Oceanic nutrient rise and the late Miocene inception of Pacific oxygen-deficient zones.

The modern Pacific Ocean hosts the largest oxygen-deficient zones (ODZs), where oxygen concentrations are so low that nitrate is used to respire organic matter. The history of the ODZs may offer key insights into ocean deoxygenation under future global warming. In a 12-My record from the southeastern Pacific, we observe a >10‰ increase in foraminifera-bound nitrogen isotopes (N/N) since the late Miocene (8 to 9 Mya), indicating large ODZs expansion.

Sulfur cycling at natural hydrocarbon and sulfur seeps in Santa Paula Creek, CA.

Biogeochemical cycling of sulfur is relatively understudied in terrestrial environments compared to marine environments. However, the comparative ease of access, observation, and sampling of terrestrial settings can expand our understanding of organisms and processes important in the modern sulfur cycle. Furthermore, these sites may allow for the discovery of useful process analogs for ancient sulfur-metabolizing microbial communities at times in Earth's past when atmospheric O concentrations were lower and sulfide was more prevalent in Earth surface environments.

Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin.

Fly ash-the residuum of coal burning-contains a considerable amount of fossilized particulate organic carbon (FOC) that remains after high-temperature combustion. Fly ash leaks into natural environments and participates in the contemporary carbon cycle, but its reactivity and flux remained poorly understood. We characterized FOC in the Chang Jiang (Yangtze River) basin, China, and quantified the riverine FOC fluxes.

Natural forcing of the North Atlantic nitrogen cycle in the Anthropocene.

Human alteration of the global nitrogen cycle intensified over the 1900s. Model simulations suggest that large swaths of the open ocean, including the North Atlantic and the western Pacific, have already been affected by anthropogenic nitrogen through atmospheric transport and deposition. Here we report an ∼130-year-long record of the N/N of skeleton-bound organic matter in a coral from the outer reef of Bermuda, which provides a test of the hypothesis that anthropogenic atmospheric nitrogen has significantly augmented the nitrogen supply to the open North Atlantic surface ocean.

Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age.

The Southern Ocean regulates the ocean's biological sequestration of CO and is widely suspected to underpin much of the ice age decline in atmospheric CO concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the N/N of fossil-bound organic matter in the stony deep-sea coral , a tool for reconstructing surface ocean nutrient conditions.