Spatial Self‐Organization on Intertidal Mudflats through Biophysical Stress Divergence

Abstract

In this study, we investigated the emergence of spatial self-organized patterns on intertidal flats, resulting from the interaction between biological and geomorphological processes. Autocorrelation analysis of aerial photographs revealed that diatoms occur in regularly spaced patterns consisting of elevated hummocks alternating with water-filled hollows. Hummocks were characterized by high diatom content and a high sediment erosion threshold, while both were low in hollows. These results highlight the interaction between diatom growth and sedimentary processes as a potential mechanism for spatial patterning. Several alternative mechanisms could be excluded as important mechanisms in the formation of spatial patterns. We developed a spatially explicit mathematical model that revealed that scale-dependent interactions between sedimentation, diatom growth, and water redistribution explain the observed patterns. The model predicts that areas exhibiting spatially selforganized patterns have increased sediment accretion and diatom biomass compared with areas lacking spatial patterns, a prediction confirmed by empirical evidence. Our study on intertidal mudflats provides a simple but clear-cut example of how the interaction between biological and sedimentary processes, through the process of self-organization, induces spatial patterns at a landscape level.

Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

“…The self-organized patches may be induced by scale-dependent feedbacks, i.e., a local positive feedback between the ecosystem state and environmental conditions within the patches, and a long-distance negative feedback around or in between the patches [121]. In the coastal zone, this self-organization manifests at the patch scale, e.g., where positive biomass and topographic growth within pioneer vegetation clusters or mudflat diatom patches is juxtaposed with adjacent erosion [145][146][147][148]. It also manifests at the ecosystem scale as the juxtaposition of upland, salt marsh, patchy pioneer salt marsh vegetation, seagrasses, and mudflat in the intertidal zone [149].…”

Biogenic gradients in algal density affect the emergent properties of spatially self-organized mussel beds

“…Theoretical studies emphasize that self-organized patterns are critically important for the functioning of ecosystem. Spatially self-organized ecosystems are more diverse, [2,3], have higher primary or secondary productivity [4][5][6] and are better able to withstand disturbance [4,[7][8][9][10][11] compared with non-patterned ecosystems. Hence, self-organized patterns may generate important emergent properties that affect ecosystem functioning.…”

Biogeomorphology of coastal seas

“…For example both for mussels (Van de Koppel et al, 2008) and diatoms (Weerman et al, 2010) regular patterns emerge from scaledependent feedback mechanisms, characterized by a local positive feeback and a longer range negative feedback (Rietkerk et al, 2004). Also, for tube-building worms selforganization is observed in the field on a patch scale , although on the landscape scale the self-organization in sand wave fields is less obvious, both in the field (Rabaut, 2009) and in the model (Figure 8.7).…”