Trace elements at the intersection of marine biological and geochemical evolution

In the paper

“This work suggests that the utilization of trace metals in biology generally follows the pattern of Fe >> Zn > Mn >> Mo, Co, Cu >> Ni > W, V.”

What the sources say

• Partly supported

  The section “Comparing Model Metallomes from Modern Genome Sequences” gives essentially the stated hierarchy, grouping Mo, Co, and Cu together. It describes this as a result for prokaryotes analyzed as a group, however, not for biology as a whole. (LLM, conf=0.84)

  cites Zerkle et al., 2005 sourceExperimental — accuracy not yet measured

In the paper

“The Co/Ti trend shows an expansion of authigenic Co enrichments in iron formations between ~2.8-1.8Ga.”

What the sources say

• Not checked yetcites Swanner et al. (2014) source

In the paper

“In several instances, fundamental differences between thermodynamic based solubility models and the sedimentary proxy record highlight the need for a multi-disciplinary approach when evaluating paleomarine trace element abundances.”

In the paper

“A unidirectional decline in molar Ni/Fe is stark and robust.”

In the paper

“(4) a direct relationship between concentrations in organic-rich sediments and dissolved concentrations in overlying anoxic and sulfidic bottom waters has been demonstrated for some trace elements (e.g., Mo, Zn; Algeo and Lyons, 2006;Scott et al., 2013).”

What the sources say

• Not checked yetcites Algeo and Lyons, 2006 source
• Not checked yetcites Scott et al., 2013 source

In the paper

“By contrast, iron would have been much more abundant in surface waters on a more reducing Earth when basic microbial metabolic machinery was being established (e.g., Poulton and Canfield, 2011;David and Alm, 2011).”

What the sources say

• Not checked yetcites Poulton and Canfield, 2011 source
• Not checked yetcites David and Alm, 2011

In the paper

“Despite these challenges, however, there is a growing consensus that favors an origin of life on Earth before ~3.5 Ga, and perhaps much earlier.”

In the paper

“For reasons still debated, complex animal life did not evolve until almost three billion years later in the Neoproterozoic (e.g., Pecoits et al., 2012).”

What the sources say

• Not checked yetcites Pecoits et al., 2012 source

In the paper

“(3) several trace elements (e.g., Mo, U) are known to scale with organic carbon during deposition and burial in euxinic water columns (Algeo and Lyons, 2006)”

What the sources say

• Not checked yetcites Algeo and Lyons, 2006 source

In the paper

“The idea that an organism's trace element requirements are dependent on the environment in which it evolved stems from the simple observation that the biogeochemical cycling of many bioessential elements can vary dramatically under different aqueous conditions (see also Williams and Rickaby, 2012).”

What the sources say

• Not checked yetcites Williams and Rickaby, 2012

In the paper

“Therefore, it is thought that their chemical composition directly reflects availability in the water column at the time of mineral precipitation and deposition.”

In the paper

“The IF and shale trace element records published to date generally support the idea that redox chemistry played a central role in the evolution of marine elemental cycling, with two particular events standing out: the Great Oxidation Event (GOE) ~2.4 billion years ago (Ga), and the Neoproterozoic oxygenation event (NOE) ~0.7 Ga.”

In the paper

“As iron-and silica-rich chemical sedimentary deposits, IF have proven useful because the trace metal content in the least metamorphosed units are almost entirely derived from seawater (see Bjerrum and Canfield, 2002;Konhauser et al., 2007;2009;2015;Robbins et al., 2013).”

What the sources say

• Not checked yetcites Bjerrum and Canfield, 2002 source
• Not checked yetcites Konhauser et al., 2007 source
• Not checked yetcites Robbins et al., 2013 source

In the paper

“Following the evolution of stem group eukaryotes in the early mid-Proterozoic (Butterfield, 2000;Knoll, 2014), there is a relatively static period in eukaryotic diversity lasting from 1.8 to 0.8 Ga.”

What the sources say

• Not checked yetcites Butterfield, 2000 source
• Not checked yetcites Knoll, 2014 source

In the paper

“that effectively disappeared from the sedimentary record between 2.45 and 2.32 Ga (e.g., Bekker et al., 2004;Farquhar et al., 2000;2011).”

What the sources say

• Not checked yetcites Bekker et al., 2004 source
• Not checked yetcites Farquhar et al., 2000 source
• Not checked yetcites Farquhar et al., 2011 source

In the paper

“In this light, some trace element limitations observed in the modern ocean might be thought of as an evolutionary legacy of earlier life adapted to more replete conditions.”

In the paper

“Thus, modern iron demand can be thought of as an evolutionary relict, stemming from the emergence of lineages under ancient environmental conditions of relative Fe abundance.”

In the paper

“(2) they provide a more continuous temporal record since shale is relatively common in the geologic record”

In the paper

“Another powerful source of information is the shale record, especially organic matter-rich, fine-grained, siliciclastics (with >0.5 wt% total organic carbon, TOC), which are attractive because (1) they have modern analogues in anoxic basins (e.g., Black Sea, Cariaco Basin)”

In the paper

“Recent studies based on the trace element proxies of Cr and U, as indicators for continental oxidative weathering have pushed the onset of the GOE back to 2.48-2.47Ga (Konhauser et al. (2011) and Partin et al. (2013a), respectively.”

What the sources say

• Not checked yetcites Konhauser et al., 2011 source
• Not checked yetcites Partin et al., 2013a

In the paper

“As well, Moore et al. (2013) have highlighted spatial heterogeneity on a global scale in surface waters with regards to both major limiting nutrients such as nitrate or phosphate, as well as trace metals.”

What the sources say

• Not checked yetcites Moore et al., 2013 source

In the paper

“Much of the current work focused on trace element proxy records (Fig. 3) has been inspired by the idea that trace metal biolimitation may have been significantly different in the deep past (Javaux et al., 2001;Anbar and Knoll, 2002).”

What the sources say

• Not checked yetcites Javaux et al., 2001 source
• Not checked yetcites Anbar and Knoll, 2002 source

In the paper

“In Anbar and Knoll's (2002) 'bio-inorganic bridge', changes in early ocean redox chemistry directly affected the bioavailability of trace elements and, in turn, the evolutionary trajectory of life.”

What the sources say

• Not checked yetcites Anbar and Knoll, 2002 source

In the paper

“Inverse modeling based on the utilization of trace elements in metalloenzymes (Zerkle et al., 2005) further supports a strong linkage between evolving ocean chemistry and biological trace element dependency.”

What the sources say

• Not checked yetcites Zerkle et al., 2005 source

In the paper

“Indeed, the genomic record for several trace metals has been linked to evolving marine geochemistry.”

In the paper

“although Zerkle et al. (2006) and Glass et al. (2009) have both shown that very low Mo concentrations are capable of supporting near modern levels of nitrogen fixation.”

What the sources say

• Not checked yetcites Zerkle et al., 2006 source
• Not checked yetcites Glass et al., 2009 source

In the paper

“The models of Saito et al. (2003) support the hypothesis that modern cyanobacterial trace element nutrient requirements may be viewed as the direct result of their early evolution in ancient oceans limited in certain trace elements (Cu, Cd, Zn) and enriched in others (Fe, Mn, Co, Ni).”

What the sources say

• Not checked yetcites Saito et al., 2003 source

In the paper

“These authors also found that if Proterozoic oceans were characterized by expanded euxinia (e.g., Canfield, 1998), many of these trace elements (e.g., Cd, Cu, Zn) could have been drawn down to concentrations that were biolimiting.”

What the sources say

• Not checked yetcites Canfield, 1998 source

In the paper

“As nitrogenases containing a Mo-Fe metal cofactor are more efficient than alternative Fe-Fe and V-Fe versions (Eady, 1996), low Mo concentrations would have negatively impacted the ability of primary producers to fix N2.”

What the sources say

• Not checked yetcites Eady, 1996 source

In the paper

“These limitations, in turn, would have effectively attenuated the carbon and oxygen fluxes from the biosphere prior to the extensive oxygenation of the deep oceans in the late Neoproterozoic.”

In the paper

“However, recent studies have suggested that the link between trace element availability, utilization, and metallome requirements may have been more complex.”

In the paper

“Under more oxic conditions first observed in the Cryogenian and continuing to develop into the Cambrian-Ordovician (Large et al., 2014;Sperling et al., 2015;Sahoo et al., 2016), the models of Saito et al. (2003) indicated that Fe and Mn concentrations in seawater would have been drawn down to modern levels as the result of oxide mineral precipitation.”

What the sources say

• Not checked yetcites Large et al., 2014 source
• Not checked yetcites Sperling et al., 2015 source
• Not checked yetcites Sahoo et al., 2016 source

In the paper

“In the case of Zn, the records of enrichments in both black shales and IFs suggest that the size of the oceanic Zn reservoir has been relatively constant since the Archean (Scott et al., 2013;Robbins et al., 2013).”

What the sources say

• Not checked yetcites Scott et al., 2013 source
• Not checked yetcites Robbins et al., 2013 source

In the paper

“Following increasing oxygenation in late Neoproterozoic (Canfield et al., 2007;Scott et al., 2008;Sahoo et al., 2012;Lyons et al., 2014a, Planavsky et al., 2014a;Sahoo et al., 2016), these sulfide complexes would have become less abundant, resulting in greater availability of Cd, Cu, and Zn.”

What the sources say

• Not checked yetcites Canfield et al., 2007
• Not checked yetcites Scott et al., 2008 source
• Not checked yetcites Sahoo et al., 2012 source

In the paper

“Links between the chemical evolution of the early oceans and the trace element complement of organisms are also informed by the emergence or disappearance of metalbinding protein fold families (FF) or fold super families (FSF).”

In the paper

“The loss or gain of these FF or FSF can be viewed as key evolutionary events that in many cases appear to track fundamental shifts in paleomarine redox chemistry (Dupont et al., 2006;2010).”

What the sources say

• Not checked yetcites Dupont et al., 2006 source
• Not checked yetcites Dupont et al., 2010 source

In the paper

“For many elements, seawater abundances are subject to kinetic controls (e.g., Broecker, 1971) where the dissolved reservoir scales with input/output fluxes without approaching solubility limits.”

What the sources say

• Not checked yetcites Broecker, 1971 source

In the paper

“Third, trace metal concentrations do have an upper limit, after which they become toxic as opposed to being beneficial for the organism.”

In the paper

“Given our knowledge regarding spatial variation both in modern oceans and as recorded by the sedimentary record, the assumption of a homogenous ocean is certainly incorrect.”

In the paper

“recent experimental work using diagenetic capsule experiments (Robbins et al., 2015) demonstrated limited mobility for Ni and Zn during simulated diagenetic treatments at high temperature and pressure that capture the transformation from ferrihydrite to hematite.”

What the sources say

• Not checked yetcites Robbins et al., 2015 source

In the paper

“Indeed, Glass and Orphan (2012) discuss how the production of methane can be stimulated by the addition of 0.2-2 µM of trace metals such as Fe, Cu, or Mo to some methanogen communities.”

What the sources say

• Not checked yetcites Glass and Orphan, 2012

In the paper

“A recent assessment of a compilation of Fe speciation data suggests that bottom waters may have remained ferruginous well into the Paleozoic (Sperling et al., 2015).”

What the sources say

• Not checked yetcites Sperling et al., 2015 source

In the paper

“The disappearance of S-MIF is perhaps the most accepted evidence for the onset of widespread and permanent oxygenation of the Earth's surface to levels above 10 -5 times present atmospheric levels (PAL) (see Pavlov and Kasting, 2002;Bekker et al., 2004;Farquhar et al., 2000;2011).”

What the sources say

• Not checked yetcites Pavlov and Kasting, 2002 source
• Not checked yetcites Bekker et al., 2004 source
• Not checked yetcites Farquhar et al., 2000 source

In the paper

“Further, studies of ancient environments have already shown that there can be basin scale differences in water column chemistry that as the result of stratification with depth or proximity to shoreline (e.g., Poulton et al., 2010).”

What the sources say

• Not checked yetcites Poulton et al., 2010 source

In the paper

“In modern marine environments, Morel and Price (2003) have demonstrated how plankton are able to utilize very low levels of trace metals via complexing ligands that likely evolved to be highly efficient at extracting low levels of these micronutrients from seawater.”

What the sources say

• Not checked yetcites Morel and Price, 2003

In the paper

“The ratio of Fe in highly reactive phases (the sum of the four aforementioned phases) to total Fe effectively diagnoses sediment deposition from anoxic water column settings.”

In the paper

“Combining this further with the ratio of pyrite extractable Fe to highly reactive Fe allows samples deemed anoxic to be further categorized as ferruginous or euxinic.”

In the paper

“the surface complexation modeling (SCM) approach, grounded in equilibrium thermodynamics through mass action expressions, has been extended beyond minerals to successfully model trace metal adsorption onto microbial surfaces (Fein et al., 1997(Fein et al., , 2005)), including marine cyanobacteria (Liu et al., 2015) and anoxygenic photosynthesizers (Martinez et al., 2016).”

What the sources say

• Not checked yetcites Fein et al., 1997 source
• Not checked yetcites Liu et al., 2015 source
• Not checked yetcites Martinez et al., 2016 source

In the paper

“Below this threshold, photolytic reactions between ultraviolet rays and sulfur gases in the atmosphere produce isotopic anomalies that deviate from mass dependent behavior and are subsequently recorded in marine sedimentary rocks.”

In the paper

“Second, most prokaryotes and single celled eukaryotes seem to favor trace metal concentrations on the order of nM to µM levels.”

In the paper

“Finally, given the low levels of trace metals in modern oceans, organisms have had to develop strategies for dealing with the possibility of micronutrient limitation (e.g., Morel and Price, 2003;Morel, 2008).”

What the sources say

• Not checked yetcites Morel and Price, 2003
• Not checked yetcites Morel, 2008 source

In the paper

“Second, and perhaps more important for the purposes of this review, even if the metals themselves do not have a direct biological role (i.e., Cr as opposed to Mo), they shed light on the production and trajectory of oxygen in the water column.”

In the paper

“Deposition of IF appears tied to periods of enhanced magmatic and hydrothermal activity (associated with large igneous province emplacement; Isley and Abbot, 1999) that delivered large amounts of ferrous iron to anoxic deep oceans (Bekker et al., 2010;2014).”

What the sources say

• Not checked yetcites Isley and Abbot, 1999
• Not checked yetcites Bekker et al., 2010 source
• Not checked yetcites Bekker et al., 2014

In the paper

“Phosphorus is typically considered to be the limiting nutrient for marine productivity on geologic time scales (Tyrell, 1999).”

What the sources say

• Not checked yetcites Tyrell, 1999 source

In the paper

“Collectively, these considerations suggest that the use of modern hydrothermal exhalites to extend the IF record is justified.”

In the paper

“These processes can alter carbonate δ 13 C and δ 18 O, as well as the trace element compositions (e.g., Schrag et al., 2013;Swart and Kennedy, 2012), limiting their use for paleoenvironmental proxies.”

What the sources say

• Not checked yetcites Schrag et al., 2013 source
• Not checked yetcites Swart and Kennedy, 2012

In the paper

“Overall, the Phanerozoic shale studies of P highlight the potential power of the black shale record in elucidating temporal trends in P availability.”

In the paper

“This strong coupling of P and Fe during burial suggests that the black shale record in deep time can be used to distinguish anoxic/nonsulfidic versus euxinic deposition.”

In the paper

“Due to strong biological scavenging and sorption to Fe oxyhydroxides, P is typically present at fairly low concentrations in seawater (0.001-3.5 µM; Bruland and Lohan (2003)).”

What the sources say

• Not checked yetcites Bruland and Lohan (2003)

In the paper

“Carbonate rocks can also capture and preserve records of ancient marine chemistry.”

In the paper

“If black shales can independently be determined to have been deposited under specific redox conditions (by Fe speciation), the degree of metal enrichment (Mo, U, Re, V, Cr) can then be used to track first order shifts in metal concentrations and the global marine redox state (Emerson and Huested, 1991;Lyons et al., 2009).”

What the sources say

• Not checked yetcites Emerson and Huested, 1991
• Not checked yetcites Lyons et al., 2009 source

In the paper

“As with the black shale and IF records, the greatest value of the pyrite record likely lies in its ability to produce broad first-order trends.”

In the paper

“As these partitioning scenarios are sensitive to matrix effects, such as different Si concentrations (e.g., Konhauser et al. (2007Konhauser et al. ( , 2009) ) and the presence of additional cations, (Jones et al. (2015), see also section 4.1), they cannot be directly equated.”

What the sources say

• Not checked yetcites Konhauser et al. (2007 source
• Not checked yetcites Jones et al. (2015 source

In the paper

“the dominant marine redox condition is the primary control on the size of the dissolved ocean inventory of redox sensitive elements (Emerson and Huested, 1991)”

What the sources say

• Not checked yetcites Emerson and Huested, 1991

In the paper

“In general, the most important hurdle for any carbonate-specific redox proxy is a thorough understanding of the behavior of the proxy during marine, meteoric, and burial diagenesis.”

In the paper

“For some trace elements, the black shale record provides valuable independent information about the evolution of seawater trace element reservoirs, such as Zn, complementing the IF record (c.f.Scott et al., 2013 andRobbins et al., 2013).”

What the sources say

• Not checked yetcites Scott et al., 2013 source
• Not checked yetcites Robbins et al., 2013 source

In the paper

“Trace element abundances themselves may also help resolve primary versus secondary signals preserved in cherts (Baldwin et al. 2011;Marin-Carbonne et al., 2014).”

What the sources say

• Not checked yetcites Baldwin et al. 2011 source
• Not checked yetcites Marin-Carbonne et al., 2014 source

In the paper

“the marine metal reservoir exerts a first order control on enrichments in euxinic and anoxic sediments (Algeo and Lyons, 2006;Lyons et al., 2009;Scott et al., 2008;Reinhard et al., 2013b).”

What the sources say

• Not checked yetcites Algeo and Lyons, 2006 source
• Not checked yetcites Lyons et al., 2009 source
• Not checked yetcites Scott et al., 2008 source

In the paper

“A temporal compilation of metal enrichments from black shales deposited in sedimentary basins with relatively unrestricted connection to the open ocean should therefore reveal the evolution of seawater metal reservoirs through time.”

In the paper

“Tribovillard et al. (2006) indicated that unless black shales are exposed to an influx of oxidizing agents after deposition, a number of trace elements commonly associated with sulfides should remain relatively immobile during diagenesis; these include Mo, Zn, Ni, and Co, amongst others.”

What the sources say

• Not checked yetcites Tribovillard et al. (2006) source

In the paper

“A final limitation on the use of the IF record is the lack of direct modern analogues.”

In the paper

“Those authors suggested that in the same way that hydrothermal pyrite can track the chemistry of ore-forming fluids (Large et al., 2009), syngenetic to early diagenetic pyrite can track changes in seawater composition.”

What the sources say

• Not checked yetcites Large et al., 2009 source

In the paper

“By contrast, organic-rich black shales deposited under anoxic and sulfidic pore waters may become enriched in redox-sensitive trace metals, especially Mo (Algeo and Lyons, 2006;März et al., 2008;Scott and Lyons, 2012).”

What the sources say

• Not checked yetcites Algeo and Lyons, 2006 source
• Not checked yetcites März et al., 2008
• Not checked yetcites Scott and Lyons, 2012 source

In the paper

“Such hydrothermal deposits provide an opportunity to test experimental and hypothesized partitioning scenarios for trace elements onto IF-but only to a limited extent.”

In the paper

“Large et al. (2014) also provided an assessment of the importance of pyrite versus matrix trace element incorporation, sulfide recrystallization, and the location in the water column or sediment where pyrite forms, which suggest the record is favorable to recording seawater signatures; a result further supported by several additional studies (Gregory et al., 2014;Large et al., 2015;Mukherjee and”

What the sources say

• Not checked yetcites Large et al., 2014 source
• Not checked yetcites Gregory et al., 2014 source
• Not checked yetcites Large et al., 2015 source

In the paper

“Algeo and Lyons (2006) showed that the dissolved Mo concentration in euxinic bottom waters is proportional to the observed Mo/TOC ratios in the underlying organic-rich sediments.”

What the sources say

• Not checked yetcites Algeo and Lyons (2006) source

In the paper

“sedimentary Fe speciation analysis (Poulton and Canfield, 2005) serves as an indicator of local paleoredox conditions on the ocean floor (i.e., oxic; anoxic, ferruginous; or euxinic) (e.g., Poulton et al., 2004;Canfield et al., 2007;2008;Lyons et al., 2009;Reinhard et al., 2009;Poulton et al., 2010;Planavsky et al., 2011;Asael et al., 2013).”

What the sources say

• Not checked yetcites Poulton and Canfield, 2005
• Not checked yetcites Poulton et al., 2004 source
• Not checked yetcites Canfield et al., 2007

In the paper

“A recent compilation of Mo isotope data for euxinic black shales also reveals that significant oscillations in ocean redox conditions, and hence the seawater Mo inventory, may have occurred across the Precambrian-Phanerozoic transition before the advent of permanent widespread ocean oxygenation”

What the sources say

• Not checked yetcites Dahl et al., 2010 source
• Not checked yetcites Kendall et al., 2015a
• Not checked yetcites Sahoo et al., 2016 source

In the paper

“Similar Mo isotope signatures for expanded ocean euxinia have also been documented from Neoproterozoic black shales, including the ~750 Ma Walcott Member of the Chuar Group, Grand Canyon (Dahl et al., 2011) and the ca.640 Ma Black River Dolomite (Kendall et al., 2015a).”

What the sources say

• Not checked yetcites Dahl et al., 2011 source
• Not checked yetcites Kendall et al., 2015a

In the paper

“Essentially, in order to record a seawater signature, a critical level of at least 11 µmol L -1 H2S(aq) is required.”

In the paper

“Regardless, changes in the paleomarine Ni reservoir would likely have had profound impacts on the Precambrian biosphere.”

In the paper

“An observation that supports this assertion is the high Ni and Co values observed in pyrites in the Late Permian (Large et al., 2014), in which case the Ni and Co may be associated with the Siberian traps volcanism and Permian mass extinction”

What the sources say

• Not checked yetcites Large et al., 2014 source
• Not checked yetcites Rothman et al., 2014 source

In the paper

“It is not until ca.560 Ma that seawater Mo isotope compositions similar to modern seawater are first inferred from the sedimentary rock record”

What the sources say

• Not checked yetcites Sahoo et al., 2016 source

In the paper

“Accordingly, in order to track the Mo isotope composition of the early oceans, black shales need to be deposited under conditions with persistent and appreciable levels of dissolved sulfide”

What the sources say

• Not checked yetcites Neubert et al., 2008 source
• Not checked yetcites Gordon et al., 2009 source
• Not checked yetcites Arnold et al., 2012 source

In the paper

“This decline would have strongly impacted methanogenic bacteria, since they are highly dependent on dissolved Ni availability over this range.”

In the paper

“A similar conclusion was drawn for the late Paleoproterozoic and early Mesoproterozoic ocean based on sedimentary Fe speciation and Mo concentration and isotope data from the ca.1.8 Ga Rove Formation (Canada) and ca.1.4 Ga Velkerri Formation (Australia)”

What the sources say

• Not checked yetcites Arnold et al., 2004 source
• Not checked yetcites Kendall et al., 2009 source
• Not checked yetcites [2011]

In the paper

“Using experimentally derived Ni partitioning coefficients to Si-rich ferrihydrite (in light of assumed elevated Precambrian silica concentrations), it was estimated that paleomarine Ni concentrations dropped by more than half between 2.7 and 2.5 Ga (Fig. 6), from close to 400 nM to less than 200 nM.”

In the paper

“in the presence of abundant (10 -3 -10 -4 M) free hydrogen sulfide, Mo is converted to a series of particle-reactive thiomolybdates and is efficiently removed from seawater (the so-called Mo”

What the sources say

• Not checked yetcites Helz et al., 1996 source

In the paper

“Initial estimates of Ni concentrations in the early ocean were derived from geochemical modeling (Saito et al., 2003) and microbial genomics (Zerkle et al., 2005). These studies suggested that seawater Ni concentrations were fairly uniform from the Archean through to the modern”

What the sources say

• Not checked yetcites Saito et al., 2003 source
• Not checked yetcites Zerkle et al., 2005 source

In the paper

“Molybdenum isotope data has also been used in conjunction with U and Fe isotope data and sedimentary Fe speciation to demonstrate that a dramatic decline in ocean oxygenation occurred following the GOE”

What the sources say

• Not checked yetcites Asael et al., 2013 source
• Not checked yetcites Partin et al., 2013b

In the paper

“Large et al. (2014) presented a suite of Ni analyses in sedimentary to early diagenetic pyrite that mirrored the observed temporal trend in Ni/Fe ratios observed in IF.”

What the sources say

• Not checked yetcites Large et al., 2014 source

In the paper

“Stüeken et al. (2015a) report a suite of fluvial to marine sedimentary rocks at 3.2 Ga that have an average nitrogen isotopic composition (δ 15 N) of 0.0 ± 1.2 ‰.”

What the sources say

• Not checked yetcites Stüeken et al., 2015a

In the paper

“This trend remained clear after a near-doubling of the available IF data (Konhauser et al., 2015), suggesting that the observed decline in Ni in IF is robust.”

What the sources say

• Not checked yetcites Konhauser et al., 2015 source

In the paper

“However, a compilation of Ni contents in IF through time (Konhauser et al., 2009) revealed a unidirectional and rapid decrease in Ni just prior to the GOE”

What the sources say

• Not checked yetcites Konhauser et al., 2009 source

In the paper

“For these reasons, the concentration of Mo in sediments deposited under well-constrained water column redox conditions can be used to track the oxygenation of the oceans through time.”

In the paper

“The presumed consistency largely stems from Ni behaving conservatively in waters under various redox conditions”

What the sources say

• Not checked yetcites Saito et al., 2003 source

In the paper

“The interpretation of euxinia was further supported by the iron speciation analysis conducted on their samples.”

What the sources say

• Not checked yetcites Asael et al., 2013 source

In the paper

“This would be physiologically consistent with observations of Mo-nitrogenase activity at very low Mo levels in culture studies”

What the sources say

• Not checked yetcites Zerkle et al., 2006 source
• Not checked yetcites Glass et al., 2009 source

In the paper

“Interestingly, the first-order trends in Ni abundances observed in the IF record (Fig. 6) are also recorded in sedimentary pyrite.”

What the sources say

• Not checked yetcites Large et al., 2014 source

In the paper

“Such agreement between two distinct proxy records is encouraging and supports the interpretation that they reflect first-order trends in paleomarine bioavailability.”

In the paper

“An examination of Co concentrations in IF and pyrite through time suggests an expansion of the paleomarine Co reservoir between 2.8 and 1.8 Ga”

What the sources say

• Not checked yetcites Swanner et al., 2014 source

In the paper

“This disparity can be linked to an overestimation of the effects of Zn aqueous complexation by sulfides during the Precambrian by early geochemical models”

What the sources say

• Not checked yetcites Saito et al., 2003 source

In the paper

“In the modern oceans, the majority of Zn in surface waters is complexed with organic ligands (90-98%).”

What the sources say

• Not checked yetcites Bruland, 1989 source

In the paper

“Consistent with this idea is recent culture work after Xu et al. (2012) and Aristilde et al. (2012), where it was demonstrated that weakly binding organic ligands can in fact increase Zn uptake rates in phytoplankton.”

What the sources say

• Not checked yetcites Xu et al., 2012
• Not checked yetcites Aristilde et al., 2012 source

In the paper

“For Cr, there are no significant authigenic enrichments in middle Proterozoic black shales and this was taken to indicate pervasive anoxia”

What the sources say

• Not checked yetcites Reinhard et al., 2013b

In the paper

“Furthermore, Cr is subject to strong stable isotope fractionation during redox reactions, especially reduction”

What the sources say

• Not checked yetcites Ellis et al., 2002 source

In the paper

“Further, production of trace hydrogen sulfide through microbial sulfate reduction may play a strong role in governing aqueous Ni concentrations, even under ferruginous conditions”

What the sources say

• Not checked yetcites Crowe et al. 2008 source
• Not checked yetcites Zegeye et al. 2012 source

In the paper

“This conclusion is indicated by a large increase in Co/Ti ratios in IF (Fig. 8), euxinic shales, and pyrite relative to the evolving continental crust, with a peak in Co/Ti values observed at ~2.4 Ga.”

What the sources say

• Not checked yetcites Swanner et al., 2014 source

In the paper

“Studies in the ferruginous ocean analogue Lake Matano, Indonesia, have shown that green rust may play an important role in scavenging Ni from ferruginous water columns”

What the sources say

• Not checked yetcites Zegeye et al. 2012 source