Phytoplankton Blooms "Like It Colorful"(BLIC) - The relative influence of biodiversity and biotic interactions on the early stages of phytoplankton bloom formation

全球生物多样性的丧失在水生生态系统中也很明显。生物多样性是如何影响生态系统功能的，从机制上讲，人们只了解了一部分。这种生物多样性与生态系统功能的关系已经在初级生产者一级得到了记录；远洋系统中的浮游植物。浮游植物参与了全球约50%的初级生产，基本上控制着重要元素的全球循环，是渔业等重要生态系统服务的基础。浮游植物具有一种特殊的动态特性，即快速积累大量生物量的能力。这些所谓的浮游植物繁殖通常可以定期发生（例如，在春季，所谓的春季繁殖），并为更高的营养水平提供重要的食物，或者可以由外部因素（例如，外部营养供应，富营养化）触发。浮游植物的大量繁殖通常由一种或几种植物支持；对于有毒或难以食用的物种，藻华会对食物网中能量和物质的转移产生重大的负面影响。浮游植物群落的多样性是否对浮游植物华的形成有影响，这一问题基本上只在理论上进行了研究。随着多样性的增加，群落中存在一个物种垄断资源形成华花的概率更高（选择效应）。同时，随着多样性的增加，资源利用的互补性和效率可能会提高，资源的垄断变得越来越困难（互补效应）。BLIC正在使用一种机械的升级方法调查这个问题。在受控的实验室实验中，越来越多的群落暴露于营养脉冲中，并量化了选择效应和互补性的强度。下一步，多样性控制的田间群落将暴露在营养脉冲中，并调查多样性的变化在多大程度上更有可能导致开花。最后，规划了沿自然多样性梯度的天然浮游植物群落的中生态实验。所有的实验都将以同样的方式在海洋和淡水实验室以及野外群落中进行。除了实验方法，第二支柱是对这些研究问题的理论模型分析。所谓的基于“特征”的多维数学模型将详细分析浮游植物繁殖的早期阶段。这些模型将从实验中获得重要的参数化，同时对个别实验的执行产生重要影响，从而可以详细研究模型中产生的水华形成的特别有趣的环境组合。

The global loss of biodiversity is also visible in aquatic ecosystems. How biodiversity affects ecosystem functions is mechanistically only partially understood. Such biodiversity - ecosystem function relationships are already documented at the level of primary producers; phytoplankton in pelagic systems. Phytoplankton is involved in about 50% of the global primary production, essentially controls global cycles of important elements and is the basis of important ecosystem services such as fisheries. Phytoplankton is characterized by a special dynamic, the ability to quickly accumulate large amounts of biomass. These so-called phytoplankton blooms can often occur on a regular basis (e.g., in spring, so-called spring blooms) and provide important food for higher trophic levels, or can be triggered by external factors (e.g., external nutrient supply, eutrophication). Phytoplankton blooms are usually supported by one or a few species; in the case of toxic or poorly edible species, blooms can have significant negative effects on the transfer of energy and matter in food webs. A question that has been studied essentially only theoretically is whether the diversity of phytoplankton communities has an impact on the formation of phytoplankton blooms. With increasing diversity, the probability that there is a species in the community that can monopolize resources and form blooms is higher (selection effect). At the same time, as diversity increases, complementarity and efficiency of resource use may increase, and it becomes increasingly difficult to monopolize resources (complementarity effect). BLIC is investigating this issue using a mechanistic up-scaling approach. In controlled laboratory experiments, increasingly diverse communities are exposed to nutrient pulses and the strength of selection effects and complementarity are quantified. In a next step, diversity-manipulated field communities will be exposed to nutrient pulses and investigated to what extent the change in diversity makes blooms more likely or not. Finally, mesocosm experiments are planned with natural phytoplankton communities along natural diversity gradients. All experiments will take place in the same way with marine and freshwater laboratory and field communities. Besides experimental approaches, the second pillar of BLIC is the theoretical model analysis of these research questions. So-called "trait" based multidimensional mathematical models will analyse in detail the early stages of phytoplankton blooms. The models will receive important parameterizations from the experiments and at the same time have an important influence on the execution of individual experiments, which can then investigate particularly interesting environmental combinations for bloom formation arising from the model in detail.