Researchers traced the carbon journey of microorganisms living in Lake Mercer, a subglacial lake tucked beneath Antarctic ice, in a study led by researchers from a major US university. The lake sits nearly a kilometer below the surface and has drawn global attention since evidence emerged in 2007 of a thriving microbial community that exists without sunlight or surface heat. The central question guiding this work asks what fuels these microbes and how they adapt to such sunless, extreme conditions under the ice.
In a targeted analysis, scientists examined the lake’s carbon chemistry to understand how carbon moves through this isolated ecosystem. Carbon forms the backbone of all living matter and appears in multiple isotopic forms. By tracking these forms, researchers can identify carbon sources and how they become part of the local food web. To investigate this, the team extracted an ice core roughly two meters long from Lake Mercer and performed radiocarbon dating on organisms found within, aiming to determine when the carbon entered this secluded system.
Results indicate that the lake received its carbon about 6,000 years ago, during a period when the lake still maintained contact with the ocean. This finding challenges earlier theories that the carbon reservoir had been sealed under ice for tens of thousands or even hundreds of thousands of years. The study notes that in Lake Mercer, beyond this 6,000-year-old carbon, microbes can harvest chemical energy produced by processes linked to the moving ice sheet itself. As the ice shifts slowly, the underlying rock breaks down into tiny particles that dissolve into the water. Microbes—primarily bacteria and archaea—derive energy from these minerals through chemosynthesis, a metabolic pathway powered by inorganic molecules rather than sunlight.
The discovery highlights a striking aspect of life in the planet’s most extreme environments: how simple chemistry can sustain a diverse microbial community deep beneath Antarctic ice. These microbes rely on mineral breakdown and chemical gradients created by the dynamic ice to drive cellular processes and build biomass in a place where solar energy never arrives. The research underscores microbial adaptability, showing how communities endure when light and heat are scarce and how carbon flow remains steady even in isolated systems. It also provides insight into ancient biogeochemical cycles, illustrating how carbon deposited long ago can persist and cycle through a modern cold environment through ongoing geochemical interactions.
The broader significance of this work lies in showing that chemosynthetic processes can sustain ecosystems in subsurface habitats, contributing to our understanding of carbon budgets in polar regions and the potential for life in similarly dark, energy-limited settings elsewhere on Earth and beyond. By combining field sampling with precise dating and isotope analyses, scientists can reconstruct the carbon’s provenance and map the routes by which it becomes incorporated into microbial life. This line of inquiry enhances knowledge about how life persists under ice, including how nutrient and energy fluxes are maintained when surface processes are absent. In essence, Lake Mercer functions as a natural laboratory for examining the resilience of microbial ecosystems and the fundamental mechanisms governing carbon cycling in extreme subglacial environments. (Cited: university-led research and field teams with isotope and dating expertise.)