Cultivation of diatoms using Tb-doped silicate minerals to characterize silicon utilized by diatoms

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Diatoms are responsible for as much as 70% of the primary product in the ocean and play a major role of biological pump. This is because they sequester the atmospheric carbon dioxide effectively by transporting assimilated carbon into deeper layer of the ocean in capsules of relatively stable silica. However, the clear explanation for the timing of diatom bloom has not been given. We have conducted cultivation experiments of diatoms to investigate the chemical form of silicon incorporated by diatoms. So far, we have made the following achievements itemized below.1) Cultivation and analysisProliferation was observed when quartz particles were exclusive source of silicon and Similar proliferation was observed in the terbium doped system. The silicon particles, diatoms and seawater were successfully separated with two filters and the determination of silicon in quartz particles and diatoms was also successful with boiling the separated samples in a sodium hydroxide solution.2) Cultivation apparatusA wave-generator was designed and set in a controlled cultivation box to mimic the natural environment of diatom growth.3) The suppression of blank value of silicon in the analysisReference cultivations should be conducted at the comparatively small level of silicon concentration, which was made possible by selecting and washing proper equipments and plastic-ware.4) Time and condition of the diatom cultivationProliferation of diatoms was suppressed with rocking and the proliferation of diatoms were observed between two weeks and one month times.5) Incorporation of terbium in diatomsDetectable amount of terbium was incorporated in diatoms, suggesting that the diatoms utilized silicon in quartz particles. However, it was found that some replicate expriments are required to confirm the results.