The Martone Lab

Biomechanics, evolution, and functional morphology of marine macroalgae

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The intertidal zone of wave-swept rocky shores is one of the most physically stressful habitats on Earth. At low tide, marine organisms are faced with terrestrial conditions (e.g., heat and desiccation stresses). At high tide, organisms are pummeled by breaking waves that can apply drag forces far greater than hurricane winds. We are interested in intertidal seaweeds, which must survive these conditions wherever they settle and grow. (rollover image...)

Selective pressures that drive diversity

The morphological diversity of marine macroalgae provides a constant source of questions. We are curious about the differential performance of seaweeds in flow and the selective pressures that shape modern diversity. Using re-circulating flumes, a high-speed water cannon, and various implements of algal torture, we compare drag and reconfiguration of intertidal fronds to forces required to break support tissues, cause dislodgement, and impact the survival of seaweeds in the field.

Convergent evolution of articulated algae

One common feature of intertidal seaweeds is flexibility. By being flexible, algae "go with the flow," thereby reducing the drag on their thalli. This paradigm holds even for some calcified algae, which grow elaborate fronds by interspersing calcified segments with flexible joints. Articulated algae have evolved several times throughout evolutionary history - three times within the corallines alone. We are studying the morphology, mechanical properties, development, and cell wall composition of joints (genicula) in coralline algae to explore their adaptation to hydrodynamic stress and the precision of their convergent evolution.

Early evolution of lignified cell walls

In our exploration of coralline genicula, we discovered the presence of lignin and secondary cell walls, two features thought to have evolved when green algae took to land. Finding these characters in a red alga suggests that, contrary to the current paradigm, some of the biosynthetic pathways may have evolved in a common ancestor to reds and greens more than 1 billion years ago. We are exploring the deep evolution of lignin biosynthesis by searching for conserved genes using cDNA data.

Biomaterials and cell wall mechanics

We are curious about the influence of cell wall chemistry and ultrastructure on the material properties of biological tissues. We have linked the strengthening of genicular tissue to an increase of cellulose within the cellwall, and data suggest that the addition of secondary walls stiffens genicular tissue and increases material toughness (i.e., energy to rupture). We plan to conduct serial chemical extractions on algal cellwalls to measure the contribution of individual cell wall constituents to mechanical performance, and plan to use birefringence techniques to link stress-strain curves to the reorientation of cellulose microfibrils within red algal cellwalls.

Algal physiology and climate change

Seaweeds provide both food and habitat in marine ecosystems, and shifts in their abundance would likely have cascading effects throughout marine communities. Several researchers in the lab are quantifying physiological performance of seaweeds to explore differences that might explain habitat distributions and to anticipate responses of intertidal species to climate change. We monitor seaweed communities along the BC coast, establishing baseline measures of species composition to help us detect shifts in seaweed abundance and distribution in the future.

Costs and benefits of epiphytism

With limited open space in the intertidal zone, some seaweeds settle and grow on other seaweeds, rather than on rock. This "epiphytic" relationship is poorly understood and complex. Epiphytic algae may increase the dislodgement risk of wave-swept hosts, as both plants grow and drag on the system increases. However, recent data suggest that hosts may actually benefit from epiphytism, delaying desiccation and avoiding herbivores that might prefer to eat the tasty epiphytes.

Department of Botany, University of British Columbia

3529-6270 University Blvd, Vancouver, BC V6T 1Z4 CANADA

Rm 3224, Biological Sciences Building

604-822-9338 (PTM office), 604-822-9413 (lab)