Weed

Seaweeds are a fascinating group of organisms. Although they contain chloroplasts (those little bits we all learned about in school which are capable of absorbing the sun’s radiant energy and using it to capture carbon from the atmosphere and to manufacture sugar) they do not possess the systems of water and nutrient conduction (xylem and phloem) that characterize the plants. Well then, if the seaweeds aren’t plants, what are they? The answer is something of a muddle because seaweeds are polyphyletic, meaning that they are derived from a number of different phylogenetic sources (fancy words which mean that this is a large group with a diverse genealogy that goes back 1.5 billion years). Most seaweeds live attached to the substrate (but do not obtain sustenance from it) and a number of different life cycles have been described. They come in a wide variety of colors and their classification reflects this fact so that the largest divisions of algae are the reds (rhodophyta), the greens (chlorophyta), and the browns (phaeophyta). One other noteworthy aspect of the seaweeds is that nearly all are beautiful. I found this very photogenic mass of Ascophyllum while visiting the seaside at Portsmouth. Many of the thickened bladders you see are filled with air and work to float and hold the thallus up in the water column. You may also notice other swellings which look somewhat rougher than the air bladders, these are receptacles which contain conceptacles which produce the gametes. Egg and sperm are released into the water and fertilization occurs externally. The young thallus then settles on an appropriate substrate and the cycle continues. Enough science … let’s end with a poem, a Seaweed Haiku courtesy of another WordPress blog, Echoes from the Silence

Below the surface
unseen entanglements.
Hope floats.

Fucus

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