Techniques for predicting the lifetimes of wave-swept macroalgae: A primer on fracture mechanics and crack growth

Katharine J. Mach, Drew V. Nelson, Mark W. Denny

Research output: Contribution to journalReview articlepeer-review

29 Scopus citations


Biomechanical analyses of intertidal and shallow subtidal seaweeds have elucidated ways in which these organisms avoid breakage in the presence of exceptional hydrodynamic forces imposed by pounding surf. However, comparison of algal material properties to maximum hydrodynamic forces predicts lower rates of breakage and dislodgment than are actually observed. Why the disparity between prediction and reality? Most previous research has measured algal material properties during a single application of force, equivalent to a single wave rushing past an alga. In contrast, intertidal macroalgae may experience more than 8000 waves a day. This repeated loading can cause cracks - introduced, for example, by herbivory or abrasion - to grow and eventually cause breakage, yet fatigue crack growth has not previously been taken into account. Here, we present methods from the engineering field of fracture mechanics that can be used to assess consequences of repeated force imposition for seaweeds. These techniques allow quantification of crack growth in wave-swept macroalgae, a first step towards considering macroalgal breakage in the realistic context of repeated force imposition. These analyses can also be applied to many other soft materials.

Original languageEnglish (US)
Pages (from-to)2213-2230
Number of pages18
JournalJournal of Experimental Biology
Issue number13
StatePublished - Jul 2007
Externally publishedYes


  • Biomechanics
  • Breakage
  • Fatigue
  • Fracture mechanics
  • Intertidal
  • Macroalgae
  • Seaweed

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


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