SPS coral calcification maximized near macroalgae

Some excerpts from Walter Adey from attending the 1996 Macna conference in Los Angeles; he references many researchers, and also his own Dynamic Aquaria book:

"I've spent most of my career on trying to learn the calcification of reefs, and I think I've got it.

"SPS calcify so they can grow upwards like trees and survive, and since they've chosen to calcify instead of lay down celulose like a tree, they have a heavy burden. And how fast they grow upwards is extremely important.

"Some stoney corals calcify without any algae; but they don't calcify very fast, and certainly could not build any reefs or anywhere near it.

"Of the TOTAL calcification that leads to reef-building capabilities, about 50% of the calcifying capability reef-building corals is due to the zoox. Now that's not too surprising... most scientists would accept that right away. BUT... I want to show you that the other 50% is due to all the other algae in the reef: The free living algae.

"When corals learned the real trick to calcification, which is to use the bicarbonate in the water, they acquired a tremendous capability. But in doing so, they needed algae. The zoox in the coral can't give them all the potential, but the other algae in the reef can. The corals need these free living algae.

"The most probable community on a reef is an algal turf. That's the dominant community in most reefs.

"Corals in tests would maximize calcification when in the vicinity of free-living algae. The zoox are important, yes, but are limited in how much calcification they can support by themselves. The free-living macro algae make up the differnece.