Modelling the impact of changes in the physical environment on plankton succession with special emphasis on Daphnia-algae interactions

全球变化预计将改变湖泊的物理条件。本计画将发展一个浮游生物演替模式，并将其与一维物理模式结合，以研究物理环境变化，特别是水温变化对浮游生物演替的影响。在两年的应用期内，浮游生物演替模型将重点放在浮游植物和水蚤，因为浮游植物的丰度主要取决于营养盐和光照的可用性，而水蚤的生长对水温高度敏感。浮游生物演替模型还将以简化的方式包括以浮游植物为食的快速生长的微型浮游动物和鱼类对水蚤的捕食。解决水蚤发展的不同细节（如大小结构，化学计量）的子模型将被包括在调查的重要性模型细节的整体模型行为与现场观察。模型校准和验证将基于康斯坦茨湖现有的广泛数据集。将利用极端热条件年份浮游生物演替的数据和模型结果的比较，调查物理环境变化对浮游生物演替的影响是否能够充分模拟，是否可能导致浮游生物群落内部相互作用的转变（匹配-不匹配）。由于春季和初夏的生态系统对外部强迫非常敏感，并且只有少数物种占主导地位，因此调查的主要部分最初将集中在春季和初夏。将利用数值试验研究全球变暖对物理参数的影响以及对浮游生物演替的影响。建模工作将补充在冬末和早春的实地测量，以提供浮游生物发展的更好的时间分辨率的数据，并提高数据质量，特别是水蚤，这是相当差的，在现有的数据集，因为只有很少的个人内获得一个浮游动物样本。根据两年应用期间建模工作的结果，我们将应用浮游生物演替模型研究一年中的其他时间段、其他湖泊、中型生态系统或通过考虑其他物种来扩展模型。

Global change is expected to alter the physical conditions in lakes. This project will develop a plankton succession model and combine it with a 1 dimensional physical model to investigate the effect of changes in the physical environment and specifically in water temperature on plankton succession. In the two year application period the plankton succession model proposed will be focused on phytoplankton and Daphnia, because phytoplankton abundance is mainly determined by the availability of nutrients and light, whereas Daphnia growth is highly sensitive to water temperature. The plankton succession model will also include in a simplified fashion fast growing microzooplankton feeding on phytoplankton and the predation of fish on Daphnia. Sub-models resolving different details (e.g. size structure, stoichiometry) of Daphnia development will be included to investigate the importance of model detail on the overall model behaviour with respect to field observations. Model calibration and validation will be based on the extensive data set available for Lake Constance. Comparison of data and model results on the plankton succession in years with extreme thermal conditions will be used to investigate whether the impact of changes in the physical environment on plankton succession can be adequately simulated and possibly leads to a shift in the interactions within the plankton community (match-mismatch). Because the ecosystem in spring and early summer is very sensitive to external forcing and dominated by only a few species, the main part of the investigations will initially concentrate on spring and early summer. Consequences of global warming on the physical parameters and the implications on the plankton succession will be studied using numerical experiments. The modeling work will be complemented by field measurements during late winter and early spring to provide data with a better temporal resolution on the plankton development, and to improve the data quality for especially daphnids, which is rather poor in the existing data set because only few individuals were obtained within one zooplankton sample. Depending on the outcome of the modeling work during the two year application period we will apply the plankton succession model to study other time periods of the year, other lakes, mesocosms or extend the model by considering additional species.