Distribution and cycling of terrigenous dissolved organic matter in the ocean

Opsahl, Stephen P.; Benner, Ronald

doi:10.1038/386480a0

Cited by 504 publications

(417 citation statements)

References 26 publications

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“…On the scale of the whole Arctic Ocean, however, it is controversial how efficiently deep-water formation transports terrigenous dissolved organic matter into the deep ocean. According to Opsahl et al (1999), a major proportion of terrigenous dissolved organic matter leaves the Arctic Ocean via surface currents and is not incorporated into deep waters.…”

Section: Resultsmentioning

confidence: 99%

Evidence for terrigenous dissolved organic nitrogen in the Arctic deep sea

Dittmar

2004

Limnology & Oceanography

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To trace the fate of terrigenous dissolved organic nitrogen (DON) in the Arctic Ocean, principal-components analyses (PCA) was used on a data set of 13 amino acids released via hydrolyses from a total of 110 water samples from Russian rivers, adjacent near-shore locations, and the Laptev Sea. The first component of the PCA distinguished significantly between terrigenous DON from the rivers (1.2 Ϯ 0.1) and marine-derived DON in the deep central Arctic Ocean (Ϫ1.1 Ϯ 0.2). The significance of this distinction was validated with amino acid data from seawater and river samples from other regions. The second PCA component correlated significantly with the proportion of D-alanine, a tracer for microbial degradation. The percentage of terrigenous DON in the Arctic Ocean was assessed from the first PCA component. The model was calibrated using data from the rivers (100% terrigenous) and the deep central Arctic Ocean (ϳ0% terrigenous) as end members. Terrigenous DON accounted for 28 Ϯ 13% of the total DON on the Laptev Sea shelf, which is in good agreement with independent, lignin-based estimates. High proportions of terrigenous DON (up to 100%) were calculated for the continental slope down to 2,000 m depth and are probably due to downward convection of brine-enriched shelf waters. The model presented here provides the first direct evidence of terrigenous DON in the deep sea. The model may be directly applied to trace the fate of terrigenous DON in other terrestrially dominated marine environments.

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Section: Resultsmentioning

confidence: 99%

Evidence for terrigenous dissolved organic nitrogen in the Arctic deep sea

Dittmar

2004

Limnology & Oceanography

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“…al., 1995 . Other investigations, however, focus on photochemical and microbial transformations of terrigenous DOM, which may contribute to the produc-Ž tivity in these nearshore systems Moran et al, 1991;Chin-Leo and Benner, 1992;Bushaw et al, 1996; . Opsahl and Benner, 1997 . Optical absorption and fluorescence of CDOM also vary across estuarine salinity gradients, indicating photobleaching and re-Ž movalrdilution of terrigenous CDOM Blough et al, .…”

Section: Introductionmentioning

confidence: 98%

Photogeneration of singlet oxygen and free radicals in dissolved organic matter isolated from the Mississippi and Atchafalaya River plumes

et al. 2000

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Ž. The photoreactivity to UV light of ultrafiltered dissolved organic matter DOM collected during cruises along salinity transects in the Mississippi and Atchafalaya River plumes was examined by measuring photogenerated free radicals and Ž 1 . singlet molecular oxygen O photosensitization. Singlet oxygen was detected by its infrared phosphorescence at 1270 nm 2 using both steady-state and time-resolved techniques. The 1 O quantum yields were corrected for self-quenching of 1 O by 2 2 Ž . the DOM substrates. Photogenerated free radicals were monitored by electron paramagnetic resonance EPR . Two size fractions of the dissolved organic matter were examined: material retained with a 3 kDa cut-off filter and material retained with a 1 kDa cut-off filter. The highest 1 O quantum yields were found in the lower molecular mass material. There was 2 little change in the 1 O quantum yields with increasing salinity, indicating that the photosensitizing ability of the estuarine 2 DOM does not decrease as terrestrial DOM is transported to sea and mixes with marine DOM. In contrast to 1 O formation, 2 the steady-state levels of photoproduced free radicals did not significantly differ between high and low molecular mass DOM, and the levels were substantially higher in riverine DOM than along plume salinity transects. This rapid transition in free radical level suggests that terrestrially-derived DOM experiences significant changes in this aspect of its photoreactivity Ž . in low -10 ppt salinity waters. Published by Elsevier Science B.V.

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“…Most of the DOC found in the sea surface has marine origin (Opsahl and Benner, 1997). Phytoplankton exudation or cell lysis (DOCp) represents a primary source of labile organic carbon-supplying bacterial metabolism (Baines and Pace, 1991).…”

Section: Introductionmentioning

confidence: 99%

Bacterioplankton niche partitioning in the use of phytoplankton-derived dissolved organic carbon: quantity is more important than quality

2016

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Some prokaryotes are known to be specialized in the use of phytoplankton-derived dissolved organic carbon (DOCp) originated by exudation or cell lysis; however, direct quantification measurements are extremely rare. Several studies have described bacterial selectivity based on DOCp quality, but very few have focused on the quantity of DOCp, and the relative importance of each of these variables (for example, quantity versus quality) on prokaryote responses. We applied an adapted version of the MAR-FISH (microautoradiography coupled with catalyzed reporter deposition fluorescence in situ hybridization) protocol using radiolabelled exudates from axenic algal cultures to calculate a specialization index (d') for large bacterioplankton phylogenetic groups using DOCp from different phytoplankton species and at different concentrations to elucidate to what extent the bacterial response to DOCp is driven by resource quantity (different DOCp concentrations) or by quality (DOCp from different phytoplankton species). All bacterial phylogenetic groups studied had lower d' at higher DOCp concentration, indicating more generalist behavior at higher resource availabilities. Indeed, at increasing resource concentrations, most bacterial groups incorporated DOCp indiscriminately, regardless of its origin (or quality). At low resource concentrations, only some specialists were able to actively incorporate the various types of organic matter effectively. The variability of bacterial responses to different treatments was systematically higher at varying concentrations than at varying DOCp types, suggesting that, at least for this range of concentrations (10-100 μM), DOCp quantity affects bacterial responses more than quality does. Therefore, resource quantity may be more relevant than resource quality in the bacterial responses to DOCp and affect how bacterioplankton use phytoplankton-derived carbon.

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Distribution and cycling of terrigenous dissolved organic matter in the ocean

Cited by 504 publications

References 26 publications

Evidence for terrigenous dissolved organic nitrogen in the Arctic deep sea

Evidence for terrigenous dissolved organic nitrogen in the Arctic deep sea

Photogeneration of singlet oxygen and free radicals in dissolved organic matter isolated from the Mississippi and Atchafalaya River plumes

Bacterioplankton niche partitioning in the use of phytoplankton-derived dissolved organic carbon: quantity is more important than quality

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