Tuesday, April 24, 2012

King of the Kelp

Species name: "Laminaria" sp. (probably Saccharina latissima)

Common name: kelp, giant kelp, Devil's apron

Location: Nova Scotia

While not truly a plant, kelp is not only of great economic importance but also a great nuisance, especially if you like swimming or boating on the Atlantic coastline in cooler water. Kelp is actually brown algae (that broad term refers not just to members of the genera Laminaria and Saccharina, but also many other species in the group), in the kingdom Chromalveolata (formerly part of the Chromista).  Until recently, the species Saccharina latissima was considered a member of the Laminaria, but modern DNA sequencing paints a different picture.

Unlike a true plant it doesn't have roots to absorb nutrients from the seabed, but rather it absorbs its nutrients from the water through it's "leaf" or blade (not a true leaf, either). The "roots" that anchor the kelp to the sea floor are collectively termed the holdfast, and the "stem" (could be short or long, prominent or not depending on the species) leading up to the blade is called the stipe. The genus Laminaria occurs widely around the world in cold salty water, with their geographic range extending from Greenland all the way south to Cape Cod in North America, and in Europe from the north shores of Russia all the way south to the north of France. There are similar species to the one pictured above that occupy the same niche in the Southern hemisphere, with species ranging from the south tip of Argentina north towards Brazil, and also from South Africa up towards the Democratic Republic of Congo. The full length of this alga can reach up to 4 meters!

Commercially, this species is incredibly important worldwide for various reasons. In fact, you probably use an extract of this alga every day and don't realize it! Historically, this was our major source of iodine to make iodized salt, but that has been replaced with much cheaper methods of iodine isolation from living "green things". Historically it was also burned to make potash, which was used extensively in the glass-making industry. To some extent currently, but also largely historically, it was dried and ground and used as a fertilizer on agricultural fields. Today, we extract a compound from it we term an "alginate" (you can probably guess where that word comes from!) which is added to toothpastes and cosmetics as a binding and thickening agent. Rarely it's used in food (that's not to say it's not edible, it's just not the thickener of choice), but it is starting to make appearances in the vegan food industry. In China and Japan, this is the main ingredient in the soup stock used to make dashi.