S1-1.7 Jan. 4 Of kelps and corallines: histological insights into seaweed strength and strengthening MARTONE, P.T.; Hopkins Marine Station of Stanford University firstname.lastname@example.org
The survival of intertidal macroalgae depends upon the ability of algal thalli to resist the drag force applied to their fronds by breaking waves. Many studies of macroalgal biomechanics have explored the effects of thallus properties (e.g., flexibility, reconfiguration, size limitation) on drag force reduction, but few have investigated the opposite side of the equation: mechanisms for increasing thallus strength. Previous studies have revealed a trade-off in macroalgal growth strategies to resist breakage: increasing girth versus growing stronger tissues. Brown macroalgae, such as kelps, grow thick stipes but have weak tissues, while red macroalgae grow slender stipes but have much stronger tissues. For example, the joints (genicula) of the articulated coralline Calliarthron cheilosporioides have tissues that are much stronger than other algal tissues but rarely exceed 1 mm in diameter. Furthermore, genicular tissue gets stronger as fronds grow. Here I present a histological analysis exploring the cellular basis for mechanical strength of Calliarthron genicula. Genicula are composed of thousands of long, fiber-like cells whose cell walls thicken over time. Cell wall thickening likely explains increased tissue strength in older genicula: mature genicula may be more than 50% cell wall. However, the strength of genicular cell wall is similar to the strength of cell wall from a freshwater green alga, suggesting that the quantity, not the quality, of cell wall material gives genicular tissue its great strength. Observed differences in tissue strength across algal taxa may be a consequence of tissue construction rather than material composition.