Experimental test of phytoplankton competition for nutrients and light in poorly mixed water columns
Experimental test of phytoplankton competition for nutrients and light in poorly mixed water columns
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DOI：
10.1890/11-0273.1
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发表时间：
2012-05
影响因子：
6.1
通讯作者：
Jarad P Mellard;K. Yoshiyama;C. Klausmeier;E. Litchman
中科院分区：
文献类型：
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作者：
Jarad P Mellard;K. Yoshiyama;C. Klausmeier;E. Litchman
浮游植物垂直分布的最新理论认为，如何相互作用的生态位建设过程，如资源枯竭，行为和人口动态有助于在水环境中的空间异质性。在营养物和光的资源梯度相反的混合不好的水柱中，理论预测一个物种应该聚集在一个单一的深度。这种聚集的深度，或生物量的最大值，应随着时间的推移，由于可用资源的枯竭而变化。此外，聚集的深度应在低量的营养负荷下较深，而在较高量的营养负荷下较浅。理论预测总生物量与养分供应呈现饱和关系。根据理论预测，表层生物量最大值受光照限制，深层生物量最大值受养分限制或受养分和光照共同限制。为了验证这一理论，我们使用了一种游动的浮游植物（莱茵衣藻）生长在圆柱形的浮游生物塔。在我们的实验中，强烈的资源环境的改变，运动，自遮光，营养盐的吸收，和生长的浮游植物。支持预测，我们经常观察到一个单一的生物量最大值在整个实验过程中的表面，并在平衡下更高的营养负荷。然而，在平衡状态下，低营养负荷导致了一个非明显的生物量最大的人口分布在大部分的水柱，而不是由理论预测的明显的地下峰。也支持预测，总生物量跨水柱是正相关的营养供应，但在高营养供应条件下饱和。进一步支持的预测，我们还发现了证据的光限制的表面生物量的最大值和营养限制的深层生物量时，没有表面最大值。此外，光水平离开底部的水柱下降，随着时间的推移，浮游植物的增长和负相关的营养负荷。在实验结束时存在生物量的地方，营养物质被强烈耗尽。本实验研究表明，浮游植物的垂直分布可能是由种内空间资源竞争驱动的。
A recent theory of the vertical distribution of phytoplankton considers how interacting niche construction processes such as resource depletion, behavior, and population dynamics contribute to spatial heterogeneity in the aquatic environment. In poorly mixed water columns with opposing resource gradients of nutrients and light, theory predicts that a species should aggregate at a single depth. This depth of aggregation, or biomass maximum, should change through time due to depletion of available resources. In addition, the depth of the aggregation should be deeper under low amounts of nutrient loading and shallower under higher amounts of nutrient loading. Theory predicts total biomass to exhibit a saturating relationship with nutrient supply. A surface biomass maximum limited by light and a deep biomass maximum limited by nutrients or co-limited by nutrients and light is also predicted by theory. To test this theory, we used a motile phytoplankton species (Chlamydomonas reinhardtii) growing in cylindrical plankton towers. In our experiment, the resource environment was strongly modified by the movement, self-shading, nutrient uptake, and growth of the phytoplankton. Supporting predictions, we routinely observed a single biomass maximum at the surface throughout the course of the experiment and at equilibrium under higher nutrient loading. However, at equilibrium, low nutrient loading led to a non-distinct biomass maximum with the population distributed over most of the water column instead of the distinct subsurface peak predicted by theory. Also supporting predictions, total biomass across water columns was positively related to nutrient supply but saturating at high nutrient supply conditions. Further supporting predictions, we also found evidence of light limitation for a surface biomass maximum and nutrient limitation for the deep biomass when no surface maximum was present. In addition, the light level leaving the bottom of the water column declined through time as the phytoplankton grew and was negatively related to nutrient loading. Nutrients were strongly depleted where biomass was present by the end of the experiment. This experimental study shows that the vertical distribution of phytoplankton may be driven by intraspecific resource competition in space.