Riverine DOM

Raymond, Peter A.; Spencer, Robert G. M.

doi:10.1016/b978-0-12-405940-5.00011-x

Cited by 121 publications

(99 citation statements)

References 205 publications

(310 reference statements)

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“…Four of the rivers examined in this study (Amazon, Congo, Paraná and Lena Rivers) account for the largest tDOC fluxes to the ocean [Raymond and Spencer , 2014]. In the same study, the Mississippi and Ganges-Brahmaputra Rivers are also listed among the top ten rivers with the highest tDOC fluxes.…”

Section: Uncertainty and Global Estimate For The Amount Of Photochemimentioning

confidence: 89%

“…The large rivers selected for this study (Table 2) drain 23% of the land area on five continents, contribute to 33% of the freshwater discharge and 28% of the tDOC flux to the ocean [Cauwet, 2002;Milliman and Farnsworth, 2011;Raymond and Spencer , 2014]. The St. Lawrence Estuary was also sampled for the examination of photochemical transformation of DOC across its freshwater end to a salinity of 31 PSU ( Table 2).…”

Section: Sample Collectionmentioning

confidence: 99%

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Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Aarnos

Gélinas

Kasurinen

et al. 2018

Global Biogeochemical Cycles

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When terrigenous dissolved organic carbon (tDOC) rich in chromophoric dissolved organic matter (tCDOM) enters the ocean, solar radiation mineralizes it partially into dissolved inorganic carbon (DIC). This study addresses the amount and the rates of DIC photoproduction from tDOC and the area of ocean required to photomineralize tDOC. We collected water samples from 10 major rivers, mixed them with artificial seawater, and irradiated them with simulated solar radiation to measure DIC photoproduction and the photobleaching of tCDOM. The linear relationship between DIC photoproduction and tCDOM photobleaching was used to estimate the amount of photoproduced DIC from the tCDOM fluxes of the study rivers. Solar radiation was estimated to mineralize 12.5 ± 3.7 Tg C yr−1 (10 rivers)−1 or 18 ± 8% of tDOC flux. The irradiation experiments also approximated typical apparent spectral quantum yields for DIC photoproduction (ϕλ) over the entire lifetime of the tCDOM. Based on ϕλs and the local solar irradiances in river plumes, the annual areal DIC photoproduction rates from tDOC were calculated to range from 52 ± 4 (Lena River) to 157 ± 2 mmol C m−2 yr−1 (Mississippi River). When the amount of photoproduced DIC was divided by the areal rate, 9.6 ± 2.5 × 106 km2 of ocean was required for the photomineralization of tDOC from the study rivers. Extrapolation to the global tDOC flux yields 45 (31–58) Tg of photoproduced DIC per year in the river plumes that cover 34 (25–43) × 106 km2 of the ocean.

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Section: Uncertainty and Global Estimate For The Amount Of Photochemimentioning

confidence: 89%

Section: Sample Collectionmentioning

confidence: 99%

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Aarnos

Gélinas

Kasurinen

et al. 2018

Global Biogeochemical Cycles

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“…This fresh organic matter is rapidly cycled through the food web in the upper ocean and up to 50% of the primary production is processed by heterotrophic bacteria (Cole et al 1988). On the other hand, the riverine DOM reaching the oceans (~0.2 Gt C yr -1 , Raymond and Spencer 2015) is a complex and heterogeneous mix of compounds of diverse origin (terrestrial and aquatic), chemical properties and reactivity.…”

Section: Introductionmentioning

confidence: 99%

When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition

et al. 2016

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Heterotrophic bacterial communities in marine environments are exposed to a heterogeneous mixture of dissolved organic compounds with different bioreactivity that may control both their activity and composition. The coastal environment is an example of a mixing area where recalcitrant allochthonous organic matter from rivers can encounter labile organic matter from marine phytoplanktonic blooms. The objective of this study was to explore the effects of mixed qualities of dissolved organic matter (DOM) on bacterial community activity (BCA) and bacterial community composition (BCC) and to test for a priming effect when DOM sources are added in combination. Coastal marine bacterial communities were incubated separately with a mixture of amino acids and with natural riverine DOM or with both sources together for 42 days. Addition of amino acids alone or in combination with riverine DOM led to a similar stimulation of BCA compared to control condition, whereas addition of riverine DOM alone did not modify BCA compared to the control. On the contrary, BCC analyzed by 16S rRNA gene pyrosequencing was not affected by the addition of amino acids alone, but changed dramatically with riverine DOM alone or in combination with amino acids. Our 2 results show that changes in BCA and BCC can be driven by different types of DOM, but that these changes are not necessarily coupled. Moreover, the addition of labile DOM did not modify the microbial decomposition of riverine DOM, nor the BCC, suggesting that a priming effect did not occur under these experimental conditions.

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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;.…”

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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Riverine DOM

Cited by 121 publications

References 205 publications

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition

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

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