Starting with the work of Ben Houlton, we have collaborated with the group of Lars Hedin in the Department of Ecology and Evolutionary Biology in isotope studies of terrestrial N cycling. We have also worked on the nitrate N and O isotopes in rain, snow, and ice as tracers of reactive nitrogen sources and processing in the modern and ancient atmosphere.
References
9 Publications
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Influence of open ocean nitrogen supply on the skeletal δ15N of modern shallow-water scleractinian corals
The isotopic composition of skeleton-bound organic nitrogen in shallow-water scleractinian corals (hereafter, CS-δ15N) is an emerging tool for studying the marine nitrogen cycle in the past. The CS-δ15N has been shown to reflect the δ15N of nitrogen (N) sources to corals, with most applications to date focusing on the anthropogenic/terrestrial N…
Isotopic composition of skeleton-bound organic nitrogen in reef-building symbiotic corals: A new method and proxy evaluation at Bermuda
The skeleton-bound organic nitrogen in reef-building symbiotic corals may be a high-resolution archive of ocean nitrogen cycle dynamics and a tool for understanding coral biogeochemistry and physiological processes. However, the existing methods for measuring the isotopic composition of coral skeleton-bound organic nitrogen (hereafter, CS-δ15N)…
Isotopic composition of carbonate-bound organic nitrogen in deep-sea scleractinian corals: A new window into past biogeochemical change
Over the last two decades, the skeletal remains of deep-sea corals have arisen as a geochemical archive of Pleistocene oceanographic change. Here we report the exploration of the isotopic composition of the carbonate-bound organic nitrogen (hereafter, CB-δ15N) in the deep-sea scleractinian coral Desmophyllum dianthus as a possible tool for…
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…
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-yearlong record of the 15N/14N of…
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 CO2 and is widely suspected to underpin much of the ice age decline in atmospheric CO2 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…
Influence of ocean heat transport on the climate of the Last Glacial Maximum
A aeries of climate simulations using on atmospheric general circulation modal shows that maintaining ocean heat transport at close to present-day values, but with otherwise glacial boundary conditions, leads to an enhanced cooling, particularly in the tropics. This is in agreement with recent geochemical evidence from fossil corals, ground waters…
Updates to instrumentation and protocols for isotopic analysis of nitrate by the denitrifier method
Rationale The denitrifier method allows for highly sensitive measurement of the 15N/14N (δ15N value) and 18O/16O (δ18O value) of nitrate dissolved in natural waters and for highly sensitive δ15N measurement of other N forms (e.g., organic N) that can be converted into nitrate. Here, updates to instrumentation and protocols are described, and…
Reduced interannual rainfall variability in East Africa during the last ice age
Interannual rainfall variations in equatorial East Africa are tightly linked to the El Niño Southern Oscillation (ENSO), with more rain and flooding during El Niño and droughts in La Niña years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from…