Fingered Kelp, Horsetail Kelp1,2
Horsetail or fingered kelp is a very recognizable perennial2 species. This particular specimen, found washed ashore in beautiful Scituate, MA, is an olive green color. However, I have seen it look rather orange when observed during snorkeling in the same area. The holdfast and stipe are incredibly strong and growth rings are visible in cross section when the stipe is cut2. The cylindrical stipe flattens out as it joins the blade2. The most conspicuous part of the thallus are the multiple “fingers” that the blade divides into. The number of “fingers” increases with age2 with as many as 30 being observed1. These act to reduce drag2 that can produce forces large enough to rip the seaweed from its substrate.
Size: The reported size will vary depending on what source you read, with some sources reporting 50 cm (20 in)1, another source says 1.1 m (3.5 ft)2.
Range: Arctic to long Island Sound2
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