Multifractal spatial distribution of epilithic microphytobenthos on a Mediterranean rocky shore

Abstract

Understanding how patterns and processes relate across spatial scales is one of the major goals in ecology. 1/f models have been applied mostly to time series of environmental and ecological variables, but they can also be used to analyse spatial patterns. Since 1/f noise may display scale‐invariant behaviour, ecological phenomena whose spatial variability shows 1/f type scaling are susceptible to further characterization using fractals or multifractals. Here we use spectral analysis and multifractal techniques (generalized dimension spectrum) to investigate the spatial distribution of epilithic microphytobenthos (EMPB) on rocky intertidal surfaces. EMPB biomass was estimated from calibrated colour‐infrared images that provided indirect measures of rock surface chlorophyll a concentration, along two 8‐m and one 4‐m long transects sampled in January and November 2012. Results highlighted a pattern of spectral coefficient close to or greater than one for EMPB biomass distribution and multifractal structures, that were consistent among transects, implying scale‐invariance in the spatial distribution of EMPB. These outcomes can be interpreted as a result of the superimposition of several biotic and abiotic processes acting at multiple spatial scales. However, the scale‐invariant nature of EMPB spatial patterns can also be considered a hallmark of self‐organization, underlying the possible role of scale‐dependent feedback in shaping EMPB biomass distribution.

Effects of grazer diversity on marine microphytobenthic biofilm: a ‘tug of war’ between complementarity and competition

“…Gaps within erect organisms are common in these assemblages and are generally occupied by a thin layer of biofilm. Biofilm assemblages at the study site show a scale-invariant spatial distribution, likely determined by the superimposition of several processes acting at different spatial scales, among which grazing by intertidal gastropods is prominent (Dal Bello et al 2015). The most common grazers are the topshell Porchus turbinatus and the limpets Patella ulyssiponensis and Patella rustica.…”

Legacy effects and memory loss: how contingencies moderate the response of rocky intertidal biofilms to present and past extreme events

“…Calafuria is a sandstone rocky shore with gently sloping platforms, whose high-shore levels (0.3-0.5 m above mean low-level water) are dominated by EMPB assemblages, mainly composed of cyanobacteria, but also including diatoms and macroalgal spores (Dal Bello et al, 2015). Calafuria is a sandstone rocky shore with gently sloping platforms, whose high-shore levels (0.3-0.5 m above mean low-level water) are dominated by EMPB assemblages, mainly composed of cyanobacteria, but also including diatoms and macroalgal spores (Dal Bello et al, 2015).…”

“…The RVI was then converted into chlorophyll a concentration (chl) using a previously calibrated relation (Murphy et al, 2006;Dal Bello et al, 2015). The RVI was then converted into chlorophyll a concentration (chl) using a previously calibrated relation (Murphy et al, 2006;Dal Bello et al, 2015).…”

Temporal clustering of extreme climate events drives a regime shift in rocky intertidal biofilms

“…NIR/red ratios are linked to the chlorophyll content in the rock by a linear relationship, calculated on the basis of laboratory chlorophyll a extractions from Calafuria sandstone cores (Dal Bello et al. ).…”