Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation

Hawkes, Jeffrey A.Uppsala universitet,Analytisk kemi,Carl von Ossietzky Univ Oldenburg, Res Grp Marine Geochem, ICBM MPI Bridging Grp, Inst Chem & Biol Marine Environm ICBM, D-26129 Oldenburg, Germany. (author)

Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood(1,2). Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212-401 degrees C. In laboratory experiments, where we heated samples to 380 degrees C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years(3).

Rossel, Pamela E.Carl von Ossietzky Univ Oldenburg, Res Grp Marine Geochem, ICBM MPI Bridging Grp, Inst Chem & Biol Marine Environm ICBM, D-26129 Oldenburg, Germany.;Alfred Wegener Inst, HGF MPG Grp Deep Sea Ecol & Technol, D-27570 Bremerhaven, Germany. (author)
Stubbins, AronUniv Georgia, Skidaway Inst Oceanog, Marine Sci, Savannah, GA 31411 USA. (author)
Butterfield, DavidUniv Washington, Joint Inst Study Atmosphere & Oceans, Seattle, WA 98115 USA.;NOAA PMEL, Seattle, WA 98115 USA. (author)
Connelly, Douglas P.Univ Southampton, Natl Oceanog Ctr, Southampton SO14 3ZH, Hants, England. (author)
Achterberg, Eric P.Univ Southampton, Natl Oceanog Ctr, Southampton SO14 3ZH, Hants, England.;GEOMAR Helmholtz Ctr Ocean Res, D-24148 Kiel, Germany. (author)
Koschinsky, AndreaJacobs Univ Bremen, D-28759 Bremen, Germany. (author)
Chavagnac, ValerieUniv Toulouse, Lab Geosci Environm Toulouse, F-31400 Toulouse, France. (author)
Hansen, Christian T.Univ Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen, Germany.;Univ Bremen, Dept Geosci, D-28359 Bremen, Germany. (author)
Bach, WolfgangUniv Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen, Germany.;Univ Bremen, Dept Geosci, D-28359 Bremen, Germany. (author)
Dittmar, ThorstenCarl von Ossietzky Univ Oldenburg, Res Grp Marine Geochem, ICBM MPI Bridging Grp, Inst Chem & Biol Marine Environm ICBM, D-26129 Oldenburg, Germany. (author)
Uppsala universitetAnalytisk kemi (creator_code:org_t)

By the author/editor: Hawkes, Jeffrey ...; Rossel, Pamela E ...; Stubbins, Aron; Butterfield, Dav ...; Connelly, Dougla ...; Achterberg, Eric ...; show more...; Koschinsky, Andr ...; Chavagnac, Valer ...; Hansen, Christia ...; Bach, Wolfgang; Dittmar, Thorste ...; show less...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Earth and Relate ...; and Geochemistry

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