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First published online January 17, 2007
Journal of Experimental Biology 210, 522-532 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02679
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The interaction of CO2 concentration and spatial location on O2 flux and mass transport in the freshwater macrophytes Vallisneria spiralis and V. americana

Gregory N. Nishihara1 and Josef D. Ackerman1,2,*

1 Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
2 Faculty of Environmental Sciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada


Figure 1
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  		Fig. 1. Vallisneria spiralis (A) and Vallisneria americana (B) in a flow chamber at a freestream velocity of 6 cm s–1. The flow is from left to right; scale bar, 2 cm.

 

Figure 2
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  		Fig. 2. O2 flux determined from O2 profiles at the upstream location (filled symbols) and downstream locations (open symbols) of Vallisneria spiralis (circles) and Vallisneria americana in a flat (squares) and twisted configuration (triangles) at (A) 17.1 mmol m–3 CO2 and (B) 1.71 mmol m–3 CO2. Solid lines are model fits for V. spiralis, dash-dotted lines are for V. americana in a flat configuration, and the broken lines are for V. americana in a twisted configuration. Thick lines fit the model data at the upstream location and the thin lines are fit to the downstream location. Note that for Fig. 1B, the models at the leading edge overlap. The two horizontal dotted lines indicate the range of O2 fluxes determined from V. americana at ~0.171 mmol m–3 CO2 (Nishihara and Ackerman, 2006Go). Values are means ± s.e.m. In A, N=6 for V. spiralis, N=6 for V. americana in the flat configuration and N=8 for V. americana in the twisted configuration. In B, N=9 for V. spiralis and N=6 for V. americana in the flat configuration.

 

Figure 3
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  		Fig. 3. The log-transformed local Sherwood number (Shx) and local Reynolds number (Rex) at the upstream and downstream locations of Vallisneria spiralis and Vallisneria americana in a flat and twisted configuration at (A) 17.1 mmol m–3 CO2 and (B) 1.71 mmol m–3 CO2. Solid lines are model fits for V. spiralis, dash-dotted lines are for V. americana in a flat configuration, and the broken lines are for V. americana in a twisted configuration. The thin dotted line indicates the theoretical turbulent Shx, and the thick dotted line indicates the theoretical laminar Shx based on Eqn 9. Values are means ± s.e.m. N and symbols are as in Fig. 2.

 

Figure 4
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  		Fig. 4. The log-transformed local Sherwood number (Shx) and local Reynolds number (Rex) at the upstream and downstream locations of Vallisneria spiralis and Vallisneria americana in a flat and twisted configuration determined from the mass transfer coefficient (Shx=kcxD–1; where kc=0.1u*Sc–0.67) calculated using the shear velocity (u*) measured using PIV measurements. The thin dotted line indicates the theoretical turbulent Shx, and the thick dotted line indicates the theoretical laminar Shx, based on Eqn 7, Eqn 9, and the 1/7 power-law (White, 1998). Symbols are as in Fig. 2.

 

Figure 5
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  		Fig. 5. The concentration boundary layer (CBL) thickness ({delta}CBL) at the upstream and downstream locations of Vallisneria spiralis and Vallisneria americana in a flat and twisted configuration. (A) and (B) are the {delta}CBL vs the freestream velocity (U) and the local Reynolds number (Rex), respectively, at 17.1 mmol m–3 CO2. (C,D) The {delta}CBL vs the U and Rex, respectively, at 1.71 mmol m–3 CO2; (E,F) diffusive sublayer thickness ({delta}DSL) determined from hydrodynamic measurements vs U and Rex, respectively. The thick and thin solid lines indicate the theoretical {delta}CBL (A–D) and the theoretical {delta}DSL at the upstream and downstream locations (E,F), respectively.

 




© The Company of Biologists Ltd 2007