Dredging stirs up sediments which make the water murky and affects the amount of sunlight that reaches the corals.
Similar dredging took place in the same area in Apr-Aug 09, and seemingly related dredging and vibracore sampling took place in Jun 09. Although these were not referenced in this current Notice.
Reef-building hard corals need sunlight because they harbour microscopic, single-celled algae (called zooxanthellae) inside their bodies. The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the coral polyp, which in return provides the algae with shelter and minerals. It is believed this additional source of nutrients from the zooxanthellae help hard corals produce their hard skeletons and thus expand the size of the colony faster. Thus clear waters that let sunlight through for photosynthesis is important for healthy reef growth.
More about hard corals on the wild fact sheets, and more about sedimentation in Singapore waters and other threats to our reefs on the Coral Reefs of Singapore website.
Sand Mining at East Keppel Fairway
from Port Marine Notice No. 112 of 2009 dated 14 Aug 09;
With effect from 20 Aug 09 to 19 Dec 09. 12 hours (0700 hrs to 1900 hrs) daily including Sundays and Public Holidays. At East Keppel Fairway and its vicinity (see attached chartlet):
Dredging works will be carried out by a Trailing Suction Hopper Dredger (TSHD) in the working areas. While dredging, Queen of Penta-Ocean will maintain a speed of about 2 knots. The TSHD will dredge in the general direction of the traffic flow, to facilitate the traffic. When moving from the dredging areas to the dumping ground, she will proceed at a safe speed of not more than 12 knots depending on the traffic conditions and visibility. The TSHD will at all times warn and re-direct craft in the vicinity to keep clear of the on-going dredging work areas. Contact with the TSHD can be made via VHF Channel 18 or 12. Further general enquiries relating to the project can be directed to Mr. Y. Mitsunari, the project manager at Tel: 9114 5774 (email: firstname.lastname@example.org).