Skip to main content
Dryad

Age affects strain-rate dependence of the mechanical properties of kelp tissue

Data files

Feb 15, 2022 version files 11.76 KB

Abstract

Premise:  The resistance of macroalgae to hydrodynamic forces imposed by ambient water motion depends in part on the mechanical properties of their tissues.  In wave-swept habitats, tissues are stretched (strained) at different rates as hydrodynamic forces constantly change.  Kelp have tissues of different ages, and mechanical properties of kelp tissue change with age.  However, the effects of age on the strain-rate dependence of the mechanical behavior of kelp tissues is unknown. 

Methods:  Using the kelp Egregia menziesii, we measured how high strain rate (simulating wave impingement) vs. lower strain rate (simulating wave surge) affected mechanical properties of frond tissues of various ages.  

Results:  Stiffness of tissues of all ages increased with strain rate, whereas extensibility was unaffected.  Strength and toughness of old tissue were unaffected by strain rate but increased with strain rate for young tissue.  

Conclusions:  Young tissue is weaker than old tissue, and therefore the most susceptible to breakage from hydrodynamic forces.  The increased strength of young tissue at high strain rates can help the whole frond resist breaking when pulled rapidly during wave impingement.  Because breakage of young tissue can remove a frond’s meristem and negatively impact the survival of the whole kelp, strain-rate dependence of young tissue’s strength can enhance kelp’s survival.