Purple sea urchins are munching their way through California’s kelp forests at a speed and scale that have stunned scientists, fishermen and divers alike. But the kelp forests have long been home to red and purple urchins, so it’s clear the three species can get along. Researchers at UC Santa Barbara sought to determine what factors disrupt this harmony.
“Why is it that in some places urchins cause the demise of a kelp forest, and in other places urchins and kelp can coexist?” asked Associate Professor Adrian Stier. “Our analysis shows what’s going on under the hood. It offers a lot more resolution in explaining when and where you might expect urchins to devour kelp.”
That analysis, led by doctoral students Mae Rennick and Bart DiFiore, appears in the journal Ecology. The authors combined laboratory experiments with 20 years of field data to uncover what prompts urchins to begin eating their way out of a home. The results suggest that the supply of kelp scraps, or detritus, may be the deciding factor.