Infaunal Hydraulic Ecosystem Engineers: The Cast of Characters, Biogeography and Possible Impacts
Sally Woodin , University of South Carolina
13 Nov 2009
Sediments cover more than 80% of the surface of the Earth and in many areas those habitats are occupied by large active animals which move hydraulically within the sediments. Such hydraulic activities cause changes in pressures within the sediments which result in porewater advection. Using a combination of pressure sensors, oxygen optodes and visual imagery, we have demonstrated that porewater bioadvection results from hydraulically generated pressure fields that change in direction and magnitude over time scales of minutes to hours and have a radial extent of 50 cm or more from the individual. Hydraulic activities thus create transient conditions within the sediment at depth and those fluxes extend radially outward to the sediment surface. My focus is three fold. First, which organisms show such activities and are there species and behavior specific bioadvective signatures in either porewater movements or pressures? I will argue that one can rank organisms as to likelihood of such activities based on how they move and orient themselves within the sediment. Secondly, how predictable are the frequencies of the behaviors which result in movement of porewater? I will show some data that are consistent with the idea that these activities are very common. Finally, what are the impacts on the functioning of benthic systems of these bioadvective porewater movements and how common are they in sediments? Obviously, since I am discussing the importance of such activities, I think they are very important and I will show you data that are consistent with that proposition.