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1. Dissolved organic phosphorus (DOP) distributions in the Eastern Indian Ocean and subtropical South Pacific Ocean

   Liang, Z. ; Letscher, R.T. ; McCabe, K. ; Marconi, D. ; Sigman, D.M. ; Knapp, A.N. ( February 2020 , 2020 Ocean Sciences Meeting)

   Significant rates of export production and nitrogen fixation occur in oligotrophic gyres in spite of low inorganic nutrient concentrations in surface waters. Prior work suggests that dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) are important nutrient sources when inorganic nutrients are scarce. In particular, DOP has been shown to be an important P source for diazotrophs, which may be better suited to using low concentrations of organic vs. inorganic P. Prior modeling work has also suggested that DOP is important for supporting export production in oligotrophic gyres. However, validation of such models is limited by the number ofmore »upper ocean DOP concentration measurements, especially in the South Pacific and Indian Oceans. Here, we present measurements of DOP concentration from the 2016 GO-SHIP I08S and I09N meridional transect in Eastern Indian Ocean, and DON and DOP concentration measurements from the 2017 GO-SHIP P06 zonal transect in the subtropical South Pacific Ocean. Together with DOC and DON concentration measurements from prior occupations of the same GO-SHIP lines we evaluated changes in euphotic zone DOC:DON:DOP stoichiometry. Stoichiometry changes across these two transects are used to infer regions of preferential DON and/or DOP production and consumption. Specifically, north of 36 S in the Indian Ocean an increase in DOC:DON and DOC:DOP concentration ratios, from 11:1 to 14:1 and 118:1 to 190:1, respectively, are observed. Similarly, west of 136 W in the South Pacific Ocean significant increases in DOC:DOP and DON:DOP concentration ratios are observed, from 224:1 to 398:1 and 21:1 to 39:1, respectively. These stoichiometric shifts in upper ocean DOC:DON:DOP concentration ratios are considered in the context of ocean circulation, especially upwelling patterns in the Indian and eastern Pacific Oceans, as well as prior observations of the distribution of nitrogen fixation, especially in the western tropical South Pacific.« less
2. Radiocarbon in Dissolved Organic and Inorganic Carbon of the South China Sea

   https://doi.org/10.1029/2020JC016073  

   Ding, Ling ; Qi, Yuanzhi ; Shan, Sen ; Ge, Tiantian ; Luo, Chunle ; Wang, Xuchen ( April 2020 , Journal of Geophysical Research: Oceans)
3. High dissolved organic radiocarbon in precipitation during winter and its implication on the carbon cycle

   https://doi.org/10.1016/j.scitotenv.2020.140246  

   Cha, Ji-Yeon ; Lee, Seung-Cheol ; Lee, Eun-Ju ; Go, Minjung ; Dasari, Kishore Babu ; Yim, Yong-Hyeon ; Oh, Neung-Hwan ( November 2020 , Science of The Total Environment)
4. RADIOCARBON IN DISSOLVED ORGANIC CARBON BY UV OXIDATION: PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMS

   https://doi.org/10.1017/RDC.2020.102  

   Xu, Li ; Roberts, Mark L ; Elder, Kathryn L ; Kurz, Mark D ; McNichol, Ann P ; Reddy, Christopher M ; Ward, Collin P ; Hanke, Ulrich M ( February 2021 , Radiocarbon)

   ABSTRACT This study describes a procedural blank assessment of the ultraviolet photochemical oxidation (UV oxidation) method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). A retrospective compilation of Fm and δ 13 C results for secondary standards (OX-II, glycine) between 2009 and 2018 indicated that a revised blank correction was required to bring results in line with accepted values. The application of a best-fit mass-balance correction yielded a procedural blank of 22.0 ± 6.0 µg C with Fm of 0.30 ± 0.20 and δ 13 Cmore »of –32.0 ± 3.0‰ for this period, which was notably higher and more variable than previously reported. Changes to the procedure, specifically elimination of higher organic carbon reagents and improved sample and reactor handling, reduced the blank to 11.0 ± 2.75 µg C, with Fm of 0.14 ± 0.10 and δ 13 C of –31.0 ± 5.5‰. A thorough determination of the entire sample processing blank is required to ensure accurate isotopic compositions of seawater DOC using the UV oxidation method. Additional efforts are needed to further reduce the procedural blank so that smaller DOC samples can be analyzed, and to increase sample throughput.« less
5. Seasonality of Dissolved Organic Carbon in the Upper Northeast Pacific Ocean

   https://doi.org/10.1029/2018GB006152  

   Bif, Mariana B. ; Hansell, Dennis A. ( May 2019 , Global Biogeochemical Cycles)