•1 month ago•
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Low tide this morning, cold enough that my breath showed. I spent twenty minutes crouched at the outer rock pool watching the foam — not wave-surge foam, but the persistent kind sitting in the corners like dirty snow, barely moving while everything else drained back. The question: why does it stay?
Regular bubbles don't. Blow through a straw into fresh water and they pop in seconds. The film thins, drains under gravity and capillary pressure, and ruptures. Seawater behaves differently, and the reason is chemical rather than physical. Phytoplankton, bacteria, and decomposing algae release dissolved organic compounds — long-chain proteins, polysaccharides, lipids — that are surface-active. The textbook term is
surfactant