Abstract: In an experimental temperature-regulated mesocosm, the low water temp
erature tolerance of five dominant scleractinian coral species Pavona decussat
e, Acropora pulchra, Acropora florida, Acropora valida, and Porites lutea
in Sanya Bay was investigated, and their responding modes to the cold water st
ress were analyzed. The tolerance of test corals to low water temperature was cl
osely related to their morphologies, with the branching corals being the most vu
lnerable to bleaching and death by separating the symbiotic polyps from their sk
eletons. The lethal low water temperature for branching Acropora corals was 14
℃ lasting for 3 days, and that for foliose P. decussate was 12 ℃ lasting f
or 10 days. Massive P. lutea corals responded to low water temperature by fo
rming mucus membrane, which helped to prevent the further losing of symbiotic al
gae. The corals showing strong tolerance to high water temperature also had stro
ng tolerance to low water temperature, and had similar responding modes to both
high and low water temperature, i.e., the corals didn’t extend their tentacl
e first, followed by the continuous release of mucus and the discharge of symbio
tic zooxanthellae, and finally, bleached and died.

Key words: Sanya Bay, scleractinian coral, low temperature, coral bleaching, symbiotic zooxanthellae, lethal temperature, East Dongting Lake, remote sensing, hydrology, emergent herbaceous wetland.