We study how organism traits and population densities of ecosystem engineering species, in combination with environmental factors, affect the formation and erosion rates of biogeomorphological structures, and focus on the widely distributed marine tube-building polychaete Lanice conchilega, which lives in patches that form mounds up to 80 cm high in soft-bottom sediments. We modeled the tube-building worms as thin solid piles that affect drag and turbulence, and thereby the local sediment dynamics and thus mound dynamics. Hydrodynamic model predictions showed good agreement with flume experiments for flow-velocity adaptations both within and in front of a patch of tube-building worms. The modeled equilibrium mound height increased with the organism trait "tube length," and with population density, but was only little affected by the strength of the tidal current, water depth, and grain size. In all cases, the modeled mound heights were within the range of the mound heights observed in the field. The effect of the tube-building worm L. conchilega reached beyond the spatial scale of their biogenic structures, and persisted longer than the lifetime of the engineering organism itself. |
