Coral & Seagrass

Background & Scope

Environmental Factors Controlling Coral and Seagrass Ecosystem Resilience

Marine infrastructure development projects (involving dredging, reclamation and construction works) are crucial for safety and economic development of regions, harbours and industrial activities worldwide. In tropical regions, however, these development activities often take place in the vicinity of critical but sensitive marine ecosystems such as coral reefs and seagrass beds. Hence, this research project aimed to:

  • Improve our understanding of the natural dynamics of critical marine ecosystems (coral reefs and seagrass beds) in tropical coastal waters in response to environmental variability in turbidity and sedimentation;
  • Generate advanced knowledge about stress responses and resilience of critical marine ecosystems (coral reefs and seagrass beds) to turbidity and sedimentation in tropical coastal waters;
  • Deepen our understanding of factors determining the success and scale of (post-impact) recovery of critical marine ecosystems (coral reefs and seagrass beds) in tropical coastal waters (including the role of recruitment).

Principal Investigators

Dr. Peter Todd (NUS), Dr. Tjeerd Bouma (Deltares)

Key Findings

Effects of Sediments on Corals

Numerous experiments on the effects of sediments (and associated shading) on corals have been conducted. These included testing for among-genotype variation for sediment rejection in the reef-building coral Diploastrea heliopora and partitioning the effects of turbidity and settling particles on the corals Galaxea fasicularis andGoniopora somaliensis. We also examined the effect of suspended sediment on fertilisation success in Pectinia lactuca and plastic responses to shading in the coralGoniastrea pectinata and the reef zoanthids Zoanthus sansibaricus and Palythoa tuberculosa. Two major review have also arisen from this project: “Impacts of pollution on marine life in Southeast Asia” and  “Environmental impacts of dredging and other sediment disturbances on corals: a review”.

By using coral growth rate as an indicator of reef health and resilience, we also aimed at ascertaining longer-term impacts of environmental changes (localised and climatic changes) on corals. As of now, coral growth records spanning as far back as the 1930s from several locations around Singapore, and selected reefs around the Thai-Malay Peninsula, have been analysed.

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Diving in Singapore on good-visibility day

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Deposited material on reefs smother organisms and limit their photosynthetic ability

Effects of Sediments on Seagrasses

In total, five field experiments were carried out, four in Singapore and one in Bintan, Indonesia, and two mesocosm experiments conducted at the Tropical Marine Science Institute (TMSI) facility on St. Johns Island in Singapore. The field experiments centered around looking at the stress responses of seagrass to low light (a proxy for turbidity) and the recovery dynamics of seagrass meadows to multiple stressors such as mechanical damage and light reduction. The two mesocosm experiments examined the photophysiological responses of seagrass to combined stressors of low light and increased temperature and also the effects of repeated light stress on the photosynthetic recovery response of seagrasses. As part of the project, a meta-analysis on the status and trends of seagrass in Singapore was also conducted, with a focus on mapping current seagrass cover and a vulnerability assessment of seagrass beds in Singapore.

Publications

  • Todd, P.A., Setiawan, W., Lui, C.Y., Chou, L.M. and Erftemeijer, P.L.A. (2010) Acute and chronic effects of sediments on scleractinian corals. 2nd Asia Pacific Coral Reef Symposium, Phuket, Thailand. (Oral and poster)
  • Todd, P.A., Ong, X. and Chou, L.M. (2010) Impacts of pollution on marine life in Southeast Asia. Biodiversity and Conservation. 19: 1063-1082
  • Ow Y.X. and Todd, P.A. (2010) Light-induced morphological plasticity in the Scleractinian coral Goniastrea pectinata and its functional significance. Coral Reefs. 29: 797-808
  • Erftemeijer, P.L.A., Riegl B., Hoeksema, B.W., Todd, P.A. (2012) Environmental impacts of dredging and other sediment disturbances on corals: a review. Marine Pollution Bulletin. 64: 1737–1765
  • Tanzil, J.T.I, Brown, B., Todd, P.A., Kaandorp, J. (2012) Growth and luminescent banding in massive Porites from the Thai-Malay Peninsula. Twelfth International Coral Reef Symposium. Cairns, Australia. (Oral)
  • Lui G.C.Y., Setiawan, W., Erftemeijer, P.L.A., Todd, P.A. (2012) Among-genotype variation for sediment rejection in the reef-building coral Diploastrea heliopora (Lamarck, 1816). Raffles Bulletin of Zoology. 60: 525–531
  • Tanzil J.T.I. (2012) Bleaching susceptibility and growth characteristics of Porites lutea from the Andaman Sea, South Thailand. Phuket Marine Biological Center (PMBC) Research Bulletin. 71: 49–56
  • Erftemeijer, P.L.A., Hagedorn, M., Laterveer, M., Craggs, J., Guest J.R. (2012) Effect of suspended sediment on fertilisation success in the scleractinian coral Pectinia lactuca. Journal of the Marine Biological Society – UK. 92:741-745
  • Ong, C. W., Reimer, J.D. and Todd, P.A. (In press) Morphologically plastic responses to shading in the zoanthids Zoanthus sansibaricus and Palythoa tuberculosa. Marine Biology
  • Chen, E., Yaakub, S.M., Erftemeijer, P.L.A., Bouma, T. and Todd, P.A. (2010) The effects of light reduction on monospecific Halophila ovalis meadows in Singapore; and a novel method for simulating shading in sedimented waters. World Seagrass Conference, November 2010, Phuket, Thailand. (Oral)
  • Yaakub, S.M., Chen, E., Todd, P.A. and Erftemeijer, P.L.A. (2011) Loss and recovery of a monospecific Halophila ovalis seagrass meadow in Singapore – responses to shading. Australian Marine Sciences Association, Perth, Australia. (Oral)
  • Yaakub, S.M., Erftemeijer, P.L.A., Bouma, T.J. and Todd, P.A. (2011) Effects of light reduction on the recovery physically disturbed seagrass beds. 21st Biennial Conference of the Coastal and Estuarine Research Federation (CERF) (Oral)
  • Bouma T.J., Erftemeijer P.L.A., Balke T., Horstma E.M., Yaakub S.M., Tanzil J.T.I., Friess D.A., Galli D., Dohmen-Janssen C.M., Jeuken, C., Todd P.A., Webb E.L. (2011) Sediment and Ecology: how to minimize impacts of dredging and create opportunities for restoration on tropical coasts? Proceedings of the Central Dredging Association conference – Dredging Days, Rotterdam, the Netherlands.
  • Yaakub, S.M., Lee, B.C.F., Bouma, T.J. and Todd, P.A. (2012) Gaps in the meadow: does gap shape affect recovery rate of seagrass? Twelfth International Coral Reef Symposium. Cairns, Australia. (Oral)
  • Yaakub, S.M., Bouma, T., Erftemeijer, P.L.A. and Todd, P.A. (2012) Effects of light reduction and repeated disturbance on the recovery of small gaps in seagrass meadows. 10th International Seagrass Biology Workshop, Búzios, Brazil. (Oral)
  • Lee, Q., Yaakub, S.M, Ng, N.K., Erftemeijer P.L.A., Todd, P.A. (2012) The crab fauna of three seagrass meadows in Singapore: a pilot study. Nature in Singapore. 5:363–368