Interplay between energy, mineral and biochemical constraints of herbivores in the pelagic food web of Lake Constance

了解营养相互作用和食物网调节及其对生物遗传改变的营养和气候条件的反应需要关于食物数量和质量的信息。化学计量理论表明，碳（C，能量的替代物）和必需营养素（如磷）之间的比例决定了初级生产者对消费者的食品质量。由于最近的研究表明，必需脂肪酸的短缺也会降低食品质量，我们打算通过额外考虑多不饱和脂肪酸（PUFA）的潜在生长限制来扩展现有的化学计量理论。为此目的，应将康斯坦茨湖浮游生物丰度、生产和浮游生物浮游食物网C和P通量的现有综合长期数据与新的实验室测量主要藻类物种的物种特异性、营养和温度依赖性脂肪酸含量相结合，并与康斯坦茨湖浮游生物丰度和大小分级C、P和脂肪酸含量的实地测量相结合。这使得能够估计不同功能组的能量，矿物质和脂肪酸的通量在整个食物网的贡献，并制定消费者增长限制的能量，营养素和/或不同的多不饱和脂肪酸的相互作用的假设，然后应明确实验测试。这提高了我们理解单个浮游生物群体和整个食物网对过去几十年再富营养化的反应的能力，并预测未来对改变的营养和气候条件的反应。

Understanding trophic interactions and food web regulation and their response to anthropogenetically altered nutrient and climate conditions demands information on the food quantity and quality. Stoichiometric theory suggests that the ratio between carbon (C, surrogate for energy) and essential nutrients, e.g. phosphorus (P), determines the food quality of primary producers for consumers. As recent studies showed that a shortage of essential fatty acids can also reduce food quality, we intend to extend the existing stoichiometric theory by additionally considering potential growth limitations by polyunsaturated fatty acids (PUFAs). For this purpose already available comprehensive long-term data on plankton abundance, production, and C and P fluxes of the pelagic food web of Lake Constance shall be combined with new laboratory measurements of species-specific, nutrient- and temperature-dependent fatty acid contents of major algal species, and with field measurements of plankton abundance and size-fractionated C, P and fatty acid contents in Lake Constance. This enables to estimate the contribution of different functional groups to the fluxes of energy, minerals and fatty acids throughout the food web, and to develop hypotheses on the interplay of consumer growth limitations by energy, nutrients and/or distinct PUFAs, which shall then be explicitly tested experimentally. This improves our ability to understand the response of individual plankton groups and the entire food web to the past decades of re-oligotrophication, and to predict future reactions to altered nutrient and climate conditions.