An intense subsurface chlorophyll enhancement was found repeatedly within the core of a modewater eddy during a 2-month period. Two controls on chlorophyll concentrations in this deep chlorophyll maximum (DCM) layer are noted: chlorophyll concentration is controlled by nutrients at low nutrient concentrations and by light when nutrients are saturating. To synthesize these results, a simple one-dimensional nutrient-phytoplankton model is developed by including the effects of phytoplankton self-shading for light attenuation, depth-dependent phytoplankton specific loss, and density-associated nutrient fluctuation in the deep layer. The model is parameterized using eddy data including not only vertical diffusivity, sinking velocity, and chlorophyll-to-carbon ratios, but also rates of phytoplankton growth and nutrient regeneration. Our results suggest that the observed DCM variability is controlled by nutrient-light interaction leading to a change of phytoplankton physiology and hence vertical enrichment of chlorophyll within the core of the stratified eddy. Further theoretical analyses indicate that variation of nutrient and light availability in the DCM layer of the eddy core is largely driven by change of the vertical nutrient fluxes as a result of isopycnal motions in the deep layer, which is also subject to influences by processes including vertical mixing, particle sinking, and nutrient regeneration.

中文翻译：

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控制模式水涡流中地下叶绿素最大值垂直变化的机制

在 2 个月的时间里，在常水涡流的核心内反复发现了强烈的地下叶绿素增强。注意到对这个深叶绿素最大值 (DCM) 层中叶绿素浓度的两个控制：叶绿素浓度由低营养浓度的营养物质和当营养物质饱和时的光控制。为了综合这些结果，开发了一个简单的一维养分-浮游植物模型，其中包括浮游植物自遮蔽对光衰减、深度依赖的浮游植物特定损失和深层密度相关养分波动的影响。该模型使用涡流数据进行参数化，不仅包括垂直扩散率、下沉速度和叶绿素碳比，还包括浮游植物生长和养分再生的速率。我们的结果表明，观察到的 DCM 变异性受养分-光相互作用控制，导致浮游植物生理学发生变化，从而导致分层涡流核心内叶绿素的垂直富集。进一步的理论分析表明，涡核 DCM 层中养分和光利用率的变化主要是由深层等密度运动引起的垂直养分通量的变化驱动的，这也受到包括垂直混合、颗粒下沉和养分再生。