Mystery Solved

The mystery deaths of hundreds of seabirds in Monterey Bay was a normally non-toxic algae.

But after water testing, the researchers found no indication of excess oil, pesticides, acids or commercial products that might have caused the foam and gooey coating on the birds. All told, 207 birds were found dead and 550 were stranded.

Then the slime disappeared.

Now, the "mystery spill" has been solved. It wasn't the Cosco Busan oil spill in nearby San Francisco Bay or a controversial aerial pesticide spraying along the Central Coast. It was harmless-looking foam from an ordinarily nontoxic algal bloom churned up by November waves, according to a study coming out in PLoS ONE on Monday.

This unassuming foam looks like "if you beat egg whites into a meringue and sprinkle a little dirt in with it," study co-author Kudela tells ScientificAmerican.com. Although the protein-rich froth didn't contain toxins, it acted as a surfactant, which lowers the surface tension of water—especially where it comes into contact with oil. This disabled the natural water-repellent coating on the feathers of floating loons, grebes, northern fulmars and other birds in the bay, soaking them through and rendering them susceptible to the chilly autumn Pacific water.