Seasonal and geographical variation in the chemical composition of the red alga Palmaria palmata (L.) Kuntze

Abstract

We examined the chemical composition of Palmaria palmata collected monthly from April 1998 to September 1999 in the Trondheimsfjord, Norway. Clear seasonal variations in ash (15–27% of dw), proteins (14–30% of dw) and the low molecular weight carbohydrate, floridoside (3.3 to 25% of dw) were observed. A new and simple method for quantification of floridoside based on extraction and dialysis is described. Ash was high during winter and spring and low during summer-autumn, and the same trend was observed for protein. The opposite trend was observed for floridoside, which showed dramatic variation from less than 5% (of dw) from January to March to more than 20% from June to August. The xylan fraction constituted 24–35% of dw. Monomer galactose and xylose were always very low. Examination of samples collected at 3-month intervals during 1998–1999 in Portaferry (Northern Ireland), Galway (Ireland) and Oviedo (Spain), in addition to Trondheim (Norway), showed geographic variations among the major constituents. A wide range of dry matter contents (10–22% of wet weight) and ash contents (17–37% of dw) was observed. Total protein was high compared to other seaweeds (maximum 30% of dw). The Portaferry samples had a peak in spring that was not observed at the other three localities, where protein levels were high during winter. The content of floridoside was highest in summer samples from Trondheim and Oviedo, while the peak occurred in autumn for the Galway samples. No peak in floridoside was observed for the Portaferry samples, probably due to a relatively high content of nitrogenous nutrients in the water at this site.