Poisonous red tide algae may be cause of squid mass suicide

Scott Sutherland
December 18, 2012
Mystery of Mass Squid 'Suicides' Possibly Solved
Red tide at sunset

Even if you are firmly convinced that the world is not ending this week, stories about animal mass suicides can still cause a moment of doubt and contemplation about the possibility of there being some truth to the rumours. However, scientists investigating the recent mass squid beachings in central California have found evidence of a far-less apocalyptic reason for these tragedies.

For years, shoals of squid have been flinging themselves onto beaches, effectively committing mass suicide, and scientists have been struggling to come up with a reason for the phenomenon.

"For some reason they just start swimming for the beach," said Hannah Rosen, according to LiveScience. Rosen is a graduate student at Stanford University's Gilly Lab, which studies the Humboldt or 'jumbo' squid. "They'll asphyxiate because they're out of the water too long. People have tried to throw them back in the water, and a lot of times the squid will just head right back for the beach."

[ Related: Mystery of mass squid 'suicides' possibly solved ]

According to William Gilly, a professor of marine biology at Stanford University, and head of the Gilly Lab, all of the recent strandings have happened on the same three-week schedule that has been seen for algae blooms that cause so-called 'red tides'. This led one of his graduate students, R. Russell Williams, to search for a connection between the two events.

Red tides are a well-understood phenomena, and some cases, such as those in France and Australia have been reported here on Geekquinox. A sudden increase in the nutrient content of the water can cause algae to multiply rapidly, and some of these algae produce a red pigment as they feed, which colours the water anywhere from strawberry-milkshake pink to blood red.

[ Related: New Zealand beaching proves rarest of whale species exists ]

Another byproduct of these red tides is a chemical called domoic acid, which, in high concentrations, is a lethal toxin that can cause brain cells to go into overdrive, firing so rapidly that they fill with calcium and eventually burst. Examination of the squid found only trace amounts of domoic acid, however, given the potency of the toxin — over 10,000 times as potent as glutamate, the neurotransmitter it mimics in mammals — there is the possibility that it could be causing intoxication in the squid. Coupled with recent findings that the squid have been expanding into unfamiliar territories, this could provide an explanation for these mass beachings.

"They could be tipped over the edge by something like domoic acid that might cloud their judgment," Gilly said.