factors such as warming, nutrient deficiency or ocean acidification, by focusing on one of the most sensitive areas on Earth, the subarctic and Arctic Ocean. Thereby, we contribute to the Helmholtz research [...] CO 2 is taken up by the ocean, concentrations of CO2 and bicarbonate increase while the concentration of carbonate ions and the pH decrease, also known as 'Ocean Acidification'. Just like warming, also [...] greenhouse gas, rising CO 2 causes ocean warming: temperatures of the surface waters have already increased by 1.1°C on average, while some regions like the Arctic Ocean changing fastest (IPCC 2022). The

coccolithophores and their responses to changes in carbonate chemistry (end of the 90’s, the term ocean acidification did not yet exist). Even though my work has often been motivated by biogeochemical questions [...] and where nutrients and CO 2 are distributed in the ocean, which has implications for primary and bacterial production and CO 2 uptake by the ocean. In order to understand how such biogeochemical cycles [...] and carbonate chemistry parameters in the Fram Strait and the Central Arctic Ocean. To monitor such parameters in the ocean, it is common practice to analyze discrete water samples obtained e.g. by rosette