Bubbles from the Sea

Remember the brightly-colored bubble photo I shared back in January? It was right after I moved to the Oregon Coast and though I was smitten with the various hues I didn’t pause to consider their source. The iridescence reminded me of similar ones I noted a dozen years ago on the beach in Carpinteria, California. Those bubbles were the result of natural seepage of petroleum from an offshore oilfield (historically, the Chumash people gathered the oil and used it to seal their boats).

Well, fast forward six months to a talk I recently attended by Stewart T. Schultz. This guy wrote the book on the Oregon Coast, I mean that literally. In 1998 he wrote The Northwest Coast: A Natural History. An Oregon native, Stewart couldn’t find a comprehensive book that described the coastal region he loved, so he wrote one (as a grad student no less).

While explaining nutrient cycling in the near shore zone Stewart described the importance of diatoms. Diatoms may be small (considered microalgae) but they are mighty; producing roughly 20% of the world’s oxygen. Plus, they are a key nutrient source for all manner of sea life. Or as Stewart put it, “A clam is basically reconstituted diatoms.”

But what do diatoms have to do with my bubbles? Everything! The daily cycle of diatoms in the ocean is a delicate dance between buoyancy and gravity. Diatoms photosynthesize which means they need to be within range of sunlight. But diatoms are unicellular and the majority of them cannot move. Diatoms have a unique solution to this problem – mucus!

Diatoms secrete mucilage which helps them float up through the water column toward the surface. During the day, the power of crashing waves can whip up a froth of mucusy diatoms which comes ashore as a foam. Hence my bubbles.

But wait, there’s more. What is mucus known for (besides being kinda gross)? It’s sticky! And diatom mucilage is no different. Throughout the day grains of sand, stirred up by wave action, adhere to the mucilage. As sand accretes throughout the day, it weighs the diatom down and causes it to slowly sink to the bottom. Overnight, the diatom creates more mucilage so that by dawn it is ascending back up to the light for another productive burst of photosynthesis.

Amazing to think about the complex dynamics involved in the creation of those beautiful bubbles!


Bubbles of Diatoms, Lincoln City, Oregon 2018

Categories: Nature Notes

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