SS1.04 Small-scale Biophysical Coupling in Plankton Ecology
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
FuchsH, Woods Hole Oceanographic Institution, Woods Hole, MA, USA, hfuchs@whoi.edu
Mullineaux, L, S, Woods Hole Oceanographic Institution, Woods Hole, MA, USA, lmullineaux@whoi.edu
McKenna, S, P, Woods Hole Oceanographic Institution, Woods Hole, MA, USA, spmckenna@tasc.com
 
SINKING BEHAVIOR OF GASTROPOD VELIGERS IN RESPONSE TO OSCILLATING GRID-GENERATED TURBULENCE
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Larvae of the mud snail Ilyanassa obsoleta pull in their velums and sink rapidly in response to turbulence intensity above a threshold level, resulting in increased sinking fluxes. This behavior was quantified for competent larvae (24-26 days old) over a range of turbulence levels in a grid-stirred turbulence tank. Acoustic Doppler Velocimetry (ADV) and video imaging were used to measure velocities and record trajectories of larvae in the tank. Neutrally buoyant particle velocities were determined using hollow glass spheres in separate experiments. The mean vertical velocity of neutral particles above the grid increased in an upward direction with increased turbulence intensity. At turbulent Reynolds numbers greater than 245, the mean vertical velocity of swimming larvae had the reverse relationship, increasing in a downward direction at higher turbulence intensities. Larval trajectories showed a higher frequency of sudden onset, rapid sinking above this threshold level, increasing the downward flux of larvae. This behavior may improve recruitment success by providing larvae with a settlement cue in the water column above habitable substrate.