The Art of Underwater Adhesion: Seaweed Holdfasts
How seaweeds create and maintain a hold in one of the most dynamic environments on the planet.
Introduction
Seaweeds live in one of the most challenging environments on earth, where they are exposed to both excess sun, rain, and freezing temperatures at low tide and the incredible oceanic forces of currents and waves pounding the shore every 5-10 seconds: “because the density of seawater is ˜800 times greater than that of air, large waves can exert almost 100 times the force as hurricane winds on the same object” {Glenn 2013}. And yet, as a microscopic sporophyte or zygote, seaweeds are able to create secure attachment within minutes of settling on a rocky substrate. Through a small but mighty structure called a “holdfast,” almost all seaweeds hold themselves in place for their entire life cycle in this mechanically-challenging environment, rife with potential for detachment and death: “Seaweeds are exposed to a range of forces that could potentially dislodge them—drag, lift, buoyancy, and an accelerational force” {Friedland and Denny 1995}.