BOUNDARY-LAYERS AROUND BLADED AQUATIC MACROPHYTES

This paper describes a model of the diffusive boundary-layer around an aquatic macrophyte blade. Nutrient uptake at the base of the modelled boundary-layer was examined using previously published laboratory dat a. The analysis showed that, over the outer velocity range 0.01-0.16 m s(-1), nutrient uptake varied between that predicted by flat plate bou ndary-layer theory and that expected with no mean advection. A ratio o f theoretical and actual nutrient uptake rates was defined as a means of categorising the transition between the two transport models. The m odelling was extended to show how fluctuating boundary conditions may enhance nutrient uptake by the macrophyte; the scenario examined here suggested that at otherwise low outer velocities, periodic stripping o f the boundary-layer by passing waves increased nutrient uptake by a f actor of 10.