Determination of background ranges of trace metals in the brown alga Sargassum pallidum from the northwestern Sea of Japan

The background concentration ranges of trace metals (Fe, Mn, Zn, Cu, Pb, Cd, and Ni) in the brown alga Sargassum pallidum sample from the Sea of Japan over the period from 1995 to 2008 were estimated to be: Fe, 60-672; Mn, 12-455; Zn, 6.2-23.8; Cu, 0.9-3.9; Pb, 0-5.5; Cd, 0.5-1.7; and Ni, 0.4-3.8 mu g/g, dry mass. The upper limit of background concentration range was taken to be Me+2MAD (median value plus double median of absolute deviations from the median). The lower threshold value corresponding to the physiological norm of trace metal was Me-15-2MAD(15) (a median of 15% of minimum values minus double median of absolute deviations from the median). The range Me-15 +/- 2MAD(15) was considered as the natural background range.