Dilution limits dissolved organic carbon utilization in the deep ocean

Arrieta, Jesús M.; Mayol, Eva; Hansman, Roberta L.; Herndl, Gerhard J.; Dittmar, Thorsten; Duarte, Carlos M.

doi:10.1126/science.1258955

Cited by 256 publications

(302 citation statements)

References 31 publications

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“…This recognized paradigm [Benner and Amon, 2015] opposes earlier ideas of "geomolecule" formation-where small DOC subunits condense to larger, recalcitrant polymers [Hedges et al, 2000]. These size-age trends are also inconsistent with recent hypotheses, suggesting that dilution of DOC ultimately governs its biogeochemical cycling [Arrieta et al, 2015]. Instead, a direct linkage between molecular size, composition, and Δ 14 C is indicative of intrinsic biological reactivity differences and 14 C age of the DOC pool.…”

Section: Discussioncontrasting

confidence: 52%

Pacific carbon cycling constrained by organic matter size, age and composition relationships

et al. 2016

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Marine dissolved organic carbon (DOC) is a major global carbon reservoir, yet its cycling remains poorly understood. Previous work suggests that DOC molecular size and chemical composition can significantly affect its bioavailability. Thus, DOC size and composition may control DOC cycling and radiocarbon age (via Δ 14 C). Here we show that DOC molecular size is correlated to DOC Δ 14 C in the Pacific Ocean. Our results, based on a series of increasing molecular size fractions from three depths in the Pacific, show increasing DOC Δ 14 C with increasing molecular size. We use a size-age distribution model to predict the DOC and Δ 14 C of ultrafiltered DOC. The model predicts both large and small surface DOC with high Δ 14 C and a narrow range (200-500 Da) of low Δ 14 C DOC. Deep model offsets suggest different size distributions and/or Δ 14 C sources at 670-915 m. Our results suggest that molecular size and composition are linked to DOC reactivity and storage in the ocean.

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Section: Discussioncontrasting

confidence: 52%

Pacific carbon cycling constrained by organic matter size, age and composition relationships

et al. 2016

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“…Our estimated E a might also be influenced by the amount, bioavailability or extreme dilution of individual organic substrates. Recently, it has been argued that the dark ocean organic matter pool contains hundreds of thousands of individual compounds at extremely dilute concentrations (Kattner et al, 2011;Arrieta et al, 2015). Thus, molecular diffusion of individual compounds could be the limiting factor for prokaryotic growth.…”

Section: Other Factors Affecting the Prokaryote Production To Temperamentioning

confidence: 99%

Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production

et al. 2016

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Marine prokaryotes play a key role in cycling of organic matter and nutrients in the ocean. Using a unique dataset (>14,500 samples), we applied a space-for-time substitution analysis to assess the temperature dependence of prokaryotic heterotrophic production (PHP) in epi-(0-200 m), meso-(201-1000 m) and bathypelagic waters (1001-4000 m) of the global ocean. Here, we show that the temperature dependence of PHP is fundamentally different between these major oceanic depth layers, with an estimated ecosystem-level activation energy (E ) of 36 ± 7 kJ mol −1 for the epipelagic, 72 ± a 15 kJ mol −1 for the mesopelagic and 274 ± 65 kJ mol −1 for the bathypelagic realm. We suggest that the increasing temperature dependence with depth is related to the parallel vertical gradient in the proportion of recalcitrant organic compounds. These E a predict an increased PHP of about 5, 12, and 55% in the epi-, meso-, and bathypelagic ocean, respectively, in response to a water temperature increase by 1 • C. Hence, there is indication that a major thus far underestimated feedback mechanism exists between future bathypelagic ocean warming and heterotrophic prokaryotic activity.

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“…Bioavailability has traditionally been linked to the chemical composition and structure of DOC, but more recently it has been shown to also vary depending on a range of other external factors (Raymond and Spencer, 2015). These factors include nutrient status, redox state, mineral-particle associations, terrestrial inputs, sunlight, biological production of recalcitrant compounds, changing microbial community composition, and the effect of priming or the extreme dilution of individual molecules (e.g., Amon and Benner, 1996;Thingstad et al, 1999;Del-Giorgio and Davies, 2003;Bianchi, 2011;Keil and Mayer, 2014;Arrieta et al, 2015;. About 4% of the ocean's net primary production escapes degradation in the surface layer to be exported as DOC to the ocean interior at a rate of about 2 Pg C year −1 (Hansell et al, 2012), roughly equalling the annual net ocean uptake of CO 2 (Sarmiento and Gruber, 2006).…”

Section: Introductionmentioning

confidence: 99%

Large Stimulation of Recalcitrant Dissolved Organic Carbon Degradation by Increasing Ocean Temperatures

et al. 2018

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More than 96% of organic carbon in the ocean is in the dissolved form, most of it with lifetimes of decades to millennia. Yet, we know very little about the temperature sensitivity of dissolved organic carbon (DOC) degradation in a warming ocean. Combining independent estimates from laboratory experiments, oceanographic cruises and a global ocean DOC cycling model, we assess the relationship between DOC decay constants and seawater temperatures. Our results show that the apparent activation energy of DOC decay (E a ) increases by three-fold from the labile (lifetime of days) and semi-labile (lifetime of months) to the semi-refractory (lifetime of decades) DOC pools, with only minor differences between the world's largest ocean basins. This translates into increasing temperature coefficients (Q 10 ) from 1.7-1.8 to 4-8, showing that the generalized assumption of a constant Q 10 of ∼2 for biological rates is not universally applicable for the microbial degradation of DOC in the ocean. Therefore, rising ocean temperatures will preferentially impact the microbial degradation of the more recalcitrant and larger of the three studied pools. Assuming a uniform 1 • C warming scenario throughout the ocean, our model predicts a global decrease of the DOC reservoir by 7 ± 1 Pg C. This represents a 15% reduction of the semi-labile + semi-refractory DOC pools.

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Dilution limits dissolved organic carbon utilization in the deep ocean

Cited by 256 publications

References 31 publications

Pacific carbon cycling constrained by organic matter size, age and composition relationships

Pacific carbon cycling constrained by organic matter size, age and composition relationships

Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production

Large Stimulation of Recalcitrant Dissolved Organic Carbon Degradation by Increasing Ocean Temperatures

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