New research led by Monterey Bay Aquarium and the University of California, Santa Cruz, reveals that denser, and more sheltered, kelp forests can withstand serious stressors amid warming ocean temperatures.
New research led by Monterey Bay Aquarium and the University of California, Santa Cruz, reveals that denser, and more sheltered, kelp forests can withstand serious stressors amid warming ocean temperatures. Published in Proceedings of the Royal Society B, the study also offers the first comprehensive assessment of how declines in kelp abundance affected marine algae, invertebrates, and fishes living in Monterey Bay. The study comes after a multi-year marine heatwave – the product of a 2014 ‘blob’ of warm water prolonged by a 2015-2016 El Niño event – bathed the North American west coast with sweltering sea temperatures.
It all started a decade ago when a triple-whammy of stressors – the large marine heatwave, a sea star die-off, and a sea urchin outbreak – led to pronounced declines in kelp abundance on California’s central coast. Using a fourteen-year dataset, researchers discovered those events caused a 51% decline on average in kelp forest density in the years following the heatwave (2017-2020 vs. 2007-2013). As of 2020, the decline had increased to 72%. Some kelp forests, though, made it through these extreme events.
“We found that larger stands of giant kelp prevented shifts in sea urchin foraging behavior, and these persistent forests were better at withstanding multiple stressors,” said Dr. Joshua Smith, the study’s lead author and Ocean Conservation Research Scientist at Monterey Bay Aquarium. “Something that surprised us was that persistent kelp forests were located in areas that are typically less productive. These persistent forests had a gradual reef slope and protection from wave exposure, which enabled them to become densely packed with kelp prior to the marine heatwave.”
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