Friday July 1, 2022


A new study led by the University of California, Santa Cruz (UCSC) has found that the dramatic outbreak of kelp-eating sea urchins along the Central Coast of California in 2014 – which led to a significant reduction in that region’s kelp forests – was mainly driven by the emergence of sea urchins from their hiding places, rather than by increases in urchin populations. In subsequent years, urchin movements allowed the recovery of kelp forests in areas from which these predators left. 

“As people are thinking about practical ways to facilitate kelp forest recovery, most people would agree we need to reduce the number of sea urchins, but it’s also really important to consider the role of sea urchin behavior,” said study lead author Joshua Smith, a former doctoral student at UCSC, and currently a postdoctoral fellow at the University of California, Santa Barbara.

According to Dr. Smith and his colleagues, a series of major disruptions to California’s kelp forest ecosystems began in 2013, when an outbreak of sea star wasting disease decimated one of the main sea urchin predators, the sunflower sea star. This was followed one year later by a massive marine heatwave, which created poor conditions for the growth of kelp, and set the stage for the unprecedented sea urchin invasion on the rocky reefs of Monterey Bay where kelp forests grew.

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