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Science Highlights


Some recent GEOTRACES science findings are reported below.  
When getting older they are compiled in the Science Highlights Archive where the "Title Filter" search box will allow you to filter them by words in title (please note that only one-word search queries are allowed e.g. iron, Atlantic, etc.).

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Isotopic chromium variations do not always reflect the occurrence of low oxygenated waters

Dissolved chromium (Cr) in the ocean is present under two oxidation states: The oxidized and soluble Cr (VI) and the reduced more reactive Cr (III). Reduction of Cr (VI) to Cr (III) is favored by the occurrence of biological particles, reducing conditions in the sediments or the water column (at least in the Pacific Oxygen Minimum Zones). In addition, the isotopic signature of Cr (δ53Cr representing the variation of the abundance of 53Cr relative to the lighter 52Cr) also reflects redox reactions in the water column. Based on the analyses of Cr speciation and isotopic composition of 5 profiles sampled off the Senegalese coast along the GEOTRACES transect GA06, Goring-Harford and co-workers (2018, see reference below) show that Cr(VI) is unlikely to be reduced under the low oxic conditions characterizing this area (minimal values above 44 µmol/kg). Contrastingly, they reveal that total Cr concentrations and δ53Cr are affected by biological processes and inputs from sediments on the shelf whereas deep waters are relatively unaffected by internal Cr cycling. Moreover, the authors establish that on a world basis, δ53Cr is independent from the concentration of dissolved oxygen, at least for the oxygen ranges as encountered off the Senegalese coast. This result weakens the use of δ53Cr values of ancient marine authigenic precipitates to reconstruct past changes in levels of dissolved oxygen in seawater.

18 Goring f
Figure 1:
 δ53Cr, dFe and dissolved oxygen profiles on one of the stations sampled. Low oxygen concentrations correlate with relatively high dFe concentrations, which are linked to high rates of organic matter remineralisation and high δ53Cr values, related to benthic supply of Cr (Adapted from Goring-Harford et al., 2018, by J. Klar).

Dissolved iron (dFe) and iron (Fe) isotopes were also collected off the same Senegalese coast as the Cr study above contributing to identify the processes leading to enhanced dFe concentrations (up to 2 nM) in the tropical North Atlantic Oxygen Minimum Zone. Negative δ56Fe values observed on the shelf could be attributed to input of dFe from both reductive and non-reductive dissolution of sediments. Contrastingly, when these benthic inputs are upwelled to surface waters, uptaken by the biological activity and remineralized in the twilight zone, they display high and positive δ56Fe and the proportion of this remineralized Fe to the total dFe pool increases with distance from the shelf. The difference of sensitivity to redox conditions between Cr and Fe isotopes is also underlined by this work. Thanks to the simultaneous aluminium concentrations, the authors also demonstrate that dust inputs were low at the time of the GEOTRACES GA06 section, strengthening the relative role of the benthic flux in the context of this study, although located next to the Saharan desert. 

18 3 Klar

Figure 2: δ53Cr and dFe profiles on one of the stations sampled (Adapted from Goring-Harford et al., 2018), B) Schematic interpretation of the Fe cycle in the study area. Shelf sediments supply dFe with a light isotopic composition (↓ δ56Fe) to bottom waters. dFe is supplied to the surface mixed layer (SML) by atmospheric dust deposition and upwelled bottom waters, where phytoplankton takes up dFe with a relatively heavy isotopic composition (↑ δ56Fe). Remineralisation of sinking organic material leads to the release of dFe with a relatively heavy isotopic composition, which is mixed with benthic dFe inputs and upwelled to the SML, where it is mixed with atmospheric dFe inputs. The flux of benthic dFe decreases with distance from the coast. The continuous recycling of dFe by biological uptake and remineralisation leads to increasingly heavy isotopic compositions of dFe in the water column with distance from the shelf. Atmospheric dust inputs (fluxes in μmol dFe m−2 d−1, in brown) to the SML, calculated from dAl concentrations, were low at the time of sampling but are potentially higher at other times of the year (Croot et al., 2004). Fluxes of vertical transport to the SML (white) and horizontal transport between the bottom of the SML and 500 m depth (yellow) are from Milne et al. (2017) and are in μmol dFe m−2 d−1 (Reprinted from Klar et al., 2018). Click here to view the figure larger.

Reference:

Goring-Harford, H. J., Klar, J. K., Pearce, C. R., Connelly, D. P., Achterberg, E. P., & James, R. H. (2018). Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone. Geochimica et Cosmochimica Acta, 236, 41–59. https://doi.org/10.1016/j.gca.2018.03.004

Klar, J. K., Schlosser, C., Milton, J. A., Woodward, E. M. S., Lacan, F., Parkinson, I. J., Achterberg, E.P., James, R. H. (2018). Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes. Geochimica et Cosmochimica Acta, 236, 60–78. https://doi.org/10.1016/j.gca.2018.02.031

Croot, P. L., Streu, P., Baker A.R. (2004) Short residence time for iron in surface seawater impacted by atmospheric dry deposition from Saharan dust events, Geophys. Res. Lett., 31 (2004), p. L23S08 https://doi.org/10.1029/2004GL020153

Milne, A., Schlosser, C., Wake, B.D., Achterberg, E.P., Chance, R., Baker, A.R., Forryan, A., Lohan, M.C. (2017) Particulate phases are key in controlling dissolved iron concentrations in the (sub)tropical North Atlantic Geophys. Res. Lett., 44, pp. 2377-238 https://doi.org/10.1002/2016GL072314

The Scottish shelf break is not a significant source of iron to North Atlantic surface waters

A high resolution survey of the distribution of dissolved iron (dFe) over the Hebridean (Scottish) shelf break was conducted as part of the U.K. Shelf Sea Biogeochemistry programme, a GEOTRACES process study (GApr04). Despite the close proximity to shelf sediments, which are known to supply large quantities of dFe to overlying water column, the results revealed surprisingly low concentrations of dFe (<0.1 nM) in surface waters overlying the shelf break. Birchill and colleagues (2019, see reference below) relate this to the prevailing physical circulation of the region, which limits off shelf transport in surface waters, and conclude that this shelf system is not a significant source dFe to high latitude North Atlantic surface waters. It is therefore suggested that the conditions leading to seasonal iron limitation of phytoplankton in the Iceland and Irminger basins extend much further eastwards than previously identified.

19 Birchill

Figure: (A) Map of the survey region with sampling locations. (B) Example of cross shelf transect of dFe distribution, detailing the contrast between shelf waters with high dFe concentrations (>2 nM) and surface oceanic waters with remarkably low dFe concentrations (<0.1 nM). (C) Depth profile of dFe: NO3-, oceanic stations close to Hebridean shelf have similar values to those previously reported for the seasonally iron limited Icelandic Basin. Dashed line denotes 0.05 dFe:NO3 (nM:μM), the lower limit observed in Fe replete cultured phytoplankton. Click here to view the figure larger.

Reference:

Birchill, A. J., Hartner, N. T., Kunde, K., Siemering, B., Daniels, C., González-Santana, D., Milne, A. Ussher, S. J., Worsfold, P. J., Leopold, K., Painter, S. C., Lohan, M. C. (2019). The eastern extent of seasonal iron limitation in the high latitude North Atlantic Ocean. Scientific Reports, 9(1), 1435. DOI: http://doi.org/10.1038/s41598-018-37436-3

All the bioactive elements are not affected by the land-ocean gradient of the atmospheric deposition along the Eastern Pacific Zonal Transect

Atmospheric dust is considered an important source of trace elements to the ocean. As part of the Eastern Pacific Zonal Transect GEOTRACES cruise (EPZT GP16), Buck and co-workers collected 17 (3-day integrated) aerosol samples along this transect known for its low dust input. Chemical composition and elemental ratios indicate crustal sources for aluminium (Al), titanium (Ti), vanadium (V), manganese (Mn), and iron (Fe), while the analyses suggest that copper (Cu), cadmium (Cd), and lead (Pb) originate from anthropogenic emission. The concentrations of the crustal elements show sharp decreasing gradients within approximately 750 km moving west from the coast of South America. This trend was also observed in the anthropogenic elements. Interestingly, although the highest aerosol concentrations were observed over the Peru upwelling zone, fluxes estimated using a beryllium-7 (7Be) method demonstrate that atmospheric deposition was a minor source of bioavailable iron in this area, while further offshore the relative input from the atmosphere had a greater impact on surface trace metal concentrations. This work also underlines that elemental ratios were more consistent with estimates in average Andesitic crust than in bulk upper continental crust, reinforcing the necessity to carefully consider the source material used to assess trace element enrichment.

19 Buck

Figure: (Top) This map shows the GP16 cruise track from coastal South America to French Polynesia completed during October – December 2013 and indicates the spatial coverage of each collection (alternating black and white line segments). (Bottom) We can assess whether the aerosol material originated from lithogenic sources or anthropogenic sources, i.e. from blowing soil dust or from industry, by normalizing the observed concentrations of aerosol elements to the concentration of aerosol titanium (Ti). For comparison, the ratio of upper continental crust (solid line) and Andesitic crust (dashed line) are included (Taylor and McLennan, 1995). The ratio of aerosol cadmium (Cd) to Ti was two to three orders of magnitude greater than the crustal ratio throughout the cruise section with the highest ratios observed near the coast indicating an anthropogenic source. Aerosol iron (Fe) to Ti ratios displayed a crustal character in the 750 km region characterized by relatively high dust transport but decreased with distance from the continent.

Reference:

Buck, C. S., Aguilar-Islas, A., Marsay, C., Kadko, D., & Landing, W. M. (2019). Trace element concentrations, elemental ratios, and enrichment factors observed in aerosol samples collected during the US GEOTRACES eastern Pacific Ocean transect (GP16). Chemical Geology. http://doi.org/10.1016/J.CHEMGEO.2019.01.002

Taylor, S.R., McLennan, S.M., 1995. The geochemical evolution of continental crust. Reviews of Geophysics, 33: 241-265.

Using the three thorium isotope toolbox to probe the particle dynamic within an East Pacific Rise hydrothermal plume

The insoluble radiogenic isotopes of thorium (Th) are produced at a known rate in the water column via the decay of soluble uranium (234Th, 230Th) and radium (228Th) isotopes. These three isotopes are radioactive and their half-lives vary from days (234Th) to years (228Th) to tens of thousands of years (230Th). Combining their known production and decay rates with their insolubility makes them excellent tools to study the particle dynamics on a wide range of timescales.

This toolbox was successfully used by Pavia and co-workers (2019, see reference below) to study particle-dissolved exchange within the hydrothermal plume detected during the GEOTRACES GP16 cruise in the southeast Pacific Ocean. The goal of these authors was to unravel how hydrothermal activity affects the different steps characterizing the scavenging processes, i.e. adsorption and desorption onto particles, particle aggregation, sinking, and eventual sedimentation.

Their main conclusions are that: 1) particle aggregation was occurring much more rapidly in the plume, 2) hydrothermal scavenging is partially irreversible, 3) off-axis hydrothermal Th scavenging rate of 0.15yr−1, value deduced from a modelling and 4) 230Th is surprisingly more depleted than the two other isotopes. This likely reflects progressive scavenging in this region of intense hydrothermal activity and underlines the complexity of interpreting the GP16 hydrothermal plume as being solely a local phenomenon.

19 Pavia

Figure: Depletion observed in three thorium isotopes in the hydrothermal plume observed downstream of the East Pacific Rise on the GEOTRACES GP16 section in the South Pacific Ocean. Plots A), B), and C) show the depletion in each thorium isotope at stations 18 (closest to the ridge axis) to station 21 (furthest from the ridge axis). The depletion increases with increasing half-life of thorium isotope, going from 234Th (half-life = 24.1 days) showing the least depletion, followed by 228Th (half-life = 1.91 years), with 230Th (half-life = 75,587 years) the most depleted. D) Shows the map of the study area, with solid white arrows proportional to current speeds at the plume depth of 2500m, and the white dashed arrow displaying the proposed flowpath of the hydrothermal plume observed in the study, along which thorium is progressively removed from the deep ocean. Click here to view the figure larger.

Reference:

Pavia, F. J., Anderson, R. F., Black, E. E., Kipp, L. E., Vivancos, S. M., Fleisher, M. Q., Charette, M. A., Sanial, V., Moore, W. S., Hult, M., Lu, Y., Cheng, H., Zhang, P., Edwards, R. L. (2019). Timescales of hydrothermal scavenging in the South Pacific Ocean from 234Th, 230Th, and 228Th. Earth and Planetary Science Letters, 506, 146–156. DOI: http://doi.org/10.1016/J.EPSL.2018.10.038

The circulation loop in the North Atlantic and Arctic oceans depicted by the artificial radionuclides

Three articles from three cruises highlighted here!

Atlantic waters have been recently recognized to play an increasing role in reducing sea-ice extent in the Arctic Ocean at a rate now comparable to losses from atmospheric thermodynamic forcing. Beyond the Arctic Ocean, the water mass transport and transformation processes in the North Atlantic Ocean substantially contribute to the Atlantic meridional overturning circulation (AMOC). Artificial radionuclides can be used as transient tracers that provide crucial information on pathways, timescales and processes of key water masses that cannot be obtained from hydrographic properties alone. In particular, radionuclides released from the two European Nuclear Reprocessing Plants, have proven to be specifically useful to trace the circulation of Atlantic waters into the Arctic and sub-Arctic oceans. Within this context, the three recent articles by Castrillejo et al. (2018), Wefing et al. (2019) and Casacuberta et al. (2018, see references below) describe the journey of the two long-lived anthropogenic radionuclides iodine-129 (129I; T1/2=15.7 · 106 y) and uranium-236 (236U; T1/2=23.4 · 106 y) from their sources through the Arctic Ocean and into the North Atlantic Ocean. Each paper corresponds to one GEOTRACES expedition that took place between 2014 and 2016 in the North Atlantic Ocean (GA01 section), Arctic Ocean (GN04 section) and Fram Strait (GN05 section). Main results show that the combination of 129I and 236U serves very well to identify the different Atlantic branches entering the Arctic Ocean: Barents Sea Branch Water (BSBW) and Fram Strait Branch Water (FSBW). Due to the uneven mixing of 129I and 236U from the two European Reprocessing Plants of Sellafield and La Hague in the North Sea, each branch brings a different 129I/236U ratio. Furthermore, this ratio allowed identifying a third Atlantic branch evolving from the Norwegian Coastal Current (NCC), that stays within the upper Polar Mixed Layer and carries a significantly larger proportion of 129I and 236U releases from the European reprocessing plants compared to the FSBW and the BSBW. The evolution of the NCC with a strong 129I and 236U signal is further observed when it returns to the Atlantic Ocean as Polar Surface Water (PSW) in the Fram Strait. This allowed estimating a transit time of 15-22 years for the PSW flowing through the Arctic Ocean. In the subpolar North Atlantic Ocean (SPNA), an increase of 129I was observed in the deep overflow waters in the Labrador and Irminger Seas, confirming the major pathways of Atlantic Waters in the SPNA that were previously suggested by other authors: a short loop through the Nordic seas into the SPNA (8-10 years) and a longer one, which includes all the way through the Arctic Ocean (>16 years). The output of these works proves the potential of using 129I and 236U as a tool for investigations on the circulation within and exchanges between the Arctic and sub-Arctic Seas.

19 Casacuberta

Figure: (Left) Map showing the main Atlantic water circulation in the North Atlantic and Arctic oceans (black arrows). Dashed lines represent the three GEOTRACES sections sampled between 2014 and 2016: North Atlantic Ocean (GA01), Arctic Ocean (GN04) and Fram Strait (GN05). Both 129I and 236U are released from the two European Reprocessing Plants of Sellafield and La Hague (purple stars). Blue triangles represent the 129I/236U atom ratios (in red) at sampling time and the transit time of Atlantic waters (in blue) from their source in the North Sea, to the sampling location. (Right) Section plots of 129I/236U atom ratio in the three GEOTRACES sections, with black contour lines representing potential temperature. Click here to view the image larger.

References:

Casacuberta, N., Christl, M., Vockenhuber, C., Wefing, A.-M., Wacker, L., Masqué, P., Synal, H.-A., Rutgers van der Loeff, M. (2018). Tracing the Three Atlantic Branches Entering the Arctic Ocean With 129I and 236U. Journal of Geophysical Research: Oceans, 123(9), 6909–6921. DOI: http://doi.org/10.1029/2018JC014168

Castrillejo, M., Casacuberta, N., Christl, M., Vockenhuber, C., Synal, H.-A., García-Ibáñez, M. I., Lherminier, P., Sarthou, G., Garcia-Orellana, J., Masqué, P. (2018). Tracing water masses with 129I and 236U in the subpolar North Atlantic along the GEOTRACES GA01 section. Biogeosciences, 15(18), 5545–5564. DOI: http://doi.org/10.5194/bg-15-5545-2018

Wefing, A.-M., Christl, M., Vockenhuber, C., van der Loeff, M. R., & Casacuberta, N. (2019). Tracing Atlantic waters using 129 I and 236 U in the Fram Strait in 2016. Journal of Geophysical Research: Oceans. DOI: http://doi.org/10.1029/2018JC014399

Artificial intelligence helps investigate the oceanic zinc cycle

What explains the hitherto mysterious correlation between zinc (Zn) and silicon, an element not involved in the Zn cycle?

Roshan and co-workers (2018, see reference below) used an artificial neural network (ANN, a machine learning technique inspired by biological neural systems) to produce a global climatology of dissolved Zn concentration, the first such global climatology of a trace metal. They first used an ensemble of ANNs to produce climatological maps of dissolved Zn with the same spatial resolution as the World Ocean Atlas 2013 (WOA13) and then coupled these dissolved Zn maps, and those of phosphate (PO43-) and silicate (SiO44-) from WOA13, to a data-constrained ocean circulation model. They then employed a restoring model to compute the biogeochemical sources and sinks of dissolved Zn, PO43- and SiO44. The main results are:

  • The Zn: PO43- uptake ratio varies by approximately tenfold across latitude and is modulated by Fe availability;
  • Zn remineralizes like PO43- in the upper ocean, but its accumulation in deep waters exceeds that of PO43-;
  • The strong Zn-SiO44- correlation is caused by a combination of surface uptake, desorption from particles, and hydrothermal input, and is therefore completely fortuitous.

19 Roshan

Figure: This schematic shows the reconstructed internal particle-associated cycling of zinc (Zn) in the ocean, as well as some recent estimates of the external sources and sinks of Zn. Funnels represent fluxes of particulate zinc (pink; in giga mol/yr), silicon (green; in tera mol/yr) and phosphorous (cyan; in tera mol/yr), which are biologically-produced in the sunlit surface ocean and exported to the subsurface. In the subsurface, the fluxes gradually attenuate due to degradation/dissolution. Particulate zinc flux attenuates quickly like particulate phosphorus, meaning that these two compounds are associated with labile soft tissues of plankton and re-enter water column at shallower depths than silicon, which is a hard-tissue compound. However, a significant amount of dissolved zinc is supplied to the deep ocean (below 2,000 m; 0.1-2.5 giga mol/yr), which is most likely resulted from a combination of seafloor hydrothermal input and desorption of the zinc ions that are passively adsorbed on the particles at shallower depths. Circles represent the mean dissolved concentrations of the above three compounds at depths below 2,000 m of different regions, which indicate that the mentioned excess input of zinc makes its deep ocean increasing trend (according to water flow arrows) more similar to silicon than phosphorous, and eventually leads to a coincidental zinc-silicon correlation in the ocean. Also annotated are some estimates of the zinc input from rivers and dust, and those of removal to deep and shelf sediments. Click here to view the figure larger.

Reference:

Roshan, S., DeVries, T., Wu, J., & Chen, G. (2018). The Internal Cycling of Zinc in the Ocean. Global Biogeochemical Cycles, 32(12), 1833-1849. DOI:  http://doi.org/10.1029/2018GB006045

Cadmium isotopes, tracers of the cadmium sequestration as cadmium sulphide in oxygen minimum zone?

The linear relationship between the seawater cadmium and phosphate dissolved concentrations lead to use the cadmium/calcium (Cd/Ca) imprinted in calcareous archives to reconstruct the past phosphate (PO4) distributions. However, variations in the Cd/PO4 ratio between different water masses and within vertical oceanic profiles were recently identified. Among the processes that could explain these variations, sequestration of Cd into sulphide phases in microenvironments within sinking biogenic particles has been suggested as a mechanism for Cd depletion (Figure C). Guinoiseau and co-workers (2018, see reference below) experimentally tested if the cadmium sulphide (CdS) precipitation results in a fractionation of Cd isotopes. These experiments were conducted under low oxygen condition, in fresh and salty water, with variable cadmium/sulphide ratios… and they demonstrate, for the first time, an enrichment of light Cd isotopes in the precipitated CdS (Figure A) and a decrease in the fractionation factor (αCdsolution–CdS) with increasing salinity. The fractionation factor between CdS and the seawater matches remarkably the Cd isotope shift observed in modern oceanic oxygen minimum zone (Figure B). In other words, this work proposes that Cd isotopes are interesting tracers of the sequestration of Cd as CdS in low oxygen environment.

18 Guinoiseau

Figure: Identification of cadmium sulphide (CdS) precipitates as an important Cd sequestration process in the ocean. A) Determination of Cd isotope fractionation (αCdsolution-CdS in the figure) during precipitation of CdS in seawater matrix. B) Agreement between the experimental fractionation factor and the seawater isotope data recorded in oxygen minimum zone (OMZ) where CdS is prone to precipitate. C) Schematic view of CdS process occurring within sinking biogenic particles. Click here to view the figure larger.

Reference:

Guinoiseau, D., Galer, S. J. G., & Abouchami, W. (2018). Effect of cadmium sulphide precipitation on the partitioning of Cd isotopes: Implications for the oceanic Cd cycle. Earth and Planetary Science Letters, 498, 300–308. DOI: http://doi.org/10.1016/J.EPSL.2018.06.039

New BioGEOTRACES data sets: Connecting pieces of the microbial biogeochemical puzzle

Microorganisms play a central role in the transfer of matter and energy in the marine food web. Microbes depend on micronutrients (e.g. iron, cobalt, zinc, and a host of other trace metals) to catalyze key biogeochemical reactions, and their metabolisms, in turn, directly affect the cycling, speciation, and bioavailability of these compounds. One might therefore expect that marine microbial community structure and the functions encoded within their genomes might be related to trace metal availability in the ocean. The overall productivity of marine ecosystems—i.e. the amount of carbon fixed through photosynthesis—could in turn be influenced by trace metal concentrations.

For over a decade, the international GEOTRACES programme has been mapping the distribution and speciation of trace metals across vast ocean regions. Given the important relationship between trace metals and the function of marine ecosystems, biological oceanographers collaborate with GEOTRACES scientists to simultaneously probe the biotic communities at some sampling sites, allowing these biological data to be interpreted in the context of detailed chemical and physical measurements.

Two recent papers published in Scientific Data (see references below) describes two new, large-scale biological data sets that will facilitate studies aimed at understanding how microbes and metals relate to one another. Collected on four different sets of GEOTRACES cruises (see figure below), these papers report the public availability of hundreds of single cell genomes and microbial community metagenomes from the Pacific and Atlantic Oceans. The single cell genomes focus on the marine photosynthetic bacteria Prochlorococcus and Synechococcus and how they and other community members vary in different regions of the ocean. The metagenomic sequences provide snapshots of the entire microbial community found in each of these samples, yielding a broad overview of which microbes—and which genes, including those important for understanding nutrient cycling—are found in each sample. These two datasets are complementary and further enhanced by the wealth of chemical and physical data collected by GEOTRACES scientists on the same water samples. In particular, iron is of key interest, since it often limits primary productivity. These data sets can directly link iron availability with microbial community structure and gene content across ocean basins.

With these data, researchers can now ask questions such as how microbes have evolved in response to the availability or limitation of key nutrients and explore which organisms may be contributing to biogeochemical cycles in different parts of the global ocean. The extensive suite of chemical and physical measurements associated with these sequence data underscore their potential to reveal important relationships between trace metals and the microbial communities that drive biogeochemical cycles. These data sets also encourage cross-disciplinary collaborations and provide baseline information as society faces the challenges and uncertainties of a changing climate.

18 BerubeFigure: Locations and depths of samples. (a) Global map of sample locations. Single cell genomes are represented by miniaturized stacked dot-plots (each dot represents one single cell genome), with organism group indicated by color, and cells categorized as “undetermined” if robust placement within known phylogenetic groups failed due to low assembly completeness/quality or missing close references. Larger points correspond to stations on associated GEOTRACES sections where metagenomes were also collected. (b) Depth distribution of metagenome samples along each of the four GEOTRACES sections. Transect distances are calculated relative to the first station sampled in the indicated orientation. For clarity, the depth distribution of samples collected below 250 m are not shown to scale (ranging from 281–5601 m). Adapted from Berube et al. (2018) Sci. Data 5:180154 and Biller et al. (2018) Sci. Data 5:180176. Click here to view the figure larger.

Authors:  Paul M. Berube (Massachusetts Institute of Technology), Steven J. Biller (Massachusetts Institute of Technology; current affiliation: Wellesley College) and Sallie W. Chisholm (Massachusetts Institute of Technology).

Published on Ocean Carbon & Biogeochemistry (OCB)  December 2018 Newsletter.

References:

Berube, P. M. et al. (2018). Single cell genomes of Prochlorococcus, Synechococcus, and sympatric microbes from diverse marine environments. Scientific Data, 5, 180154. http://doi.org/10.1038/sdata.2018.154

Biller, S. J.,et al. (2018). Marine microbial metagenomes sampled across space and time. Scientific Data, 5, 180176. http://doi.org/10.1038/sdata.2018.176

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