Figure 1.
Growth and survival of coral juveniles at Magnetic Island (a+c) and the Keppel Islands (b+d).
See materials and methods for nomenclature of the experimental groups. +indicates significant difference between juvenile corals harboring Symbiodinium C1 and those harboring D (p<0.05), and # indicates significant difference between KKA and KKC1/KKD corals (growth, p<0.05) or between KKD and KKA/KKC1 corals (survival, p<0.001). C1 corals grew and survived better at Magnetic Island than the D corals. At the Keppel Islands, KKC1 and KKD corals grew at similar rates, but KKD corals had a better survival rate. KKA corals grew slowest at the Keppel Islands and had a low survival rate.
Table 1.
Results of ANOVA analyses. GLM = General Linear Model, RM = Repeated Measures, F = Factorial.
Figure 2.
Heat-stress experiment 1: PAM-fluorometry.
Effect of four different temperature regimes on the excitation pressure over photosystem II of four groups of juvenile coral outplanted to Magnetic Island. See materials and methods for nomenclature. L:D = light-dark regime, $ = target temperature is reached, # = significant difference between C1 corals and D corals. C1 corals responded stronger to the highest temperature treatment than D corals, as indicated by a stronger increase in Q for C1 corals towards the end of the experiment.
Figure 3.
Heat-stress experiment 1: relative algal symbiont densities and coral condition.
End effect of four different temperature regimes on the relative algal symbiont densities (bars) and coral condition (pies) of four groups of juvenile coral outplanted to Magnetic Island. See materials and methods for nomenclature. Blue = healthy, purple = pale, white = bleached. # = significantly different from lower temperatures within a group (p<0.05). All four experimental groups exhibited a bleaching response at the highest temperature treatment, as indicated by significant reductions in relative algal symbiont densities, and the visual assessment indicated a stronger response (more bleached colonies) for C1 corals than for D corals.
Figure 4.
Heat-stress experiment 2: PAM-fluorometry.
Effect of three different temperature regimes on the excitation pressure over photosystem II of three groups of juvenile coral outplanted to the Keppel Islands, and one outplanted to Magnetic Island. See materials and methods for nomenclature. $ = target temperature is reached, + = significant difference between KKA and MKC1/KKC1/KKD corals (p<0.001), # = significant difference between all three symbiont types (p<0.05). KKA corals responded much stronger to the heat-stress than the other three juvenile coral groups, as indicated by a sharp increase in Q values for KKA corals in the highest temperature treatment relatively early in the experiment.
Figure 5.
Heat-stress experiment 2: relative algal symbiont densities and coral condition.
End effect of three different temperature regimes on the relative algal symbiont densities (bars) and coral condition (pies) of three groups of juvenile coral outplanted to Magnetic Island, and one outplanted to Magnetic Island. Blue = healthy, purple = pale, white = bleached. # = significantly different from lower temperatures within the same group (p<0.05), $ = significantly different from KKC1/MKC1 and KKD corals at the same temperature (p<0.05), + = significantly different from KKA and KKD corals at same temperature (p<0.05). KKA corals showed the strongest bleaching response as indicated by the strongest reduction in relative algal symbiont densities and bleached appearances, KKC1/MKC1 corals showed an intermediate bleaching response as indicated by intermediate reductions in relative algal densities, and KKD corals showed no signs of a bleaching response.
Table 2.
Comparison of Magnetic Island and the Keppel Island field locations and their A. millepora populations.