Each year the burning of fossil fuels adds around 10 gigatons of carbon to the ~900 gigatons of atmospheric carbon, fueling the climate emergency. Meanwhile, marine algae fix ~50 gigatons of inorganic carbon via photosynthesis into building blocks of long-chain sugar molecules also known as glycans. The growth of these algae, the aggregation and sinking of algae cells and algae-derived organic material in the ocean plays a central role in carbon dioxide removal from the atmosphere. In this process, known as the biological carbon pump, fixed carbon is moved to depths below 1000m and sediments, where it can be stored for centuries. Key of this process is that the algae material remains stable preventing bacteria from degrading it and releasing carbon back into the atmosphere.
Algae invest up to 80% of their organic carbon into glycans, which are also found in high concentrations in sinking particles and marine sediments, suggesting their substantial role in sequestering carbon at global scale. However, to this day the structural characteristics and quantities of algal glycans relevant in carbon sequestration remain largely unknown due to their immense diversity, which arises from many different building blocks, various connection patterns, branching structures, and chemical modifications. Current analytical approaches do not provide sufficient resolution and bulk concentration measurements blur our view on the role of individual glycans in the process. Our developments of enzyme-based methods to quantify individual glycans and antibody techniques to identify trace amounts of glycans enable us for the first time to structurally describe and quantify individual algal glycans.
In this project, we use and develop these methods further to identify which structures make glycans difficult to degrade and quantify the export of selected glycans via the biological carbon pump. In addition, we investigate the potential co-evolution of algal glycan structures and bacterial enzymes that degrade those glycans. Our insights will help us to understand the role of algal glycans in the global carbon cycle, explore their potential for carbon sequestration and reveal molecular principles that govern carbon sequestration in and beyond the ocean. This will help to understand how and how much the ocean stores carbon, which is key knowledge for managing the climate emergency.
