Algal carbohydrates and their role in the carbon cycle - identifying polysaccharides in marine particles

Growth of microalgae in the surface ocean generates about 45 gigatonnes of organic carbon per year, most of which in the form of polysaccharides. Although the majority of these glycans are consumed by heterotrophs, some of them scape degradation and may act as sink of atmospheric carbon dioxide. Indeed, it is known that a fraction of the microalgal secreted polysaccharides spontaneously assemble into transparent exopolymer particles, which in turn aggregate with diatom cells, minerals and other materials into marine snow particles, exporting carbon to the deep ocean. Which polysaccharides are produced in the surface ocean? Which ones assemble into particles and promote sinking? Which polysaccharides scape degradation through the water column and reach the ocean floor? These questions are yet to be answered.

The commonly used methods to analyse marine glycans cannot distinguish different polysaccharide types (different structures), and in order to be able to investigate the above questions and to reveal key processes involved in the biological carbon pump we need higher molecular resolution.

In this project, to identify specific polysaccharide structures in sinking particles we will use carbohydrate microarrays in combination with monoclonal antibodies. Additional methods that will be used to analyse glycans include fluorescence microscopy, quantitative ELISA and chromatography. If you want to know more about our research approach, please have a look at our latest publication: https://www.nature.com/articles/s41467-021-21009-6