L. Rogers-Bennett, C. A. Catton

Scientific Reports

Published date October 21, 2019

Marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens

  • States that climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps
  • Describes the rapid climate-driven catastrophic shift in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in northern California
  • Finds that bull kelp canopy was reduced by >90% along more than 350 km of coastline
  • Twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014–2017), and sea urchin barrens (2015-)
  • Multiple stressors led to the unprecedented and long-lasting decline of the kelp forest
  • Kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated $44 M and the collapse of the north coast commercial red sea urchin fishery (2015-) worth $3 M
  • Key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase
  • Concludes that science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services