The evolution of land plants in terrestrial environments brought about one of the most dramatic shifts in the history of the Earth system — the birth of modern soils — and likely stimulated massive changes in marine biogeochemistry and climate. In particular, multiple marine mass extinctions characterized by widespread anoxia, including the Late Devonian mass extinction around 375 million years ago (Ma), may have been linked to terrestrial nutrient release driven by newly-rooted landscapes. Here, we use recently generated constraints from Earth’s lacustrine rock record as variable inputs in an Earth system model of the coupled C-N-P-O 2 -S biogeochemical cycles in order to evaluate whether recorded changes to phosphorus fluxes would be adequate to sustain Devonian marine biogeochemical perturbations and extinction dynamics. Results show that globally scaled riverine phosphorus export during the Late Devonian mass extinction generates widespread marine anoxia and produces carbon isotope, temperature, oxygen, and carbon dioxide perturbations generally consistent with the geologic record. Similar results for a competing extinction mechanism, large scale volcanism, suggest the Late Devonian mass extinction was likely multifaceted with both land plants and volcanism as contributing factors.

The evolution and expansion of land plants brought about one of the most dramatic shifts in the history of the Earth system — the birth of modern soils — and likely stimulated massive changes in marine biogeochemistry and climate. Multiple marine extinctions characterized by widespread anoxia, including the Late Devonian mass extinction around 372 million years ago, may have been linked to terrestrial release of the nutrient phosphorus driven by newly-rooted landscapes. Here we use recently published Devonian lake records as variable inputs in an Earth system model of the coupled carbon-nitrogen-phosphorus-oxygen-sulfur biogeochemical cycles to evaluate whether recorded changes to phosphorus fluxes could sustain Devonian marine anoxia sufficient to drive mass extinction. Results show that globally scaled increases in riverine phosphorus export during the Late Devonian mass extinction could have generated widespread marine anoxia, as modeled perturbations in carbon isotope, temperature, oxygen, and carbon dioxide data are generally consistent with the geologic record. Similar results for large scale volcanism suggest the Late Devonian mass extinction was likely multifaceted with both land plants and volcanism as contributing factors.

Because of the poor accessibility of embedded active sites, platinum (Pt)-based electrocatalysts suffer from insufficient Pt utilization and mass transport in membrane electrode assemblies (MEAs), limiting their performance in polymer electrolyte membrane fuel cells. Here, we report a simple and universal approach to depositing sub-3-nm L10-PtM nanoparticles over external surfaces of carbon supports through pore-tailored amino (NH2)-modification, which en-ables not only excellent activity for the oxygen reduction reaction, but also enhanced Pt utilization and mass transport in MEAs. Using a low loading of 0.10 mgPt center dot cm-2, the MEA of PtCo/KB-NH2 deliv-ered an excellent mass activity of 0.691 A center dot mgPt-1, a record-high power density of 0.96 W center dot cm-2 at 0.67 V, and only a 30-mV drop at 0.80 A center dot cm-2 after 30,000 voltage cycles, which meets nearly all targets set by the Department of Energy. This work provides an effi-cient strategy for designing advanced Pt-based electrocatalysts and realizing high-power fuel cells.

The evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, we report geochemical records from a survey of Middle and Late Devonian lacustrine and near-lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery, and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites in Greenland and northern Scotland/Orkney reveal a near-identical net loss of P. Additionally, all sites are temporally proximal to one or more Devonian extinction events, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian/Famennian mass extinction. For all sites, weathering, climate, and redox proxy data, coupled with nutrient input variability, reveal similar geochemical responses as seen in extant lacustrine systems. Orbitally forced climatic cyclicity appears to be the catalyst for all significant terrestrial nutrient pulses, which suggests that expansion of terrestrial plants may be tied to variations in regional and global climate.

The Devonian was a dynamic period in Earth’s past, the Late Devonian particularly so. The expansion and radiation of the first land plants, the evolution of significant root systems and the initiation of pseudo-modern soil formation processes drove a host of substantial biogeochemical changes in the terrestrial and likely, marine realms. Several significant marine extinction events coincide with these terrestrial developments, including the Kellwasser Event, one of the big five mass extinctions. While the initiation of the Kellwasser Event has been attributed to large scale volcanic eruptions of the Viluy Traps, extinction events are complex, often with multiple contributing and exacerbating factors. The eruption of the Viluy Traps created a favorable environment for rapid plant growth (i.e., relatively warm, wet, high CO 2 environment). It is possible that this favorable environment accelerated the expansion and radiation of land plants into formally arid regions such as the Devonian Basin in East Greenland, enhancing terrestrial nutrient input into the Panthalassic and Rheic oceans. To test this concept, we utilized an oceanic advection–diffusion–reaction biogeochemical cycle model ( CANOPS ), driven by geochemical records we generated from sedimentary fluvial/lacustrine sequences, to model global terrestrial phosphorus flux to Devonian oceans and the subsequent biosphere response during the Late Frasnian in the Devonian basin in East Greenland. Results show nutrient perturbations detected in East Greenland, when scaled globally, are sufficient to drive eutrophication and significant increases in deoxygenation in Devonian oceans. Model results for inorganic carbon ( δ 13 C carb ) show enhanced carbon