Determination of threshold concentrations of metals in indicator algae of coastal waters in the northwest Sea of Japan

Abstract

Background concentrations of Fe, Mn, Cu, Zn, Pb, Cd, and Ni were calculated for thalli of abundant algae of Fucus, Silvetia, Sargassum, Cystoseira spp. from the northwest Sea of Japan during 1987–2008. As the upper threshold levels of metal background concentrations, the median values plus double medians of absolute deviations from the medians were used (Me + 2MAD). The lower threshold level of the background concentration equal to the physiological need for an element is the median of 15% minimum values in the sampling minus the double median of absolute deviations from the median (Me₁₅–2MAD₁₅). The range of Me₁₅ ± 2MAD₁₅ is considered the natural background range of concentrations.