Seasonal kelp primary production at a rocky shore site: Integrating physiology and biochemistry into ecological modelling

温带地区的沿海硬底区主要是茂密的水下海藻林，作为主要的初级生产者，从而产生大量的生物量和碳，这是对这些海洋生态系统的主要营养贡献。海带森林提供了三维的、异质结构的栖息地，为相关的丰富的海洋动植物提供了食物和庇护所。然而，由于全球变暖，这些水下森林面临着风险，因为海藻需要较低的水温。自20世纪60年代以来，赫尔戈兰岛周围北海的表层海水已经变暖了1摄氏度以上，预计这一趋势将持续到下个世纪。尽管海藻在沿海生态系统中具有重要的生态意义，但世界范围内关于现存量、分布和粗初级生产量估计的数据很少。北海黑尔戈兰区是一个例外地区，拥有关于海带生物量、生长和垂直分布的合理数据库。然而，为了准确计算海带初级生产量，仍然缺少两个主要空白：(1)光合氧产生到固碳单位的准确转换；(2)温度上升对季节性海带光合作用性能的影响，以动态评估初级生产量。这两个过程不仅对温带地区的海带未知，而且对世界各地的所有其他海藻群落也是未知的。因此，本项目的主要目标是首次确定这些大型藻类的初级生产力和碳收支的季节变化。这将通过结合使用不同的方法(O2-和14C-方法)以及使用最先进的方法(如层析和质谱仪)对实际的碳固定进行生理和生化测量来实现。还将调查预测的全球变暖对季节性初级生产力的影响。这些结果，连同赫尔戈兰周围现有的海带数据库，将首次用于开发海带初级生产的生态模型，即动态生理箱模型。这将成为模拟各种全球变化情景和确定生物敏感性和可能的阈值的工具。这种广泛的方法以前从未被应用于世界各地的海带，因此是这项提议的关键创新之一。

Coastal hard bottom zones of temperate regions are dominated by dense underwater kelp forests as key primary producers, thereby generating high amounts of biomass and carbon, which represent a major trophic contribution to these marine ecosystems. Kelp forests provide three-dimensional, heterogeneously structured habitats, providing food and shelter for the associated rich marine flora and fauna. However, these underwater forests are under risk due to global warming as kelp needs low water temperatures. Surface waters in the North Sea around Helgoland have already warmed by more than 1°C since the 1960s and this trend is predicted to reach into the next century. Despite the ecological importance of kelps in coastal ecosystems, only very few data exist worldwide on standing biomass, distribution and crude primary production estimates. The study area Helgoland in the North Sea is an exceptional region with a reasonable database on kelp biomass, growth and vertical distribution. However, for an accurate calculation of kelp primary production, two main missing gaps remain: (1) the exact conversion of photosynthetic oxygen production into carbon fixation units and (2) the impact of increasing temperatures on seasonal kelp photosynthetic performance for a dynamic assessment of primary production. Both processes are not only unknown for kelps in the temperate region, but also for all other kelp communities worldwide. Therefore, the main goal of this project is to determine for the first time the seasonal changing primary production and carbon budget in these macroalgae. This will be achieved by using a combination of different approaches (O2- and 14C-method) as well as physiological and biochemical measurements of the actual carbon fixation with state-of-the-art methods such as chromatography and mass spectrometry. The impact of the forecasted global warming will be also investigated on the seasonal primary production rates. These results, together with the existing database on kelps around Helgoland, will be used to develop for the first time an ecological model for kelp primary production, i.e. a dynamic physiological box model. This will serve as a tool to simulate various global change scenarios and to identify biological sensitivities and possible thresholds. Such a broad approach has never been applied before to kelps worldwide and hence represents one of the key innovations of this proposal.