GLOWING CORALS: Like a forest canopy, the branched corals can scatter and absorb light at multiple levels. In this study, branching corals scattered light over such a large area that the researchers could not measure it with their detector. Coral colonies that form flat structures (not shown), such as Echinopora lamellosa, also have high scattering. Like solar panels, flat structures allow coral to maximize absorption of light coming from above; they also permit scattering of light among the colony’s polyps. This inter-polyp light sharing also occurs in coral species that form massive colonies, which have moderate scattering. The phaceloid corals have low scattering; their thick, upright walls prevent them from sharing light among polyps. (Branched coral: Pocillopora damicornis; massive coral: Orbicella faveolata; phaceloid coral: Eusmilia fastigiata)COURTESY OF SUSANA ENRÍQUEZ
Around 2005, Susana Enríquez discovered “something extraordinary” in her work on blue crust corals. She reported that corals housing photosynthetic algal symbionts absorbed light more efficiently than plant leaves, and that the algae collected significantly more light when inside the coral skeleton than they did when isolated. More light absorption, it was known, would lead to greater algal photosynthesis. In other words, the skeleton somehow made it possible for the algae, which provide corals with glucose and other nutrients, to produce more hydrocarbons with the same amount of sunshine.
Looking into the phenomenon further, Enríquez, a photobiologist at the National Autonomous University of Mexico, found that the coral skeleton enhanced light absorption through scattering. The more light scatters and bounces around within the coral skeleton, ...
