Towards a deeper Understanding of Cyanobacteria Blooms in the Baltic Sea

在波罗的海，蓝藻物种在夏末经常形成大量的表面浮渣或水华。因为它们产生毒素（被怀疑进入食物网），它们受到越来越多的关注-研究人员和公众。不太突出但对波罗的海生态系统同样重要的是它们固定大气氮的能力，这对波罗的海的生物化学循环产生了重大影响，因为蓝藻为已经过度施肥的系统提供了额外的生物可利用氮。这一输入可能是巨大的（与河流和大气分解的总养分负荷相比，高达40%）。因此，蓝藻有可能抵消管理决策，以限制富营养化。尽管他们的至关重要的，蓝藻水华是令人惊讶的了解少，这是反映在建模和预测水华的主要困难准确。为了更全面的理解，我们建议系统地探索一套潜在的重要因素的预测技能。与现有的研究相比，我们的目标是阐明控制在水华形成的早期阶段，而不是集中在水华的高峰。另一个新的要素将是结合高分辨率海洋环流模型输出和观测数据，以追溯蓝藻水华的起源和条件。一个主要的重点将放在非生物因素上，例如水华形成期间的光合有效辐射、盐度和温度。此外，还将对传统的氮磷比例调控理论进行重新审视。将测试新的假设，并与波罗的海现有最先进的生物地球化学模型的预测技能进行比较。波罗的海特别适合这些调查，因为可用的观测量非常高。预期的结果很可能对全球海洋固氮（固氮）建模产生重大影响。

In the Baltic Sea, cyanobacteria species regularly form massive surface scums or blooms in late summer. Because they produce toxins (that are suspected to enter the food web) they receive more and more attention from both - researchers and the public. Less prominent, but equally important for the Baltic Sea ecosystem, is their ability to fix atmospheric nitrogen which substantially impacts on the biogeochemical cycle of the Baltic, because cyanobacteria supply the already over-fertilized system with additional bioavailable nitrogen. This input can be substantial (up to 40% compared to the overall nutrient loads from rivers and atmospheric decomposition). Thereby cyanobacteria have the potential to counteract management decisions to limit eutrophication.Despite their crucial importance, cyanobacteria blooms are surprisingly little understood which is reflected in major difficulties to model and forecast blooms acurately. Towards a more comprehensive understanding we propose to systematically explore the predictive skill of a suite of potentially important factors. In contrast to existing studies we aim to elucidate controls during the early stages of bloom formation rather than focusing on the bloom peaks. Another novel element will be a combination of high resolution ocean circulation model output and observational data to back-trace the origin and conditioning of cyanobacteria blooms. One major focus will be set on abiotic factors, as e.g. photosynthetically active radiation, salinity and temperature, during bloom formation. In addition, the accustomed theory on controlling effects of the ratio of nitrogen and phosphorus supply will be reexamined. New hypotheses will be tested and compared to the forecast skill of an existing state-of-the-art biogeochemical model for the Baltic Sea. The Baltic Sea is particularly suitable for these investigations, since the amount of available observations is extraordinary high. Anticipated results may well have major implications for modeling nitrogen fixation (diazotrophy) in the global oceans.