The algae produce a compound called domoic acid, a type of amino acid that leads to a condition commonly known as "amnesic shellfish poisoning" in humans. Shellfish and some small fish, like sardines and anchovies, feed on the algae and concentrate the toxin in their flesh. When animals further up the food chain—like birds—eat those fish and shellfish, the domoic acid seeps into the bloodstream and eventually the brain, where it attacks cells in the hippocampus, the brain's command center for memory and learning. The result: amnesia-stricken birds that will repeatedly fly into windows, and sea lions that writhe on the shore, plagued by seizures. Both are symptoms of rapidly firing neurons in the hippocampus, which will eventually burn out and kill the animal. Beaches have been littered with dead fish, birds, and sea lions up and down the Pacific coast since May—all the way up to Alaska, where NOAA is investigating the deaths of fin whales in connection with the toxin.
Poor thing
Full article here: http://www.motherjones.com/environment/2015/08/heres-everything-you-need-know-about-deadly-algae-california-coast