Marine Bacteria Collaborate to Degrade Fucoidan, Key Ocean Carbon Molecule

Researchers have uncovered the cooperative strategy used by marine bacterial communities to break down fucoidan, a complex sulfated polysaccharide that plays a pivotal role in sequestering carbon in the ocean. The study, published in *Nature Microbiology*, shows that distinct bacterial taxa specialize in different stages of fucoidan degradation, allowing the entire process to proceed efficiently in the cold, low‑nutrient waters of the Southern Ocean.

Using metagenomic sequencing and stable‑isotope probing, the team identified three functional groups: primary degraders that cleave fucoidan into oligosaccharides, secondary degraders that further hydrolyze these fragments into monosaccharides, and tertiary scavengers that consume the resulting simple sugars. The researchers also demonstrated that the spatial distribution of these groups along the microbial biofilm enhances carbon flux to the deep sea, thereby reinforcing fucoidan’s role as a carbon sink. The findings were obtained from samples collected during the 2023 Arctic expedition, with the collaboration of the University of Bergen and the Scripps Institution of Oceanography.

This insight into the microbial ecology of fucoidan degradation clarifies how oceanic carbon storage is maintained and may inform predictive models of climate change. By delineating the specific bacterial functions involved, scientists can better assess how shifts in marine microbial communities might influence the efficiency of carbon sequestration in the world's oceans.