Agarum sp. – Sea Colander
I go back and forth on which common name I like best for this perennial3 seaweed. I usually end up calling it Sea Colander because that is what I learned first. Many students prefer to call it Shotgun Kelp; I suppose that’s a hipper name. Visual observation of the characteristic perforations (i.e. holes) leads you to believe that another organism made a snack of the seaweed. However, the porous appearance is naturally occurring, rendering the thallus less susceptible to disturbances from moving water (i.e. tidal influence, wave action, etc.).
Sea colander has a prominent midrib1 and is dark brown3, but can have tinges of red or olive green depending on its decay and light exposure. Sea colander is found subtidally – I have yet to see sea colander snorkeling in areas where it is commonly found washed up on the beach in Massachusetts.
Size: Reports on the size vary considerably with one source describing the length as 45 cm (18 in)1, and another author describing the specimen as growing to 1.8 m (6 ft)3. If anyone has the pleasure of seeing a 6’ long shotgun kelp, please leave your observations in our comment section below.
Range: Arctic to Cape Cod2,3
1. Watling, L., Fegley, J., Moring, J., White, S., Sulzer, A. (2003) Life Between the Tides. Tilbury House Pub
2. Martinez, A.J. (2011) Marine Life of the North Atlantic: Canada to Cape May. Aqua Quest Publications
3. Gosner, Keneth L. (1978), Peterson Field Guides: Atlantic Seashore – A field guide to sponges, jellyfish, sea urchins, and more