No interactions present.
It is OK to be supportive even when there imight be a little uncertainty.
I believe that BOTH species L.hyperborea and :L.digitata are present in the photo but these are not so easy to tell apart sometimes.
See http://www.ispotnature.org/node/874627 and read my Descriptive notes
I have agreed to digitata because the foregound speciment is smooth and probably without epiphytes (don't assume that proves anything).
It's sort of shameful that no-one has commented in nearly five years, despite nearly 200 reads.
I am wandering through all historical Laminarian posts
THREE MARINE PROJECTS
Lat/Lng: 57.67951, -2.26225
OS grid ref: NJ844655