Sediment resuspension in a shallow Thalassia testudinum banks ex Konig bed

Seagrass beds have been described as depositional environments due to their capacity to reduce current velocity and to attenuate wave energy. As sedim ent accretes in seagrass beds, they become shallower and may reach a depth where an equilibrium between deposition/erosion and plant mortality: mainta ins the depth of the bed relatively constant. Although data on sediment dep osition in seagrass beds is available, little is known about sediment resus pension in these plant communities. In the present study, suspended sedimen t concentrations in a Thalassia testudinum bed and an adjacent unvegetated area were compared over part of a neap tide and correlated with the prevail ing hydrodynamic conditions. Sediment resuspension in the unvegetated area was induced mainly by waves while in the seagrass meadow it was caused by i ntensification of speed near the bottom during the flood tide. Under these conditions, suspended solid concentrations were higher within the meadow th an in the adjacent unvegetated area, The sediment resuspension within the m eadow during non-extreme conditions (neap tide and relatively calm winds) s uggests that sediment resuspension is an integral part of sedimentary proce sses occurring in healthy seagrass beds which may bt:contrary to the common ly-held perception that seagrass beds are only sinks and not sources of sus pended matter. (C) 1999 Elsevier Science B.V. All rights reserved.