http://nr.stic.gov.tw/ejournal/ProceedingB/v22n4/150-158.pdf Here's an interesting document I found that shows that in coral bleaching Zooxanthellae are released. It also states that bleached coral might not be dead. And that heat is major issue in coral bleaching. Hmm this is getting interesting..... They kept their acros under 80 m mol photons m–2 s–l during the experiment. What kind of lighting do you suppose they used to achieve this?