Viruses—Agents of Change in the Oceans

Viruses are usually thought of as the cause of countless diseases. However, in the oceans, viruses are part of the natural cycle of life and death. This article discusses marine viruses that infect phytoplankton—the tiny micro-algae that form the base of the marine food web and affect Earth’s climate. Through an ongoing “arms race” between viruses and the cells they infect, viruses can promote the evolution of their hosts, and even help their hosts acquire genes that can help them survive. By killing phytoplankton species that become very abundant, viruses can allow other species to grow, promoting biodiversity. Finally, viruses affect global cycles of carbon and other elements, indirectly influencing the climate of our planet.

Reallocation and Productivity during Commodity Cycles

I study the firm-level dynamic response of a commodity-exporting economy to global cycles in commodity prices. To do so, I develop a heterogeneous-firms model that endogenizes declines in aggregate productivity through reallocation towards less productive firms. Within a given sector, commodity booms reallocate market share away from exporters because of currency appreciation and away from capital-intensive firms because of the increase in capital cost. I provide empirical evidence for these channels using microdata for Chile, the worlds largest copper producer. When fed with the commodity super-cycle of 2003-2012, the calibrated model generates about 50% of the observed productivity decline.

Promoting Developmental Potential in Early Childhood: A Global Framework for Health and Education

In the early years of life, children’s interactions with the physical and social environment- including families, schools and communities—play a defining role in developmental trajectories with long-term implications for their health, well-being and earning potential as they become adults. Importantly, failing to reach their developmental potential contributes to global cycles of poverty, inequality, and social exclusion. Guided by a rights-based approach, this narrative review synthesizes selected studies and global initiatives promoting early child development and proposes a universal intervention framework of child-environment interactions to optimize children’s developmental functioning and trajectories.

Microbial sulfate reduction and organic sulfur formation in sinking marine particles

Climate change is driving an expansion of marine oxygen-deficient zones, which may alter the global cycles of carbon, sulfur, nitrogen, and trace metals. Currently, however, we lack a full mechanistic understanding of how oxygen deficiency affects organic carbon cycling and burial. Here, we show that cryptic microbial sulfate reduction occurs in sinking particles from the eastern tropical North Pacific oxygen-deficient zone and that some microbially produced sulfide reacts rapidly to form organic sulfur that is resistant to acid hydrolysis. Particle-hosted sulfurization could enhance carbon preservation in sediments underlying oxygen-deficient water columns and serve as a stabilizing feedback between expanding anoxic zones and atmospheric carbon dioxide. A similar mechanism may help explain more-extreme instances of organic carbon preservation associated with marine anoxia in Earth history.

Global phosphorus dynamics in terms of phosphine

Since the detection of phosphine in the wastewater treatment plants in 1988, more and more investigations revealed that phosphine is closely related to ecological activities on a global scale. Here, we present perspectives on the whole dynamic cycles of phosphorus, particularly in terms of phosphine and its interactions with natural ecosystems, as well as the impacts from human activities. It may conclude that the phosphine-driving cycles of phosphorus depend on the coordination of human activities with natural ecosystems. Most importantly, the extensive recovery of phosphorus in numerous urban wastewater treatment plants may seriously obstruct its global cycles to catch up with the ecological needs in natural ecosystems. Phosphine gas plays an important role in the biogeochemical phosphorus cycle. Phosphorus might be one of the important elements participating in the global climate change together with carbon and nitrogen.

Latitudinal gradient in the respiration quotient and the implications for ocean oxygen availability

Climate-driven depletion of ocean oxygen strongly impacts the global cycles of carbon and nutrients as well as the survival of many animal species. One of the main uncertainties in predicting changes to marine oxygen levels is the regulation of the biological respiration demand associated with the biological pump. Derived from the Redfield ratio, the molar ratio of oxygen to organic carbon consumed during respiration (i.e., the respiration quotient, r−O2:C) is consistently assumed constant but rarely, if ever, measured. Using a prognostic Earth system model, we show that a 0.1 increase in the respiration quotient from 1.0 leads to a 2.3% decline in global oxygen, a large expansion of low-oxygen zones, additional water column denitrification of 38 Tg N/y, and the loss of fixed nitrogen and carbon production in the ocean. We then present direct chemical measurements of r−O2:C using a Pacific Ocean meridional transect crossing all major surface biome types. The observed r−O2:C has a positive correlation with temperature, and regional mean values differ significantly from Redfield proportions. Finally, an independent global inverse model analysis constrained with nutrients, oxygen, and carbon concentrations supports a positive temperature dependence of r−O2:C in exported organic matter. We provide evidence against the common assumption of a static biological link between the respiration of organic carbon and the consumption of oxygen. Furthermore, the model simulations suggest that a changing respiration quotient will impact multiple biogeochemical cycles and that future warming can lead to more intense deoxygenation than previously anticipated.

Using the silica isotope composition of biogenic materials in marine sediments to reconstruct ocean chemistry

<div><span>The silicon isotopic composition of sedimentary biogenic opal can be used to track shifts in the balance between silicon inputs to the ocean and outputs by burial. In addition to biosilicification and opal burial, the global cycles of climate (hydrology, weathering, glaciation, etc.), tectonics (volcanoes, LIPs, mountain building, etc.) and geochemistry (reverse weathering, inorganic Si precipitation, etc.) have driven variations in the global Si cycle over geologic time. Prior to the start of the Phanerozoic it is thought that burial in the global oceans was controlled inorganically through chert formation. The evolution of the Si depositing organisms, radiolarians and sponges, reduced oceanic dissolved Si, but the largest reductions occurred with the evolution of the diatoms bringing dissolved Si to the low concentrations (relative to saturating concentrations) observed today. However, the timing of the depletion of dissolved Si by diatoms is currently under debate.</span></div><div><span> </span></div><div><span>Our understanding of the biological components of the Si cycle has grown enormously. In the last decade, silicon isotope ratios (expressed as δ30Si) in marine microfossils are becoming increasingly recognised for their ability to provide insight into silicon cycling. In particular, the δ30Si of deep-sea sponge spicules has been demonstrated to be a useful proxy for past dissolved Si concentrations. However, more recent studies find anomalies in the isotopic fractionation of sponge spicules that relate to skeletal morphology: reliable reconstructions of past dissolved Si can only be obtained using silicon isotope ratios derived from sponges with certain spicule types. We are applying δ30Si proxies from biosiliceous material contained in sediments to generate robust estimates of the timing and magnitude of dissolved Si drawdown. We will provide fundamental new insights into the drawdown of dissolved Si and other key events, which reorganized the distribution of carbon and nutrients in seawater, with implications for productivity of the biological communities within the ancient oceans. </span></div>