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首页> 外文期刊>Journal of Theoretical Biology >Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.
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Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.

机译：上层混合层影响下浮游植物的垂直分布和组成。

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The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems.
机译：浮游植物的垂直分布对于水生群落的动态和结构至关重要。在这里，我们使用对流反应扩散模型研究水柱中浮游植物种类的分布和竞争，其中光和养分的逆资源梯度会限制生物量的增长。这个问题对生态学家构成了挑战，因为生产层的位置不是固定的，而是取决于许多内部参数和环境因素。特别是，我们研究了上层混合层（UML）在此系统中的影响，并表明它会导致多种动态影响：（i）我们的模型预测在UML内或以下的最大生物量的替代密度分布，因此系统可能是双稳态的，或者从不稳定状态中放松可能需要持久的过渡。 （ii）深层混合减少会引起生物质的振荡;我们表明，即使扩散率小于沉没浮游植物种群的临界混合，UML仍能维持这些振荡。 （iii）UML可以极大地改变不同浮游植物物种之间竞争的结果，从而在空间分布和物种组成方面产生双稳性。 （iv）如果将深层中的扩散率降低到临界值以下，那么受光限制的物种将获得竞争优势。这产生了一种微妙的竞争排斥效应，其中深层的振荡状态被UML中的稳定解所取代。最后，我们提出了一种新颖的图形方法，用于推论竞争结果并分析UML在水生系统中的作用。

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