Seaweeds Employ Various Strategies for Surviving Crashing Waves
Posted on May 13, 2012
New research on seaweeds has found that it takes more than just being flexible to survive the constant barrage of crashing waves. Patrick Martone from the University of British has spent a considerable amount of time standing on the shore watching big waves crash against intertidal rocks and wondering how the seaweeds manage to survive there.
Martone says, "Many animals can run and hide when storms roll in and the waves increase. But seaweeds don't have that option; they have to just hold on tight and face the waves head-on."
Previous research has found that one solution seaweeds have come up with is flexibility. Blades of seaweed may curl up and branches may collapse, thereby changing the shape of the seaweed and reducing drag as water velocity increases. But different seaweeds may utilize different strategies to effectively reduce drag, such that some may be better at changing shape and others at reducing size. Martone and colleagues from Stanford University and St. John Fisher College were interested in teasing apart some of these variables and published their findings here in the American Journal of Botany.
The authors collected fronds from six different species of algae (four branched, two bladed) along the intertidal zone of the central Californian coast, placed them in a recirculating water flume, and measured the drag they experienced and the changes in shape and size they underwent under 15 different rates of water flow, ranging from 0 to 4 m/sec. The researchers found that while all six species of seaweed underwent severe reconfiguration as water velocity increased - thus limiting the drag they would otherwise experience if they were rigid - the two types of algae accomplished this in slightly different ways.
Martone says, "Unbranched algae seem to be 'shape changers,' reducing drag primarily by folding and collapsing in flow. Certain branched algae, on the other hand, are 'area reducers,' compensating for drag-prone shapes by reducing frond size through branch reorientation and compression. Thus, we demonstrate that flexibility acts in two distinct ways: permitting wave-swept algae to change shape and to reduce frond area projected into the flow."