Interactions between sediment microbial ecology and physical dynamics drive heterogeneity in contextually similar depositional systems

This study focuses on the strong interactions between the stability of different sediments and the biological and physical variables that influence the erodibility of the bed. Sampling at short-term temporal scales illustrated the persistence of the microphytobenthic (MPB) community even during periods of frequent, high physical disturbance. The role of MPB in biological stabilisation along a changing sedimentary habitat was also assessed . Key biological and physical properties, such as the MPB biomass, composition and extracellular polymeric substances, were used to predict sediment stability (erosion threshold) of muddy and sandy habitats within close proximity to one another over multiple days as well as within emersion periods. This allowed the effects of dewatering, MPB growth and productivity to be examined as well as the resilience and recovery of the MPB community after physical disturbance from tidal currents and wave exposure. Canonical analysis of principal components (CAP) ordinations were used to illustrate the trends observed in bio-physical properties between the sites, while marginal and sequential distance-based linear models (DistLM) were used to identify key properties influencing sediment erodibility. While grain size was important for site differences in the CAP analysis, it contributed less to the variability in sediment erodibility than other key biological parameters. Among the biological predictors, MPB diversity explained very little variation in marginal tests but was a significant predictor in sequential tests when MPB biomass was also considered with diversity and biomass key predictors of sediment stability, contributing 9% and 10% respectively to the final model across all sites.