Water samples were taken at 5 locations at both I-Minus2 and Toolik River thermokarst sites (10 sampling locations total). A combination of ISCO and manual grab samples were taken depending on the sampling location and year.
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We measured total suspended sediment (TSS) in the Reference and Impacted reach using standard methods (USGS method I-3765). For each sample, a known volume of stream water was filtered in the field through a pre-dried (105°C) and pre-weighed 47-mm diameter glass fiber filter (GF/F) and re-dried and re-weighed. TSS was calculated as the difference in filter mass before and after filtration divided by the volume filtered (mg L-1). Turbidity sensors (DTS-12 from FTS Environmental, Victoria, BC, Canada) were installed in conjunction with automated ISCO samplers (Teledyne ISCO, Lincoln, NE, USA) to collect 5-minute turbidity measurements in the Reference and Impacted reaches for the 2010 season only.
A WTW handheld meter was used to measure pH, Specific Conductance, Temperature &amp;amp;amp;amp;amp;amp;amp;amp; Dissolved Oxygen.
Water samples for chemical analyses were collected with an ISCO autosampler (daily composite stream samples collected four times per 24 hours at 00:00; 06:00; 12:00; 18:00) at the Reference (M2) and Impacted (M3) stations in 2009 and 2010. Grab water samples were taken opportunistically from hillslope locations (T1, T2, T3) 2009-2011 and stream water grab samples were taken biweekly from the Reference and Impacted reaches in 2011 since the ISCO samplers were not used in 2011. Seasonal mean values were calculated using daily (2009 and 2010) or biweekly (2011) measurements. All water samples were filtered through pre-combusted (450°C) 25-mm diameter GF/Fs with a nominal pore size of 0.07 um, with the exception of the water designated for base cation analyses, which were filtered with nylon syringe filters with a pore size of 0.45um. Separate samples were taken for each analyte. Samples for soluble reactive ortho-phosphate (SRP or PO43--P), nitrate (NO3--N), and ammonium (NH4+-N) were frozen; samples for DOC (dissolved organic carbon), TDN (total dissolved nitrogen), TDP (total dissolved phosphorus); and base cations (calcium, Ca2+; magnesium, Mg2+; potassium, K+; and sodium, Na+); micronutrients and metals (aluminum, Al; iron, Fe; manganese, Mn; boron, B; copper, Cu; zinc, Zn; sulfur, S; strontium, Sr; lead, Pb; nickel, Ni; chromium, Cr; and cadmium, Cd) were acidified with 100ul 6N hydrochloric acid for every 50-mL of sample; and anions (chloride, Cl- and sulfate, SO42--S) and alkalinity samples were refrigerated. Samples were shipped back to the University of Vermont in Burlington, Vermont; the Ecosystems Center in Woods Hole, Massachusetts; or the University of Michigan for analysis within six to nine months. LTER Streams Protocols were followed.
Arctic LTER Streams Protocol
annual data is updated into new file
v1. October 2014: metadata added, file contains water chemistry data - JL