Photoacclimation of corals in the turbid waters of the Northern Malacca Straits, Malaysia.

Reefs in the Northern Straits of Malacca are exposed to low-light conditions mainly due to sedimentation. Corals can be found in the urban reefs of Pulau Kendi (PK) and Pulau Songsong (PS) despite being exposed to low-light stress. Rapid Light Curve (RLC) measurements were performed in situ using a Diving Pulse Amplitude Modulated (PAM) fluorometer to investigate the photoacclimation of hard corals in the turbid waters of the non-protected reefs in PK and PS. The photosynthetic responses of corals suggested two distinct patterns of photoacclimation which are preferential dynamic non-photochemical quenching and preferential photochemical quenching. When the light response curves were plotted against E/Ek, all coral species from PK and Pavona danai from PS were light saturated (E/Ek > 1) indicating the activation of the NPQ mechanism. However, Goniastrea aspera and Cyphastrea chalcidicum exhibited a different trend of photoacclimation in which the light did not reach saturation (light is limited (E/Ek < 1) indicating the preferential photochemical quenching as photoacclimation strategy. The results indicated that the photoacclimation mechanism may vary between species and corals can acclimate to changes in the environment. However, the extent of the acclimation may depend on other physiological factors such as Symbiodiniaceae type which needs to be investigated in the future.