There was a recent post about sea lions having the seizures and dying along the California coast. They are accumulating a neurotoxin, domoic acid, being at the top of the food train. The post went on to say:
First discovered in 1987 when 107 people on Prince Edward Island fell ill after eating mussels harboring domoic acid, the algae occasionally produce this deadly toxin, which scientists believe is triggered by changing ocean conditions and surges of nitrogen into bodies of water.
Once produced by the algae, domoic acid quickly works its way up the food chain, first gobbled up by shellfish and plankton-eating fish, like sardines and anchovies, that harbor the toxin in their guts. Next in line are sea lions, brown pelicans, otters, whales and dolphins, all of which have been stranding in large numbers recently, or, in the case of pelicans, literally dropping dead out of the sky.