Earth's Biogeochemical Cycles Research Articles

Global distribution pattern of soil phosphorus-cycling microbes under the influence of human activities.

Human activities have profoundly altered the Earth's phosphorus (P) cycling process and its associated microbial communities, yet their global distribution pattern and response to human influences remain unclear. Here, we estimated the abundances of P-cycling genes from 3321 global soil metagenomic samples and mapped the global distribution of five key P-cycling processes, that is, organic phosphoester hydrolysis, inorganic phosphorus solubilization, two-component system, phosphotransferase system, and transporters. Structural equation modeling and random forest analysis were employed to assess the impact of anthropogenic and environmental factors on the abundance of P-cycling genes. Our findings suggest that although less significant than the climate and soil profile, human-related factors, such as economic activities and population, are important drivers for the variations in P-cycling gene abundance. Notably, the gene abundances were increased parallel to the extent of human intervention, but generally at low and moderate levels of human activities. Furthermore, we identified critical genera, such as Pseudomonas and Lysobacter, which were sensitive to the changes in human activities. This study provides insights into the responses of P-cycling microbes to human activities at a global scale, enhancing our understanding of soil microbial P cycling and underscoring the importance of sustainable human activities in the Earth's biogeochemical cycle.

Toward a Natural History of Microbial Life

For most of Earth's history life was microbial, with archaeal and bacterial cells mediating biogeochemical cycles through their metabolisms and ecologies. This diversity was sufficient to maintain a habitable planet across dramatic environmental transitions during the Archean and Proterozoic Eons. However, our knowledge of the first 3 billion years of the biosphere pales in comparison to the rich narrative of complex life documented through the Phanerozoic geological record. In this review, we attempt to lay out a microbial natural history framework that highlights recent and ongoing research unifying microbiology, geochemistry, and traditional organismal evolutionary biology, and we propose six broadly applicable principles to aid in these endeavors. In this way, the evolutionary history of microbial life—once considered only a prelude to the much more storied history of complex metazoan life in the Phanerozoic—is finally coming into its own. ▪The outlines of microbial natural history are now starting to appear through the integration of genomic and geological records.▪Microorganisms drive Earth's biogeochemical cycles, and their natural history reflects a coevolution with the planet.▪Past environmental changes have induced microbial biotic transitions, marked by extinction, taxonomic shifts, and new metabolisms and ecologies.▪Microbial evolution can benefit from a historical perspective of processes and successions as established by macropaleontology.

Perturbation to North Atlantic Ocean‐Climate Dynamics Tripled Whitings Mud Production in the Bahamas

AbstractProfound changes in Earth's biogeochemical cycles are recorded in the sedimentology and geochemistry of carbonate sediments, with much of the early geological history of our planet recorded in carbonate mud precipitated from seawater. Despite their relevance for understanding early Earth, the trigger for whitings—carbonate spontaneously precipitated from the water column—remains intensely debated. Here, we used a neural network to map whitings imaged by daily MODIS Aqua satellite overpasses between 2003 and 2018 on Great Bahama Bank (GBB). Our results show that the frequency of whitings after 2011 increased by 3.3× compared to those recorded between 2003 and 2010, with the frequency of winter whitings increasing more than those in the summer. We contend that the period of increased whitings frequency was spurred by concurrent perturbations to the North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and the El Niño Southern Oscillation in 2010 that facilitated enhanced hydrodynamic mixing between the waters atop GBB and those that surround it. We conclude that whitings can exhibit a sensitive but non‐linear response to ocean‐atmosphere dynamics which is unlikely to be resolved in the geological record using conventional stratigraphic techniques. This pronounced fluctuation in mud production on short timescales contrasts with expectations of persistent tranquility in the depositional environments that produce lime mud. Our results suggest that long‐established links between ocean‐atmosphere dynamics and the lime mud budget through Earth history may require reevaluation.

Production and cross-feeding of nitrite within Prochlorococcus populations.

Prochlorococcus is an abundant photosynthetic bacterium in the open ocean, where nitrogen (N) often limits phytoplankton growth. In the low-light-adapted LLI clade of Prochlorococcus, nearly all cells can assimilate nitrite (NO2-), with a subset capable of assimilating nitrate (NO3-). LLI cells are maximally abundant near the primary NO2- maximum layer, an oceanographic feature that may, in part, be due to incomplete assimilatory NO3- reduction and subsequent NO2- release by phytoplankton. We hypothesized that some Prochlorococcus exhibit incomplete assimilatory NO3- reduction and examined NO2- accumulation in cultures of three Prochlorococcus strains (MIT0915, MIT0917, and SB) and two Synechococcus strains (WH8102 and WH7803). Only MIT0917 and SB accumulated external NO2- during growth on NO3-. Approximately 20-30% of the NO3- transported into the cell by MIT0917 was released as NO2-, with the rest assimilated into biomass. We further observed that co-cultures using NO3- as the sole N source could be established for MIT0917 and Prochlorococcus strain MIT1214 that can assimilate NO2- but not NO3-. In these co-cultures, the NO2- released by MIT0917 is efficiently consumed by its partner strain, MIT1214. Our findings highlight the potential for emergent metabolic partnerships that are mediated by the production and consumption of N cycle intermediates within Prochlorococcus populations. IMPORTANCE Earth's biogeochemical cycles are substantially driven by microorganisms and their interactions. Given that N often limits marine photosynthesis, we investigated the potential for N cross-feeding within populations of Prochlorococcus, the numerically dominant photosynthetic cell in the subtropical open ocean. In laboratory cultures, some Prochlorococcus cells release extracellular NO2- during growth on NO3-. In the wild, Prochlorococcus populations are composed of multiple functional types, including those that cannot use NO3- but can still assimilate NO2-. We show that metabolic dependencies arise when Prochlorococcus strains with complementary NO2- production and consumption phenotypes are grown together on NO3-. These findings demonstrate the potential for emergent metabolic partnerships, possibly modulating ocean nutrient gradients, that are mediated by cross-feeding of N cycle intermediates.

The Role of Phytoplanktons in the Environment and in Human Life, a Review

Phytoplankton is microscopic organisms that lie in watery environment and make their own food from sunlight through photosynthesis. Phytoplanktons are the core producers and major role play to the food web. They produce the similar amount of biomass of CO2 as all terrestrial plants combined. Several environmental factors, many of which are currently undergoing significant changes as a result of human-caused global warming, control phytoplankton productivity. Generally, ocean ecosystem is based on phytoplankton. It contributes about half of the world’s primary production, and diverse phytoplankton taxa play distinctive roles in the earth biogeochemical cycles, biological pump, ocean food chain, bioindicator, food industry and drugs. In the present paper an effort has been made to give broad review of literature on phytoplankton. This review clearly indicates that such research is necessary and emphasis the urgency of present work. The recent review highlights the value of phytoplankton in our lives and environment.

Cyanoseq: A database of cyanobacterial 16S rRNA gene sequences with curated taxonomy.

Cyanobacteria are photosynthetic bacteria that occupy various habitats across the globe, playing critical roles in many of Earth's biogeochemical cycles both in both aquatic and terrestrial systems. Despite their well-known significance, their taxonomy remains problematic and is the subject of much research. Taxonomic issues of Cyanobacteria have consequently led to inaccurate curation within known reference databases, ultimately leading to problematic taxonomic assignment during diversity studies. Recent advances in sequencing technologies have increased our ability to characterize and understand microbial communities, leading to the generation of thousands of sequences that require taxonomic assignment. We herein propose CyanoSeq (https://zenodo.org/record/7569105), a database of cyanobacterial 16S rRNA gene sequences with curated taxonomy. The taxonomy of CyanoSeq is based on the current state of cyanobacterial taxonomy, with ranks from the domain to genus level. Files are provided for use with common naive Bayes taxonomic classifiers, such as those included in DADA2 or the QIIME2 platform. Additionally, FASTA files are provided for creation of de novo phylogenetic trees with (near) full-length 16S rRNA gene sequences to determine the phylogenetic relationship of cyanobacterial strains and/or ASV/OTUs. The database currently consists of 5410 cyanobacterial 16S rRNA gene sequences along with 123 Chloroplast, Bacterial, and Vampirovibrionia (formally Melainabacteria) sequences.

Deep Proteogenomics of a Photosynthetic Cyanobacterium.

Cyanobacteria, the evolutionary ancestors of plant chloroplasts, contribute substantially to the Earth's biogeochemical cycles and are of great interest for a sustainable economy. Knowledge of protein expression is the key to understanding cyanobacterial metabolism; however, proteome studies in cyanobacteria are limited and cover only a fraction of the theoretical proteome. Here, we performed a comprehensive proteogenomic analysis of the model cyanobacterium Synechocystis sp. PCC 6803 to characterize the expressed (phospho)proteome, re-annotate known and discover novel open reading frames (ORFs). By mapping extensive shotgun mass spectrometry proteomics data onto a six-frame translation of the Synechocystis genome, we refined the genomic annotation of 64 ORFs, including eight completely novel ORFs. Our study presents the largest reported (phospho)proteome dataset for a unicellular cyanobacterium, covering the expression of about 80% of the theoretical proteome under various cultivation conditions, such as nitrogen or carbon limitation. We report 568 phosphorylated S/T/Y sites that are present on numerous regulatory proteins, including the transcriptional regulators cyAbrB1 and cyAbrB2. We also catalogue the proteins that have never been detected under laboratory conditions and found that a large portion of them is plasmid-encoded. This dataset will serve as a resource, providing dedicated information on growth condition-dependent protein expression and phosphorylation.

New approach to soil management focusing on soil health and air quality: one earth one life (critical review).

Soil plays a key role in ecosphere and air quality regulation. Obsolete environmental technologies lead to soil quality loss, air, water, and land systems pollution. Pedosphere and plants are intertwined with the air quality. Ionized O2 is capable to intensify atmosphere turbulence, providing particulate matter (PM2.5) coalescence and dry deposition. Addressing environmental quality, a Biogeosystem Technique (BGT*) heuristic transcendental (nonstandard and not direct imitation of nature) methodology has been developed. A BGT* main focus is an enrichment of Earth's biogeochemical cycles through land use and air cleaning. An intra-soil processing, which provides the soil multilevel architecture, is one of the BGT* ingredients. A next BGT* implementation is intra-soil pulse continuously discrete watering for optimal soil water regime and freshwater saving up to 10-20 times. The BGT* comprises intra-soil dispersed environmentally safe recycling of the PM sediments, heavy metals (HMs) and other pollutants, controlling biofilm-mediated microbial community interactions in the soil. This provides abundant biogeochemical cycle formation and better functioning of the humic substances, biological preparation, and microbial biofilms as a soil-biological starter, ensuring priority plants and trees nutrition, growth and resistance to phytopathogens. A higher underground and aboveground soil biological product increases a reversible C biological sequestration from the atmosphere. An additional light O2 ions photosynthetic production ensures a PM2.5 and PM0.1 coalescence and strengthens an intra-soil transformation of PM sediments into nutrients and improves atmosphere quality. The BGT* provides PM and HMs intra-soil passivation, increases soil biological productivity, stabilizes a climate system of the earth and promotes a green circular economy.

Functional Potential of Soil Microbial Communities and Their Subcommunities Varies with Tree Mycorrhizal Type and Tree Diversity.

Soil microbial communities play crucial roles in the earth's biogeochemical cycles. Yet, their genomic potential for nutrient cycling in association with tree mycorrhizal type and tree-tree interactions remained unclear, especially in diverse tree communities. Here, we studied the genomic potential of soil fungi and bacteria with arbuscular (AM) and ectomycorrhizal (EcM) conspecific tree species pairs (TSPs) at three tree diversity levels in a subtropical tree diversity experiment (BEF-China). The soil fungi and bacteria of the TSPs' interaction zone were characterized by amplicon sequencing, and their subcommunities were determined using a microbial interkingdom co-occurrence network approach. Their potential genomic functions were predicted with regard to the three major nutrients carbon (C), nitrogen (N), and phosphorus (P) and their combinations. We found the microbial subcommunities that were significantly responding to different soil characteristics. The tree mycorrhizal type significantly influenced the functional composition of these co-occurring subcommunities in monospecific stands and two-tree-species mixtures but not in mixtures with more than three tree species (here multi-tree-species mixtures). Differentiation of subcommunities was driven by differentially abundant taxa producing different sets of nutrient cycling enzymes across the tree diversity levels, predominantly enzymes of the P (n = 11 and 16) cycles, followed by the N (n = 9) and C (n = 9) cycles, in monospecific stands and two-tree-species mixtures, respectively. Fungi of the Agaricomycetes, Sordariomycetes, Eurotiomycetes, and Leotiomycetes and bacteria of the Verrucomicrobia, Acidobacteria, Alphaproteobacteria, and Actinobacteria were the major differential contributors (48% to 62%) to the nutrient cycling functional abundances of soil microbial communities across tree diversity levels. Our study demonstrated the versatility and significance of microbial subcommunities in different soil nutrient cycling processes of forest ecosystems. IMPORTANCE Loss of multifunctional microbial communities can negatively affect ecosystem services, especially forest soil nutrient cycling. Therefore, exploration of the genomic potential of soil microbial communities, particularly their constituting subcommunities and taxa for nutrient cycling, is vital to get an in-depth mechanistic understanding for better management of forest soil ecosystems. This study revealed soil microbes with rich nutrient cycling potential, organized in subcommunities that are functionally resilient and abundant. Such microbial communities mainly found in multi-tree-species mixtures associated with different mycorrhizal partners can foster soil microbiome stability. A stable and functionally rich soil microbiome is involved in the cycling of nutrients, such as carbon, nitrogen, and phosphorus, and their combinations could have positive effects on ecosystem functioning, including increased forest productivity. The new findings could be highly relevant for afforestation and reforestation regimes, notably in the face of growing deforestation and global warming scenarios.

Spatiotemporal evolution of aeolian dust in China: An insight into the synoptic records of 1984–2020 and nationwide practices to combat desertification

AbstractAeolian dust is closely related to land degradation, desertification, and sand and dust storm weather, and is a significant factor influencing the Earth's biogeochemical cycles. Here we present an investigation of the recent synoptic features of atmospheric dust in China and analyze its spatiotemporal change based upon meteorological observation data and satellite products. It shows that aeolian dust frequency in China has decreased gradually from 1984 to 2020. The outbreak frequency of dust storms declined significantly by 97.7%, followed by severe dust storm, dust in suspension, and blowing dust with 88.8%, 75%, and 64.3% reduction, respectively. The main dust sources influencing China are the Mongolian Gobi Desert, the Taklimakan Desert, the Hexi Corridor, the Alxa Plateau Desert, the Qaidam basin Desert, and the northeast‐southwest stretching semiarid farming‐pasture ecotone. Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO) may play an important role in teleconnection with aeolian dust event occurrence in China. Their correlation coefficients are −0.6 and 0.37, respectively. For more than 40 years, China has made huge investments in ecological restoration projects, and enacted national policies and laws to mitigate desertification. Significant environmental improvement has consequently ensued in China in the early 21st century, and the aeolian dust events were reduced to a record minimum in 2020. In contrast to the growing nationwide greenness, China is now facing up to an incremental dust risk generated from extraterritorial source regions such as the Mongolian Gobi Desert and Central Asian desiccated salt lakes.

Chromium isotopes track redox fluctuations in Proterozoic successions of the Chapada Diamantina, São Francisco craton, Brazil

AbstractThe Chapada Diamantina region in the São Francisco craton of eastern Brazil is composed of sedimentary successions containing both Mesoproterozoic and Neoproterozoic carbonate levels, making it a key natural laboratory for understanding the fluctuations of Earth's biogeochemical cycles during its middle age. The ca. 1.4–1.2 Ga Caboclo Formation stromatolites yielded unfractionated δ53Crauth (authigenic) (~−0.54‰ to +0.08‰). Ediacaran cap carbonates and phosphatic stromatolites of the Salitre Formation, on the other hand, yielded fractionated δ53Crauth reaching as high as +0.51‰, suggesting the input of 53Cr-rich Cr(VI), first delivered through meltwater-induced post–snowball Earth fluctuating redox conditions and then through weathering and mobilization under a fully oxygenated environment. The acquired data set highlights the very distinct redox conditions throughout the Proterozoic and reinforces the suggestion that after the Cryogenian global glaciations, Earth's atmosphere and hydrosphere became progressively oxygenated during the Ediacaran-Cambrian transition.

Global‐Scale Shifts in Rooting Depths Due To Anthropocene Land Cover Changes Pose Unexamined Consequences for Critical Zone Functioning

AbstractRooting depth is an ecosystem trait that determines the extent of soil development and carbon (C) and water cycling. Recent hypotheses propose that human‐induced changes to Earth's biogeochemical cycles propagate deeply into Earth's subsurface due to rooting depth changes from agricultural and climate‐induced land cover changes. Yet, the lack of a global‐scale quantification of rooting depth responses to human activity limits knowledge of hydrosphere‐atmosphere‐lithosphere feedbacks in the Anthropocene. Here we use land cover data sets to demonstrate that root depth distributions are changing globally as a consequence of agricultural expansion truncating depths above which 99% of root biomass occurs (D99) by ∼60 cm, and woody encroachment linked to anthropogenic climate change extending D99 in other regions by ∼38 cm. The net result of these two opposing drivers is a global reduction of D99 by 5%, or ∼8 cm, representing a loss of ∼11,600 km3 of rooted volume. Projected land cover scenarios in 2100 suggest additional future D99 shallowing of up to 30 cm, generating further losses of rooted volume of ∼43,500 km3, values exceeding root losses experienced to date and suggesting that the pace of root shallowing will quicken in the coming century. Losses of Earth's deepest roots—soil‐forming agents—suggest unanticipated changes in fluxes of water, solutes, and C. Two important messages emerge from our analyses: dynamic, human‐modified root distributions should be incorporated into earth systems models, and a significant gap in deep root research inhibits accurate projections of future root distributions and their biogeochemical consequences.

Autogenic Signals in the Sedimentary Record of Organic Carbon Preservation

The burial of organic carbon (OC) preserves paleoenvironmental archives and drives the evolution of Earth's biogeochemical cycles. While the impact of kinetic heterogeneity on OC preservation has been studied, the effects of sedimentation dynamics remain largely unknown. Here, we incorporate the expected stochastic variability in sedimentation rates into a reactive-transport model, generate predictions for stratigraphic variability of OC burial efficiency, and compare the model outputs to field observations. We find that internal sedimentation dynamics profoundly influence OC preservation efficiencies and create autogenic signals that may obscure signals originated from external forcings. Simulations match observations in terms of power spectra when our model considers transient periods of erosion during net deposition, implying that the manifestation of sedimentation dynamics and their interactions with biogeochemistry in chemostratigraphic records are prevalent in nature. As sedimentary OC records reflect both internal variability and external forcing, they may be used as proxies for past depositional conditions.

Uniting diversity to create a more inclusive academic environment.

Uniting diversity to create a more inclusive academic environment.

A reduction in metabolism explains the tradeoffs associated with the long-term adaptation of phytoplankton to high CO2 concentrations.

Phytoplankton are responsible for nearly half of global primary productivity and play crucial roles in the Earth's biogeochemical cycles. However, the long-term adaptive responses of phytoplankton to rising CO2 remains unknown. Here we examine the physiological and proteomics responses of a marine diatom, Phaeodactylum tricornutum, following long-term (c. 900 generations) selection to high CO2 conditions. Our results show that this diatom responds to long-term high CO2 selection by downregulating proteins involved in energy production (Calvin cycle, tricarboxylic acid cycle, glycolysis, oxidative pentose phosphate pathway), with a subsequent decrease in photosynthesis and respiration. Nearly similar extents of downregulation of photosynthesis and respiration allow the high CO2 -adapted populations to allocate the same fraction of carbon to growth, thereby maintaining their fitness during the long-term high CO2 selection. These results indicate an important role of metabolism reduction under high CO2 and shed new light on the adaptive mechanisms of phytoplankton in response to climate change.

Effects of fire on the aggregate stability of clayey soils: A meta-analysis

Fire is a natural phenomenon that affects the Earth's biogeochemical cycle. Wildland fires are increasing in frequency and magnitude, possibly owing to climate change. In addition, fire is applied as a tool in agro-ecosystem management. However, several detrimental effects on soil properties, particularly on soil aggregate stability, might occur. A general explanation is that “the effects of fire on soil aggregate stability in soil with high clay content, calcium carbonate, and Fe and Al oxides as the principal cementing substances cause gradual improvement in aggregate stability, following fire-heating severity.” In short, the higher the fire severity, the higher is the aggregate stability. A meta-analysis was conducted for assessing the laboratory and field studies to verify this concept. The Scopus® platform was used to search for the literature related to “soil aggregate stability” AND fire OR heating AND clay OR “clayey soil.” A total of 10 studies were selected with 16 soil types, 244 burned or heated samples, and 160 control samples. The meta-analysis was performed using RevMan 5.3 software. Meta-analysis was delineated according to the following assumptions: a) field and laboratory studies were tested as two independent subgroups, and a pooled effect was subsequently calculated; b) a random-effects model was used; c) mean differences with 95% confidence intervals were computed for continuous variables. Laboratory and field measurements showed dissimilar effects on soil aggregate stability and evidenced positive effects in the laboratory experiments compared with those in the field. Aggregate stability measured in the laboratory increased by 2.80% after heating. Fire effects measured in the field did not show a significant increase in soil aggregate stability (−0.16%). The overall effects of combined subgroups showed an aggregate stability improvement of 1.49% (confidence intervals 0.80% to 2.17%). However, the weight of the results from the laboratory studies played an important role in the overall effect. The soil clay content was found to be inversely associated with aggregate stability, i.e., the lower the clay content the higher the aggregate stability in soil subjected to fire heating. In conclusion, the aggregate stability of clayey soils rich in Al and Fe oxides does not necessarily improves following fire heating.

A Participatory Approach for Balancing Accuracy and Complexity in Modeling Resilience and Robustness.

Robustness and resilience are widely used in the biological sciences and related disciplines to describe how systems respond to change. Robustness is the ability to tolerate change without adapting or moving to another state. Resilience refers to the ability for a system to sustain a perturbation and maintain critical functions. Robustness and resilience transcend levels of biological organization, though they do not scale directly across levels. We live in an era of novel stressors and unprecedented change, including climate change, emerging environmental contaminants, and changes to the Earth's biogeochemical and hydrological cycles. We envision a common framework for developing models to predict the robustness and resilience of biological functions associated with complex systems that can transcend disciplinary boundaries. Conceptual and quantitative models of robustness and resilience must consider cross-scale interactions of potentially infinite complexity, but it is impossible to capture everything within a single model. Here, we discuss the need to balance accuracy and complexity when designing models, data collection, and downstream analyses to study robustness and resilience. We also consider the difficulties in defining the spatiotemporal domain when studying robustness and resilience as an emergent property of a complex system. We suggest a framework for implementing transdisciplinary research on robustness and resilience of biological systems that draws on participatory stakeholder engagement methods from the fields of conservation and natural resources management. Further, we suggest that a common, simplified model development framework for describing complex biological systems will provide new, broadly relevant educational tools. Efficient interdisciplinary collaboration to accurately develop a model of robustness and resilience would enable rapid, context-specific assessment of complex biological systems with benefits for a broad range of societally relevant problems.

Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics

The quantitative description of marine systems is constrained by a major issue of scale separation: phytoplankton production processes occur at sub-centimeter scales, while the contribution to the Earth's biogeochemical cycles is expressed at much larger scales, up to the planetary one. In spite of vastly improved computing power and observational capabilities, the modeling approach has remained anchored to an old view that sees the microscales as unable to substantially affect larger ones. The lack of a widespread theoretical appreciation of the interactions between vastly different scales has led to the proliferation of numerical models with uncertain predictive capabilities. In this paper, we use the phenology of phytoplankton blooms as one example of a macroscopic ecosystem feature affected by microscale interactions. We describe two distinct mechanisms that produce patchiness within a productive water column: turbulent entrainment of less-productive water at the base of the mixed layer, and stirring by slow turbulence of a vertical phytoplankton gradient sustained by depth–dependent light availability. In current eddy–diffusive models, patchiness produced in this way is wiped out very rapidly, because the time scales of irreversible mixing largely overlap those of mechanical stirring. We propose a novel Lagrangian modeling framework that allows for the existence of microscale patchiness, even when that is not fully resolved. We show, with a mixture of theoretical arguments and numerical simulations of increasing realism, how the presence of patchiness, in turn, affects larger-scale properties, demonstrating that the timing of phytoplankton blooms and vertical variability of chlorophyll in the oceanic upper layers is determined by the mutual interplay between the stirring, mixing and growing processes.

Corrigendum to “Reorganisation of Earth's biogeochemical cycles briefly oxygenated the oceans 520 Myr ago” by Dahl et al., 2017

Corrigendum to “Reorganisation of Earth's biogeochemical cycles briefly oxygenated the oceans 520 Myr ago” by Dahl et al., 2017

Integrated records of environmental change and evolution challenge the Cambrian Explosion

The 'Cambrian Explosion' describes the rapid increase in animal diversity and abundance, as manifest in the fossil record, between ~540 and 520 million years ago (Ma). This event, however, is nested within a far more ancient record of macrofossils extending at least into the late Ediacaran at ~571 Ma. The evolutionary events documented during the Ediacaran-Cambrian interval coincide with geochemical evidence for the modernisation of Earth's biogeochemical cycles. Holistic integration of fossil and geochemical records leads us to challenge the notion that the Ediacaran and Cambrian worlds were markedly distinct, and places biotic and environmental change within a longer-term narrative. We propose that the evolution of metazoans may have been facilitated by a series of dynamic and global changes in redox conditions and nutrient supply, which, potentially together with biotic feedbacks, enabled turnover events that sustained multiple phases of radiation. We argue that early metazoan diversification should be recast as a series of successive, transitional radiations that extended from the late Ediacaran and continued through the early Palaeozoic. We conclude that while the Cambrian Explosion represents a radiation of crown-group bilaterians, it was simply one phase amongst several metazoan radiations, some older and some younger.