Interspecific comparison of hydrodynamic performance and structural properties among intertidal macroalgae

Abstract

Macroalgae use flexibility and reconfiguration, i.e. the alteration of shape, size and orientation as water velocity increases, to reduce the hydrodynamic forces imposed in the wave-swept rocky intertidal zone. Quantifying the effects of flexibility on hydrodynamic performance is difficult, however, because the mechanisms of reconfiguration vary with water velocity and the relationship between algal solid mechanics and hydrodynamic performance is poorly understood. In this study, the hydrodynamic performance, morphology and solid mechanics of 10 rocky shore macroalgal species were quantified to evaluate the influences of flexibility and morphology on reconfiguration. Hydrodynamic performance was measured in a flume by direct measurement of changes in size and shape during reconfiguration across a wide range of velocities, material stiffness was quantified with standard materials testing, and structural properties were calculated from material and morphological data. Hydrodynamic parameters varied significantly among species, indicating variation in the magnitude of reconfiguration and the velocities required for full reconfiguration. Structural properties also varied among species, and were correlated with hydrodynamic performance in some instances. The relationship between hydrodynamic and structural properties is velocity dependent, such that flexibility influences different aspects of reconfiguration at low and high velocities. Groups are identifiable among species based on hydrodynamic and structural properties, suggesting that these properties are useful for addressing functional-form hypotheses and the effects of hydrodynamic disturbance on macroalgal communities.

Biomechanical properties of aquatic plants and their effects on plant–flow interactions in streams and rivers

“…Comparisons with the flexibility of macroalgae is difficult since flexibility measures typically used in macroalgae studies are different from flexural rigidity (e.g. the ratio E t /E c of 'Tension' E t and 'Compression' Young's moduli E c as in Biedka et al 1987;Gaylord and Denny 1997; structural flexibility as in Boller and Carrington 2007; or 'Tension' Young's modulus E t as in Denny and Gaylord 2002).…”

Posidonia oceanica and Cymodocea nodosa seedling tolerance to wave exposure

“…Most aquatic vegetation is flexible and becomes streamlined with increasing flow velocities and it is very difficult to measure accurately the frontal area under waves and currents (SandJensen 2003(SandJensen , 2005; but see Boller and Carrington 2007). For this reason, the total surface area was used as the frontal area as it can be accurately measured.…”

Modeling of smart mixing regimes to improve marine biorefinery productivity and energy efficiency

“…Previous studies have shown that macroalgae exhibit a highly adaptable flow structures to reduce their resistance to flow [3,4,19]. The connection between the algae size and drag coefficient is not straightforward and depends on the thallus branches, flexibility, compressibility and physiological ability of a specific species to adapt to flows.…”

“…The connection between the algae size and drag coefficient is not straightforward and depends on the thallus branches, flexibility, compressibility and physiological ability of a specific species to adapt to flows. These relationships between hydrodynamic and structural properties depend on velocity of the water [3,4,19]. In Fig.…”