FT-ICR MS peak lists of dissolved organic matter along a seasonal oxygen-recovery gradient in a coastal bay of the North Yellow Sea
Description
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) peak lists for solid-phase-extracted dissolved organic matter (SPE-DOM) from bottom waters of a seasonally low-oxygen, mariculture-influenced bay around Yangma Island, North Yellow Sea, China. Water was sampled at four stations (S1-S4) on four cruises between August and October 2019 (10 August, 18 August, 29 September and 20 October), spanning a bottom-water dissolved oxygen recovery gradient of 2.5-7.2 mg/L generated by the breakdown of summer thermal stratification. All samples are bottom water collected about 1 m above the seafloor, so the layer is not coded in the sample names. Spectra meeting the quality criteria were obtained for 14 of the 16 station-cruise combinations: S3 on 18 August and S1 on 20 October are absent. The dataset comprises one CSV file with 6,588 assigned molecular formulae, one per row. For each formula it reports elemental composition (C, H, O, N, S), heteroatom class (CHO, CHON, CHOS, CHONS), theoretical neutral monoisotopic mass, H/C and O/C ratios, double bond equivalent (DBE), modified aromaticity index (AImod) and nominal oxidation state of carbon (NOSC), followed by the relative peak intensity in each of the 14 samples, normalized to the total assigned signal intensity of that sample so that each sample column sums to 1. A value of 0 means the formula was not detected in that sample. Sample columns are named MP<yymmdd>_<station>, for example MP190810_S1. An accompanying README file documents every column, the sample naming scheme and the acquisition parameters. These data support the research article "Selective reorganization of DOM and lifestyle-dependent microbe-DOM coupling along a coastal seasonal oxygen gradient" (Marine Pollution Bulletin, Manuscript No. MPB-D-26-02329), in which the station positions are shown in Figure 1a.
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Steps to reproduce
1. Sample collection. Bottom water was collected with a 10 L Niskin bottle approximately 1 m above the seafloor at four stations (S1, S2, S3, S4) on four cruises in 2019 (10 August, 18 August, 29 September, 20 October). Temperature, salinity and dissolved oxygen were recorded in situ with a WQMx water quality monitor (WET Labs) fitted with a Sea-Bird SBE 43 oxygen sensor. 2. Filtration. Approximately 2 L of seawater was filtered through pre-combusted Whatman GF/F filters (450 C, 4 h) in an acid-cleaned all-glass filtration system under gentle vacuum. A 1 L aliquot of the filtrate was collected in a combusted amber glass bottle and acidified to pH 2-3 with formic acid (98%, CNW). 3. Solid-phase extraction. The acidified filtrate was passed by gravity through a PPL cartridge (Agilent Bond Elut PPL, 500 mg, 6 mL) previously activated with methanol (LC-MS grade) and rinsed with acidified Milli-Q water (pH 2, formic acid). After loading, cartridges were rinsed again with acidified Milli-Q water to remove salts, dried with ultrapure N2, and eluted with 3 mL methanol. Extracts were stored at -20 C until analysis. 4. FT-ICR MS acquisition. Extracts were diluted to approximately 50 mg C/L in methanol and infused into the electrospray source (ESI, Bruker Apollo II) in negative-ion mode on a 9.4 T Apex Ultra FT-ICR mass spectrometer (Bruker Daltonics) at the State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing. Spectra were acquired over 500 scans with a data size of 4 M and an ion accumulation time of 1.0 s. 5. Molecular formula assignment. Peaks between 200 and 800 Da were assigned formulae within the bounds C1-60 H4-100 O1-30 N0-3 S0-1 using an in-house routine, with a mass tolerance of +/-1.0 ppm and a signal-to-noise ratio of at least 6. Isotopologues were excluded. Spectra of sufficient quality were obtained for 14 of the 16 station-cruise combinations. 6. Table construction. Peak intensities were normalized to the total assigned signal intensity of each sample, so that each sample column sums to 1. DBE, AImod and NOSC were calculated from the assigned formulae following Koch and Dittmar (2006, 2016) and LaRowe and Van Cappellen (2011). Formulae detected in none of the 14 bottom-water samples were removed, leaving 6,588 rows.
Institutions
- Shandong UniversityShandong, Jinan