Smart Seaweed Uses Laws of Fluid Dynamics to Survive Big Waves

By Sarah Zhang | May 14, 2012 2:23 pm

Seaweeds showing off their drag reducing skills.

Littered with the dehydrating corpses of seaweeds, beaches after a big storm are a reminder that life can be tough out there in the crashing waves. But seaweeds aren’t totally defenseless. A recent study in the American Journal of Botany studied two different strategies that seaweeds use to reduce drag so that fast-moving waves don’t uproot them.

Drag is proportional to the total area of the seaweed multiplied by drag coefficient, which depends on the seaweed’s shape. (For example, a boxy school bus has a higher drag coefficient than a race car.) That means seaweeds can either get smaller or more streamlined to ride out the waves.

Sea plants have adopted two main shapes—bladed and branched—to pursue these two strategies: Smoothly shaped bladed seaweeds crumple into smaller shapes when a wave hits them, while branched seaweeds fold their many (drag-generating) fronds into a more streamlined shape. The two approaches aren’t mutually exclusive, but they do manipulate different physical characteristics. Seaweed’s long, trial-and-error evolution has devised the same drag-reducing strategies that engineers have come up with.

Image courtesy of P. Martone et al. / American Journal of Botany


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