Environmental and DOM FTICRMS data for Spiekeroog Beach

This dataset was acquired to investigate the sources and sinks of dissolved organic matter in a high-energy beach subterranean estuary on Spiekeroog Island, German North Sea. The North Beach sampling location is approximately at 53°46'45N, 7°42'40E. Data were collected during a total of five sampling campaigns in the period of September 2016 - September 2019, spanning over all four seasons. The samples collected were from beach porewaters, seawater, and groundwater from the islands' freshwater lens. Pore water samples were collected with push-point lances (10-100 cm depth), seawater samples with bottles in the surf zone, and groundwater samples from inland monitoring wells (4-40 m depth). Samples were filtered onsite and preserved for storage (acidification for dissolved organic carbon, dissolved organic nitrogen, and trace metals, and poisoning with HgCl2 for dissolved nutrients). In situ data were collected, including temperature, salinity, oxygen concentrations (instrument: WTW Multi 3430), and humic-like fluorescent DOM (instrument: Turner Aquafluor). Laboratory analyses were conducted within a week of sampling and included spectrophotometry for nutrients, ICP-OES for trace metals, and TOC-VCPH analysis for DOC and TDN. Acidified subsamples were desalted and concentrated by solid-phase extraction, then analyzed on via ultra-high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS on a 15T Bruker solariX XR.