Geochemical data to characterize physical and chemical properties of the Cenote Bang, a component of the Ox Bel Ha cave network within the subterranean estuary coastal aquifer of the Yucatan Peninsula, from December 2013 to January 2016

Discrete water samples were collected from Cenote Bang during four sampling events: December 2013, August 2014, January 2015, and January 2016. Cenote and cave samples were collected by scuba divers followed protocols established by the American Academy of Underwater Sciences and the National Speleological Society Cave Diving Section. Water samples for geochemical analysis of dissolved materials were collected near sonde profile locations in plastic 60 ml syringes fitted with 3-way stopcocks. The syringes were rinsed with distilled water and dried prior to the dive, and flushed with sample water prior to closing the stopcock. Samples were kept cool during transport to the field lab and processed within eight hours of collection.
Full details related to the processing of the samples, storage, and analysis are provided in the Methods section and Supplementary Materials of Brankovits and others, 2017, Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem, Nature Communications, vol. XXX, XXXX. Processing took place each year of data collection - 2013 to 2016.

Analysis of the samples was performed at the Woods Hole Oceanographic Institution (WHOI) and U.S. Geological Survey (USGS) in Woods Hole MA, USA. Sulfate and chloride concentrations were determined using a Metrohm 881 Compact Plus ion chromatograph (IC) equipped with a Metrosep A Supp 5-250 anion column. Chloride concentrations (mM) were converted to mg l-1 and multiplied by 0.0018066 to determine salinity (psu). The analytical error for chloride and sulfate was +/- 3.5% of the IAPSO standard sulfate and chloride values.
Dissolved inorganic carbon (DIC) concentrations were determined with a Model 5011 UIC coulometer and quantified relative to a seawater certified reference material (CRM) with a relative standard deviation of 4% relative to the CRM value (2.2 millimolar, mM). The stable carbon isotopic content of the DIC was measured with a Thermo-Finnigan DELTAplus XP IRMS with an analytical error (1-sigma) of 1.1 per mil.
Headspace methane concentrations were determined using a Shimadzu 14-B gas chromatograph (GC) equipped with a flame ionization detector (FID). Headspace concentrations were converted to dissolved concentrations using the method of Magen and others, 2014 and are reported with an relative standard deviation of 2%.
The stable carbon isotope composition of methane from the headspace of the serum vials was determined using a Thermo-Finnigan DELTAPlus XL isotope ratio mass spectrometer (IRMS) coupled to an Agilent 6890 Gas Chromatograph (GC) via a Finnigan GCCIII combustion interface with 1-sigma deviation of 1.6 per mil.
DOC concentration and d13C were analyzed by high-temperature combustion-isotope ratio mass spectrometry (HTC-IRMS) at the USGS-WHOI Dissolved Carbon Isotope Lab (DCIL). The DCIL HTC-IRMS system consists of an OI 1030C total carbon analyzer and a Graden molecular sieve trap interfaced to a Thermo-Finnigan DELTA-PLUS XL IRMS. DOC concentratins are reported with an RSD of less than 5% of the measured value. Stable carbon isotope ratios for DIC, methane and DOC are reported in the standard delta-notation relative to VPDB (Vienna Pee Dee Belemnite) with a 1-sigma deviation of less than 0.5 per mil.
All sample analyses were performed by David Brankovits under the supervision of John Pohlman. Full details of the laboratory analysis of samples is described in the Methods section and Supplementary Materials of Brankovits and others, 2017, Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem, Nature Communications, vol. XXX, XXXX. Sample processing occured between 2014 and 2016.

Added keywords section with USGS persistent identifier as theme keyword.