Description: To investigate links between biological, biogeochemical and physical parameters, we closely monitored an artificially induced spring bloom. Our mesocosm approach mimicked a neritic North Sea water body. Three biological replicates (P2-P4) were inoculated with a phytoplankton and associated bacterial community, which was retrieved in March 2018 from the southern North Sea. The incubation was monitored for 38 days. The experiment additionally covered the investigation of two biota-free controls. A variety of parameters were sampled, the results of some can be found in Mori et al. (2021; doi:10.1016/j.gca.2021.08.002). Total alkalinity was sampled daily. For the analysis we used a multiscan GO microplate spectrophotometer (Thermo Scientific) and followed the method described by Sarazin et al. (1999; doi:10.1016/S0043-1354(98)00168-7).

Description: 22 environmental metagenomic surface water (20 m depth) samples from two transects to the Southern and Atlantic Ocean (RV Polarstern ANT-XXVIII/4 and ANT-XXVIII/5 in 2012). Samples were filtered on 0.2µm polycarbonate filters and stored at -80°C until extraction and sequencing unsing an Illumina HiSeq2500.

Description: A PHREEQC model was written to investigate complexation of dREEs with components of the dissolved OM pool. Based on the data measured during a mesocosm experiment (maybe link the original dataset) the model simulated chemical speciation of the dREEs in the mesocosms. A new databank was created that includes stability constants for complexes of dREEs with the main inorganic ligands (Cl⁻, SO₄⁻, OH⁻, CO₃⁻) as well as with the strong organic ligand desferrioxamine B (DFOB) after Christenson and Schijf (2011). The model outcome includes concentrations of inorganic and organic dREE complexes as well as abundances as free ions (REE^3+) and total dREE concentrations. Additionally, we calculated the proportions of the different complexes to the total dREE pool. We used two different approaches for the PHREEQC simulations that followed Schijf et al. (2015; doi:10.1016/j.marchem.2015.06.010) and were characterized by the concentration of the strong organic ligand and the resulting proportion of organic complexes to the dREE pool. The 'High-DOC' approach results in a maximal proportion of organic REE-DOC complexes of 40%, the 'Low-DOC' approach results in maximum of 10% organic complexes. To keep an eye on variations in carbonate complexes, total alkalinity (TA) was monitored as well. TA was sampled daily, for the analysis we used a multiscan GO microplate spectrophotometer (Thermo Scientific) and followed the method described by Sarazin et al. (1999; doi:10.1016/S0043-1354(98)00168-7).

Description: To investigate the influence of organic matter (OM) on rare earth element (REE) distributions and patterns in the marine environment we monitored concentrations of dissolved REEs (dREEs) during an artificially induced spring bloom. Our mesocosm approach mimicked a neritic North Sea water body. Three biological replicates (P2-P4) were inoculated with a phytoplankton and associated bacterial community, which was retrieved in March 2018 from the southern North Sea. The incubation was monitored for 38 days. The experiment additionally covered the investigation of two biota-free controls. A variety of parameters were sampled, the results of some can be found in Mori et al. (2021; doi:10.1016/j.gca.2021.08.002). Samples for dREE analyses were taken at intervals of 1-5 days. Preconcentration, analysis and quantification of dREEs followed the method described in Behrens et al. (2016; doi:10.1016/j.marchem.2016.08.006.). Concentrations were normalized to the Post Archaen Australian Shale (Rudnick and Gao, 2003). We further normalized concentrations throughout the experiment to initial concentrations (T0-normalization) and calculated loss and gains of dREEs.

Description: In order to investigate the influence of organic matter (OM) on rare earth element (REE) distributions and patterns in the marine environment we monitored concentrations of dissolved REEs (dREEs) during an artificially induced spring bloom. Our mesocosm approach mimicked a neritic North Sea water body. Three biological replicates (P2-P4) were inoculated with a phytoplankton and associated bacterial community, which was retrieved in March 2018 from the southern North Sea. The incubation was monitored for 38 days. The experiment additionally covered the investigation of two biota-free controls. A variety of parameters were sampled, the results of some are published by Mori et al. (2021). Samples for dREE analyses were taken at intervals of 1-5 days. Preconcentration, analysis and quantification of dREEs followed the method described by Behrens et al. (2016). In order to investigate possible complexation of dREEs with components of the dissolved OM pool, a PHREEQC model was written that simulated chemical speciation of the dREEs in the mesocosms. A new databank was created that includes stability constants for complexes of dREEs with the main inorganic ligands (Cl⁻, SO₄⁻, OH⁻, CO₃⁻) as well as with the strong organic ligand desferrioxamine B (DFOB) after Christenson and Schijf (2011). The model outcome includes concentrations of inorganic and organic dREE complexes as well as abundances as free ions (REE3+) and total dREE concentrations. Additionally, we calculated the proportions of the different complexes to the total dREE pool. We used two different approaches for the PHREEQC model approach that followed Schijf et al. (2015) and were characterized by the concentration of the strong organic ligand and the resulting proportion of organic complexes to the dREE pool. The 'High-DOC' approach results in a maximal proportion of organic REE-DOC complexes of 40%, the 'Low-DOC' approach results in maximum of 10% organic complexes. To keep an eye on variations in carbonate complexes, total alkalinity (TA) was monitored as well. TA was sampled daily, for the analysis we used a multiscan GO microplate spectrophotometer (Thermo Scientific) and followed the method described by Sarazin et al. (1999).

Description: To investigate the influence of organic matter (OM) on rare earth element (REE) distributions and patterns in the marine environment we monitored concentrations of dissolved REEs (dREEs) during an artificially induced spring bloom. Our mesocosm approach mimicked a neritic North Sea water body. Three biological replicates (P2-P4) were inoculated with a phytoplankton and associated bacterial community, which was retrieved in March 2018 from the southern North Sea. The incubation was monitored for 38 days. The experiment additionally covered the investigation of two biota-free controls. A variety of parameters were sampled, the results of some can be found in Mori et al. (2021; doi:10.1016/j.gca.2021.08.002). Samples for dREE analyses were taken at intervals of 1-5 days. Preconcentration, analysis and quantification of dREEs followed the method described in Behrens et al. (2016; doi:10.1016/j.marchem.2016.08.006.).

Description: The Pacific Ocean constitutes about half of the global oceans and thus microbial processes in this ocean have a large impact on global elemental cycles. Despite several intensely studied regions large areas are still greatly understudied regarding microbial activities, organic matter cycling and biogeography. Refined information about these features is most important to better understand the significance of this ocean for global biogeochemical and elemental cycles. Therefore we investigated a suite of microbial and geochemical variables along a transect from the subantarctic to the subarctic Pacific in the upper 200 m of the water column. The aim was to quantify rates of organic matter processing, identify potential controlling factors and prokaryotic key players. The assessed variables included abundance of heterotrophic prokaryotes and cyanobacteria, heterotrophic prokaryotic production (HPP), turnover rate constants of amino acids, glucose, and acetate, leucine aminopeptidase and β-glucosidase activities, and the composition of the bacterial community by fluorescence in situ hybridization (FISH). The additional quantification of nitrate, dissolved amino acids and carbohydrates, chlorophyll a, particulate organic carbon and nitrogen (POC, PON) provided a rich environmental context. The oligotrophic gyres exhibited the lowest prokaryotic abundances, rates of HPP and substrate turnover. Low nucleic acid prokaryotes dominated in these gyres, whereas in temperate and subpolar regions further north and south, high nucleic acid prokaryotes dominated. Turnover rate constants of glucose and acetate, as well as leucine aminopeptidase activity, increased from (sub)tropical toward the subpolar regions. In contrast, HPP and bulk growth rates were highest near the equatorial upwelling and lowest in the central gyres and subpolar regions. The SAR11 clade, the Roseobacter group and Flavobacteria constituted the majority of the prokaryotic communities. Vertical profiles of the biogeochemical and microbial variables markedly differed among the different regions and showed close covariations of the microbial variables and chlorophyll a, POC and PON. The results show that hydrographic, microbial, and biogeochemical properties exhibited distinct patterns reflecting the biogeographic provinces along the transect. The microbial variables assessed contribute to a better and refined understanding of the scales of microbial organic matter processing in large areas of the epipelagic Pacific beyond its well-studied regions.