Journal of Oceanography

, Volume 61, Issue 6, pp 1059–1073 | Cite as

Processes Causing the Temporal Changes in Si/N Ratios of Nutrient Consumptions and Export Flux during the Spring Diatom Bloom

  • Naoki YoshieEmail author
  • Yasuhiro Yamanaka


Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other. Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its sinking rate.


Ecosystem model spring diatom bloom regeneration of nitrogen western North Pacific 


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Copyright information

© The Oceanographic Society of Japan/TERRAPUB/Springer 2005

Authors and Affiliations

  1. 1.Faculty of Environmental Earth ScienceHokkaido UniversityKita-ku, SapporoJapan
  2. 2.Frontier Research Center for Global ChangeShowamachi, Kanazawa-ku, Yokohama, KanagawaJapan

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