It turns out the local density of corals can affect one another’s growth (friends are good). But this is independent of predators (things that eat you are bad!).
This paper is authored by Andy Shantz (Florida International University), Josh Idjadi (Eastern Connecticut University), and Adrian Stier (me, UF) and appears in the May issue of Coral Reefs, 2011.
Abstract: The influence of predation on the growth of stony corals has gained increased attention, although the degree to which coral conspecific density can modify the effects of corallivores remains poorly studied. Here, a field experiment was used to quantify the independent and combined effects of coral colony density and coral predators on the skeletal growth of massive Porites . Predator exclusion increased coral growth by 20%. Increasing coral density increased growth by 30%. However, the effect of. predators was independent of coral density. Possible alternative mechanisms for increased skeletal growth at higher colony density include changes in near-field flow, resulting in increases in photosynthetic activity, nutrient uptake, or the increased accessibility of coral mutualists.
See the full abstract and download the paper here or e-mail me (firstname.lastname@example.org) for a copy of the manuscript