ABSTRACT

Sediment traps were used to measure the rate of deposition in a Thalassia seagrass meadow and in an adjacent (sandy) grass-free area. The average depositional rate of mud in the Thalassia bed was 4.96 g trap^-1 week^-1, and in the sandy area, it was 3.04 g trap^-1 week^-1 in the summer. In winter, these rates were 1.60 and 1.50 g mud trap^-1 week ^-1, respectively.

Electromagnetic current-meter measurements showed that the mean flow velocity in the grass-free area is higher than in the seagrass area. Therefore, the increased depositional rate of mud within the seagrass is due to slowing of water currents by the grass blades. Confirmation of the blade baffle effect was obtained by placing a 1-m² plot of artificial Thalassia in a grass-free area. Sediment traps in the artificial Thalassia contained 5.45 g mud trap^-1 week^-1 as compared to 3.04 g mud trap^-1 week^-1 in the adjacent grassfree area in summer. In winter, these rates were 1.82 and 1.50 g mud trap^-1 week^-1, respectively.

Epiphytes in the Indian River Lagoon had no detectable effect on the amount of mud deposited in Thalassia beds.