Carbohydrate and pigment composition of macroalgae in a kelp-dominated Arctic fjord

Abstract

A vast expanse of macroalgae is growing on the Arctic coasts under the changing environment. With a high content of carbohydrates, macroalgae are an important component of the coastal carbon cycle and an attractive raw material for bioethanol production. Biochemical composition of macroalgae vary with species and environment. In this study, we analysed the composition of carbohydrates (monosaccharides) and pigments of four brown macroalgae species Alaria esculenta, Fucus distichus, Laminaria digitata, and Saccharina latissima, and one red alga Palmaria palmata collected from the coast of Kongsfjorden- an Arctic fjord in Svalbard in June and August, 2019. L. digitata, S. latissima, and A. esculenta belong to the order Laminariales in the class Phaeophyceae, phylum Ochrophyta. F. distichus is in the Fucales order of Phaeophyceae. P. palmata is classified under the Palmariales order in the class Florideophyceae, phylum Rhodophyta. In our samples, chlorophyll a (40.53–229.04 µg g−1 fresh weight) and fucoxanthin (12.71–71.18 µg g−1 fresh weight) were the major pigments with more concentration in August than in June. Violaxanthin concentration was higher in August, whereas zeaxanthin and lutein concentration were higher in June. In the monosaccharide profile, glucose was most abundant followed by mannuronic and guluronic acids indicating abundance of laminarin and alginate, respectively, in A. esculenta and L. digitata. In S. latissima, mannuronic acid was present in the highest concentration followed by guluronic acid and glucose. In F. distichus, fucose was most abundant followed by uronic acids (mannuronic and guluronic acids) in June and glucose in August. Overall, concentration of storage sugars, mannitol and glucose, were higher in August while structural sugars like fucose, guluronic and mannuronic acids showed very less variation. The mannuronic/guluronic acid (M/G) ratios in the brown macroalgae samples were greater than 1. We discussed the pigment and monosaccharide composition and variation with species, month of collection, and environmental parameters.