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Biogeochemical variables from a Multidisciplinary BASS Mesocosm Study at Wilhelmshaven, 2023

This dataset contains biogeochemical variables measured during the same mesocosm experiment at Sea Surface Facility (SURF) in Wilhelmshaven, Germany (53.5148° N, 8.1461° E) in 2023. Variables include surfactants and nutrient concentrations, chlorophyll a, pigments, particulate and dissolved organic carbon and nitrogen, and several other biogeochemical parameters. These data complement the daily averaged physical parameters (PANGAEA DOI: https://doi.pangaea.de/10.1594/PANGAEA.983975) and together support the assessment of ecosystem and biogeochemical dynamics associated with the experiment, as described in the related publication Bibi et al., 2025.

Daily averaged physical parameters from the Multidisciplinary BASS Mesocosm Study at Wilhelmshaven, 2023

This dataset contains daily averaged physical and chemical parameters measured during a mesocosm experiment conducted at Sea Surface Facility (SUR) in Wilhelmshaven, Germany (53.5148° N, 8.1461° E) in 2023. Parameters include daily average air temperature, Daily Average Incoming Solar Irradiance, Daily Average Reflected Solar Irradiance, and Daily Average Albedo derived from in situ measurements. The dataset provides an overview of environmental conditions throughout the experiment, supporting the interpretation of biogeochemical and ecological processes described in the related publication Bibi et al., 2025.

Physical, chemical, and biogeochemical parameters from a mesocosm experiment at the Sea Surface Facility (SURF), Wilhelmshaven, Germany, spring 2023

This collection (bundled publication) includes datasets from a mesocosm experiment conducted in spring 2023 at the Sea Surface Facility (SURF), Wilhelmshaven, Germany (53.5148° N, 8.1461° E). The experiment initiated a phytoplankton bloom under controlled conditions to examine surface ocean biogeochemistry and sea-surface microlayer (SML) processes. Daily samples were collected from the SML and underlying water (40 cm depth) and analyzed for physical, chemical, and biological parameters. Measurements include meteorological conditions (air temperature, solar irradiance, and albedo), surfactants, nutrients, pigments, particulate and dissolved organic carbon and nitrogen, and additional biogeochemical variables. These datasets provide environmental and biogeochemical context supporting studies on surface ocean processes and are described in detail in the related publication Bibi et al. (2025).

Colored dissolved organic matter (CDOM) absorption coefficients in the sea-surface microlayer and the underlying water during a mesocosm phytoplankton bloom in 2023

The effects of a phytoplankton bloom and photobleaching on colored dissolved organic matter (CDOM) in the sea-surface microlayer (SML) and the underlying water (ULW) were studied in a month-long mesocosm study, in May and June of 2023, at the Institute for Chemistry and Biology of the Marine Environment (ICBM) in Wilhelmshaven, Germany. The mesocosm study was conducted by the DFG research group BASS (Biogeochemical processes and Air–sea exchange in the Sea-Surface microlayer, Bibi et al., 2025) in the Sea Surface Facility (SURF) of the ICBM. The facility contains an 8 m × 1.5 m × 0.8 m large outdoor basin with a retractable roof, which was closed at night and during rain events. The basin was filled with North Sea water from the adjacent Jade Bay. Homogeneity of the ULW in the basin was achieved by constant mixing of the water column. The daily SML and ULW samples were collected alternating in the morning, about 1 h after sunrise, and in the afternoon, about 10 h after sunrise. The alternation of sampling times intended to capture a potential effect of sun-exposure duration on DOM transformations and elucidated the day and night variability of the layers. The SML was collected via glass plate sampling (Cunliffe and Wurl, 2014). The ULW was sampled via a submerged tube and a connected syringe suction system in 0.4 m depth. The removed sample volume was refilled with Jade Bay water every day. SML and ULW samples were filtered through pre-flushed 0.7 µm Whatman GF/F and 0.2 nucleopore filters into brown bottles and were stored dark and at 4 °C until measurement within weeks of the study. The brown bottles were previously combusted at 500 °C. CDOM was measured with three liquid waveguide capillary cells (LWCC, WPI, USA) of different pathlengths (10 cm, 50 cm, 250 cm) to increase the measurement sensitivity following the protocols of Röttgers et al. (2024) using a spectral detector (Avantes, Netherlands) for a total spectral range from 230 to 750 nm. A sodium chloride (NaCl) solution was used for the salinity correction. The blank-corrected absorbance spectra were then converted into Napierian absorption coefficients (Bricaud et al., 1981).

PARAFAC components and fluorescent dissolved organic matter (FDOM) indices on organic matter transformation processes in the sea-surface microlayer and the underlying water during a mesocosm phytoplankton bloom in 2023

The effects of a phytoplankton bloom and photobleaching on colored dissolved organic matter (CDOM) in the sea-surface microlayer (SML) and the underlying water (ULW) were studied in a month-long mesocosm study, in May and June of 2023, at the Institute for Chemistry and Biology of the Marine Environment (ICBM) in Wilhelmshaven, Germany. The mesocosm study was conducted by the DFG research group BASS (Biogeochemical processes and Air–sea exchange in the Sea-Surface microlayer, Bibi et al., 2025) in the Sea Surface Facility (SURF) of the ICBM. The facility contains an 8 m × 1.5 m × 0.8 m large outdoor basin with a retractable roof, which was closed at night and during rain events. The basin was filled with North Sea water from the adjacent Jade Bay. Homogeneity of the ULW in the basin was achieved by constant mixing of the water column. The daily SML and ULW samples were collected alternating in the morning, about 1 h after sunrise, and in the afternoon, about 10 h after sunrise. The alternation of sampling times intended to capture a potential effect of sun-exposure duration on DOM transformations and elucidated the day and night variability of the layers. The SML was collected via glass plate sampling (Cunliffe and Wurl, 2014). The ULW was sampled via a submerged tube and a connected syringe suction system in 0.4 m depth. The removed sample volume was refilled with Jade Bay water every day. SML and ULW samples were filtered through pre-flushed 0.7 µm Whatman GF/F and 0.2 nucleopore filters into clear 40 ml SUPELCO bottles. These bottles were acid-washed twice and combusted at 500 °C for 5 h. The samples were stored dark and at 4 °C and measured within a few months of the study. FDOM was measured using a Aqualog fluorescence spectrometer (Horiba Scientific, Japan) with 10 seconds integration time and high gain of the CCD (charge-coupled device) sensor within an excitation range from 240 to 500 nm, and an emission range from 209.15 to 618.53 nm. The Aqualog measures fluorescence as well as absorption. The resulting data includes an excitation-emission-matrix (EEM) of the blank (MilliQ Starna cuvette), an EEM of the sample, and the absorption values of the sample. The raw exported Aqualog data was corrected for errors and lamp shifts. The corrected EEM data is then decomposed by PARAFAC (Murphy et al., 2013) for its underlying fluorophore components. Before running the PARAFAC routine, the corrected data needed to undergo a correction process by subtracting the blank from the sample EEM and canceling the influences of the inner-filter effect (IFE, Parker & Rees, 1962; Kothawala et al., 2013). The fluorescence intensity of the IFE-corrected EEM is calibrated by using the Raman scatter peak of water (Lawaetz & Stedmon, 2009). For PARAFAC the corrected data was processed using the drEEM and NWAY toolbox (version 0.6.5; Murphy et al., 2013) in MATLAB (R2020b). A 4-component model was validated with the validation style S4C6T3 for the split half analysis with nonnegativity constraints and 1-8e as the convergence criteria with 50 random starts and a maximum number of 2500 iterations. The resulting final model had a core consistency of 82.04 and the explained percentage was 99.54%. Furthermore, four fluorescence indices were calculated from the corrected EEM data (HIX – Humification index, Zsolnay et al., 1999; BIX – Biological index, Huguet et al., 2009; REPIX – Recently produced index, Parlanti et al., 2000, Drozdowska et al., 2015; ARIX, Murphy, 2025).

Polysaccharides present in HMWDOM and POM during a microalgae bloom period in the North Sea

High molecular weight dissolved organic matter (HMWDOM) and particulate organic matter (POM) samples were harvested during a spring phytoplankton bloom period in the North Sea for about three months. Polysaccharides from all HMWDOM and POM samples were extracted and analysed by carbohydrate microarray analysis. Additionally, glycans in the HMWDOM samples were also studied by monosaccharide analysis.

Dissolved and particulate trace metal and rare earth element (REE) concentrations during a mesocosm based phytoplankton bloom simulating intertidal coastal conditions

We analyzed concentrations of dissolved and particulate trace metals, including iron (Fe), manganese (Mn), vanadium (V), molybdenum (Mo), thallium (Tl), and rare earth elements (REE), during a mesocosm-based phytoplankton summer bloom mimicking the intertidal zone of the southern North Sea (Jade Bay). The studies aimed to identify key drivers controlling their biogeochemical cycling in dynamic, high-productivity coastal environments. Our results highlight the tidally influenced coastal zone as a critical interface that alters the behavior of supposedly conservative elements such as Mo and Tl (Mori et al., 2021) as well as natural and anthropogenic REE (incl., lanthanum, samarium, and gadolinium) (Mori et al., under review). Trace metal concentrations and shale-normalized REE patterns, determined by quadrupole inductively coupled plasma–mass spectrometry (ICP-MS) and inductively coupled plasma–optical emission spectrometry (ICP-OES), were combined with biogeochemical bulk parameters and pigment-based assessments of phytoplankton growth and community composition (Mustaffa et al., 2020). Trace metal and REE cycling were evaluated in relation to phytoplankton dynamics, particulate organic matter composition (C, N, P), dissolved organic carbon, total dissolved nitrogen, and macronutrient concentrations (nitrate, ammonium, silicate, and inorganic phosphate). The dataset was obtained during a Planktotron-based mesocosm experiment conducted within the framework of the Coastal Ocean Darkening project (Mustaffa et al., 2020).

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