Meeting Abstract

P2.142  Jan. 5  How plant aggregation density affects fluid flow and particle settlement: All that glitter is not gold YANG, S.*; CARRINGTON, E.; Univ. of Washington, Seattle; Univ. of Washington, Seattle sy3@u.washington.edu

Sessile organisms modify their local fluid environments by changing mean velocity and turbulence. How these modifications affect local particle dispersion and settlement is relevant to understanding local recruitment and spatial patterning of plants, such as macroalgae. Terrestrial and aquatic vegetation has been known to decrease flow through a canopy, increase flow above a canopy, and increase turbulent mixing. The interaction of above- and below-canopy fluid modifications with propagule settlement has the potential to influence plant population spread and community structure over time. One descriptor of a plant population is density. In this study, we investigate how aggregation density of a dominant, canopy-forming, intertidal macroalga, Fucus distichus, affects mean velocity, turbulence, and particle sedimentation. We configured F. distichus individuals into five densities which we subjected to unidirectional flow in a laboratory flume. We measured velocity profiles upstream, downstream, above, and below each plant aggregation using video particle tracking and an acoustic doppler velocimeter. We also measured stipe angles and canopy height. To mimic spore dispersal, we released glitter at points above and below the canopy upstream, downstream, and in the center of the aggregation. We counted the number of glitter particles settled per centimeter through the length of the flume on an adhesive strip and calculated the median and variance of distance traveled by particles. Results suggest that as density of plants increases, mean velocity above the canopy increases and below the canopy decreases. As plant density increases, plant stipes become more perpendicular and the canopy is more upright.