Shaken and stirred: the fundamental role of water motion in resource acquisition and seaweed productivity
Hurd, Catriona L.
Water motion is the least studied of the primary drivers of seaweed productivity. In 50% of field studies, seaweed growth and productivity is reduced in slow compared to fast flows and this is partly explained by the reduced transport of dissolved nutrients (e.g. nitrogen) across thicker diffusion boundary layers (DBLs) that form in slow flows. Alternative/additional explanations include increased light heterogeneity stimulating productivity at wave-exposed sites, and a drag-induced enhancement of inorganic carbon uptake and allocation to structural material. Higher growth rates at wave-sheltered sites may be explained by the accumulation of nitrogen regenerated by associated fauna within DBLs, whereas reduced growth in slow flows may be a result of OH- or O2 accumulation rather than reduced nutrient supply.