Reef-building corals contain endosymbiotic
dinoflagellates (zooxanthellae) within their
gastrodermal cells. Various types of stress
can cause corals to lose symbionts leading to
coral bleaching, which if prolonged can cause
the death of a colony (Brown 1997). While sea
surface temperature anomalies appear to be the
main cause of mass bleaching episodes, field
and laboratory studies have revealed that solar
radiation also plays an important role in coral
bleaching, either alone or in synergy with high
temperatures (see review by Baird et al. 2009a).
Planulae of broadcast-spawning corals have
an obligate planktonic duration of 2-4 d before
they are competent to settle (Fadlallah 1983),
and planulae of species with large eggs require
up to 48 h before they become motile (Babcock
and Heyward 1986).