Algae: The Unsung Hero of the Intertidal


Hello Foldscopers!

When people visit the intertidal, most think about all the animals they can see: limpets, urchins, hermit crabs…the list goes on and on.  Quietly, in the background, algae is playing an important role for those organisms. They cover rocks in various shapes and sizes; providing nutrients, habitat, and even protection from the sun.  This became starkly apparent to me on a recent trip to the intertidal at Point Piños, California.

As I began to head out into the intertidal, I noticed huge flats of surfgrass (Phyllospadix) covering the rocks. Technically, this is not an algae.  This is actually an angiosperm that lives at the waters edge. This picturesque site drew me in to get a closer look, which led me to look at all the algae that was alongside the surf grass.

Surfgrass and algae in the intertidal at Poiñt Pinos, California.

There are three groups of algae in the intertidal zone: Chlorophyta (green algae), Rhodophyta (red algae), and Phaeophyta (brown algae).  I tend to gravitate towards the red algae.  These algae have a range of colors depending on how much of the pigment phycoerythrin is present in them.  Some of these algae have have a calcium shell around their cells.  This is called coralline algae.  I found a piece of coralline algae that was in stages of bleaching since it had been pulled from the rocks (below).  This sample was a bit to big to get good images under my foldscope…but the key is to keep trying!

Coralline algae in a bleached and living state.
Coralline algae with pigment.
Bleached coralline algae.

Next, I looked at another red algae species. After some searching through an algae guidebook, I think this is Sarcodiotheca gaudichaudii .  

Another red algae intertidal species.


The variety of red algae seen on any given day in the intertidal can be seen in yet another sample. I was not able to determine exactly what kind of algae this was, but it is beautiful.


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Until the next adventure!


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