Morphology and herbivory of Egregia menziesii at sites from California to Washington

Herbivores can drastically alter the morphology of macroalgae by directly consuming tissue and by inflicting structural wounds.  Wounds, in particular, can result in large amounts of tissue breaking away from macroalgae, amplifying the damage initially caused by herbivores.  Herbivores that commonly wound macroalgae often only occur over a portion of a macroalga’s lifespan or geographic range.  However, we know little about the influence of these periodic or regional occurrences of herbivores on the large-scale seasonal and geographical patterns of macroalgal morphology.  We used the intertidal kelp Egregia menziesii to investigate how the kelp’s morphology and the prevalence of two prominent kelp-wounding herbivores (limpets and gammarid amphipods) changed over two seasons (spring and summer) and over the northern extent of the kelp’s geographic range (six sites from central California to northern Washington).  Wounds from limpets and amphipods often result in the kelp’s fronds being p...