Accumet ap61

As the Ankom^RF is a vented system, a second closed system composed by serum bottles was used to investigate both in vitro enteric CH₄ and CO₂ production (Exp. 2). Each serum bottle (155 mL) was filled with 0.2 g of each ingredient. Bottles were inoculated with 20 mL of rumen/buffer solution keeping the headspace of bottle continuously flushing with N₂. After inoculation, bottles were sealed with butyl rubber stoppers and aluminum caps, and then placed into an air-ventilated shaker incubator (39^°C). At the end of each fermentation batch, CO₂ and CH₄ production were measured from the headspace using a Gow Mac thermal conductivity series 580 gas chromatograph (Gow Mac Instrument, Bridgewater, NJ) equipped with a Porapak Q (Supelco) column (60°C, 30 mL/min of helium (999.9 mL/L) as the carrier gas). The bottles’ enteric CH₄ and CO₂ productions were corrected for inoculum contribution by subtracting the final GP of the blank bottles. The solution pH was measured (Accumet™ AP61, Fisher Scientific, Atlanta, GA) at the beginning and at the end of each incubation (48 h).

Inorganic water chemistry from each of the sample sites has been compiled from raw data provided by the National Park Service (United States) and (Back, 2011 ; Table 1). Water pH was measured in the field using an Accumet AP61 portable pH meter (Fisher Scientific, Pittsburg, PA, United States). Total organic carbon (TOC) analysis was carried out by WATERS laboratories (Western Kentucky University, Kentucky, United States) using high temperature combustion method (SM5310B) in a Shimadzu TOC analyzer TOC-V series. Due to the very low biomass observed in the lakes we decided to also measure (1,3)-(β)-D-glucan, a common polysaccharide of both Gram negative and positive bacteria, to assess total microbial biomass (Duenas et al., 2003 (link)). Quantification was carried out via a chromogenic method using the Glucatell reagent in a BioTek ELx808 microplate reader, with measurements averaged from samples collected over a two-year period.