Ecogeomorphology of Tidal Flats

Coastal landscapes are often dominated by extensive tidal flats. Tidal flats are characterized by near-horizontal topography and are typically depositional environments that store sediments transported by rivers and nearshore currents. These environments support a diverse biota that modifies the erosive characteristics of the substrate and mediates sediment transport processes. Biofilms are a ubiquitous feature of intertidal mudflats and stabilize the bottom by secretion of extracellular polymeric substances and formation of a tough layer protecting the underlying sediments. Seagrasses on subtidal flats also play an important role in regulating near-bed flow and particle dynamics. A positive feedback between seagrasses, substrate stabilization, and turbidity of the water column ultimately controls the morphological stability of these landforms. In this chapter, an overview of the sedimentological and physical processes acting on tidal flat sediments have been presented. The effects of biofilms and seagrasses on tidal flat substrates and sediment transport processes are then introduced

Ecogeomorphology of Salt Marshes

The coupling of geomorphological and ecological processes is critical for the maintenance or disappearance of salt marshes. Emergent macrophytes dampen wave- and tide-generated shear stresses, promoting sediment deposition and marsh formation. The complex interactions among marsh primary productivity, sea level, and sedimentation determine the equilibrium elevation of the marsh platform and its resilience against external drivers. The strength of the root system can affect the ability of marsh edge scarps to resist erosion. Some marshes are commonly inhabited by a number of species of crab, whose burrows have been implicated in marsh-edge erosion, whereas mussels and other bivalves can be very important in stabilizing marsh sediment by both slowing wave and current velocities and binding sediment to the root mat. Nutrient enrichment has the potential to invoke negative feedbacks that will ultimately affect marsh geomorphic configuration and biogeochemical cycling, by altering plant production and community characteristics and increasing microbial decomposition of organic matter. In this chapter, we present a broad overview of the feedbacks between biota and sedimentological processes in salt marshes, including recent numerical models that have been utilized to study the ecogeomorphic evolution of intertidal areas

Super typhoon induced high silica export from Arakawa River, Japan

This is a post-peer-review, pre-copyedit version of an article published in Environmental Science and Pollution Research. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11356-020-09634-y.autho