Accumulation of alkaline earth metals by the green macroalga Bryopsis maxima

作者：Takahashi Shigekazu; Aizawa Kyoko; Nakamura Saki; Nakayama Katsumi; Fujisaki Shingo; Watanabe Soichiro; Satoh Hiroyuki^*

来源：Biometals, 2015, 28(2): 391-400.

DOI：10.1007/s10534-015-9843-y

• Alkaline earth metal
• Strontium
• Bryopsis maxima
• Nuclear accident
• Phytoaccumulation
• Ulva arasakii

Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of I-131, Cs-134, Cs-137, and Ba-140 as fission products of U-235. Interestingly, B. maxima contained naturally occurring radionuclides derived from Ra-226 and Ra-228. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive Sr-85 incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the Sr-85 was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that Sr-85 radioactivity was permeable through a dialysis membrane, the Sr-85 was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70 % of the Sr did not precipitate as SrSO4, indicating that a proportion of the Sr may bind with small molecules in B. maxima.

• 出版日期2015-4