The McMurdo Long Term Ecological Research (LTER) project monitors patterns of inorganic material transport in perennial ice-capped lakes. This data set addresses this core area of research and quantifies dissolved inorganic carbon concentrations at specific depths in McMurdo Dry Valley lakes. Dissolved inorganic carbon is also necessary for the computation of primary productivity.
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Lake water samples are collected at specific depths with a five-liter Niskin bottle during normal LTER limnological sampling. Dissolved inorganic carbon samples (1 at each depth) are decanted through tubing directly from the Niskin bottle into a 30 mL serum vial. Lake water is allowed to overflow from the serum vial and completely displace the initial sample volume. Each sample is preserved with 0.15 mL chloroform, capped with a rubber stopper and crimped with an aluminum cap. Samples are stored in the dark at 4 degrees C until analysis. Samples are analyzed in at least duplicate following a method of sample acidification followed by infrared gas analysis using an IRGA (Infrared Gas Analyzer), and comparison to a standard curve. The standard curve is created by analyzing incremental samples of a 60 mgC/L DIC standard. The reported dissolved inorganic carbon concentrations of the lake water samples are averages of the replicate sample analyses. Analyses were performed with either an MSA Lira IRGA with HP Integrator or a Licor 6252 CO2 analyzer prior to the 2003-2004 season, with an MSA Lira IRGA with HP Integrator or Peak Simple Chromatography Data System from the 2003-2004 – 2006-2007 season, and with a Qubit Systems Infrared CO2 Analyzer with Peak Simple Chromatography Data System from the 2007-2008 season to present.
Notes on 2006-2007 Season DIC Data and methods
The IRGA malfunctioned during the 0607 season yielding DIC data that were highly suspect. Alkalinity titrations were done according to standard methods and DIC was estimated based on Wetzel R.G. and G.E. Likens. 1991. Limnological Analyses. 2nd Edition. Springer-Verlag New York Inc. pp. 111-118. Note that hydrogen acceptors other than the carbonate system exist in the lakes yielding an overestimate of DIC. We also computed average DIC values from the 05-06 and 07-08 seasons. DIC data changes relatively little over time; A paired t-test revealed that there was no significant difference between DIC for these 2 years (p>0.05). We report in the database DIC data computed from alkalinity titrations, and provide a link in the metadata to DIC data computed from averages of 05-06 and 07-08 DIC. The file containing DIC values computed from the average of previous and next season DIC values can be found in the following link: http://mcmlter.org/data/lakes/chemistry/core/LIMNO_DIC_0607.csv">http://mcmlter.org/data/lakes/chemistry /core/LIMNO_DIC_0607.csv
Data contained in these files has been subjected to quality control standards imposed by the investigator. The user of this data should be aware that, while efforts have been taken to ensure that these data are of the highest quality, there is no guarantee of perfection for the data contained herein and the possibility of errors exists. If you encounter questionable data, please contact the MCM LTER data manager corrected or qualified. Thus, these data may be modified and future data will be appended.