Changes in diatom patch‐size distribution and degradation in a spatially self‐organized intertidal mudflat ecosystem

Abstract

Self‐organized spatial patterns have been proposed as possible indicators for regime shifts in ecosystems. Until now, this hypothesis has only been tested in drylands. Here, we focus on intertidal mudflats where regular spatial patterns develop in early spring from the interaction between diatom growth and sedimentation but disappear when benthic herbivore abundance increases in early summer, accompanied by a dramatic shift to a bare mudflat. We followed the patch‐size distributions of diatom biofilms during this degradation process. As time progressed, we found a temporal change in the spatial configuration occurring simultaneously with the loss of the diatom–sediment feedback. This indicates a gradual failure in time of the self‐organization process that underlies regular patterning in this ecosystem. The path to degradation co‐occurred with the loss of the larger patches in the ecosystem, which resulted in a decrease of the truncation in the patch‐size distribution. Hence, our study in mudflat ecosystems confirms the general hypothesis that spatial patterns can provide important clues about the level of degradation. Nevertheless, our study highlights the need for thorough study about the type of spatial patterns and the nature of the underlying feedbacks before a reliable assessment of ecosystem status can be made, as changes in patch‐size distribution differed markedly with those observed in other ecosystems.

Experimental evidence for inherent Lévy search behaviour in foraging animals

“…The result that mud snails were most efficient in finding food in fractal landscapes concurs well with the insight that diatoms are fractally distributed in the natural habitat of our mud snails [59,61]. However, the animals were still performing the same strategy in the other landscapes.…”

An ecological engineer maintains consistent spatial patterning, with implications for community‐wide effects

“…Consequences of spatial pattern have been observed at fine scales and modeled at broader scales for other systems and ecological contexts, with examples in food web dynamics (Sanders et al 2014), demographic rates (de la Cruz et al 2008), and competition (Raventós et al 2010). Additionally, changes in spatial patterns of self-organized organisms may indicate impending ecosystems transitions such as desertification in terrestrial ecosystems (Dakos et al 2011) and degradation of intertidal diatom patches (Weerman et al 2012).…”

Nonlinear Dynamics and Alternative Stable States in Shallow Coastal Systems

“…Waves and tidal currents also affect the presence of biofilms on mudflat substrates, driving the total biofilm biomass toward either zero or fully developed (Mariotti and Fagherazzi, 2012) and favoring spatial patchiness that can be used as an indicator of an impending regime shift (Weerman et al, 2012 Figure 3. coupled hydrodynamic-vegetation-growth model for the seagrass Zostera marina based on the positive feedback of seagrass vegetation on sediment suspension and light availability, which leads to the emergence of alternative stable states in shallow coastal bays.…”