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MEPS 502:129-143 (2014)  -  DOI:

Photo-physiological costs associated with acute sediment stress events in three near-shore turbid water corals

Nicola K. Browne1,2,*, Elimar Precht1, Kim S. Last3, Peter A. Todd2,4

1DHI Water and Environment, 1 Cleantech Loop, #03-05 CleanTech One, Singapore 637141
2Experimental Marine and Ecology Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117543
3Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK
4Tropical Marine Science Institute, National University of Singapore, Singapore 117543
*Corresponding author:

ABSTRACT: Many coral reef communities thriving in inshore coastal waters characterised by chronically high natural turbidity (>5 mg l-1) have adapted to low light (<200 µmol photons m-2 s-1) and high sedimentation rates (>10 mg cm-2 d-1). Yet, short (hours) acute sediment stress events driven by wind waves, dredging operations involving suction or screening, or shipping activities with vessel wake or propeller disturbance, can result in a rise in turbidity above the natural background level. Although these may not be lethal to corals given the time frame, there could be a considerable impact on photo-trophic energy production. A novel sediment delivery system was used to quantify the effects of 3 acute sediment resuspension stress events (turbidity = 100, 170, 240 mg l-1; sedimentation rates = 4, 9, 13 mg cm-2 h-1) on 3 inshore turbid water corals common in the Indo-Pacific (Merulina ampliata, Pachyseris speciosa and Platygyra sinensis). Coral photo-physiology response (respiration, net photosynthesis, and maximum quantum yield) was measured immediately after 2 h of exposure. The respiration rate increased (from 0.72-1.44 to 0.78-1.76 µmol O2 cm-2 h-1) as the severity of the acute sediment resuspension event increased, whereas the photosynthetic rate declined (from 0.25-0.41 to -0.19-0.25 µmol O2 cm-2 h-1). Merulina was the least tolerant to acute sediment resuspension, with a photosynthesis and respiration ratio (P/R ratio) of <1.0 when turbidity levels reached >170 mg l-1, while Platygyra was most tolerant (P/R > 1.0). Fluorescence yield data suggest that the rapid photo-acclimation ability of Platygyra enabled it to maintain a positive carbon budget during the experiments, illustrating species-specific responses to acute sediment stress events.

KEY WORDS: Turbidity · Sedimentation · Sediment resuspension · Mesocosm experiments · Coral photosynthesis · Singapore

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Cite this article as: Browne NK, Precht E, Last KS, Todd PA (2014) Photo-physiological costs associated with acute sediment stress events in three near-shore turbid water corals. Mar Ecol Prog Ser 502:129-143.

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