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Mackintosh, SA, Dodder NG, Shaul NJ, Aluwihare LI, Maruya KA, Chivers SJ, Danil K, Weller DW, Hoh E.  2016.  Newly identified DDT-related compounds accumulating in Southern California bottlenose dolphins. Environmental Science & Technology. 50:12129-12137.   10.1021/acs.est.6b03150   AbstractWebsite

Nontargeted GCxGC-TOF/MS analysis of blubber from 8 common bottlenose dolphins (Tursiops truncatus) inhabiting the Southern California Bight was performed to identify novel, bioaccumulative DDT-related compounds and to determine their abundance relative to the commonly studied DDT-related compounds. We identified 45 bioaccumulative DDT-related compounds of which the majority (80%) is not typically monitored in environmental media. Identified compounds include transformation products, technical mixture impurities such as tris(chlorophenyl)methane (TCPM), the presumed TCPM metabolite tris(chlorophenyl)methanol (TCPMOH), and structurally related compounds with unknown sources, such as hexa- to octachlorinated diphenylethene. To investigate impurities in pesticide mixtures as possible sources of these compounds, we analyzed technical DDT, the primary source of historical contamination in the region, and technical Dicofol, a current use pesticide that contains DDT-related compounds. The technical mixtures contained only 33% of the compounds identified in the blubber, suggesting that transformation products contribute to the majority of the load of DDT-related contaminants in these sentinels of ocean health. Quantitative analysis revealed that TCPM was the second most abundant compound class detected in the blubber, following DDE, and TCPMOH loads were greater than DDT. QSPR estimates verified 4,4',4"-TCPM and 4,4'4,"-TCPMOH are persistent and bioaccumulative.

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.

Meador, TB, Aluwihare LI, Mahaffey C.  2007.  Isotopic heterogeneity and cycling of organic nitrogen in the oligotrophic ocean. Limnology and Oceanography. 52:934-947. AbstractWebsite

We measured the nitrogen (N) isotopic composition (delta N-15) of a large set (n = 38) of high-molecular-weight (HMW) dissolved organic nitrogen (DON) samples isolated from the tropical and subtropical North Atlantic and Pacific Oceans. The delta N-15 signature of surface HMW DON is relatively invariable in both oligotrophic basins (4.1 +/- 0.6 in the Atlantic; 5.4 +/- 0.8 in the Pacific) and shows little correlation with sources or concentrations of N supporting new production in the euphotic zone. While large variations in delta N-15 of bulk HMW DON are not apparent, delta N-15 of proteins isolated from sites with relatively high rates of N-2 fixation (> 80 mu mol N m(-2) d(-1)) were consistently depleted in N-15 relative to bulk HMW DON and to proteins isolated from sites where N-2 fixation does not routinely occur. This small component of HMW DON appears to be cycling more rapidly than bulk HMW DON and may be indicative of fresh DON contributed by organisms in the surface ocean. Furthermore, delta N-15 of DNA extracted from the bacterial size fraction (0.2 - 0.5 mu m) revealed that free-living bacteria may be an important sink for isotopically depleted N produced during N-2 fixation. We suggest that there exists a tight coupling between the production and uptake of DON contributed by diazotrophs (N-2 fixers) in regions where N-2 fixation provides a major input of new nitrogen.

Meador, TB, Aluwihare LI.  2014.  Production of dissolved organic carbon enriched in deoxy sugars representing an additional sink for biological C drawdown in the Amazon River plume. Global Biogeochemical Cycles. 28:1149-1161.   10.1002/2013gb004778   Abstract

In North Atlantic waters impacted by discharges from the Amazon and Orinoco Rivers, where planktonic diatom-diazotroph associations (DDA) were active, we observed that an average ( standard deviation) of 61 +- 12% of the biological drawdown of dissolved inorganic carbon (DIC) was partitioned into the accumulating total organic carbon pool, representing a flux of up to 94 Tg C yr(-1). This drawdown corresponded with chemical alteration of ultrafiltered dissolved organic matter (UDOM), including increases in stable C isotopic composition (C-13) and C:N. The dissolved carbohydrate component of UDOM also increased with biological DIC drawdown and diatom-associated diazotroph (i.e., Richelia) abundance. New carbohydrates could be distinguished by distinctively high relative abundances of deoxy sugars (up to 55% of monosaccharides), which may promote aggregate formation and enhance vertical carbon export. The identified production of non-Redfieldian, C-enriched UDOM thus suggests a mechanism to explain enhanced C sequestration associated with DDA N-2 fixation, which may be widespread in mesohaline environments.

Moran, MA, Kujawinski EB, Stubbins A, Fatland R, Aluwihare LI, Buchan A, Crump BC, Dorrestein PC, Dyhrman ST, Hess NJ, Howe B, Longnecker K, Medeiros PM, Niggemann J, Obernosterer I, Repeta DJ, Waldbauer JR.  2016.  Deciphering ocean carbon in a changing world. Proceedings of the National Academy of Sciences of the United States of America. 113:3143-3151.   10.1073/pnas.1514645113   AbstractWebsite

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.