Aquatic Sciences Meeting, Albuquerque 2001

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

Date: Tuesday, February 13, 2001, Time: 12:15:00 PM

Location: Galisteo

Cornelisen, C, D, University of South Florida, Tampa, USA, Cornelis@chuma.cas.usf.edu

Thomas, F, I, University of South Florida, Tampa, USA, Fthomas@chuma1.cas.usf.edu

USE OF A STABLE ISOTOPE TRACER FOR ASSESSING THE EFFECTS OF WATER FLOW ON AMMONIUM UPTAKE BY SEAGRASS EPIPHYTES

Results from a series of flume experiments indicate that uptake of labeled 15N ammonium by epiphytes on Thalassia testudinum blades is positively related to water velocity. A linear relationship exists between rates of 15N uptake in epiphytes and rates of ammonium depletion from the water column. By normalizing 15N uptake rates to planar area of uptake surfaces, modeled ammonium uptake for the entire seagrass community can be compared to uptake by epiphytes. In addition, normalization of uptake rates to nitrogen content of the epiphytes provides a measure of uptake efficiency, in uM N per g tissue/time. The use of stable isotope tracers in field flume experiments presents a new approach for investigating the effects of water flow on nutrient transport at both the scale of individual organisms and the entire community. Potential applications include investigating physically versus biologically limited uptake in organisms and comparing uptake efficiencies for different members of a community.

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Aquatic Sciences Meeting, Albuquerque 2001

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