The effect of climate change on the carbon balance between photosynthesis and respiration in planktonic and benthic microalgae

南极海洋碳循环的生物过程受浮游和底栖初级生产者的光合作用活动控制。固定碳的数量不仅取决于光合作用的活性，还取决于呼吸作用造成的碳损失。因此，光合作用/呼吸比率(Rp/R)是预测气候变化对南极生态系统影响的一个重要参数，因为实验室研究表明，该比率随环境条件的变化而变化。微藻RP/R的数量变化还没有得到很好的研究，对真实的自然界的变化也知之甚少。这主要是由于方法上的限制。光合作用可以通过14C吸收、放氧或荧光装置来评估，但对光养生物的呼吸进行定量估计仍然是困难的。在这个项目中，我们想要测量在全球变化条件下(气温升高，铁限制)与南极初级生产力相关的物种的光合作用/呼吸比率的变化。然后，通过比较有无校正呼吸速率的日生物量生产量，证明了Rp/R可变比率的相关性。在第二部分中，将开发一种无需气体交换测量即可测量呼吸速率的方法，并且适用于田间条件下的高通量方法。该方法将有助于改进研究南极初级生产力的所有其他项目的数据集。

The biological process of the carbon cycle in the Antarctic Ocean is controlled by the photosynthetic activity of the planktic and benthic primary producers. The amount of fixed carbon does not only depend on the photosynthetic activity but also on the carbon losses due to respiration. Therefore, the ratio photosynthesis/respiration (rP/R) is an important parameter to predict the effect of climate change on the Antarctic ecosystem, since it was demonstrated by lab studies that this ratio is highly variable in response to environmental conditions. The quantitative changes in the rP/R of microalgae is not well studied and nothing is known about the changes in real nature. This is mainly due to methodological limitations. Photosynthesis can be assessed by 14C uptake, oxygen evolution or by fluorometric devices, a quantitative estimate of the respiration from phototrophs is still difficult. In this project we want to measure the changes in the ratio photosynthesis/respiration in species which are relevant for the antartic primary production under global change conditions (rising temperature, iron limitation). The relevance of variable ratios of rP/R is then demonstrated by comparing the daily biomass production with and without corrected respiration rates. In a second part a method will be developed to measure respiration rates without gas exchange measurements and applicably as high throughput method under field conditions. The methodology will help to improve the data set of all other projects studying primary productivity in the Antartic.