Mangrove sinkholes (cenotes) of the Yucatan Peninsula, a global hotspot of carbon sequestration

Sampling was conducted in September 2019 with SCUBA equipment (See Supplementary Video or https://www.youtube.com/watch?v=lGVYxnlkHu8&feature=youtu.be). We sampled two cores at Cenote Jaguar and Yaxchen, and four cores at Casa Cenote. For each core, we used a 60 mL syringe to take one sample at each of the following depths: 0 –15, 15 – 30, 30 – 50, 50 – 100 cm, and every 100 cm until the bottom of the peat. Soil samples were analysed for soil organic carbon (SOC) and δ13C with an elemental analyser coupled with an isotope ratio mass spectrometer (EA-IRMS, Serco System, Griffith University, Brisbane, Australia) with analytical standard deviation < 0.1‰.