Native SpeciesKnotted wrack

Ascophyllum nodosum
FOUND by 2018ejm
Falmouth Maine
ID Confirmed
Quality checked by Wilson
Peer reviewed by jackson
Field Notes
When we went to Mackworth Island on October 4th, 2018, the temperature was in the low 60’s, it was slightly breezy, and the weather was overcast. The time was around noon. Our study site was a rocky intertidal, the section ranging from the rocks at the bank to the shore on the water. On either side of our transect, there was just more rocks and seaweed. The whole sight was divided into 4 sections, one for each group. There were 6 people in our group, each looking for a different coastal species. I personally was looking for knotted wrack, which is a native seaweed. I found plenty of knotted wrack covering the rocks along our transect, along with bladderwrack, another native seaweed. The knotted wrack was affecting the species in the habitat, but in a good way. There were plenty of crabs that we found that we nestled in the thick layer of knotted wrack, so it was clearly providing shelter for the crabs. Also, you could find periwinkles attached to the knotted wrack as well, using it just to rest.
Supporting Evidence
Photo of my evidence.
This photo shows the growth pattern of the knotted wrack, proving that it is axial, since the seaweed is growing off the stem in random directions, which is what axial means
Photo of my evidence.
This photo shows the air bladders on the stems, which is a characteristic of the knotted wrack.
Photo of my evidence.
This photo shows the color of the knotted wrack, which is commonly a yellow-green or a green-brown color. Additionally, this photo shows how much of the knotted wrack there actually was
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Ascophyllum nodosum
Common name:
Knotted wrack
Sampling method: 
Photo of our sampling method.
Place Studied
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Map this species
N 43.689722 °
W -70.226944 °
Observation Site Information
A photo of our study site.
Coastal - Rocky intertidal
Trip Information
2018 Mackworth Upland
Trip date: 
Thu, 2018-10-04 15:06
Town or city: 
Falmouth Maine
Type of investigation: 
Species Survey


Nice work. Was it hard to differentiate this species from the other types of seaweed?