Oscar Branson

• BSc Biology, MSc Oceanography, PhD Earth Sciences
• Lecturer at University of Cambridge

The Mg/Ca ratio of foraminiferal calcite is a widely accepted and applied empirical proxy for ocean temperature. The analysis of foraminifera preserved in ocean sediments has been instrumental in developing our understanding of global climate, but the mechanisms behind the proxy are largely unknown. Analogies have been drawn to the inorganic precip...

The isotopic ratio and concentration of B in foraminiferal calcite appear to reflect the pH and bicarbonate concentration of seawater. The use of B as a chemical proxy tracer has the potential to transform our understanding of the global carbon cycle, and ocean acidification processes. However, discrepancies between the theory underpinning the B pr...

Plankton, corals, and other organisms produce calcium carbonate skeletons that are integral to their survival, form a key component of the global carbon cycle, and record an archive of past oceanographic conditions in their geochemistry. A key aspect of the formation of these biominerals is the interaction between organic templating structures and...

The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show tha...

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) is an increasingly popular analytical technique, that is able to provide spatially resolved, minimally destructive analyses of heterogeneous materials. The data produced by this technique are inherently complex, and require extensive processing and subjective expert interpretati...

Algal ridges are protective features for coral reefs that form through the accretion and encrustation of reef rubble and debris by crustose coralline algae (CCA) and processes of diagenetic cementation. Carbonate precipitation and dissolution dynamics on and within algal ridge frameworks are poorly understood. We studied the surface and subsurface...

Understanding the drivers of net coral reef calcium carbonate production is increasingly important as ocean warming, acidification, and other anthropogenic stressors threaten the maintenance of coral reef structures and the services these ecosystems provide. Despite intense research effort on coral reef calcium carbonate production, the inclusion o...

Coral skeletal growth is sensitive to environmental change and may be adversely impacted by an acidifying ocean. However, physiological processes can also buffer biomineralization from external conditions, providing apparent resilience to acidification in some species. These same physiological processes affect skeletal composition and can impact pa...

The Mg/Ca of planktic foraminifera is widely used to determine past surface ocean temperatures but temperature is not the only factor that controls test Mg/Ca. Here we quantify the combined influence of seawater temperature, carbon chemistry, and cation chemistry on Orbulina universa Mg/Ca, based on experimental cultures where these factors were va...

The boron concentration (B/Ca ratio) and isotopic composition (δ11B) of biogenic calcite are widely applied to reconstruct past changes in seawater carbonate chemistry. Knowledge of B incorporation pathways into calcite is critical for these applications and for improving the theoretical basis of B proxies. While the canonical interpretation of δ11...

Atom probe tomography (APT) is a powerful technique that is able to determine the distribution of single atoms in three dimensional space with sub-nanometer resolution and a chemical sensitivity in the range of parts-per-million (ppm) [1, 2]. Initially, it was only possible to analyse metals and alloys using APT, but with the development of laser-a...

Atom probe tomography (APT) is a powerful technique to acquire 3D (geo-)chemical information at nanometre length scales. Originally used to study conductive materials (e.g. metal alloys), more recent applications include semiconductors, and insulators such as geological and biomineral materials like bone, teeth, and foraminifera [1-4]. Research int...

The isotopic composition (δ¹¹B) and abundance (B/Ca) of boron in the marine CaCO3 minerals calcite and aragonite are used as paleoceanographic tracers for past oceanic pH and carbon chemistry. These environmental proxies depend upon the ability of CaCO3 minerals to incorporate trace concentrations of B within their structure, and record the state o...

The Mg and Sr content of ostracod valves have been used to reconstruct past temperature and salinity, and their stable isotopes have been used to reveal aspects of marine, lake and estuary hydrology. However, significant uncertainties surround ostracod calcification processes, the incorporation mechanisms of trace elements, and the sensitivity of p...

We have used STXM and PEEM to reveal the underpinning chemistry and nanoscale structure behind palaeo-climate geochemical signatures, such as trace Mg in shells- proposed proxies for palaeo-ocean temperature. This has allowed us to test the chemical assumptions and mechanisms underpinning the use of such empirical proxies. We have determined the co...

We use LA-ICP-MS depth profiling to explore the sensitivity of shell chemistry of the symbiotic planktic foraminifer Orbulina universa to diurnal changes in the holobiont physiology, over a wide range of seawater pH and DIC compositions. B/Ca and U/Ca vary in concert with diurnal Mg/Ca banding, forming compositional bands that are qualitatively con...

The Mg and Sr content of ostracod valves have been used to reconstruct past temperature and salinity, and their stable isotopes have been used to reveal aspects of marine, lake and estuary hydrology. However, significant uncertainties surround the ostracod calcification processes, the incorporation mechanisms of trace elements, and the sensitivity...

The calcite tests of foraminifera lie in marine sediments for thousands to millions of years, before being analysed to generate trace element and isotope palaeoproxy records. These sediments constitute a distinct physio-chemical environment from the conditions in which the tests formed. Storage in sediments can modify the trace element and isotopic...

Although numerous studies have revealed aspects of the physiology of biomineralization and architecture of biominerals [1], and inorganic crystal growth experiments have advanced our understanding of mineral precipitation in the context of biological systems [2], the structure and chemical composition of the mineralising interface between these two...

Ostracods are a prominent source of freshwater [1,2] and marine [3] palaeoproxies. The Mg/Ca and Sr/Ca ratios of their ‘calcitic’ carapace are used as proxies for salinity and temperature. Recently, a number of uncertainties have been raised regarding several aspects of our understanding of these proxies: the hydrological processes ostracods are us...

Growth and calcification of the marine coccolithophorid Emiliania huxleyi is affected by ocean acidification and macronutrients limitation and its response varies between strains. Here we investigated the physiological performance of a highly calcified E. huxleyi strain, NZEH, in a multiparametric experiment. Cells were exposed to different CO2 lev...

The analysis of boron in foraminiferal calcite is a burgeoning palaeo-proxy for past ocean-acidification events [1]. This is particularly relevant to today’s ‘carbonated ocean’ [2]. However, considerable uncertainty surrounds the mechanisms of boron incorporation into the shell. Foraminiferal calcite is known to be highly chemically heterogeneous [...