Reddened seascapes: experimentally induced shifts in 1/f spectra of spatial variability in rocky intertidal assemblages.

Ecological tests of 1/f-noise models have advanced our understanding of how environmental fluctuations affect population abundance and species distributions. Most empirical studies have been conducted under controlled laboratory conditions and have focused on individual drivers. We present the results of a four-year field experiment in which canopy presence/absence and the availability of primary space were manipulated as red-noise and white-noise spatial processes, respectively, to evaluate their separate and compounded effects on algal turf distribution in a rocky intertidal community. Algal turfs closely tracked spatial variation in canopy distribution, displaying a reddened spectrum of spatial variation. Surprisingly, white-noise clearings also induced a red-shift in turf distribution, a pattern that was related to a nonlinear relation between gap size and turf colonization. The two disturbances interacted antagonistically, dampening the red-shift of turf distribution. Our results provide evidence of experimentally induced shifts in the spectrum of a spatial variable under natural environmental conditions.