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First published online May 21, 2007
Journal of Experimental Biology 210, 1874-1884 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02775
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Interspecific comparison of hydrodynamic performance and structural properties among intertidal macroalgae

Michael L. Boller* and Emily Carrington{dagger}

Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881, USA


Figure 1
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  		Fig. 1. Conceptual model of macroalgae reconfiguring in flow. Gray and black stick figures represent macroalgae at low and high velocity, respectively. Large gray arrows represent bending force applied by drag. Small black arrows represent the bending moment applied to the beam. (A) Blade-like species, for which force applied along the length of the blade causes deflection and reduction in frontal area. (B) Tree-like species, for which force applied to branches causes bending inward and compression of the branches, reducing the frontal area. Not all forces and moments are drawn.

 

Figure 2
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  		Fig. 2. Normalized area and drag coefficient as functions of velocity for three representative species. (A) Each line is aU, the curve fit of Eqn 2 to pooled data from 3–5 individuals of each species. (B) Each line is CU, the curve fit of Eqn 3 to pooled data from 3–5 individuals of each species. Species labeled as: Grateloupia ({blacksquare}, Figure 2), Agardhiella (Figure 2) and Mastocarpus (Figure 2). Form is denoted by the color of the line, where black=blade-like, red=whip-like and blue=tree-like.

 

Figure 3
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  		Fig. 3. Summary curves of normalized area and drag coefficient as functions of velocity for 10 species of rocky intertidal macroalgae. (A) Each line is aU, the curve fit of Eqn 2 to pooled data from 3–5 individuals of each species. (B) Each line is CU, the curve fit of Eqn 3 to pooled data from 3–5 individuals of each species. Species labeled as: Grateloupia (Figure 3), Laminaria (– – –), Petalonia (- - -), Agardhiella (Figure 3), Scytosiphon (Figure 3), Chondrus (Figure 3), Codium (Figure 3), F. distichus (Figure 3), F. vesiculosus (Figure 3) and Mastocarpus (Figure 3). Form is denoted by the color of the line, where black=blade-like, red=whip-like and blue=tree-like.

 

Figure 4
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  		Fig. 4. Ucrit,a and Ucrit,C versus the structural flexibility and modulus. (A) Ucrit,a versus structural flexibility. (B) Ucrit,a versus modulus. (C) Ucrit,C versus structural flexibility. (D) Ucrit,C versus modulus. No linear regressions were significant (P>0.05). Species labeled as: Grateloupia ({blacksquare}), Laminaria (•), Petalonia ({diamondsuit}), Agardhiella (Figure 4), Scytosiphon (Figure 4), Codium (Figure 4), Chondrus (Figure 4), F. distichus (Figure 4), F. vesiculosus (Figure 4) and Mastocarpus (Figure 4). Form is denoted by the color of the line, where black=blade-like, red=whip-like and blue=tree-like.

 

Figure 5
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  		Fig. 5. Compaction, the proportion of area lost because of reconfiguration, versus structural properties. (A,B) Low velocity (0.5 m s–1). (C,D) High velocity (3.0 m s–1). Regression of low velocity compaction to modulus (slope=–0.005, R2=0.39, P=0.05) and high velocity compaction to log structural flexibility were significant (slope=0.029, R2=0.73, P<0.01). Other regressions were not significant (P>0.05). Species labeled as per Fig. 4.

 

Figure 6
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  		Fig. 6. Drag coefficient versus structural properties. (A,B) Low velocity (0.5 m s–1). (C,D) High velocity (3.0 m s–1). Linear regressions of CD to log-transformed structural flexibility (slope=–0.093, R2=0.47, P=0.03) and CD to modulus (slope=0.026, R2=0.50, P=0.02) were significant at low velocity. Neither relationship was significant at high velocity (P>0.05). Species labeled as per Fig. 4.

 

Figure 7
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  		Fig. 7. The critical velocities of normalized area (Ucrit,a), the velocity at which area reaches within 5% of the minimum area, versus the critical velocity of drag coefficient (Ucrit,C), the velocity at which CD reaches within 5% of the minimum CD. The line is unity. Note that most species fall below the line, indicating that CD asymptotes at a lower velocity than normalized area for those species. Species labeled as per Fig. 4.

 




© The Company of Biologists Ltd 2007