Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 14, issue 9
Biogeosciences, 14, 2371–2386, 2017
https://doi.org/10.5194/bg-14-2371-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 2371–2386, 2017
https://doi.org/10.5194/bg-14-2371-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 10 May 2017

Research article | 10 May 2017

Analytical solution of the nitracline with the evolution of subsurface chlorophyll maximum in stratified water columns

Xiang Gong1,2, Wensheng Jiang2,3, Linhui Wang2, Huiwang Gao2,4, Emmanuel Boss5, Xiaohong Yao2,4, Shuh-Ji Kao6, and Jie Shi2 Xiang Gong et al.
  • 1School of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266061, PR China
  • 2Key Laboratory of Marine Environment and Ecology (Ministry of Education of China), Ocean University of China, Qingdao 266100, PR China
  • 3Key Laboratory of Physical Oceanography (Ministry of Education of China), Ocean University of China, Qingdao 266100, PR China
  • 4Qingdao Collaborative Center of Marine Science and Technology, Ocean University of China, Qingdao 266100, PR China
  • 5School of Marine Sciences, University of Maine, Orono 04469-5706, USA
  • 6State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, PR China

Abstract. In a stratified water column, the nitracline is a layer where the nitrate concentration increases below the nutrient-depleted upper layer, exhibiting a strong vertical gradient in the euphotic zone. The subsurface chlorophyll maximum layer (SCML) forms near the bottom of the euphotic zone, acting as a trap to diminish the upward nutrient supply. Depth and steepness of the nitracline are important measurable parameters related to the vertical transport of nitrate into the euphotic zone. The correlation between the SCML and the nitracline has been widely reported in the literature, but the analytic solution for the relationship between them is not well established. By incorporating a piecewise function for the approximate Gaussian vertical profile of chlorophyll, we derive analytical solutions of a specified nutrient–phytoplankton model. The model is well suited to explain basic dependencies between a nitracline and an SCML. The analytical solution shows that the nitracline depth is deeper than the depth of the SCML, shoaling with an increase in the light attenuation coefficient and with a decrease in surface light intensity. The inverse proportional relationship between the light level at the nitracline depth and the maximum rate of new primary production is derived. Analytic solutions also show that a thinner SCML corresponds to a steeper nitracline. The nitracline steepness is positively related to the light attenuation coefficient but independent of surface light intensity. The derived equations of the nitracline in relation to the SCML provide further insight into the important role of the nitracline in marine pelagic ecosystems.

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The subsurface chlorophyll maximum layer (SCML) forms near the nitracline. By incorporating a piecewise function for the approximate Gaussian vertical profile of chlorophyll, we derive analytical solutions of a specified nutrient–phytoplankton model. Nitracline depth is deeper than SCML depth, and a thinner SCML corresponds to a steeper nitracline. A higher light attenuation coefficient leads to a shallower but steeper nitracline. Nitracline steepness is independent of surface light intensity.
The subsurface chlorophyll maximum layer (SCML) forms near the nitracline. By incorporating a...
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