Common or Sugar Kelp

Sugar Kelp1, Common Southern Kelp2

Laminaria saccharina1, Laminaria agardii2

 common kelp sugar kelp

Phylum: Phaeophyta
Family: Laminariaceae2

This perennial2 kelp appears in field guides as either Common Southern Kelp (L. agardii)2 or Sugar Kelp (L. saccharina)1.  Some field guides list only one out of the two1, others claim that L. agardii is a form of L. saccharina2, and a few claim that microscopic analysis is required to discern the two.

The species name saccharina refers to the sweet residue found on dry blades2.  Sugar Kelp is olive green to brownin color with a long, flat, slippery blade that has no midrib.  It can have ruffled or smooth edges1 and has a very prominent holdfast.  The texture of the blade is thicker during the winter months and becomes thinner with more of a ruffled margin during the warmer months2.  I often spot colonies of lacy bryozoans growing on the blade that bear a resemblance to tiny white rectangles joined together1. This specimen was collected after it washed up on the beach in Scituate, MA, but it usually inhabits lower intertidal to subtidal zones1, where is acts as a primary food source for sea urchins1. Commercial harvest of sea urchins in some areas has increased the abundance of this and other kelps1.

An important characteristic for distinguishing this species from Laminaria longicruris is its short, solid stipe.  L. Longicruis has a hollow stipe that is much longer1,2; it is also much longer (i.e. up to 15 ft.)3 and inhabits deeper waters1.  The holdfast of Sugar Kelp divides into branches1,2 called haptera1, which distinguish Sugar Kelp from Saccorhiza dermatodea and Ribbon weeds (Punctaria sp.), two similar species that have cup and paddle shaped holdfasts respectfully.

Size: up to 3 m (10 ft.)1,2,

Range: Arctic to New York2


1. Watling, L., Fegley, J., Moring, J., White, S., Sulzer, A. (2003) Life Between the Tides. Tilbury House Pub

2.  Gosner, Keneth L. (1978), Peterson Field Guides: Atlantic Seashore – A field guide to sponges, jellyfish, sea urchins, and more

3. Alden, P., Cassie, B. (1998). National Audubon Society Field Guide to New England. New York: Alfred A. Knopf, inc..

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