Model diatom aggregates were produced from the diatom Skeletonema marinoi and the natural microbial community of seawater collected in Oeresund (Stief et al. 2023), Central Arctic Ocean, and Japan Trench. S. marinoi was grown to stationary phase in L1 medium plus silicate (Guillard & Hargraves 1993) at 15°C under a light/dark regime of 14/10 h. The diatom aggregates were individually incubated at either atmospheric pressure (0.1 MPa = control treatment) or at gradually increasing hydrostatic pressure (0.1-100 MPa = pressure treatment) throughout 20 days in darkness and at 3°C. The pressure treatment simulated the sinking of diatom-bacteria aggregates from the ocean surface down into a hadal trench of 10 km depth. Pressure-induced leakage of dissolved organic matter (DOM) was followed throughout the incubations. Ambient concentrations of different DOM components were measured: Dissolved organic carbon (DOC), total dissolved nitrogen (TDN), protein-like and humic-like DOM fluorescence.
Stored surface seawater originally collected in the North Sea was amended with dissolved organic matter (DOM) obtained from the diatom Skeletonema marinoi by exposing the diatom culture to a hydrostatic pressure level of 40 MPa for 24 h. To this end, S. marinoi had been grown to stationary phase in L1 medium plus silicate (Guillard & Hargraves 1993) at 15°C under a light/dark regime of 14/10 h. Diatom-cell-free DOM was added to aliquoted seawater samples at initial concentrations of 250 µmol C/L. The microbial degradation of the added DOM and the microbial response to DOM-amendment at 15°C and in darkness was followed for 2 weeks. The seawater was subsampled at defined time intervals to analyze a number of variables.
Supplementary information for "A physical model for accurate paleotemperature reconstruction from fluid inclusions in halite" (Guillerm et al., 2025). The supplementary material contains a model-data comparison of the equation of state for aqueous solutions used in the associated paper. Also contains details about, and developments of, the equations of the associated article (Guillerm et al., 2025).