Stubbins Aron

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Stubbins
First Name
Aron
ORCID
0000-0002-3994-1946

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  • Article
    Drivers of organic molecular signatures in the Amazon River
    (American Geophysical Union, 2021-06-11) Kurek, Martin ; Stubbins, Aron ; Drake, Travis W. ; Moura, José M. S. ; Holmes, Robert M. ; Osterholz, Helena ; Dittmar, Thorsten ; Peucker-Ehrenbrink, Bernhard ; Mitsuya, Miyuki ; Spencer, Robert G. M.
    As climate-driven El Niño Southern Oscillation (ENSO) events are projected to increase in frequency and severity, much attention has focused on impacts regarding ecosystem productivity and carbon balance in Amazonian rainforests, with comparatively little attention given to carbon dynamics in fluvial ecosystems. In this study, we compared the wet 2012 La Niña period to the following normal hydrologic period in the Amazon River. Elevated water flux during the La Niña period was accompanied by dilution of inorganic ion concentrations. Furthermore, the La Niña period exported 2.77 Tg C yr−1 more dissolved organic carbon (DOC) than the normal period, an increase greater than the annual amount of DOC exported by the Mississippi River. Using ultra-high-resolution mass spectrometry, we detected both intra- and interannual differences in dissolved organic matter (DOM) composition, revealing that DOM exported during the dry season and the normal period was more aliphatic, whereas compounds in the wet season and following the La Niña event were more aromatic, with ramifications for its environmental role. Furthermore, as this study has the highest temporal resolution DOM compositional data for the Amazon River to-date we showed that compounds were highly correlated to a 6-month lag in Pacific temperature and pressure anomalies, suggesting that ENSO events could impact DOM composition exported to the Atlantic Ocean. Therefore, as ENSO events increase in frequency and severity into the future it seems likely that there will be downstream consequences for the fate of Amazon Basin-derived DOM concurrent with lag periods as described here.
  • Preprint
    Deciphering ocean carbon in a changing world
    ( 2016-01-13) Moran, Mary Ann ; Kujawinski, Elizabeth B. ; Stubbins, Aron ; Fatland, Rob ; Aluwihare, Lihini I. ; Buchan, Alison ; Crump, Byron C. ; Dorrestein, Pieter C. ; Dyhrman, Sonya T. ; Hess, Nancy J. ; Howe, Bill ; Longnecker, Krista ; Medeiros, Patricia M. ; Niggemann, Jutta ; Obernosterer, Ingrid ; Repeta, Daniel J. ; Waldbauer, Jacob R.
    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.
  • Article
    Dissolved organic matter dynamics in the epipelagic Northwest Pacific low-latitude western boundary current system: insights from optical analyses
    (American Geophysical Union, 2021-08-17) Wang, Chao ; Li, Yizhen ; Li, Yan ; Zhou, Hui ; Stubbins, Aron ; Dahlgren, Randy A. ; Wang, Zhiheng ; Guo, Weidong
    High-resolution horizontal and vertical distribution of dissolved organic carbon (DOC), chromophoric, and fluorescent dissolved organic matter (CDOM and FDOM) were investigated in the western boundary current system of the tropical Northwest Pacific (<200 m) in autumn 2017. A strong correlation between DOC and stratification index indicated that the vertical DOC profile was primarily regulated by physical processes. The association of high aCDOM(254) with the maximum chlorophyll (Chl a) layer infers phytoplankton-sourced dissolved organic matter (DOM). The aCDOM(325) and humic-like FDOM (FDOMH) showed an accumulation in the deeper layer and positive correlations with apparent oxygen utilization and Chl a concentration at the maximum chlorophyll layer, suggesting that these components are related to microbial degradation of biogenic materials. Elevated Chl a at the frontal area between the North Equatorial Current (NEC) and cold Mindanao Eddy enhanced DOM production. Input waters from the NEC showed higher DOC, but lower FDOMH, than inflow waters from the New Guinea Coastal Current/Undercurrent (NGC(U)C). A mass balance model estimated a 6-times higher lateral DOC flux from the NEC tropical-gyre branch (12°N–7.5°N) than that from the subtropical-gyre branch (12°N–17°N). Based on comparison with long-term (1994–2015) average DOC fluxes for the same season, eddy and upstream processes contributed 38%, 46% and 40% of lateral DOC fluxes for the NEC tropical-gyre branch, NGC(U)C and export North Equatorial Counter Current, respectively. These results demonstrated that the quasi-permanent Mindanao and Halmahera eddies greatly enhance lateral export of DOM with altered properties throughout this large conjunction area.
  • Article
    Hydrological and biogeochemical controls on absorption and fluorescence of dissolved organic matter in the northern South China Sea
    (John Wiley & Sons, 2017-12-29) Wang, Chao ; Guo, Weidong ; Li, Yan ; Stubbins, Aron ; Li, Yizhen ; Song, Guodong ; Wang, Lei ; Cheng, Yuanyue
    The Kuroshio intrusion from the West Philippine Sea (WPS) and mesoscale eddies are important hydrological features in the northern South China Sea (SCS). In this study, absorption and fluorescence of dissolved organic matter (CDOM and FDOM) were determined to assess the impact of these hydrological features on DOM dynamics in the SCS. DOM in the upper 100 m of the northern SCS had higher absorption, fluorescence, and degree of humification than in the Kuroshio Current of the WPS. The results of an isopycnal mixing model showed that CDOM and humic-like FDOM inventories in the upper 100 m of the SCS were modulated by the Kuroshio intrusion. However, protein-like FDOM was influenced by in situ processes. This basic trend was modified by mesoscale eddies, three of which were encountered during the fieldwork (one warm eddy and two cold eddies). DOM optical properties inside the warm eddy resembled those of DOM in the WPS, indicating that warm eddies could derive from the Kuroshio Current through Luzon Strait. DOM at the center of cold eddies was enriched in humic-like fluorescence and had lower spectral slopes than in eddy-free waters, suggesting inputs of humic-rich DOM from upwelling and enhanced productivity inside the eddy. Excess CDOM and FDOM in northern SCS intermediate water led to export to the Pacific Ocean interior, potentially delivering refractory carbon to the deep ocean. This study demonstrated that DOM optical properties are promising tools to study active marginal sea-open ocean interactions.
  • Dataset
    Dissolved black carbon (DBC) concentrations and related data from water samples collected between 2011 and 2019 in the Pacific and Atlantic Oceans and from rivers in North America, South America, Africa, and Russia
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-08-19) Wagner, Sasha ; Brandes, Jay ; Stubbins, Aron
    Pacific Ocean samples were collected from Station ALOHA (22.45°N, 158.00°W) during the Hawaii Ocean Time-series (HOT) 301 cruise aboard the R/V Ka`imikai-O-Kanaloa in April 2018. Atlantic Ocean samples were collected from Hydrostation S (31.67°N, 64.17°W) during the Bermuda Atlantic Time Series (BATS) 358 cruise aboard the R/V Atlantic Explorer in April 2019. River samples were collected from the main stem of the Amazon (Brazil), Congo (Democratic Republic of the Congo), Northern Dvina (Russia), Kolyma (Russia), and Mississippi Rivers (USA) at various time points between 2011 and 2018. Samples were analyzed for dissolved black carbon (DBC), dissolved organic carbon (DOC), and stable carbon isotopes. Data are published in Table 1 and as Supplemental Data in Wagner et al., 2019 (doi: 10.1038/s41467-019-13111-7). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/878750