Selected lakes of King George Island and Penguin Island: water physicochemistry and sediment carbon 2025

The dataset contains high-frequency in situ measurements and laboratory water and sediment chemistry for selected Antarctic lakes sampled during the 2025 austral summer field campaign. High-frequency monitoring was conducted in five lakes in the Admiralty Bay region of King George Island: Ecology, Ginger, Mud, Pond and Krak. Water temperature and specific electrical conductivity were recorded with CTD-Diver probes, while pH was recorded with Onset HOBO MX2501 pH and Temperature Loggers. Measurements were recorded at 10-minute intervals. The published CTD-Diver and HOBO resources retain the actual timestamps of the source instruments after conversion to UTC. The two instrument series were not resampled or matched to a common timestamp. CTD-Diver clocks were set to UTC+0. The HOBO exports for Ecology, Mud, Pond and Krak used GMT. The Ginger HOBO export used Chile Standard Time and was converted to UTC by adding 3 hours before publication. For Ecology, Mud, Pond and Krak, the first three and last three records of each high-frequency deployment were removed to reduce the influence of sensor installation and retrieval. For Ginger, the first three records were removed and all observations from 20 February 2025 onward were excluded because the deployed sensor was no longer submerged in the lake and subsequent measurements did not represent in-lake conditions. No missing observations were interpolated. Laboratory water chemistry is provided for Vieville, Krak, Pond, Ecology, Mud, Ginger and Petrel lakes. Variables include complex and total alkalinity and the major ions Ca, Mg, Na, K, Cl, SO4, CO3, HCO3 and OH. Results reported with a less-than sign in the laboratory report are stored using a numeric threshold value, a separate qualifier column containing "<", and a separate uncertainty column. Sediment chemistry is provided for Vieville, Krak, Pond, Ecology, Mud and Ginger lakes and includes total carbon, inorganic carbon, total organic carbon (TOC), all expressed as percent, and sediment pH measured in H2O. The research was conducted with the support of the Henryk Arctowski Polish Antarctic Station. The field campaign is related to NCN-funded research on King George Island lakes, including the “King George Island lakes: Water physicochemistry and sediment carbon content”, NCN grant no. 2024/08/X/ST10/00723. A second project title “ Bathymetric surveys of lakes on King George Island (South Shetland Island, West Antarctica)” NCN grant no. 2024/08/X/ST10/00760. This work was created using the infrastructure of the Henryk Arctowski Polish Antarctic Station.