This file contains data collected from thermokarst impacted soils, lakes, and streams near Toolik Lake Alaska. Data are also presented for experimental manipulations of water (e.g., time course experiments). Sample descriptors include a unique sortchem #, site, date, time, depth, distance, elevation, treatment, date-time, category, and water type (e.g., lake, surface, soil). Physical/chemical measures collected in the field include temperature, conductivity, and pH. Chemical analyses performed later include alkalinity; dissolved inorganic and organic carbon (DIC and DOC); inorganic and total dissolved nutrients (NH4, PO4, NO3, TDN, TDP); particulate carbon, nitrogen, and phosphorus (PC, PN, and PP); cations (Ca, Mg, Na, K, and Si); anions (SO4 and Cl); chlorophyll a, and oxygen. Note that archived data from before the NSF ARCSS-Thermokarst project started in 2009, and funded by NSF from 1988-2008 (e.g., by the NSF ARC LTER), are included in this dataset.
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In general, water samples are collected in polyethylene bottles and filtered in the field then kept cold and dark until analyses. For specific sampling protocols see the LTER Land-Water protocol manual accessible from the Land-Water mainpage on the Arctic LTER web page or at http://www-personal.umich.edu/~gwk and clicking on the protocol link at the bottom of the page. Specific methodologies are described in the protocol book listed above, and a general description is provided below. Information on the precision and limit of detection of analyses is found in the LTER Landwater protocol manual.
Field data for surface sites (soil waters, streams, lakes not sampled from boats) include temperature, conductivity, and pH measured with hand-held Orion or WTW meters. On lakes sampled from a boat we used a Hydrolab Surveyor 4 to measure temperature, conductivity, pH, dissolved oxygen. Electrical conductivity of water samples is reported as Specific conductivity which has been corrected to a temperature of 25degC using a slope of 2% increase per degree C increase.
Sediment traps in lake NE-14:
We deployed two clusters of three sediment traps at a depth of approximately 5 m. Each sediment trap cluster consisted of three 9 cm diameter tubes suspended vertically in the water column approximately 1 m from the bottom of the lake. A single float rope extending from the center of each sediment trap cluster to the surface of the lake marked the location of the trap. Sediment trap clusters were allowed to collect material falling from the water column for durations of 2 to 3 weeks based on how frequently the individual lakes could be accessed with helicopter support. Traps were sampled by carefully raising the trap cluster to the surface and pouring the contents of each sediment trap into a separate 4 L cubitainer. Once each trap was sampled the entire cluster was immediately redeployed at roughly the same location in approximately 5 m of water. Once collected, we returned the water to Toolik Field Station and filtered aliquots through precombusted (500 degrees Celsius for 2 hours),~ 0.7 micrometer pore size, glass fiber filters (Whatman GF/F) for the analysis of percent organic matter, concentrations of particulate carbon, nitrogen and phosphorus, concentrations chlorophyll a and pheophytin, and stable isotopes carbon-13 and nitrogen-15. For analytical methods see ‘Protocols of the Arctic Lakes LTER' http://ecosystems.mbl.edu/ARC/lakes/protocols.html on the Arctic LTER webpage. We calculated bulk sedimentation rate as well as carbon, nitrogen and phosphorus flux rate (mg per m2 per day) by first measuring the mass of bulk particulate matter and macronutrients carbon, nitrogen and phosphorus in each trap (mg), and then dividing by the area of the trap (m2) and the duration that the trap was deployed (d).
Dissolved inorganic nutrients (NH4 and PO4) were analyzed by wet chemistry techniques at Toolik Field Station usually within 24 hours of sampling. Prior to 1999, the phenate method was used to analyze the ammonium content. In the years 1999-2001, a comparison study of the OPA method and the phenate method was performed and starting in 2001 the OPA method was used to analyze ammonium content. Gas samples were analyzed at Toolik Field Station on a Shimadzu GC14 gas chromatograph with TCD and FID detectors. DIC samples were acidified in the field and analyzed on a Shimadzu GC14 gas chromatograph at Toolik Field Station. DOC, TDN, TDP, particulate C, N, P, anions and cations were brought back to the University of Michigan for analysis. DOC and TDN are analyzed on a Shimadzu TOC-Vcph with TN Module. Particulate Carbon and Nitrogen on a Perkin Elmer 2400 CHN analyzer, TDP and Particulate P were digested and run at the University of Michigan on an Alpkem autoanalyzer, NO3 is analyzed by cadmium reduction on an Alpkem autoanalyzer, Cl and SO4 on a Dionex ion chromatograph, and cations on an inductively coupled plasma optical emission spectrometer (ICP-OES). Alkalinity samples were run on a Radiometer autotitrator either at Toolik Field Station or in Michigan. Chla was analyzed in the field using an acetone extraction and analysis on a Turner AU10 Fluorometer.
For all analyses, sample values that were less than zero were assigned a value of zero. A missing value is assigned a "period", " . "
LTER Land-Water Protocol manual
At the above web location, the protocol manual is titled " Protocol_vXX.doc or *.pdf ", where the XX is a version number. As of this file construction on 18 October 2012 the version is 29, filename = Protocol_v29.doc
Version1 (ver1) File created 22 October 2012
Version2 added missing data explianation and corrected file download Url - it had and extra ARC in it. Jiml 23Sep13
Version 3 url corrected after file reorganization (JD 12Dec2013)
Changed Distribution URL since the LTER network DAS system is being discontinued. JimL 9Apr2015
Download a comma delimited (csv) or Excel file (includes metadata and data sheets).
Use of the data requires acceptance of the data use policy --> Arctic LTER Data Use Policy
To cite this data set see the citation example on the LTER Network Data Portal page for this data set.