Elements and sugars in kelp and fucoid species in Greenland, correlation and seasonality

Greenland seaweeds constitute an arctic marine resource as well as being important monitoring organisms in connection with arctic mining activities. In both cases, the natural element content, and its potential seasonal variation, is important knowledge for designing a monitoring programme and for planning of harvest for highest biomass quality and value. Therefore, concentration levels of 54 elements and two sugars (laminarin and mannitol) were obtained in seven different seaweed species of relevance for monitoring and commercial harvest sampled in the same location in Greenland across all seasons during two years. The kelp species sampled were Agarum clathratum, Alaria esculenta, Hedohyllum nigripes, Saccharina latissima, and the fucoids Ascophyllum nodosum, Fucus distichus and F. vesiculosus. The thallus samples were analysed for element concentration levels by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the monosaccharides were separated by HPAEC ion exchange and detected using Pulsed Amperometric Detection (gold electrode). The results showed, in the studied location, and on average, that the dominant major and minor elements are potassium, sodium, calcium, magnesium and phosphorus with mean concentration levels > 4800 mu g g(-1). The trace elements are dominated by iron, aluminium and arsenic with mean concentration levels > 61 mu g g(-1). Concentration levels of elements were in general seaweed species specific. Seasonality was not tested statistically significant for most of the elements when data were pooled in summer and winter months, although higher concentration levels during winter could be observed. Thus, the content of laminarin and mannitol is highest during late summer, thus July-October/November may be the time window for optimal harvest yield with respect to those compounds, although narrower time windows may be considered, depending on the species harvested. Regarding unwanted compounds such as As and I, harvesting time of the year seems not to cause a profound difference on the quality of the biomass.