Metadata

Description
Sampling Description Water samples were collected monthly during January 2018 to January 2021 from a total of 14 sampling stations located in the coastal estuaries of the southern tip of the Florida Peninsula, USA. These stations were established for an on-going water quality monitoring program (http://www.serc.fiu.edu/wqmnetwork). Sampling stations can be largely grouped into 3 distinct districts based on the geomorphological features, that is, Florida Bay (FB, 3 sampling stations), Shark River Slough (SRS, 6 sampling stations), and Taylor Slough (TSPH, 8 sampling stations). Surface water samples were taken from these stations. The samples were collected using pre-washed, brown Nalgen polyethylene bottles (Nalge Nunc International). The samples were stored on ice and returned to the laboratory within 8 h for analysis. Subsamples for dissolved carbon and lignin analysis were filtered through precombusted Whatman GF/F glass fiber filters once received in the laboratory and acidified to pH 2 then kept at 4C until analysis at North Carolina State University could occur.

Description
Dissolved organic carbon (DOC) and stable isotope of DOC DOC stable C isotope ratios were measured using high-temperature combustion on an OI Analytical 1030D TOC analyzer coupled in continuous flow to the Delta V+ IRMS. Prior to analysis samples were acidified with 85% H3PO4 to pH 2 and sparged for 10 min with ultra-high purity argon to remove inorganic carbon as CO2). DOC concentrations were calibrated each analytical day with prepared solutions of caffeine, and δ13C values were calibrated VPDB scale with prepared solutions from IAEA-CH6 (δ13C = −10.8‰) and IAEA-600 (δ13C = −27.77‰).

Description
Dissolve lignin-derived phenols were isolated from FCE waters using solid-phase extraction (SPE) with 6 mL Agilent Bond Elut PPL filters, which contain 1 g of styrene-divinylbenzene polymer with a non-polar surface (Louchouarn et al., 2000; Arellano et al., 2018). Briefly, the filtered and acidified sample was conditioned with methanol and acidified Milli-Q Ultrapure water to ensure that the sorbent was saturated before the SPE (Louchouarn et al., 2000). An approximately 2 L acidifed sample was pumped through a PPL filter using a peristaltic pump at a rate of 10 mL min-1. The PPL cartridge was rinsed with 18 mL of acidified (pH 2) Milli-Q water to remove any remaining salts (Louchouarn et al., 2000). The PPL cartridge was then dried under ultra-high purity nitrogen gas (10-12 psi) and then eluted into borosilicate glass vials that were baked at 450C for 5 hours, using 9 mL HPLC grade methanol (Arellano et al., 2018). The cupric oxide oxidation (CuO) and liquid-liquid extraction methods (Hedges and Ertel, 1982, modified by Goñi and Hedges, 1995; Louchouarn et al., 2000; Goñi and Montgomery, 2000; Benner and Kaiser, 2011, respectively) were used to extract lignin oxidation products. 500 mg of CuO, 100 mg of ferrous ammonium sulfate (FAS), and 10 mg of glucose was then added to 6 mL Salvillex Teflon reaction vessels. The methanol eluent was split into two subsamples and then dried using nitrogen. One subsample of dried eluent was then redissolved in 3.5 mL of nitrogen-sparged 2 N NaOH and added to the Teflon reaction vessel. The reaction vessel was then briefly sparged with nitrogen to remove excess oxygen and then capped. Samples were then oxidized in a muffle furnace for 150 minutes at 155C (5C min -1 ramp rate). Once oxidation was complete the Teflon vessels were cooled in an ice bath, then vortexed, transferred to polycarbonate tubes and centrifuged at 3200 rpm for 20 minutes. Supernatant was transferred to a new centrifuge tube then ethyl vanillin and t-cinnamic acid are added prior to liquid-liquid extraction to be used as recovery standards. Next the sample was acidified with 85% H3PO4 to pH 2 and then vortexed and centrifuged. Liquid-liquid extraction was completed by addition of 4 mL of ethyl acetate to the acidified sample, followed by vortex and centrifuge, then passed over a Na2SO4 column to remove residual water. Lignin liquid-liquid extracts were then dried under nitrogen, redissolved in 500 uL of pyridine, and stored at -20C until analysis. 50 uL of liquid-liquid extract is then derivatized using 50 uL of N,O-bis (trimethylsilyl) trifluoroacetamide (BSTFA) at 60°C for 1 hour. Derivatized samples were then dried under nitrogen, redissolved in 100 uL of dichloromethane and then measured and quantified immediately on an Agilent Gas Chromatograph-Mass Spectrometer (GC-MS) according to the method provided by Kaiser and Benner (2012). Relative response factors were calculated using t-cinnamic acid to account for instrument variability. Concentrations of dissolved lignin oxidation products are calculated using calibration curves of 9 phenols (vanillyl, syringyl, cinnamyl, and 3,5 Bd) over the range of expected values.