The Physics-Biology Links in Suspended and Settled Estuarine Mud Dynamics: A Review

Abstract

In marine, coastal and estuarine environments, it is not possible to understand the ecological processes unless there is a very good understanding of the physical forcing factors. In turn, once the physics of an area creates the conditions for colonisation by the biota, then, very often, the biota modifies the physical and biogeochemical processes. This review details the physical processes involved both in the substratum and the water column, especially in muddy sedimentary systems typical of estuaries and coastal areas. Using recent studies to show that the physical and biological structure and processes work in tandem to create the water column and sedimentary features, the analysis shows that the physics creates the conditions both for chemical mediation and for biological colonisation. The responses on and by the biota include both the micro- and macroorganisms that influence flocculation, floc creation and disintegration, especially through the production of extracellular mucous substances, bioerosion and biostabilisation. Colonisation is firstly by microorganisms and then by macroorganisms. These organisms then create feedback loops where they modify the structure of both the flocs and the bed sediment. It is emphasised that these aspects need to be incorporated into the engineering models of fine sediment dynamics of estuarine and coastal waters, in order to increase their reliability.