Characterisation and chemometric evaluation of 17 elements in ten seaweed species from Greenland

Abstract

Several Greenland seaweed species have potential as foods or food ingredients, both for local consumption and export. However, knowledge regarding their content of beneficial and deleterious elements on a species specific and geographical basis is lacking. This study investigated the content of 17 elements (As, Ca, Cd, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, Ni, P, Pb, Se and Zn) in 77 samples of ten species (Agarum clathratum, Alaria esculenta, Ascophyllum nodosum, Fucus distichus, Fucus vesiculosus, Hedophyllum nigripes, Laminaria solidungula, Palmaria palmata, Saccharina latissima and Saccharina longicruris). Element profiles differed between species but showed similar patterns within the same family. For five species, different thallus parts were investigated separately, and showed different element profiles. A geographic origin comparison of Fucus species indicated regional differences. The seaweeds investigated were especially good sources of macrominerals (K > Na > Ca > Mg) and trace minerals, such as Fe. Iodine contents were high, especially in macroalgae of the family Laminariaceae. None of the samples exceeded the EU maximum levels for Cd, Hg or Pb, but some exceeded the stricter French regulations, especially for Cd and I. In conclusion, these ten species are promising food items.

Fig 1. Sampling locations in Greenland with coordinates in decimal degrees (latitude, longitude).

For Sarfannguit, coordinates are given for one central location (fish factory), specific coordinates for all three sampling sites are provided in Table 1.

Fig 2. Diagram showing the individually examined algal thallus parts of Greenland seaweeds: A. clathratum, A. esculenta, L. solidungula, S. latissima, and S. longicruris.

Fig 3. Principal component analysis of element content on family level of Greenland seaweeds.

Agaraceae (A. clathratum), Alariaceae (A. esculenta), Fucaceae (A. nodosum, F. distichus, F. vesiculosus and Fucus spp.), Laminariaceae (H. nigripes, L. solidungula, S. latissima and S. longicruris) and Palminariales (P. palmata). Hg and Se were excluded from the analysis due to the low number of quantifiable samples. Ellipses denote 95% confidence intervals for Alariaceae, Fucaceae and Laminariaceae.

Fig 4. Concentrations of elements (As, Cd, I, Fe, K and Pb) in different thallus parts of Greenland seaweeds for A. clathratum, A. esculenta, L. solidungula, S. latissima and S. longicruris.

The lower and upper hinges of the box represent the first and third quartile, around the median; the whiskers extend no further from the hinge than 1.5 * inter-quartile range. Outliers beyond the whiskers are shown as circles.

Fig 5. Principal component analysis of element content of Greenland seaweeds depending on geographic location.

All samples of F. distichus, F. vesiculosus and Fucus spp. were used in a pooled investigation. Hg and Se were excluded from the analysis due to the low number of quantifiable samples. Ellipses denote locations with at least three samples.

Fig 6. Matrix of element correlations for Greenland seaweeds, expressed as Kendall’s tau coefficient.

Elements are ordered alphabetically for ease of reading. Hg and Se were excluded from the analysis due to the low number of quantifiable samples. Only statistically significant correlations (p < 0.05) are shown.