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This dataset includes the concentrations of particulate total sulfur, particulate iron, dissolved hydrogen, and dissolved methane measurements for a subset of near-seafloor (< 40 m above bottom) and background water column samples collected on the 18 September to 6 November 2021 PLUME RAIDERS cruise to the 16-18ºS sector of the Southern East Pacific Rise on R/V Roger Revelle. Particulate iron and particulate total sulfur samples were collected at sea and later measured in lab using energy dispersive X-ray fluorescence (ED-XRF). Dissolved hydrogen and methane measurements were collected and processed shipboard using gas chromatography. Dr. Tamara Baumberger and Anson Antriasian generated the dissolved hydrogen and methane data. Nathan Buck generated the particulate iron and particulate total sulfur data."],"Methods":["Samples were collected on the R/V Roger Revelle (cruise RR2106, “PLUME RAIDERS”) expedition to the 16-18ºS section of the southern East Pacific Rise from 18 September to 6 November 2021. Teflon-Lined Go-Flo samplers (General Oceanics) were used to collect water column seawater samples from a trace metal clean CTD-rosette (Seabird Scientific; Cutter and Bruland 2012). Subsamples (100 mL) for dissolved hydrogen and methane were collected via syringe on deck and then analyzed onboard using gas chromatography following the methods outlined in Baumberger et al. (2014) and Kelley et al. (1998). Samples for pFe and pStot were collected in a shipboard clean-air laboratory by filtering seawater (average ~ 6 L) onto 0.2um polycarbonate track etched membrane filters (Whatman) with cellulose ester filter backings (Whatman), followed by a 15 mL rinse step using pH 8 MilliQ-NH4OH solution to remove excess sea salts. Samples were stored in a desiccator until the end of the cruise then later analyzed in the lab using energy dispersion X-ray fluorescence (ED-XRF) following the methods outlined in Buck et al. (2021). References: Baumberger, T., M. D. Lilley, J. A. Resing, J. E. Lupton, E. T. Baker, D. A. Butterfield, E. J. Olson, and G. L. Früh-Green. 2014. Understanding a submarine eruption through time series hydrothermal plume sampling of dissolved and particulate constituents: West Mata, 2008–2012. Geochem. Geophys. Geosystems 15: 4631–4650. doi:10.1002/2014GC005460.Received\n\nBuck, N. J., P. M. Barrett, P. L. Morton, W. M. Landing, and J. A. Resing. 2021. Energy dispersive X-ray fluorescence methodology and analysis of suspended particulate matter in seawater for trace element compositions and an intercomparison with high-resolution inductively coupled plasma-mass spectrometry. Limnol. Oceanogr. Methods 19: 401–415. doi:10.1002/lom3.10433\n\nCutter, G. A., and K. W. Bruland. 2012. Rapid and noncontaminating sampling system for trace elements in global ocean surveys. Limnol. Oceanogr. Methods 10: 425–436. doi:10.4319/lom.2012.10.425\n\nKelley, D. S., M. D. Lilley, J. E. Lupton, and E. J. Olson. 1998. Enriched H2, CH4, 3He concentrations in hydrothermal plumes associated with the 1996 Gorda Ridge eruptive event. Deep-Sea Res. Part II Top. Stud. Oceanogr. 45: 2665–2682. doi:10.1016/S0967-0645(98)00088-5"],"Other":["Funding provided by the National Science Foundation\n\nCrossref Funder Registry ID: https://ror.org/021nxhr62\n\nAward number: 1756402"]} 

This dataset includes the concentrations of total dissolvable iron and manganese, dissolved iron and manganese, and dissolved organic iron-binding ligands collected on the PLUME RAIDERS expedition. Samples were collected during the PLUME RAIDERS cruise (RR2106) on the R/V Roger Revelle from 18 September – 6 November 2021. The main study area was located along the 16-18ºS section of the Southern East Pacific Rise, and the sampling was focused near the ride crest at depths below 1,500 m. Both the total dissolvable and dissolved iron and manganese concentrations were determined shipboard using flow injection analysis. The total organic iron-binding ligand data was generated both shipboard and in the lab using competitive ligand exchange adsorptive cathodic stripping voltammetry. The siderophore concentrations were measured following a solid phase extraction step, and then eluents were measured using inductively coupled plasma mass spectrometry. The dissolvable and dissolved metal data was generated by Dr. Joe Resing and Nathan Buck at NOAA-PMEL and the ligand and siderophore data was generated by Dr. Laura Moore and Dr. Randelle Bundy at the University of Washington. 

Abstract The North Pacific subtropical gyre is a globally important contributor to carbon uptake despite being a persistently oligotrophic ecosystem. Supply of the micronutrient iron to the upper ocean varies seasonally to episodically, and when coupled with rapid biological consumption, results in low iron concentrations. In this study, we examined changes in iron uptake rates, along with siderophore concentrations and biosynthesis potential at Station ALOHA across time (2013–2016) and depth (surface to 500 m) to observe changes in iron acquisition and internal cycling by the microbial community. The genetic potential for siderophore biosynthesis was widespread throughout the upper water column, and biosynthetic gene clusters peaked in spring and summer along with siderophore concentrations, suggesting changes in nutrient delivery, primary production, and carbon export seasonally impact iron acquisition. Dissolved iron turnover times, calculated from iron‐amended experiments in surface (15 m) and mesopelagic (300 m) waters, ranged from 9 to 252 d. The shortest average turnover times at both depths were associated with inorganic iron additions (14  9 d) and the longest with iron bound to strong siderophores (148  225 d). Uptake rates of siderophore‐bound iron were faster in mesopelagic waters than in the surface, leading to high Fe : C uptake ratios of heterotrophic bacteria in the upper mesopelagic. The rapid cycling and high demand for iron at 300 m suggest differences in microbial metabolism and iron acquisition in the mesopelagic compared to surface waters. Together, changes in siderophore production and consumption over the seasonal cycle suggest organic carbon availability impacts iron cycling at Station ALOHA. 

Transport processes along the river-ocean continuum influence delivery of nutrients, carbon and trace metals from terrestrial systems to the marine environment, impacting coastal primary productivity and water quality. Although trace metal transformations have been studied extensively in the Mississippi River Delta region of the Northern Gulf of Mexico, investigations of manganese (Mn) and the presence of ligand-stabilized, dissolved manganese (Mn(III)-L) and its role in the transformation of trace elements and organic matter during riverine transport and estuarine mixing have not been considered. This study examined the chemical speciation of dissolved and particulate Mn in the water column and sediment porewaters in the Mississippi River and Northern Gulf of Mexico in March of 2021 to explore transformations in Mn speciation along the river-ocean continuum and the impact of different processes on the distribution of Mn. Total dissolved Mn concentrations were highest in the Mississippi River and decreased offshore, while Mn(III)-L contributed most to the dissolved Mn pool in near-shore waters. Porewater profiles indicated that ligand stabilization prevented dissolved Mn(III) reduction below the depth of oxygen penetration and in the presence of equimolar dissolved iron(II). Dissolved Mn(III)-L was enriched in bottom waters at all Northern Gulf of Mexico stations, and diffusive flux modelling of porewater dissolved Mn suggested that reducing sediments were a source of dissolved Mn to the overlying water column in the form of both reduced Mn(II) and Mn(III)-L. A simple box model of the Mn cycle in the Northern Gulf of Mexico indicates that Mn(III)-L is required to balance the Mn budget in this region and is an integral, and previously unconsidered, piece of the Mn cycle in the Northern Gulf of Mexico. The presence of Mn(III)-L in this system likely has an outsized impact on trace element scavenging rates, oxidative capacity, and the carbon cycle that have not been previously appreciated. 

Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are not well-constrained by observations. Across four expeditions to the North Pacific transition zone, we document a repeated supply of isotopically light iron from an atmospheric source in spring, reflecting an estimated 39 ± 9 % anthropogenic contribution to the surface ocean iron budget. Expression of iron-stress genes in metatranscriptomes, and evidence for colimitation of ecosystem productivity by iron and nitrogen, indicates that enhanced iron supply should spur spring phytoplankton blooms, accelerating the seasonal drawdown of nitrate delivered by winter mixing. This effect is consistent with regional trends in satellite ocean color, which show a shorter, more intense spring bloom period, followed by an earlier arrival of oligotrophic conditions in summer. Continued iron emissions may contribute to poleward shifts in transitional marine ecosystems, compounding the anticipated impacts from ocean warming and stratification. 

Abstract The ocean microbe‐metabolite network involves thousands of individual metabolites that encompass a breadth of chemical diversity and biological functions. These microbial metabolites mediate biogeochemical cycles, facilitate ecological relationships, and impact ecosystem health. While analytical advancements have begun to illuminate such roles, a challenge in navigating the deluge of marine metabolomics information is to identify a subset of metabolites that have the greatest ecosystem impact. Here, we present an ecological framework to distill knowledge of fundamental metabolites that underpin marine ecosystems. We borrow terms from macroecology that describe important species, namely “dominant,” “keystone,” and “indicator” species, and apply these designations to metabolites within the ocean microbial metabolome. These selected metabolites may shape marine community structure, function, and health and provide focal points for enhanced study of microbe‐metabolite networks. Applying ecological concepts to marine metabolites provides a path to leverage metabolomics data to better describe and predict marine microbial ecosystems. 

The growth of diatoms in the Southern Ocean, especially the region surrounding the West Antarctic Peninsula, is frequently constrained by low dissolved iron and other trace metal concentrations. This challenge may be overcome by mutualisms between diatoms and co-occurring associated bacteria, in which diatoms produce organic carbon as a substrate for bacterial growth, and bacteria produce siderophores, metal-binding ligands that can supply diatoms with metals upon uptake as well as other useful secondary compounds for diatom growth like vitamins. To examine the relationships between diatoms and bacteria in the plankton (diatom) size class (> 3 µm), we sampled both bacterial and diatom community composition with accompanying environmental metadata across a naturally occurring concentration gradient of macronutrients, trace metals and siderophores at 21 stations near the West Antarctic Peninsula (WAP). Offshore Drake Passage stations had low dissolved iron (0.33 ± 0.15 nM), while the stations closer to the continental margin had higher dissolved iron (5.05 ± 1.83 nM). A similar geographic pattern was observed for macronutrients and most other trace metals measured, but there was not a clear inshore-offshore gradient in siderophore concentrations. The diatom and bacteria assemblages, determined using 18S and 16S rDNA sequencing respectively, were similar by location sampled, and variance in both assemblages was driven in part by concentrations of soluble reactive phosphorous, dissolved manganese, and dissolved copper, which were all higher near the continent. Some of the most common diatom sequence types observed were Thalassiosira and Fragilariopsis , and bacteria in the plankton size fraction were most commonly Bacteroidetes and Gammaproteobacteria. Network analysis showed positive associations between diatoms and bacteria, indicating possible in situ mutualisms through strategies such as siderophore and vitamin biosynthesis and exchange. This work furthers the understanding of how naturally occurring gradients of metals and nutrients influence diatom-bacteria interactions. Our data suggest that distinct groups of diatoms and associated bacteria are interacting under different trace metal regimes in the WAP, and that diatoms with different bacterial partners may have different modes of biologically supplied trace metals. 

Abstract Siderophores are strong iron‐binding molecules produced and utilized by microbes to acquire the limiting nutrient iron (Fe) from their surroundings. Despite their importance as a component of the iron‐binding ligand pool in seawater, data on the distribution of siderophores and the microbes that use them are limited. Here, we measured the concentrations and types of dissolved siderophores during two cruises in April 2016 and June 2017 that transited from the iron‐replete, low‐macronutrient North Pacific Subtropical Gyre through the North Pacific Transition Zone (NPTZ) to the iron‐deplete, high‐macronutrient North Pacific Subarctic Frontal Zone (SAFZ). Surface siderophore concentrations in 2017 were higher in the NPTZ (4.0–13.9 pM) than the SAFZ (1.2–5.1 pM), which may be partly attributed to stimulated siderophore production by environmental factors such as dust‐derived iron concentrations (up to 0.51 nM). Multiple types of siderophores were identified on both cruises, including ferrioxamines, amphibactins, and iron‐free forms of photoreactive siderophores, which suggest active production and use of diverse siderophores across latitude and depth. Siderophore biosynthesis and uptake genes and transcripts were widespread across latitude, and higher abundances of these genes and transcripts at higher latitudes may reflect active siderophore‐mediated iron uptake by the local bacterial community across the North Pacific. The variability in the taxonomic composition of bacterial communities that transcribe putative ferrioxamine, amphibactin, and salmochelin transporter genes at different latitudes further suggests that the microbial groups involved in active siderophore production and usage change depending on local conditions.