Drift Line Foam Could be Phytoplankton Remains

Every so often the surf zone is extra foamy and wave surge pushes gobs of it onto the beach. I even wrote a few words about it once – one of the first posts I wrote for theoutershores. It was just a photograph and a short descriptive paragraph about sea foam, acknowledging I had no idea what its source was. I pretty much summed up all I had to say in Foam in the Wrack.

Spume coasting the mirror
Sea foam, or spume, in the mirror

How little I knew about sea foam until a couple of months ago when I read a tweet by Richard Kirby @PlanktonPundit that changed my connection with sea foam forever. All he said was:

This foam at the waves edge reveals the sea is a solution of phytoplankton remains.

I now know that sea foam, also known as spume, occurs when turbulent seas shake up high concentrations of dissolved organic matter. A big source of dissolved organic matter is phytoplankton. Thus, a foamy surf zone may indicate an offshore phytoplankton bloom.

In celebration of spume, here are a couple modest foam galleries:

May 18, 2015

February 23, 2011


I wasn’t thinking about sea foam when, from across an impassibly low sandy tide pool, I took the photo below. My thoughts were on the intertidal zones; of Pisaster and Anthopluera on the low side, the barnacles, Pollicipes, and Semibalanus, and mussels, Mytilus, in the middle, and of acorn barnacles, Balanaus glandula, on the high side. I was thinking about whether the starfish were survivors of the current bout of sea star wasting syndrome, and about how high up the rocks those acorn barnacles can creep.

Patches of sea foam on the surface of a low tidepool
Patches of sea foam on the surface of a low tidepool

Thanks to @PlanktonPundit, the previously unnoticed sea foam floating on the surface of this tide pool now reminds me about connections between sea and the intertidal. How many of the creatures exposed at low tide began life in the plankton, or depend on plankton directly or indirectly as adults?

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