But as rising ocean temperatures threaten to make fishery closures routine, it will be even harder to count on crab for holiday meals—or livelihoods. Over the past decade, warming sea waters have produced harmful algal blooms that contaminate crab meat with domoic acid, a neurotoxin that can cause seizures, memory loss and other serious symptoms and has been blamed for poisoning and stranding scores of sea lions in California every year. State officials delayed three out of the last six crab seasons to protect public health after an unprecedented multiyear marine heat wave, dubbed “the blob,” hit the north Pacific Ocean in 2013.