Fig 6. Increased in situ degradation of algae during acute cold shock but not under other stress conditions.

In experiments like those of Figs 2A–2F and 4A–4D, symbiotic anemones were fixed after collection from populations under standard culture conditions (control experiments 1–4) or under stress conditions at times coinciding with maximal rates of bleaching (for acute cold shock, this is1 d after the return to standard culture conditions). Anemone sections were then examined by electron microscopy as described in Materials and Methods. In each experiment, every algal profile observed in multiple fields of a randomly chosen section of one animal was classified as Intact, Degrading, or Ambiguous following the examples shown in a section of an anemone from standard culture conditions (A; and see Materials and Methods). (B) Percentages of algae classified into each category in anemones exposed to the various stresses. Total numbers of algal profiles scored are indicated in parentheses. (C) A typical section from one of the acute-cold-shock experiments.