Abstract
AbstractWe tested for depth‐dependent vertical zonation in coral reef community structure with surveys conducted in 2013 at 10 m and 27 m depth off the islands of Moorea, Tahiti, Maiao, and Tetiaroa, which are distributed over ~3500 km2 of the tropical south Pacific. Benthic communities were censused using photoquadrats to obtain percentage cover, first by functional groups (scleractinians, macroalgae, and crustose coralline algae, algal turf, and bare space combined [CTB]), and second by genus for scleractinians and Millepora. Virtually every aspect of community structure differed between the two depths, but the effects were dependent on spatial scale of investigation. Interactive effects of islands and depths determined the abundance of functional groups, as well as seven of eight common coral genera. On the two islands at which two sites were censused, the abundance of functional groups also differed between sites, and was affected by depth × site interactions. The spatially variable effects of depth on community structure underscores the importance of context‐specific synergy between biotic and abiotic factors in driving these patterns. Spatial scale‐dependent vertical zonation also shows the potential for these effects to be modulated by the changes that have affected coral community structure on contemporary reefs over the last few decades.
Highlights
Vertical zonation of community structure characterizes multiple biomes, mediating, for example, the distribution of species of trees among altitudes on mountains (Ashton 2003), lichens and birds among heights in trees (MacArthur 1958, Harris 1971), and algae and invertebrates on rocky intertidal shores (Connell 1972). These effects are controlled by gradients of biotic and abiotic factors, and they have served as a ractive systems for the study of mechanisms determining the distributions of organism through biotic interactions and physiological tolerance of extreme physical conditions (MacArthur 1958, Connell 1972)
Overview Coral reef community structure was sampled in April and May 2013 using two permanently marked sites on Moorea (Adam et al 2011), and six unmarked sites on Tahiti, Tetiaroa, and Maiao
While our focus on genera is well matched to the limitations of photographic analyses, and provides a resolution similar to that used in many studies of Indo-Pacific reefs (McClanahan et al 2007, Adjeroud et al 2009), it may increase the probability of Type II errors in testing for depth-dependent variation in coral community structure
Summary
Vertical zonation of community structure characterizes multiple biomes, mediating, for example, the distribution of species of trees among altitudes on mountains (Ashton 2003), lichens and birds among heights in trees (MacArthur 1958, Harris 1971), and algae and invertebrates on rocky intertidal shores (Connell 1972). For example, strong gradients of temperature, desiccation, and maritime influence support classic examples of vertical zonation (Connell 1972, Somero 2002), and in the shallow subtidal, comparable biological patterns are created on a vertical scale of 10s of meters by the a enuation of wave force and light intensity (Wellington 1982, Witman and Dayton 2001)
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