page_title: Subglacial lake
section_title: Antarctica
hierarchical_section_title: Subglacial lake / Ecology / Biology / Biological diversity in explored subglacial lakes / Antarctica
caption_attribution_description: English: First view of the bottom of Antarctic subglacial Lake Whillans, captured by the high-resolution imaging system aboard the Micro-Submersible Lake Exploration Device. The imagery and other data from the mini-sub were used to survey the lake floor and help the WISSARD team verify that the rest of their instruments could be safely deployed into the lake. Image credit: NASA/JPL-Caltech
context_page_description: A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point of ice. Over time, the overlying ice gradually melts at a rate of a few millimeters per year. Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years.
  Since the first discoveries of subglacial lakes under the Antarctic Ice Sheet, more than 400 subglacial lakes have been discovered in Antarctica, beneath the Greenland Ice Sheet, and under Iceland's Vatnajökull ice cap. Subglacial lakes contain a substantial proportion of Earth's liquid freshwater, with the volume of Antarctic subglacial lakes alone estimated to be about 10,000 km³, or about 15% of all liquid freshwater on Earth.
  As ecosystems isolated from Earth's atmosphere, subglacial lakes are influenced by interactions between ice, water, sediments, and organisms.
context_section_description: In subglacial Lake Whillans, the WISSARD expedition collected sediment cores and water samples, which contained 130,000 microbial cells per milliliter and 3,914 different bacterial species. The team identified active bacteria that were metabolizing ammonia, methane, and sulfur from the 120,000-year-old sediments. The most abundant bacteria identified were related to Thiobacillus, Sideroxyans, and pscyhrophilic Polaromonas species.
  In January 2019, the SALSA team collected sediment and water samples from subglacial Lake Mercer and found diatom shells and well-preserved carcasses from crustaceans and a tardigrade. Although the animals were dead, the team also found bacterial concentrations of 10,000 cells per milliliter, suggesting the potential for animals to survive in the lake by consuming bacteria. The team will continue analyzing the samples to further investigate the chemistry and biology of the lake.
  Lake Vostok is the best-studied Antarctic subglacial lake, but its waters have only been studied through analysis of accretion ice from the bottom of ice cores taken during Russian drilling efforts above the lake. Actively growing bacteria and thousands of unique DNA sequences from bacteria, archaea, and eukaryotes have been found in Lake Vostok's accretion ice. Some DNA appeared to come from multicellular eukaryotes, including species seemingly related to freshwater Daphnia, tardigrades, and mollusks. These species may have survived in the lake and slowly adapted to the changing conditions since Vostok was last exposed to the atmosphere millions of years ago. However, the samples were likely contaminated by drilling fluid while being collected, so some of the identified organisms probably did not live in the lake.
  Other subglacial sampling efforts in Antarctica include the subglacial pool of anoxic, hypersaline water under Taylor Glacier, which harbors a microbial community that was sealed off from the atmosphere 1.5 to 2 million years ago. Bacteria under Taylor Glacier appear to have a novel metabolic strategy that uses sulfate and ferric ions to decompose organic matter.
caption: The first view of the sediment at the bottom of subglacial Lake Whillans, captured by the WISSARD expedition. Image credit: NASA/JPL, California Institute of Technology
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