“There's a change in the structure of the mussel bed.” “You can see where instead of a continuous mussel bed, you're seeing gaps of bare rock,” Sones said. Patches of the bivalves, usually stuck to the rock by thread-like fibers, are beginning to detach and wash away. Much of the tissue has since been washed away by the waves or consumed by other animals, leaving the mussel beds a gleaming surface of white and blue from the inside of the shells. They were left yawning open, some still with tissue inside. The mussels were so physiologically stressed that they died.
The mussels would likely have been exposed to high air temperatures for six hours or more on each of those days, Sones said. The high reached 81 degrees at the reserve the next day, when low tide again hit at midday. No temperature sensors are currently planted in the mussel bed, but earlier research suggests that June 10, when Santa Rosa's record high hit 101 degrees - and the Bodega Marine Lab topped out at 77 degrees - the temperature inside the mussels would have reached about 105 degrees or more, Sones said. Their dark shells would have absorbed the harsh sunlight, elevating the creatures' internal heat well above the ambient air temperatures, Sones said. The heat spell coincided with midday low tides that left the shellfish exposed to the sun during the hottest part of the day without tidal relief or wave splash. Nearby mussels, she soon discovered, suffered even heavier damage. She was heading out to the rocky shoreline behind the Bodega Head lab to survey for signs of recovery in the local sea star population, which has been virtually wiped out up and down the North Coast by a wasting disease since 2013.īut what caught her eye were patches of snow-white seaweed on the rocks, apparently bleached during the record high temperatures a week earlier. Sones works out of the UC Davis Bodega Marine Laboratory, where scientists have long studied a variety of impacts related to climate change, from ocean acidification to strange marine wildlife migrations to the “warm blob,” the band of unusually warm water that has drastically altered the environment off the North Coast, which has seen a collapse in its abalone fishery and bull kelp forest.Įvidence of the latest die-off, the mussels, surfaced for Sones in the middle of last month. “If the mussels go away, all the things that live in the mussel bed get exposed.” “There's like a hundred different species that you find in a typical mussel bed,” said Mark Denny, professor of marine sciences at Stanford University and director of the university's Hopkins Marine Station in Pacific Grove. So the mortality event may extend to other species, Sones suggested. Snails, worms, barnacles and anemones are among dozens of species found where California mussels live. They help to ameliorate the energy of the surf and shade out the sun so smaller creatures can find refuge. The bivalves attach themselves to the rocks in tightly packed colonies in both the intertidal zone, which lies above water at low tide, and the subtidal zone, which sits below the low-tide mark. In addition, mussels are a foundation species that provides habitat for other organisms, creating the structure in which they live. The alarm is not just over the enormous number of mussels that basically cooked in the sun. Sones has heard from researchers and citizen scientists about similar episodes ranging from Dillon Beach in Marin County to an area of the Mendocino Coast near Westport, suggesting a widespread problem. Up to 70% of the specimens died in the hardest hit, most exposed areas of the mussel bed along the mile or so that Sones has been able to survey so far. But as a person, that was a challenging thing to be doing.” “You're doing this as a scientist, to document the situation. “It was just really hard to be surrounded by all these dead animals,” Sones, research coordinator for the UC Davis Bodega Marine Reserve, said after a weekend survey of the mussels. In yet another sign of the toll exacted by rising temperatures on the ocean environment, a period of extreme heat last month appears to have killed off a large portion of the mussel bed in Bodega Bay. BODEGA BAY - As a scientist, Jackie Sones trains her focus on observable data - what can be documented, quantified and compared.īut it's taken some effort recently to keep her emotions at bay as she worked among tens of thousands of empty, gaping mussel shells, appraising the scope of a rare mass die-off along the rocky shoreline of the North Coast.
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