PARTICLE RETENTION IN SEAGRASS CANOPIES

CICLO DE SEMINARIOS DEL DEPARTAMENTO DE RECURSOS NATURALES
Seagrass canopies decrease flow velocity and reduce turbulence, promoting sedimentation and reducing particle resuspension. However, there might be additional mechanisms that cause enhanced sedimentation within seagrass meadows. Recent works revealed that a large proportion of deposited material consists of seston. This points at large fluxes toward seagrass meadows that cannot be explained by hydrodynamics alone. Another mechanism of particle trapping is direct physical interception of particles by the plants themselves within the canopy. Direct retention of particles can be caused by e.g. physical binding to the plants or by loss of energy of the particles upon hitting a leaf and subsequent redirection towards the sediment surface. Field results of particle retention time and the proportion of direct effects are discussed and conceptionalised with a two dimensional model. Particle trapping rates are also influenced by canopy structure. We present experimental results on the influence of changing canopy structure on flow properties and particle retention. Implications of changes in hydrodynamic properties of coastal areas caused by invading macroalgae such as Caulerpa are discussed.