Seasonal variation in the nutritional composition and potentially toxic elements of the red macroalga Palmaria palmata in the Arctic

Algae can be a sustainable food source rich in proteins, polysaccharides, minerals and vitamins. These compounds will vary greatly due to seasonal and environmental fluctuations. The present study investigated the seasonal variations in the nutritional composition and potentially toxic elements of P. palmata harvested monthly in the Arctic, characterized by polar nights and midnight sun. A seasonal trend for the biochemical constituents was observed, where the dry matter and sugar content were higher during late summer and autumn and lower during late winter and spring. The ash and protein content show an opposing trend, with higher content during late winter and spring and lower during late summer and autumn, with the lowest being in August. Notably, the high iodine content varies substantially, withhigher levels in spring and summer, limiting the recommended daily intake of P. palmata to maximum 0.63-0.92 g DW for a 70 kg individual. Seasonal fluctuations were also found for toxic elements such as arsenic, cadmium and lead, with higher concentrations observed in winter and spring. The high concentrations of the main components responsible for the characteristic umami taste, glutamic acid and aspartic acid, during the year affect the sensory properties of the algae, making it a valuable taste enhancer. The present study highlights the importance of considering seasonal variations when assessing the nutritional value and safety of P. palmata as a food source.