Intermittency in the plankton: A multifractal analysis of zooplankton biomass variability

We present the first evidence that variability in zooplankton biomass can be characterized as a multifractal. An hourly tune series of vertically integrated acoustic biomass measurements, taken from a fixed mooring on the Atlantic coastline, provided the data for our analysis. Two measures of variability were analyzed: the first difference squared and the squared difference from the mean. When integrated over time, these quantities provide estimates of biomass variability. The distribution in time of these measures of variability is highly intermittent. We show that such intermittency is well described by the scaling properties of multifractals. In zooplankton ecology, potential applications of this analysis include comparing plankton variability distributions to those of passive scalars and environmental variables, quantifying spatial or temporal heterogeneity in intermittent quantities, and determining scales over which similar processes are operating.