Seaweed primer

Green and brown leaves coat the exposed rocks at low tide, or wash up on the shore in great tangles. This is seaweed—renowned delicacy, condiment, and seaside plaything. One nice thing about the seaweeds for the amateur botanist is that none are toxic; some may be tasteless, and others may lead to mild stomach upset, but none are poisonous (though keep in mind that when it washes up on the beach it is dead—and not that good to eat as it has probably started to rot). But in general seaweeds are touted as being packed with vitamins and highly nutritious. And if you ever get stranded on a deserted island, feel free to munch away.

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Though most seaweeds look very plant-like, things aren’t at all that simple. There are three main types of seaweed and they all are considered algae–green algae, red algae, and brown algae. But though they all seem to have a lot in common, they are actually three very separate groups. The green algae are in the plant kingdom, but the brown algae (such as kelp) are actually in the Chromista kingdom, along with the seemingly not-at-all-similar microscopic diatoms. Red algae are in yet a third kingdom, the Protista (along with amoebas and slime molds). All seaweeds have chlorophyll and photosynthesize sunlight, but brown and red algae also have extra pigmentation. Red algae has a compound called phycoerythrin, which lets it absorb blue light waves and hence live deeper in the water than the other algae types.

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