The effect of the depth of immersion on the chemical constitution of some of the sub‐littoral seaweeds common to Scotland

An investigation into the variations in chemical constitution of the common British Laminariaceae, L. cloustoni, L. digitata and L. saccharina, collected at depths of 1–24 m., has been carried out in Orkney. At certain times of the year variations in chemical composition, in addition to those due to the recognized seasonal variations, have been found to occur in the fronds with very little variation., in the stipes. In general, in the fronds an increase in mannitol occurs with depth, reaching a maximum at 6–10 m., indicating that maximum photosynthesis probably occurs at that depth, in agreement with the observations of previous workers. Below 10 m., the mannitol decreases again. Laminarin decreases progressively with depth, being at a maximum at 3–6 m., and is absent in samples from 3 depth below 16 m.