Beneath the Arctic waters of a Norwegian fjord, a kingdom long associated with forests and soil has been quietly reshaping the ocean's carbon ledger. New research from Kongsfjorden reveals that marine fungi — not just bacteria — are significant architects of carbon storage in seafloor sediments, converting dissolved organic matter into solid biomass with surprising efficiency. The discovery arrives at a moment of urgency: these fjords hold more than a tenth of all carbon buried beneath the global seafloor, and the Arctic is transforming faster than our models can follow.