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CA - How Two Radically Different Communities Coexist Beneath the Canopies of California's Iconic Kelp Forests

Walk along the beach after a winter storm and you'll see a shore littered with wracks of giant kelp, some 30 to 40 feet long—evidence of the storm's impact on coastal kelp forests.

Less apparent to the casual beachgoer is what happens to the submarine forests after the storm's fury dies down. This is precisely the topic of a new study led by Raine Detmer a graduate student at UC Santa Barbara. She developed a mathematical model describing the effects of severe storms on kelp forest ecosystems, particularly the seafloor, or benthic, communities. The research, published in Ecology reveals an ecosystem whose variability is key to its diversity.

Giant kelp forests are a wonder of the underwater world. They share many similarities with terrestrial forests: lush understories, diverse fauna and verdant canopies that stretch skyward toward the sunlight. However, they also have features completely foreign to any woodland. Giant kelp is among the fastest growing organisms on Earth—able to grow up to two feet per day under ideal conditions—with a lifecycle much shorter than that of any tree. Also, unlike trees, the presence of the giant algae can change rapidly: Storms can uproot entire kelp forests in February that grow back by September.

These factors make for a forest that is always in flux. "If you have a really dynamic foundation species, like giant kelp, this can cause fluctuations in environmental conditions," said Detmer, a first-year doctoral student in the lab of Holly Moeller an assistant professor in the Department of Ecology, Evolution and Marine Biology. conducted the research her senior year at UC Santa Barbara.

Detmer, who conducted the research her senior year at UC Santa Barbara, sought to determine how storms affect the kelp forest floor, which hosts a diverse community of invertebrates and understory macroalgae. To this end, she and her coauthors developed a mathematical model of the ecosystem's intricate relationships. It accounts for factors like the growth rate and mortality of algae and invertebrates, the life stages of giant kelp and the amount of light reaching the seafloor.

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