Pulau Semakau – Inter-tidal Walk

Introduction

Pulau Semakau is located to the south of the main island of Singapore. It was once home to a small fishing village as was the nearby island of Pulau Sakeng.  In 1987, the Singapore government, after having acquired the land on both islands from the islanders, set about relocating the islanders to the mainland. Subsequently, Pulau Sakeng was subsumed by the land reclamation process of Pulau Semakau and the combined islands was converted into a landfill.

The Semakau Landfill is Singapore’s first and only offshore landfill. It covers 350ha (about 440 football fields) and has a landfill capacity of 63 million mor a lifespan of 30 years.  The landfill  is filled mainly with ash produced by Singapore’s four incineration plants, which incinerate the country’s waste, shipped there in a covered barge (to prevent the ash from getting blown into the air) every night.

To safeguard against pollution of the sea, a 7km confinement bund surrounds the landfill site covering part of the sea off Pulau Semakau and the former Pulau Sakeng. This bund is lined with an impermeable membrane and a layer of marine clay to prevent the leakage of leachate, which is waste water generated within the landfill area.

Today, after years of careful environmental management, the ecosystem of Pulau Semakau is flourishing. Birds can be seen in the air and on the open landscape, fishes swim in and out of the lagoons, and marine life continues to thrive in the mangrove mudflats and the western shorelines of Pulau Semakau.

(Reference article: http://infopedia.nl.sg/articles/SIP_1008_2010-03-22.html, http://en.wikipedia.org/wiki/Pulau_Semakau)

Excursion

We joined an inter-tidal walk in Pulau Semakau organised by the Nature Society of Singapore (NSS). The meeting time and venue of the tour was 8.00 am at Marina South Pier. From there, we took an hour ferry to reach Pulau Semakau. Amazing, the the number of people turning up for this tour was really big, by conservative estimate at least 50 people from different age group.

Upon reaching Pulau Semakau passenger jetty, the visitors were divided into smaller groups of 10 – 15 people, each group being guided by a volunteer guide from the NSS. We took a 3 min journey by mini-coach to reach the starting point of the trail for the inter-tidal walk. Our coach journey was slightly delayed by a 1.5 m long monitor lizard which was sun-bathing in the middle of the road, and the driver had to stopped for a while for it to slowly crawled back into the mangrove swamp.

From the trail-head, we embarked on a brief 3 min walk, through a secondary forest to reach the beach area. The tide level was really low at about 0.4m with much of the sea bed exposed, revealing a maze of marine life and sea grasses which are usually unseen during high tide. We walked for 15-20 min out into the sea and the sea level was still way below knee level. The water visibility was good and we could see the sea bed clearly, but we had to move slowly so as not to stir up the sand which will cloud the water. Our guide carried a small plastic container with him to scoop up some marine life for the group close-up viewing. During the walk, we had a close encounter with hairy crab, flower crab, starfish, carpet anemone, sea sponge, nudibranch, sting-ray, jellyfish, clam, oyster, mud-skipper and even some soft coral.

One mischievous boy threw a small hairy crab onto the anemone and within seconds the crab sunk into the spongy mouth of the anemone and was completely gone from sight – being consumed. We saw the poor crab trying to claw out of the anemone but  was no match for the anemone “quick sand” action.

There also a cute looking translucent body slug-like creature with a pair of horn-like tentacles, which is actually a family of sea-slug called nubibranch. We were advised to wade through the water carefully so as not to step upon poisonous creatures like urchin, scorpion-fish, stingray etc. In fact, it is mandatory for all participants of the inter-tidal walk to don covered shoes when in water.  At times, one or two jelly fish would swim closely pass our legs. Other than marine life, we also saw some herons perching on some raised mould above water taking advantage of the low tide for a food feast. We came out of the water after an hour or so and proceeded back to the coach which brought us back to the NEA office just beside the jetty where we came from initially.

At the NEA office, we were directed to a lecture room for a 15 min documentary film that described in details the development of Semakau Landfill and the importance of waste management and recycling for Singapore sustainable growth. The film was followed by a Q&A session between the visitors and one of the NEA staffs. After the session, we boarded the return ferry to mainland Singapore.  It was almost 2pm sharp when we arrived back at Marina South Pier.

Forest trekking to benchfront

A mangrove tree

The roots of the mangrove tree will be fully submerged in water during high tide. From the size of the participants in the background, you can image how much the water had receded during low tide.  Mangrove trees have many uses which included charcoal, scaffolding woods and tannin used for dyes, leather preservatives and furniture stains.

Captain Hook?

This crab species has a left pincer that is much bigger than its right pincer. Do you know why crab walks side way? (http://sciencefocus.com/qa/why-do-crabs-walk-sideways)

Hairy Crab

This is not the Hairy Crab that you see in Chinese Restaurant. Other than Captain Hook and Hairy, we also saw other species of crab including the common flower crab and mud crab (smaller cousin of Sri Lanka Crab/Chili Crab) –  favourite Singapore Cuisines.

Jellyfish

Do you know that 98% of jellyfish body mass is water. That’s why it looks so transparent? We saw a lot of them and they really look like plastic bags drifting in water. During jellyfish season, much of the coastal area will be “flooded” with swam of jellyfish being sweep in by the incoming tides.

Carpet Anemone

This innocuous looking organism is a voracious predator, stinging and killing anything (fish, crab, starfish)  that gets too close to their sticky tentacles. Interestingly, they form a symbiotic alliance with clownfish, which are protected by a mucus layer that makes them immune to the anemone’s sting. Clownfish live within the anemone’s tentacles, getting protection from predators, and the anemone snacks on the scraps from the clownfish’s meals.

Corals are interesting animals  which derived most of their nutrients from the byproducts of the algae’s photosynthesis (that live within the coral’s tissue), they also have  venomous tentacles to grab zooplankton and even small fish.

Generally there are two main types of corals – hard and soft. Hard corals have six (or multiples of six) tentacles, while soft corals have eight tentacles around their mouth. Hard corals have a hard skeleton, which is the part you see when a coral dies and is the part that is artificially coloured and sold in shops. Soft corals do not.

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Some reefs are  so big that they formed islands like the Maldives. Do you know that there are also coral reefs around Singapore sea (http://coralreef.nus.edu.sg/)

The foot is almost as hard as the shell – one big lump of muscle. We also saw the common cockle (“hum” in hokkian) and Chut Chut (conical shellfish) which are popular dishes in zi char stores.

Camouflaged “house” of tube worm

 Do not mistaken it as a bunch of dead twigs and leaves. It is actually the “house” of the Solitary tube worm. The Solitary tube worm makes a tube about 1cm in diameter. The portion that sticks out from the mud is reinforced with scraps of twigs, dead leaves, and sometimes shells. You can actually buy them from some fishing tackle shops in Singapore. They are excellent baits and unlike live prawns, do not need portable air pump to keep them alive while fishing. You need to squeeze the worm out of the tube before using as baits.

Nudibranch

Nudibranch is part of the sea slug family. It bear some of the most fascinating shapes, sumptuous hues, and intricate patterns of any animal on Earth (http://www.sergeyphoto.com/underwater/nudibranchs.html)

Sea sponge

Although they may look plant-like, sponges are the simplest of multi-cellular animals. They attach themselves permanently to an anchorage, and move sea water through their bodies, filtering out bacteria, plankton, and other organic particulates for food. Interestingly, before the invention of synthetic sponge, they were being harvested by divers for use as household cleaning tools.

Starfish flipped upside down with suction cups revealed

Starfish are famous for their ability to regenerate limbs, and in some cases, entire bodies. Some require the central body to be intact to regenerate, but a few species can grow an entirely new sea star just from a portion of a severed limb.

One of the highlights of this trip is actually seagrass. Seagrasses are the only flowering plants adapted to grow submerged in the sea. On the seabed around Pulau Semakau are vast tracts of  seagrasses that stretch for kilometres. Seagrasses on seabeds are analogous to rainforests on lands, they provide shelters and food (indirectly via algae that grow on them) for marine organism. Seagrasses also provide a space for animal to lay eggs and hide from predators. Few animals eat seagrasses as the cellulose of the plants is not easily digestible. However, it is the main food for Dugong, (aka Sea Cow). Yes, there are Dugongs in Singapore Sea. There is actually a group of volunteers from Seagrass Watch who conduct regular  seagrass assessment and monitoring program around Singapore seashores (http://www.seagrasswatch.org/Singapore.html, http://teamseagrass.blogspot.com/).

To the north of Pulau Semakau, less than 2km away, is Pulau Bukom which is the site of Shell biggest oil refinery in the world, with crude distillation capacity of 500,000 barrels-per-day. Just beside Pulau Bukom are Pulau Ular which houses Shell Ethylene Cracker Complex and Pulau Busing which houses Tankstore oil and chemical storage complex. These three islands, Bukom, Ular and Busing are now joined togher by land reclamation. This is really the testimony of excellent environmental management whereby ecosystem and industrial activities can co-exit in such near proximity.

Walkway lined with Casuarina treesCostal tress like Sea Hibiscus and Casuarina were planted on the island by the National Environment Agency (NEA). To replace some of the mangrove lost during land reclamation, NEA also planted 400,000 mangrove saplings on 14ha of specially created mud-beds in 1998. The mangroves are thriving, and they act as a biological indicator giving early warning if toxins leak into the sea.

Lalang field

According to one of the NEA staff, Pulau Semakau is opened to public for wedding photo shoots. Till now, at least one wedding couple had done their photo shoots in Pulau Semakau. Not a bad idea if your fiancee insists on overseas photo shoot. Just take an hour ferry ride and here you are=)

Location of Pulau Semakau

Pulau Semakau is located 8km south of Singapore.

How to get there

As of now, Pulau Semakau is only accessible through activities conducted by designated interest groups.

Relevant Links

 

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