Carbon Isotopic Signatures of Microbial Lipids in Geothermal Deposits: Elucidating Thermophilic Ecology. Lipid biomarkers were extracted and fractionated using standard methods. They were analysed via GC-MS for identification and determination of lipid distributions and abundances, and via GC-C-IRMS for carbon isotopic compositions. These methods, except for GC-IRMS, are available in in Kaur et al. (2014) DOI: 10.1007/s00792-014-0719-9. GC-IRMS methods are the same as those used in Badger et al. (2013) DOI: 10.1098/rsta.2013.0094 Sinters were collected from six active geothermal systems in the Taupo Volcanic Zone, North Island, New Zealand. Champagne Pool is located in the Waiotapu geothermal system. Opaheke Pool is located in the Reporoa Caldera situated approximately 6 km south of the Waiotapu geothermal field. These two fields are believed to be hydrologically linked (Nairn et al., 1994). Loop Road hot springs are situated in a flat, low-lying alluvial plain, a few kilometres south of Waiotapu. The Orakei Korako geothermal region is approximately 2 km2 in area and is located on the eastern margin of the Moroa Volcanic Centre. OK1 was sampled from the edge of Fred and Maggie Pool, whilst OK2 and OK3 were sampled from the outflow channel; OK1D originates from Diamond Geyser. The Sinter Flat area of Rotokawa is a cluster of geothermal springs on the northern margin of Lake Rotokawa that have created a flat terrace, mostly covered in hot pools. Further details of these sites are available in Kaur et al. (2014) DOI: 10.1007/s00792-014-0719-9.