Marine fungi and the biological carbon pump - a quest for novel biomarkers for key players in the carbon cycle

The biological carbon pump (BCP) has a major role in the ability of the oceans to control the global climate and carbon cycle. Inorganic carbon is assimilated by phytoplankton in the surface ocean and converted into organic matter. The organic matter is transported to the deeper ocean interior by the BCP and degraded by microbes en route or sequestered to the deep ocean [1]. Marine fungi are understudied compared to other marine microbes, yet can account for as much biomass as prokaryotes on sinking organic matter in the BCP [2]. Fungi, both unicellular and filamentous, are active in carbon degradation throughout the water column in coastal and open ocean marine ecosystems [3–5]. However, the exact nature and importance of marine fungi in the BCP and marine carbon cycle remains poorly understood, including biomass stocks and turnover.