Title: Low Molecular Weight Dissolved Organic Carbon: Aging, Compositional Changes, and Selective Utilization During Global Ocean Circulation

Abstract

The composition and cycling dynamics of marine dissolved organic carbon (DOC) have received increased interest in recent years; however, little research has focused on the refractory, low molecular weight (LMW) component that makes up the majority of this massive C pool. In this study, we measured stable isotopic (δ¹³C), radioisotopic (Δ¹⁴C), and compositional (C/N, ¹³C solid-state NMR) properties of separately isolated high molecular weight (HMW) and LMW DOC fractions collected using a coupled ultrafiltration and solid phase extraction approach from throughout the water column in the North Central Pacific and Central North Atlantic. The selective isolation of LMW DOC material allowed the first investigation of the composition and cycling of a previously elusive fraction of the DOC pool. The structural composition of the LMW DOC material was homogeneous throughout the water column and closely matched carboxylic-rich alicyclic material that has been proposed as a major component of the marine refractory DOC pool. Examination of offsets in the measured parameters between the deep waters of the two basins provides the first direct assessment of changes in the properties of this material with aging and utilization during ocean circulation. While our direct measurements largely confirm hypotheses regarding the relative recalcitrance of HMWmore » and LMW DOC, we also demonstrate a number of novel observations regarding the removal and addition of DOC during global ocean circulation, including additions of fresh carbohydrate-like HMW DOC to the deep ocean and large-scale removal of both semilabile HMW and recalcitrant LMW DOC.« less

Authors:

Broek, Taylor A. B.  ^[1];

• Search DOE PAGES for author "Broek, Taylor A. B."
• Search DOE PAGES for ORCID "0000-0003-2508-3431"

Walker, Brett D.  ^[2];

• Search DOE PAGES for author "Walker, Brett D."
• Search DOE PAGES for ORCID "0000-0003-4904-826X"

Guilderson, Thomas P.  ^[3];

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• Search DOE PAGES for ORCID "0000-0001-9371-7059"

Vaughn, John S.  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-8883-8777"

Mason, Harris E.  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-1840-0550"

McCarthy, Matthew D.  ^[4]

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• Search DOE PAGES for ORCID "0000-0002-5426-7005"

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+ Show Author Affiliations

1. Univ. of California, Santa Cruz, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Univ. of Ottawa, ON (Canada); Univ. of California, Irvine, CA (United States)
3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
4. Univ. of California, Santa Cruz, CA (United States)

Publication Date:

Mon Jun 08 00:00:00 EDT 2020

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)

OSTI Identifier:

1658694

Report Number(s):

LLNL-JRNL-801378
Journal ID: ISSN 0886-6236; 1005159

Grant/Contract Number:  

AC52-07NA27344; 1358041

Resource Type:

Accepted Manuscript

Journal Name:

Global Biogeochemical Cycles

Additional Journal Information:

Journal Volume: 34; Journal Issue: 6; Journal ID: ISSN 0886-6236

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; dissolved organic carbon; solid‐state NMR; molecular weight; CRAM; radiocarbon; carbon stable isotopes