Scientists reveal details of unprecedented mass mortality on West Coast that began summer 2011

“Many millions” of deaths before sea star wasting syndrome — Multiple species wiped out in days — Mortality rate of 99.99% over large region — “No documented event has been so severe”


June 4th, 2015

Univ. of California (Davis), Jun 3, 2015 (emphasis added): In August 2011, scientists at the UC Davis Bodega Marine Laboratory walked into their labs to a strange, disturbing sight: Thousands of purple sea urchins and other marine invertebrates were dead in their tanks, which are fed directly by seawater. [The] ocean washed up carcasses of red abalone, large sea stars, and football-sized, snail-like chitons… even more heavily impacted as a population were the millions of purple sea urchins and tiny sea stars that died along a 62-mile stretch of coast… “We might not have known urchins and six-armed sea stars were affected if lab-held animals hadn’t died right in front of us,” said the study’s lead author Laura urchins_NCJurgens… “We’re expecting real ecological changes in how these tide pools operate”… this die-off was fast, wiping out these two species in as little as a few days. The die-off also occurred about two years before [observance of] sea star wasting syndrome

Santa Cruz Sentinel, Jun 3, 2015: [It was] a grim scene, with dead red abalone, purple sea urchins and tiny sea stars rotting across the Northern California shoreline… the same carnage [took place] at the UC Davis Bodega Marine Lab… scientists tallied almost 100 percent mortality of purple sea urchins and six-armed sea stars throughout the 62-mile study area… Researchers found only 10 purple sea urchins in the area once home to millionsStudy by scientists from CA Dept. of Fish & Wildlife, Bodega Marine Lab, UC Davis/Santa Cruz/Merced, Jun 3, 2015: Patterns of Mass Mortality among Rocky Shore Invertebrates across 100 km of Northeastern Pacific Coastline — In late August 2011, formerly abundant intertidal populations of the purple sea urchin [and] six-armed sea star were functionally extirpated from ~100 km of coastline… studies by others indicated moderate to severe impacts on… red sea urchin… and red abalone… There were no obvious physical stressors (e.g., a storm, heavy rainfall)… we did not find a single six-armed star at these six locations… Ochre sea stars and gumboot chitons also experienced elevated mortality… We found only ten surviving intertidal purple urchins out of a prior regional population we estimate at many millions…. [The] mortality rate was therefore >99.99% over 100 km[N]o previously documented mortality event has been so severe over such a large region… its sudden onset [is] a pattern that is rare in marine systems… typically [it takes] several months or years… [W]e cannot unambiguously ascribe the current die-off to a particular cause or set of causes… A disease outbreak is plausible… The most likely cause… appears to be a toxin produced by phytoplankton… yessotoxins have not previously been known as lethal… the possibility remains that unidentified species and/or toxin(s) were responsible.

Press Democrat (Sonoma), Feb 2014: Biologists were initially stumped by the die-off, which stunned local divers and was erroneously attributed to a red tide. The cause has since been identified as a bloom of microscopic algae called Gonyaulax membranacea, which produce a toxin called yessotoxin…


Watch a video documenting the 2011 mass mortality event here

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