Coastal residents near Santa Monica awoke to a foul odor Sunday that probably was caused by a large release of methane in the ocean, authorities said.
Fire departments in Los Angeles and Santa Monica began receiving calls shortly after dawn from residents as far north as Sunset Blvd. and south of Venice Beach reporting a rank smell blowing in off Santa Monica Bay.
A Santa Monica fire hazardous-materials team took readings off the coast near San Vicente Blvd. and found methane in the water, said communications officer Justin Walker.
Authorities said that recent changes in water temperature may have caused plankton and algae beds to bloom, releasing methane just below the surface.
The gas also might have been produced by a geologic event, such as a shift in tectonic plates.
More information about hydrogen sulfide and methane in the ocean:
Methane is a colorless, odorless gas with a wide distribution in nature. It is the principal component of natural gas, a mixture containing about 75% CH4, 15% ethane (C2H6), and 5% other hydrocarbons, such as propane (C3H8) and butane (C4H10). The “firedamp” of coal mines is chiefly methane. Anaerobic bacterial decomposition of plant and animal matter, such as occurs under water, produces marsh gas, which is also methane.