Singapore
Singapore
Seagrass meadows in Singapore, are an important component of the marine ecosystems of island nation and seagrass meadows are distributed throughout the city state’s shallow waters.
To the north of Singapore Island, seagrass meadows tend to be mangrove associated, whereas meadows found among the southern islands are associated with reefs.
Overall, the seagrass ecosystems of the Singapore are a complex mosaic of different habitat types comprised of multiple seagrass species in which timing as well as mechanisms that capture their dynamism are relatively poorly understood.
There are 10 seagrass species found in Singapore: Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, Halodule uninervis, Halophila beccarii, Halophila decipiens, Halophila ovalis, Halophila spinulosa, Syringodium isoetifolium and Thalassia hemprichii . An additional 2 species (Halophila minor, Halodule pinifolia) are currently under review for synonymy 1
Seagrass-Watch in Singapore
To provide an early warning of change, long-term monitoring has been established in Singapore as part of the Seagrass-Watch, Global Seagrass Observing Network (www.seagrasswatch.org). Establishing a network of monitoring sites in Singapore provides valuable information on temporal trends in the health status of seagrass meadows in the region and provides a tool for decision-makers in adopting protective measures. It encourages local communities to become involved in seagrass management and protection. Working with both scientists and local stakeholders, this approach is designed to draw attention to the many local anthropogenic impacts on seagrass meadows which degrade coastal ecosystems and decrease their yield of natural resources.
 | McKenzie, L.J., Yaakub, S.M., Tan, R., Seymour, J. and Yoshida, R.L. (2016). Seagrass habitats in Singapore: Environmental drivers and key processes. Raffles Bulletin of Zoology Supplement 34, 60-77. [2.1Mb] |
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Location
Chek Jawa (Pulau Ubin)
Tanjong Chek Jawa is a cape and the name of its surrounding areas located on the south-eastern tip of Pulau Ubin, a small island (10.19 km2) off the north-eastern coast of the main island of Singapore. The island was once a cluster of five smaller ones separated by tidal rivers, but the building of bunds for prawn farming has since united these into a single island. Two other islets, Pulau Ketam (Crab Island) and Pulau Sekudu (Frog Island), lie to its south. Pulau Ubin is one of the last areas in Singapore that has been preserved from urban development.
Located at the eastern tip of Pulau Ubin, Chek Jawa is a collection of six distinct habitats – coastal forest, mangroves, sand bars, seagrass lagoon, rocky shore & coral rubble. Slated for land reclamation in 1992, the assets of Chek Jawa wetlands were unveiled only in December 2000. After carefully considering all public submissions and extensive consultations with scientific experts and relevant government agencies, it was announced in 2001 that reclamation works would be deferred as long as Pulau Ubin is not required for development.
Eight seagrass species have been reported from Chek Jawa: Halophila beccarii, Halophila spinulosa, Cymodocea rotundata, Halophila ovalis, Halophila minor, Halodule uninervis, Thalassia hemprichii and isolated clumps of Enhalus acoroides. The meadows are predominately within a shallow protected lagoon behind a large sand bank. Meadows are mainly intertidal, however the seaward edges of the sand bank are fringed by large Halophila spinulosa meadows.
Monitoring: ongoing, triannual
Principal watchers: TeamSeagrass
Location: shallow lagoon on north east shore of Pulau Ubin
Site code: CJ1, CJ2
Issues: marine debris/litter, coastal development, land reclamation, land runoff
Comments: Tanjong Chek Jawa is a cape and the name of its surrounding areas located on the south-eastern tip of Pulau Ubin. Pulau Ubin is a small island (10.19 km2) situated in the north east of mainland Singapore, to the west of Pulau Tekong. Granite quarrying supported a few thousand settlers on Pulau Ubin in the 1960s, but only about a hundred villagers live there today. It is also one of the very few off-shore islands in Singapore that is still inhabited.
- Seagrass cover is generally between 25 and 65%, and is slightly higher at CJ1 than CJ2.
- The long-term trend in abundance suggests the meadow abundance has stabilised, after increasing in 2007-2008.
- A seasonal trend in seagrass abundance is apparent at both sites, with higher abundances from April to June, and lower abundance October to December.
- Of the eight seagrass species found at Chek Jawa, five are within the monitoring sites: Halophila spinulosa, Cymodocea rotundata, Halophila ovalis, Halodule uninervis, and Thalassia hemprichii.
- Site CJ1 has been mainly dominated by C. rotundata since monitoring commenced, but from Jun08-Jun11, the abundance of Halophila spinulosa increased across the meadow. Species composition has fluctuated greatly at CJ2, but has been dominated by Halophila species.
- Canopy height is greater at CJ1 as the site has a high composition of C. rotundata. Although H. ovalis dominates CJ2, canopy height is driven by the H. uninervis present
- Of the eight seagrass species found at Chek Jawa, five are within the monitoring sites: Halophila spinulosa, Cymodocea rotundata, Halophila ovalis, Halodule uninervis, and Thalassia hemprichii.
- Site CJ1 has been mainly dominated by C. rotundata since monitoring commenced, but from Jun 2008-Jun 2011, the abundance of Halophila spinulosa increased across the meadow. Species composition has fluctuated greatly at CJ2, but has been dominated by Halophila species.
- Macro-algal abundance is similar at both sites (25-30% on average) and fluctuates greatly within and between years. The long-term average for macroalgae abundance at Chek Jawa is 25%. Patterns in epiphyte abundance are similar between sites, however the amplitudes differ. Epiphytes were higher at CJ2 in 2008, however abundances are now slightly higher at CJ1. The long-term average for epiphyte abundance at Chek Jawa is 22%.
- Epiphyte abundances has increased at both sites in 2012 to above the long-term average. Whether this is natural fluctuations or a consequence of elevated nutrients is currently unknown.
Seagrass cover, species composition and canopy height
Macroalgae and Epiphyte cover
Location
Cyrene Reef
Cyrene is comprised of 3 patch reefs – Terumbu Pandan, Pandan Beacon and South Cyrene Beacon, and is one of the largest patch reef systems in Singapore. Cyrene Reef is a key maritime crossroad where east-west traffic routes cross north-south routes. Approximately five hundred ships transit the waters around the reef every day. The reef is also next to massive industrial sites like Jurong Island and Pulau Bukom, and opposite Singapore’s container terminals. With abundant seagrass meadows and other marine life, Cyrene is a natural wonder. The reef top meadow is a mixture of Enhalus acoroides, Cymodocea serrulata, Cymodocea rotundata, Halodule uninervis, Halophila ovalis, Thalassia hemprichii and Syringodium isoetifolium.
Monitoring: ongoing, quarterly
Principal watchers: TeamSeagrass
Location: reef platform on patch reef within harbour, south of mainland Singapore
Site code: CR1, CR2
Issues: marine debris/litter, port/industrial development, land reclamation, industrial runoff
Comments: Cyrene is comprised of 3 patch reefs- Terumbu Pandan, Pandan Beacon and South Cyrene Beacon,and is one of the largest patch reef systems in Singapore. Cyrene Reef is a key maritime crossroad where east-west traffic routes cross north-south routes. Approximately five hundred ships transit the waters around the reef every day. The reef is also next to massive industrial sites like Jurong Island and Pulau Bukom, and opposite Singapore’s container terminals. With abundant seagrass meadows and other marine life, Cyrene is a natural wonder. The reef top meadow is a mixture of Enhalus acoroides, Cymodocea serrulata, Cymodocea rotundata, Halodule uninervis, Halophila ovalis, Thalassia hemprichii and Syringodium isoetifolium.
- Seagrass abundance long-term trend for the location appears stable, however there are differences between the sites.
- Seagrass abundance increased at CR2 in 2011-12, but this appears a consequence of increasing abundance of Halophila ovalis. As H. ovalis is an early colonising species, this may suggest an increased level of disturbance (e.g. sediment movement, wave action) at the site.
- Seagrass abundance at CR1 decreased, although composition of Thalassia hemprichii appears unchanged. Cover also appears to show a seasonal trend, with increases Mar-May, and decreasing until late in the year.
- The long-term (5 year) average for macroalgae abundance at Cyrene Reef is 14%, which is lower than Pulau Semakau and Chek Jawa (30% and 25%, respectively). Macroalgae abundance has also decreased slightly at CR1 over the long-term, but has remained relatively stable at CR2.
- The long-term (5 year) average for epiphyte abundance at Cyrene Reef is 17%, which is lower than Pulau Semakau and Chek Jawa (43% and 22%, respectively). Epiphyte cover has similarly decreased over the long-term at CR1 and remained relatively stable at CR2.
- Seagrass canopy height has decreased at both sites over the long-term
Seagrass cover, species composition and canopy height
Macroalgae and Epiphyte cover
Location
Labrador
Labrador Nature Reserve, also known as Labrador Park, is located on the southern coast of mainland Singapore. It contains the only rocky sea-cliff on the mainland that is accessible to the public for recreation, education and scientific research. Since 2002, 10 hectares of coastal secondary vegetation and its rocky shore have been gazetted as a Nature Reserve. Labrador Nature Reserve has a rich variety of flora and fauna. The rocky shore contains a multitude of corals and crabs, seagrasses (Halophila ovalis, Thalassia hemprichii, and Enhalus acoroides), sandworms and horseshoe crabs. The Common Hairy Crab (Pilumnus vespertilio) is often spotted in the area. At the eastern end of the Reserve is Berlayar Creek (aka Berlayar Canal), which is adjacent to the Keppel Golf Club.
Monitoring: ongoing, ad hoc
Principal watchers: TeamSeagrass
Location: intertidal rocky shore
Site code: LP1 (Labrador Nature Reserve). LP2 (Berlayar Creek)
Issues: marine debris/litter, port/industrial development, land reclamation, industrial runoff.
Comments:LP1 transects run parallel to shoreline due to elongated shape of the meadow. LP2 at Berlayar Creek is haphazard sampling from a point on the east bank and a point on the west bank.
- mean total seagrass abundance has decreased between 2007 and 2012, however due to limited available data, the trend cannot be investigated.
- Site LP2 has also been examined over the last couple of years, however, data is similarly unavailable to examined trends or condition.
- In 2007 only two seagrass species were present (Enhalus acoroides and Halophila ovalis), however in 2012 four species were reported, the additional species including Thalassia hemprichii and Syringodium isoetifolium. Only Halophila ovalis is present at Berlayar Creek
- With a limited dataset, it is not possible to examine trends is abundance of macroalgae or epiphytes.
Seagrass cover, species composition and canopy height
Macroalgae and Epiphyte cover
Location
Pulau Semakau
Pulau Semakau is located to the south of the main island of Singapore, off the Straits of Singapore. The Semakau Landfill is located on the eastern side of the island, by the amalgamation of the smaller Pulau Sakeng and “anchored” to Pulau Semakau with a rock bund. In operation since 1999, Semakau landfill is Singapore’s first offshore landfill and now the only remaining landfill in Singapore. Semakau Landfill is filled mainly with inert ash produced by Singapore’s 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.
The western half of Pulau Semakau was left natural, unaffected by the landfill construction, and this is where the seagrass monitoring sites are located. Vast tracts of Enhalus acoroides (tape seagrass) fringe the island, stretching for kilometres. Pulau Semakau is one of the few places in Singapore where Syringodium isoetifolium occurs in abundance.
Monitoring: ongoing
Principal watchers: TeamSeagrass
Location: fringing reef platform on western shore of island
Site code: PS1, PS2, PS3, PS4
Issues:marine debris/litter, industrial runoff
- Seagrass cover is significantly lower at PS1 than the other sites, and has remained low since monitoring was established.
- Seagrass abundance at PS1 varies between 8-18% on average.
- PS2 and PS3 decreased in abundance in late 2008 (18 months after being established). Since 2008, abundance has changed little, varying between 15-40%.
- Although seagrass abundance has declined over the long term, there has been little decline since 2008 with abundance remaining relatively stable between 2009-2012. Within years, a seasonal trend in abundance is apparent, with higher abundances Mar-May, and lower from Aug-Dec.
- Canopy height has not changed greatly over the monitoring period, and canopy heights are representative of the change in species dominance between sites.
- There appears a transition in species composition between the sites, from Enhalus to Cymodocea dominating, from PS1 to PS3 respectively in the period prior to 2009.
- Species composition appears to fluctuate, primarily a consequence of the composition of Halophila ovalis or Cymodocea serrulata. The decline in composition of C. serrulata corresponds with the decreasing abundance. In 2009-2010 the composition of Syringodium isoetifolium also increased at PS2.
- The Pulau Semakau epiphyte long-term average is 43%, the highest of all monitoring locations in Singapore. Epiphyte abundance is also seasonally higher in Sep-Nov of each year.
- The Pulau Semakau macroalgae long-term average is 30%, the highest of all monitoring locations in Singapore. Macroalgae has differed between years, decreasing at PS2 and PS3 in 2011 and at PS1 in 2012. Within years, macroalage is seasonally higher in Aug-Nov of each year.
Seagrass cover, species composition and canopy height
Macroalgae and Epiphyte cover
Location
Sentosa
Sentosa, which means peace and tranquillity in Malay, is a popular island resort in Singapore, visited by some five million people a year. Attractions include a two-kilometre long sheltered beach, Fort Siloso, two golf courses, two five-star hotels and the Resorts World Sentosa; featuring the theme park Universal Studios Singapore and the worlds largest aquarium (S.E.A. Aquarium). Sentosa contains 5ha of natural rocky shore beneath Fort Siloso, between Underwater World and Rasa Sentosa, with coral reefs and some seagrasses (Enhalus acoroides and Halophila ovalis). In 2006, a group of volunteers conducted a seagrass survey of Sentosa. As a result of the Sentosa transect, TeamSeagrass was established.
Monitoring: ongoing
Principal watchers: TeamSeagrass
Location: fringing reef on north western shore of island
Site code: SE1
Issues: marine debris/litter, coastal development
Comments:Â Because the Sentosa shore is narrow, haphazard quadrat sampling from 4 points is used at this site.
- Prior to July 2009, seagrass cover did not vary greatly between years, although a seasonal pattern may be apparent with years, with lower abundance later in the calendar year. In August 2009, seagrass abundance declined, however whether it has since improved is unknown.
- The site is dominated by Halophila ovalis, however in 2008, the abundance of H. ovalis declined for 6 months, during which period Enhalus acoroides dominated.
- Enhalus acoroides canopy height has changed little over the monitoring period.
- Macroalgae cover is generally between 10 – 30% on average. There is a significant (p<0.05) inverse relationship between epiphyte cover and macroalgae cover (i.e. epiphyte increases when macroalgae decreases).
Seagrass cover, species composition and canopy height
Macroalgae and Epiphyte cover
Location
Tuas
Tuas is largely an industrial zone located in the western part of Singapore. The Tuas Planning Area is located within the West Region, and is bounded by Tengah Reservoir to the north, Strait of Johor to the west, Straits of Singapore to the south, and the Pan Island Expressway to the east. Seagrass meadows (Enhalus acoroides and Halophila ovalis) are scattered over the narrow intertidal banks of Tuas. The site is monitored by volunteers from Schering Plough, with assistance from TeamSeagrass. Schering Plough volunteers also replant mangroves along the Tuas shoreline.
Monitoring: ongoing
Principal watchers:Â Schering Plough
Location: fringing reef platform on western shore of island
Site code: TU1, TU2
Issues: marine debris/litter, industrial runoff, coastal development, land reclamation
Comments:Â Because the Tuas shore is narrow, haphazard quadrat sampling is used at this site.
- Seagrass cover is moderate along the shore, although patchy. Current status is unknown.
- The only species present in the Tuas sites was Halophila ovalis.