Dataset: Biochemical data on dissolved organic matter composition from Galveston Bay collected on five one-day trips aboard R/V Trident following Hurricane Harvey from September 4 to 28, 2017

Surface water samples were collected on five consecutive one-day trips aboard R/V Trident along a transect from the Port of Houston to the Galveston Bay entrance following Hurricane Harvey from September 4 to September 28, 2017. Samples were filtered on board through 0.2-micrometer (μm) Whatman-Nucleopore Q-TEC filters (Filtration Solutions) for dissolved organic carbon (DOC), optical, and chemical analysis.

Concentrations of DOC were measured by high-temperature catalytic oxidation using a Shimadzu TOC-V total organic carbon analyzer. Deep seawater reference standards (Consensus Reference Program, University of Miami) were used to assure the accuracy of DOC measurements. Absorbance was measured in a 1-centimeter (cm) quartz cuvette from 200 to 800 nanometers (nm) using a dual-beam spectrophotometer (UV-1800, Shimadzu) with Milli-Q water as the reference blank. Specific UV absorbance (SUVA254 ) was determined by dividing the UV absorbance at 254 nm by the DOC concentration. The spectral slope (S275−295) was calculated using the linear regression of natural log-transformed absorption spectra (Helms et al., 2008).

Samples for dissolved lignin (900 milliliters (mL)) were acidified to pH 2.5 using 6 moles per liter (mol L-1) sulfuric acid and extracted through Agilent PPL cartridges (1 gram (g)) at 10 milliliters per minute (mL min-1). After extraction, cartridges were rinsed with 10 mL of deionized water acidified to pH 2.5 and dried for 30 seconds to remove residual water. The cartridges were eluted with 20 mL of methanol at 2 mL min-1, and the eluate was stored in glass vials at -20 degrees Celsius until analysis. Concentrations of lignin phenols were determined using ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry after CuSO4 oxidation, following the methods described in Yan and Kaiser (2018a,b). Aliquots of methanol extracts (∼30 microgram (μg) sample OC content) were dried in reaction vials and re-suspended in 200 microliters (μL) of 1.1 mol L-1 argon-sparged NaOH, followed by addition of 10 μL of 10 millimoles per liter (mmol L-1) CuSO4 and 10 μL of 0.2 mol L-1 ascorbic acid. Reaction vials were vigorously mixed and placed into 60-mL pressure-tight Teflon vessels filled with 5 mL of 1 mol L-1 NaOH. The oxidation was conducted at 150 degrees Celsius for 120 minutes. Sample solutions were spiked with 13C-labeled surrogate standards and purified with Waters HLB cartridges (30 milligram (mg), 1 mL). Separation and detection of lignin phenols was performed on an Agilent Infinity 1260 series UHPLC system coupled to an Agilent 6420 QqQ detector operating in alternating positive and negative modes with dynamic multiple reaction monitoring. Eleven lignin phenols were determined in all samples, including vanillyl phenols (V; vanillin, acetovanillone, and vanillic acid), syringyl phenols (S; syringaldehyde, acetosyringone, and syringic acid), p-hydroxyl phenols (P; p-hydroxybenzaldehyde, p-hydroxyacetophenone, and p-hydroxybenzoic acid), and cinnamyl phenols (C; p-coumaric acid and ferulic acid).

Total hydrolyzable enantiomeric dissolved amino acids (free and combined), including L-and D- forms of aspartic acid, glutamic acid, serine, histidine, threonine, glycine, arginine, alanine, tyrosine, valine, isoleucine, phenylalanine, leucine, and lysine were analyzed using high-performance liquid chromatography and fluorescence detection. After microwave-assisted vapor phase hydrolysis (Kaiser and Benner, 2005), amino acid monomers were derivatized with a mixture of N-isobutyryl- L-cysteine and o-phthaldialdehyde and separated on an Agilent Poroshell 120 EC-C18 column (4.6 millimeters (mm) × 100 mm, 2.7 μm). A binary solvent system was employed: mobile phase A was 48 mmol L-1 KH2PO4 with pH adjusted to 6.25, and mobile phase B was methanol/acetonitrile (13/1, v/v). The linear gradient program was: 0% B at 0 minutes, 39% B at 13.3 minutes, 54% B at 19.2 minutes, 60% B at 21.3 minutes, 80% B at 22 minutes, and hold at 80% B for 1 minute. The flow rate was 1.5 mL min-1 and column temperature was maintained at 35 degrees Celsius. Excitation and emission wavelength of the detector was set to 330 nm and 450 nm, respectively. Racemization of amino acid enantiomers occurring during acidic hydrolysis was corrected using the average rates determined on free and protein amino acids (Kaiser and Benner, 2005). Total D-amino acids (D-AA) was defined as the sum of the four D-enantiomers of aspartic acid (D-Asx), glutamic acid (D-Glx), serine (D-Ser), and alanine (D-Ala), which were ubiquitously present in all samples.