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The Case of the Decaying Sea Lettuce


Photo Credit: H. Krisp via Wikimedia Commons

Over the past several weeks, Seattle Public Utilities (SPU) has received a number of calls about a smell in the 4600-4800 blocks of Beach Drive SW. The callers complained of a persistent sewage-like odor (a.k.a hydrogen sulfide).

After extensive investigation—water sampling, beach surveys, and other research—in coordination with King County, the Washington State Department of Ecology, and the Puget Sound Clean Air Agency, SPU has identified the culprit: decaying sea lettuce!

Yes. Lettuce. (Though not the kind you’ll want to add to your salad repertoire.) Decaying sea lettuce can be extremely foul—it smells exactly like sewage—but it’s a natural process and there is little that can be done except to wait it out.