The seasonal variation in weight and chemical composition of the common British Laminariaceae

Abstract

The seasonal variations in the total ash, crude proteins, mannitol, laminarin and alginic acid contents are given for monthly samples of the Laminariaceae, L. cloustoni, L. digitata and L. saccharina from November 1946 to October 1948, samples of L. digitata and L. saccharina having been taken at different localities to determine the effect, if any, of the degree of exposure on the chemical composition.The results agree favourably with those of the first 2 years examined and indicate that, with only a few exceptions, results might be reproducible in the corresponding season of any year, and it should be possible, therefore, to predict the approximate composition in subsequent years.As before, the marked seasonal variations in chemical constitution occur in the fronds, where the bulk, if not all, of the photosynthesis occurs. The stipes undergo some variation parallel to that in the fronds, but within narrower limits, while laminarin is absent throughout the year.