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2019
Malfatti, F, Lee C, Tinta T, Pendergraft MA, Celussi M, Zhou YY, Sultana CM, Rotter A, Axson JL, Collins DB, Santander MV, Morales ALA, Aluwihare LI, Riemer N, Grassian VH, Azam F, Prather KA.  2019.  Detection of active microbial enzymes in nascent sea spray aerosol: Implications for atmospheric chemistry and climate. Environmental Science & Technology Letters. 6:171-177.   10.1021/acs.estlett.8b00699   AbstractWebsite

The oceans cover nearly three-quarters of the Earth's surface and produce vast quantities of sea spray aerosols (SSA). Studies have shown that due to ocean biology SSA particles are comprised of much more than just sea salt and often include proteins, lipids, sugars, viruses, and bacteria. In this study, we show for the first time that a diverse array of microbial enzymes (protease, lipases, and alkaline phosphatase) are transferred from the ocean into the atmosphere and often become even more active with measured activities in SSA particles that are 1-2 orders of magnitude higher than those in bulk seawater. We hypothesize that these enzymatic reactions are enhanced in the interfacial environment of droplets and aerosols that can dynamically modify surface chemical species and properties. Simulations reveal that enzyme-containing SSA particles can rapidly coagulate with other preexisting aerosols, thus transferring the impact of enzyme reactions to a broad range of marine aerosols. These biotic reaction pathways are expected to profoundly change the composition of marine aerosols, particularly at the interface, and thus will impact cloud properties in marine environments. Future studies are needed to determine how photochemistry, changing ocean conditions in a warming climate, and other external factors will influence the activities of these enzymes and their impact on the composition of the marine atmosphere.

2017
Stukel, MR, Aluwihare LI, Barbeau KA, Chekalyuk AM, Goericke R, Miller AJ, Ohman MD, Ruacho A, Song H, Stephens BM, Landry MR.  2017.  Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction. Proceedings of the National Academy of Sciences of the United States of America. 114:1252-1257.   10.1073/pnas.1609435114   AbstractWebsite

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from U-238:Th-234 disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C.m(-2).d(-1)) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front wasmechanistically linked to Fe-stressed diatoms and high-mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional similar to 225 mg C.m(-2).d(-1) was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.

1996
Eglinton, TI, Aluwihare LI, Bauer JE, Druffel ERM, McNichol AP.  1996.  Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating. Analytical Chemistry. 68:904-912.   10.1021/ac9508513   AbstractWebsite

This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for C-14 analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the C-14 time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons), Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that Delta(14)C values generally agreed well (+/- 10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon, Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses, Fractionation of isotopes during isolation of individual compounds was minimal (< 5 parts per thousand for delta(13)C), provided the entire peak was collected during PCGC, Trapping of partially coeluting peaks did cause errors, and these results highlight the importance of conducting stable carbon isotopic measurements of each trapped compound in concert with AMS for reliable radiocarbon measurements, The addition of carbon accompanying derivatization of functionalized compounds (e.g., fatty acids and sterols) prior to chromatographic separation represents a further source of potential error, This contribution can be removed using a simple isotopic mass balance approach, Based on these preliminary results, the PCGC-based approach holds promise for accurately determining C-14 ages on compounds specific to a given source within complex, heterogeneous samples.