Mangrove Walk and Cleanup with Deutsche Bank 050409

It's been a really long time since I last blogged! After 3 weeks with no trips, 5th April was really something to look forward to. It was my first time setting foot on St John's Island (SJI)! Upon reaching our destination, we soon set off. A mangrove walk was first conducted for the employees of Deutsche Bank followed by a subsequent cleanup (brings back memories of the International Coastal Cleanup I participated in last year).

After putting down some belongings at the Tropical Marine Science Institute's (TMSI) pantry, we soon set off! For this trip, I was attached to Robert's group.

The guided walk kicked off with Robert talking about epiphytes. These refer to plants which grow on other plants, like trees, so that they can get better access to light. They are not parasitic though. One example of a common epiphyte in Singapore is the Pigeon Orchid (Dendrobium crumenatum) which can be found growing on roadside trees.

Greenery, away from the city.

Saw many of these pretty flowers growing among the grass and couldn't resist taking a picture of one. (ID?)

After a short walk, we soon reached the back mangroves where a very dead (it looked dried up) Paradise Tree Snake (Chrysopelea paradisi) lay among the grass. Live specimens are able to glide from tree to tree by projecting themselves into the air using a special technique.

The Sea Hibiscus (Hibiscus tiliaceus) and its characteristic heart-shaped leaves. Though there seemed to be no flowers, there were a handful of fruits.

This sight greeted us the moment we stepped into the mangroves. Unbelievable. For every small convenience that we take for granted, like eating packed lunches (above), the environment has to pay the price one way or the other. These bags of rubbish were supposed to be brought to the mainland for proper disposal, but as you can see...

...someone has been burning rubbish right in the mangroves. The stink of garbage lingered in the mangroves with acrid fumes of burnt metal and plastic. Needless to say, it was also an eyesore.

Charred mangrove plants from the burning.

Nevertheless, there was still life around. Looking like a 'botak' broom are these aerial roots. If I'm not wrong, these will grow into prop roots upon reaching the ground.

Developing aerial roots with small lenticels.

Let the cleanup begin! The participants got down to work right away, enthusiastically picking up rubbish.

Fishing nets and other rubbish often gets washed up along shores. Such discarded items often entangle animals, killing them. In total, the group collected 56 kg of rubbish (and that's not counting what the other two groups collected). Great job, everyone! :)

The mangroves of SJI are more or less rubbish-free for now, but within the next few days even, trash will start to accumulate again. This happens everywhere, at our mainland coasts, parks and housing estates. Without cleaners, I don't think Singapore would be clean at all. Green, yes, but not clean. If a small group of people are able to collect so much rubbish within an hour, can you imagine the amount of trash that can be gathered in one minute if each of Singapore's 4 million plus individuals simultaneously picks up a piece of litter? Better still, why not kick the littering habit and start picking up after ourselves...

Semakau, in the Early Morning Light 140309

A couple of days back marked the last of afternoon and evening low tide windows. So, from now till several months along, trips are scheduled for the early morning.

In the wee hours of Saturday morning, dozens of Project Semakau volunteers left their homes in order to reach Marina South Pier by 5 am. We were going to the island to conduct the first transect survey.

It was still dark when we got to the pier and similarly when the ferry reached Semakau.

As transport is not provided at such an early hour, we had to walk to the intertidal zone from the visitor centre. The early morning air was cool and punctuated with bird calls, as our diurnal feathered friends slowly awoke from their slumber.

In no time, we had walked through the secondary forest and reached the intertidal area. At the beginning of the seagrass meadow, we had an encounter with...

...an unknown sea hare (Order Anaspidea).

Wen Qing, Samuel and myself were in seagrass transect team 2. While doing the survey, we saw plenty of seagrass in the 30 m stretch (but not as much as before like during the transect training) and also some interesting things like the mucus coating made possibly by a wrasse (Family Labridae) or some other kind of fish [edit]. One interesting fact about wrasses is that they can change their gender! O.O

Seagrass is indeed tricky as we soon realised for ourselves...

1) Thalassia hemprichii.

According to the ID sheet, the leaves have "short, black bars of tannin cells". But as you can see, these bars aren't obvious at all. This is a good example of how things in the field often differ from what is on paper... So how to ID Thalassia? Though their sickle-shaped leaves are a good giveaway, if unsure, it's best to feel for their rhizomes which are scarred and appear reddish-brown :)

2) Cymodocea serrulata.

Often confused with Enhalus acoroides and Thalassia hemprichii, this species does have one visible distinguishing feature - a serrated leaf edge! If that does not help, feel for the rhizomes, which are smooth and closer to the surface than Thalassia.

3) Halodule uninervis.

We didn't think we'd encounter this species, so we had to confirm its ID with Ron. The above is a young specimen. It has a white rhizome with black scars. In mature specimens, a distinctive centre vein is visible, and leaf tips have three distinct points.

Mostly, there was a lot of Tape Seagrass (Enhalus acoroides), noticeable numbers of Syringodium isoetifolium (Noodle Seagrass), some Cymodocea serrulata (Serrated Ribbon Seagrass), a little of Halophila ovalis/minor (Spoon Seagrass), even less of Thalassia hemprichii (Sickle Seagrass) and only one quadrat with Halodule uninervis (Needle Seagrass). For more info, visit the I.D. Seagrass page of the Seagrass-Watch website :)

After completing the transect survey, we were given some time to explore. One group followed Ron, while the other followed July. Saw this Sandfish Sea Cucumber (Holothuria scabra) soon after heading out.

There were numerous juvenile Knobbly Sea Stars (Protoreaster nodosus) out that day! Yay! They really come in a myriad of colours. As echinoderms have a water vascular system, they will get stressed and die if left out of water for too long. That's why we always replace them after a quick photo.

Knobbly no. 1.

Underside of Knobbly no. 1

Knobbly no. 2. One of its arms is slightly shorter than the rest which could be a result of an injury and subsequent regeneration.

Knobbly no. 3.

Underside of Knobbly no. 3, with focus on its mouth (centre) and the ambulacaral areas which house its tube feet.

Knobblies no. 4 and 5. The Knobbly on the left looks really 'juvenile' (but that's just my opinion).

Knobbly no. 6. With two of its arms closer than normal to each other, this sea star here looks like it's getting ready to dance.

Saw a few more Knobblies, but didn't upload all the pics here.

Growing in bunches were some green algae (Caulerpa sp.).

This is a first for me! In one of the tidal pools, this Heart Cockle (Corculum cardissa) was clearly visible in the shallow and clear water. When it dies, the heart breaks...

An Orange-edged Black Flatworm (probably Pseudobiceros uniarborensis). Another 'first' for me on Semakau.

Looking like a protrusion from the substrate was this Common Hairy Crab (Pilumnus vespertilio). The hairs on its body trap sediment which, over time, allows it to look like a piece of the substrate itself.

A view of the coral rubble area.

Growing in between this magnificent Staghorn Acropora Coral (Acropora sp.) was a fan shell (Family Pinnidae).

Hmm..egg cases of a mollusc? It's likely an egg ribbon of a nudibranch or some other species of slug.*

This sea cucumber (Actinopyga sp.) is thought to be a juvenile Stonefish Sea Cucumber due to similar physical traits, but that is based on speculation and not yet confirmed*.

This is by far the smallest Noble Volute (Cymbiola nobilis) that I have seen. Is it a juvenile? From its shell alone, I wouldn't have been able to ID it as the typically associated 'mountain ranges' pattern is absent. Lucky its black with orange spots muscular foot was showing.

Saw a lot of these Common Sea Stars aka Sand-sifting Sea Star (Archaster typicus). Here is a pair getting ready to mate with the male on top (such pairing behaviour is known as pseudocopulation) [edit]. Like other sea stars, external fertilisation takes place (meaning reproductive organs don't actually meet).

References:

Wild Fact Sheets of marine life on Singapore shores - http://www.wildsingapore.com/wildfacts/

Acknowledgements:

[edit], *Thanks to Ron for the corrections and IDs!

The Sun Blazes Down on Semakau 080309

Remember how in primary school there were a couple of 'standard' phrases used in writing compositions? I've never been a fan of them but if there ever was a time to use one, it would be to describe the weather on Sunday. So here goes:

The sun beat mercilessly down on us...(haha!). After doing battle with the mozzies (they love me but the feeling isn't mutual) in the forest trail, we finally arrived at the intertidal area. Split into 2 groups, Wen Qing, Nonis, Xiu Li and myself followed Luan Keng while Hui Yi, Ying Wei and Elvin had Ron as their leader. We were there to pile in the transect markers for the upcoming transect this Saturday. As we headed out...

...LK spotted this Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda). Two species can be found in Singapore - the one above as well as the Coastal Horseshoe Crab (Tachypleus gigas). Two easy indicators to look out for are colour and tail structure. The mangrove species is brownish with a rounded tail while its coastal relative is greyish with spines on its tail. Read more about horseshoe crabs in general here, and the 2 species that can be found in Singapore here.

Kinda seemed apt that the first animal spotted was a horseshoe crab, for on that very day in the evening, a Horseshoe Crab Population & Distribution Survey was conducted around the mainland, organised by the Nature Society (Singapore). I sure hope that minimal damage was incurred for volunteers had to dig up (a lot of) mud in order to locate the horseshoe crabs...

After crossing the seagrass meadow, we entered the coral rubble/coral reef area where two huge pore corals (Porites sp.)* caught our attention with their different colouration.

Sadly, the top of both corals are dead and the scorching sun didn't help matters.

After piling in the transect markers, we had some time to explore. Hunter-seekers who arrived before everyone else found this synaptid sea cucumber (Family Synaptidae) and marked out its location.

Another find by the hunter-seekers was this Noble Volute (Cymbiola nobilis) and its eggs. Was amazed to see that the mass of eggs it laid was as big as it was. Its shell kind of looked faded to me, compared to the previous ones I'd seen at Changi before. Also, it was smaller. Size can't be used to judge its maturity, I realised.

A dead octopus (Class Cephalopoda, Order Octopoda).* Wen Qing's close examination of it revealed that some of its tentacles were shorter than the others. We learned from one of the visitors that tentacles can get bitten off by predators and are subsequently regenerated. Cool!

Bakaus (Rhizophora spp.) greet visitors to the Semakau intertidal area. Learned that 2 species can be found growing on the edges of the sandy shore - R. apiculata and R. stylosa.

Though both species look similar, they can be told apart even at a distance by their roots. Both mangroves have stilt or prop roots, but those of R. apiculata are not so spread out as compared to that of R. stylosa. In addition, the stipule^ of the former is red while that of the latter is yellow. The stipule wraps over the apical bud, protecting it. The red stipules will eventually drop off as the young leaves grow.* Can you tell which picture is of which species? One last thing to note, R. apiculata has a shorter flower stalk than R. stylosa.

Another Rhizophora species, R. mucronata has big leaves which distinguish it from the two above.

Taking one last look at a Rhizophora stylosa before we leave.

Some other things seen but not photographed:
i. Mosaic Crab (not too sure...it ducked for cover really quickly so I only caught a glimpse)

ii. Crab with yellowish-brown carapace (ditto the above)

iii. Black-lipped Conch

iv. Sand-sifting Sea Star aka Common Sea Star

v. Ovum Cowrie

vi. Eagle

Heard about the sightings of Knobbly Sea Stars and turtles from Ron but didn't get to see them D:

Acknowledgements:
Thanks to LK for the info! And to everyone for the company :)

*Ron, thanks for the corrections!

^Thanks to Anonymous for bringing my attention to the terms used (ie. stipule and apical bud)! [Refer to Anonymous' comment]

Notes:

Given the weather, a cap and a lot of water are essentials!

For other takes on the trip, check these entries out:

i. Ron's - http://tidechaser.blogspot.com/2009/03/scorching.html

ii. July's - http://wherediscoverybegins.blogspot.com/2009/03/discover-semakau-landfill-island-8.html

iii. Samson's - http://mantamola.blogspot.com/2009/03/semakau-tidal-walk-8-march-09.html

iv. Meiyi's - http://appreciateandlove.blogspot.com/2009/03/semakau-after-so-long.html

v. Eunice's - http://naturallyours.blogspot.com/2009/03/48-semakau-guiding-w-meiyi-giant-clams.html