TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 65 (No. 6), pp. 885-891, 2009

Short Contribution

Diatoms Grow Faster Using Ammonium in Rapidly Flushed Eutrophic Dokai Bay, Japan

Kuninao Tada1*, Marut Suksomjit1, Kazuhiko Ichimi2, Yui Funaki1, Shigeru Montani3, Machiko Yamada4 and Paul J. Harrison5

1Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan
2Aji Marine Station, Seto Inland Sea Regional Research Center, Kagawa University, Aji, Takamatsu, Kagawa 761-0130, Japan
3Graduate School of Fisheries Sciences, Hokkaido University, Sapporo 060-0813, Japan
4Kitakyushu City Institute of Environmental Sciences, Tobata-ku, Kitakyushu 804-0082, Japan
5AMCE Program, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong

(Received 22 March 2009; in revised form 28 July 2009; accepted 29 July 2009)

Abstract: The importance of the nitrogen source for phytoplankton growth in a highly eutrophic embayment, Dokai Bay, was investigated. The DIN concentration often exceeded 100 μM of which 40-70% was NH4+. During two incubation experiments, the natural assemblage of mainly diatoms took up NH4+ instead of NO3-. The growth of two Skeletonema species isolated in Dokai Bay were significantly faster on NH4+ (1.86 and 1.27 div. d-1 respectively) than on NO3- (1.55 and 1.04 div. d-1 respectively). Our results indicated that these diatoms could grow faster by using NH4+ compared to NO3- in this eutrophic bay.

*Corresponding author E-mail: tada@ag.kagawa-u.ac.jp

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