Katha Paetz, M.Sc.

Over the last decade, the brown seaweed pelagic Sargassum has gained global attention due to the massive beaching events occurring on both sides of the Atlantic. Numerous local initiatives and companies are trying to valorize its biomass by creating valuable products such as bioethanol that can be used both as a precursor for sustainable plastics or as biofuel. However, attempts to ferment Sargassum using commercial yeasts have previously resulted in very low yields. Even though there are a few studies describing Sargassum microbiomes, no information is available regarding the function of the microorganisms growing on Sargassum and their role in providing nutrients or degrading it. 

One hypothesis is that its microbiome provides Sargassum with extra nutrients enabling it to grow fast in oligotrophic waters. Furthermore, Sargassum excretes a high percentage of carbon as dissolved organic carbon (DOC). Part of this excreted carbon has been hypothesised to be recalcitrant and therefore contribute to long-term carbon sequestration in the ocean. 

SargBiome aims to elucidate the biodiversity of microorganisms growing on healthy and degrading Sargassum, assess their potential to provide the algae with nutrients via nitrogen fixation or iron chelation, and to degrade its biomass and excreted DOC. Through a combination of field sampling, lab experiments, and metagenomic analysis, we will characterise the biodiversity and functions of Sargassum microbiomes and isolate marine yeasts capable of producing bioethanol through Sargassum fermentation. 

This project will not only advance our basic understanding of the ecology of this relevant macroalgae, but it will also provide crucial knowledge to the nascent blue economy sector.