Figure 4. The loss of the symbiotic algae was monitored with confocal microcopy (MFI) and Imaging-PAM (photosynthetic yield).

Coral microfragments were bleached up to 1 week and the loss of their symbionts was monitored with confocal microscopy and Imaging-PAM. (A) Paired microfragments from the same genotypes (n = 25) were left untreated or bleached with menthol & light. These pairs demonstrated a 78% loss in in the Mean fluorescence Intensity or the number of symbiont-like fluorescing particles (Controls = 212.1 ± 19.6; Bleached = 47.0 ± 2.5). (B) When bleached and untreated microfragments from the same genotypes (n = 10) were examined with an Imaging-PAM, a 98% loss in photosynthetic yield (Y) was observed. The control fragments had a mean Y-value of 0.567 ± 0.006, whereas the bleached values were reduced to 0.013 ± 0.007, suggesting that none of the remaining symbiont-like particles in the bleached fragments were functional. Means with an asterisk (*) were different p < 0.001, paired parametric t-test (A) and nonparametric non-paired Mann-Whitney U test (B), all errors represented by SEM.