Aquatic Sciences Meeting, Albuquerque 2001

SS01 Submerged Aquatic Vegetation and the Water Column (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 10:30:00 AM

Location: Galisteo

Zimmerman, R, C, Moss Landing Marine Laboratories, Moss Landing, CA 95039, USA, rzimmer197@aol.com

Buddemeier, R, W, Kansas Geological Survey, University of Kansas, Lawrence, KS 66047, USA,

THE COST OF GOING WITH THE FLOW: IMPACT OF CURRENT VELOCITY ON SEAGRASS CANOPY PHOTOSYNTHESIS

Water motion enhances seagrass productivity by increasing the delivery of dissolved substances to the leaf surface. But coherent currents also collapse the vertical biomass distribution of the seagrass canopies and increase the leaf area projected toward the incoming light. The increased projected leaf area increases light attenuation in the upper layers of the canopy, but reduces radiative transfer to the lower portion of the canopy where most of the biomass resides. Consequently, total canopy photosynthesis decreases as leaf tissue in the upper illuminated portion of the canopy cannot utilize all the absorbed photons for photosynthesis, even though lower regions of the canopy are increasingly light limited. Current velocities of 20 cm per sec may reduce canopy photosynthesis by as little as 10 percent in clear shallow waters. In turbid water, however, canopy photosynthesis may be reduced by as much as 50%, which can enough to limit seagrass density and depth distribution in certain environments.

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Aquatic Sciences Meeting, Albuquerque 2001

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