Net accumulation and flux of dissolved organic carbon and dissolved organic nitrogen in marine plankton communities

Søndergaard, Morten; Williams, Peter; Cauwet, Gustave; Riemann, Bo; Robinson, Carol; Terzić, Senka; Woodward, E. Malcolm S.; Worm, Jakob

doi:10.4319/lo.2000.45.5.1097

Cited by 137 publications

(107 citation statements)

References 51 publications

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“…4a). Conversely, the POM C/N ratio decreased after 15 August while the DOM C/N ratio increased, which could be related to the release of carbohydrate (Norrman, Zweifel, Hopkinson, & Fry, 1995;Søndergaard et al, 2000). Therefore, the fresh organic matter produced inshore at the origin of the filament was still present off-shore.…”

Section: The Filament Studymentioning

confidence: 92%

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Álvarez-Salgado

Doval

Borges

et al. 2001

Progress in Oceanography

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Daily changes in the concentrations of carbon and nitrogen species were monitored during the course of a Lagrangian drifter experiment in a recurrent upwelling filament south of Cape Finisterre (NW Iberian Upwelling System). A drifting buoy released at the southern edge of the upwelling centre generated by the Cape moved 60km southwestwards from 3 to 7 August 1998. Organic matter in the 50m deep study water mass (average 77±2 µM C) consisted of: 57µM C of dissolved organic matter (DOM) with a C/N molar ratio of 19±2; 6µM C of DOM with a C/N ratio of 9±2, and 14µM C of 50% DOM and 50% suspended organic matter (POM susp ) with a C/N ratio of 6.0±0.4.Net conversion of consumed inorganic salts into accumulated TOM=POM susp +DOM was ෂ40% for nitrogen and ෂ30% for carbon. Since the parcel of water crossed the shelf-edge, these conversion efficiencies are equivalent to net horizontal export-ratio of 0.4 and 0.3 respectively. A second drifter was deployed in the offshore-end of the filament, and was displaced 20km west between 14 and 17 August 1998. Nitrate was exhausted in the surface water and no significant changes were observed in the variables measured during the course of the second experiment. Low C/N ratios (6.5±0.4) and rapid POM susp /DOM inter-conversion in the 20 µM C excess observed in the study volume points to the persistence of the labile materials formed on the shelf during transport to the ocean. Our data demonstrate a) the key role of upwelling filaments in off-shelf export of organic materials and b) the major contribution of DOM to this horizontal export, a previously unaccounted amount.The high nitrogen content of the materials exported make them attractive organic substrates for use by microbial populations in the adjacent oligotrophic ocean. 

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Section: The Filament Studymentioning

confidence: 92%

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Álvarez-Salgado

Doval

Borges

et al. 2001

Progress in Oceanography

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“…Experimental blooms in enclosures and mesocosms have shown exponential growth of algae with tight covariation of carbon and nutrients, increases in pH, and little DOC accumulation as long as nutrients were replete (Antia et al 1963;Banse 1994;Alldredge et al 1995;Sondergaard et al 2000;Engel et al 2002). Maximum Chl a concentrations were usually observed near the time of nutrient depletion (Alldredge et al 1995;Norrman et al 1995;Engel et al 2002).…”

Section: Discussionmentioning

confidence: 99%

“…Maximum Chl a concentrations were usually observed near the time of nutrient depletion (Alldredge et al 1995;Norrman et al 1995;Engel et al 2002). After nutrient depletion, carbon and nitrogen dynamics were usually decoupled, as reflected in the accumulation of DOC (Banse 1994;Norrman et al 1995;Sondergaard et al 2000), increases in particulate C : N ratios caused by excess particulate carbon (Banse 1994;Alldredge et al 1995;Engel et al 2002), and release of carbon-rich DOM (Biddanda and Benner 1997;Wetz and Wheeler 2003). Most of these studies involved the addition of nutrients and focused on the uncoupling of POC and PN dynamics (Alldredge et al 1995;Engel et al 2002).…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, the traditional biogeochemical paradigm that the use and release of nutrients at the ecosystem level obeys a simple constant stoichiometry (the Redfield ratio), recorded in the fixed ratio of C to N and P in seston (Redfield et al, 1963), has been successfully challenged. Temporal decoupling of carbon and nutrient dynamics has been reported repeatedly after bloom events (Engel et al 2002;Wetz and Wheeler 2003) and is reflected, for instance, in the temporal accumulation of carbon-rich dissolved organic matter (DOM; Duursma 1961;Sondergaard et al 2000), increases in the particulate C : N ratio, and the formation of transparent carbon-rich exopolymeric particles (Alldredge et al 1995). The decoupling of carbon and nutrient cycling at the community level is related to the different abilities of autotrophs and heterotrophs to maintain homeostasis (Sterner and Elser 2003) and to the different dynamics of the particulate and DOM pools (Banse 1994).…”

Section: Acknowledgmentsmentioning

confidence: 99%

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Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a ¹³C tracer experiment

Meersche

Middelburg

Soetaert

et al. 2004

Limnology & Oceanography

108

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We tracked flows of carbon and nitrogen during an experimental phytoplankton bloom in a natural estuarine assemblage in Randers Fjord, Denmark. We used 13 C-labeled dissolved inorganic carbon to trace the transfer of carbon from phytoplankton to bacteria. Ecosystem development was followed over a period of 9 d through changes in the stocks of inorganic nutrients, pigments, particulate organic carbon and nitrogen, dissolved organic carbon (DOC), and algal and bacterial polar-lipid-derived fatty acids (PLFA). We quantified the incorporation of 13 C in phytoplankton and bacterial biomass by carbon isotope analysis of specific PLFA. A dynamic model based on unbalanced algal growth and balanced growth of bacteria and zooplankton adequately reproduced the observations and provided an integral view of carbon and nitrogen dynamics. There were three phases with distinct carbon and nitrogen dynamics. During the first period, nutrients were replete, an algal bloom was observed, and carbon and nitrogen uptake occurred at a constant ratio. Because there was little algal exudation of DOC, transfer of 13 C from phytoplankton to bacteria was delayed by 1 d, compared with the labeling of phytoplankton. In the second phase, the exhaustion of dissolved inorganic nitrogen resulted in decoupling of carbon and nitrogen flows caused by unbalanced algal growth and the exudation of carbon-rich dissolved organic matter by phytoplankton. During the final, nutrient-depleted phase, carbon and nitrogen cycling were dominated by the microbial loop and there was accumulation of DOC. The main source (60%) of DOC was exudation by phytoplankton growing under nitrogen limitation. Heterotrophic processes were the main source of dissolved organic nitrogen (94%). Most of the carbon exudated by algae was respired by the bacteria and did not pass to higher trophic levels. The dynamic model successfully reproduced the evolution of trophic pathways during the transition from nutrient-replete to -depleted conditions, which indicates that simple models provide a powerful tool to study the response of pelagic ecosystems to external forcings.Understanding the transfer of carbon and nutrients between the environment and autotrophs and heterotrophs is key to furthering our knowledge on biogeochemical cycling and ecosystem functioning and how both relate. Ecologists have long distinguished two trophic pathways in the pelagic environment-the herbivorous or classical food web and the microbial loop-but now acknowledge the existence of a continuum of trophic structures with the herbivorous food 1 Corresponding author (K.vdMeersche@nioo.knaw.nl). AcknowledgmentsWe thank Joop Nieuwenhuize for analytical and logistic support, our Eurotroph colleagues for a stimulating research environment, and two anonymous reviewers for constructive feedback. We thank Wim Vyverman and Luc De Meester for constructive remarks. The modeling part of this research was performed in the frame of a master's thesis at Ghent University (K.V.d.M.).

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“…The temporally increased concentration of TOC in the upper layer in summer throughout observation might be due to the accumulation of P-omitted DOM. Søndergaard et al [2000] also demonstrated the increase in the C/N ratio in the latter half of the incubation experiment during 30 days. They concluded that this increase in the C:N ratio resulted from the accumulation of DOC.…”

Section: Seasonal Variations In Uvs and Uvl Oc Compositionmentioning

confidence: 97%

Concentration and UV reactivity of total organic carbon in the upper layer in the oligotrophic subtropical western North Pacific

Sangkyun¹,

Hama²,

Ishii³

et al. 2010

J. Geophys. Res.

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[1] Characteristics of temporal variation in the vertical profile of total organic carbon (TOC) were investigated in the upper layer of the ocean at various latitudes (10-30°N) of 137°E in the western North Pacific subtropical gyre. Bulk TOC was divided into labile and stable fractions by the specific UV irradiation to evaluate their contributions to the temporal fluctuation of TOC. Authentic specimens and dissolved organic carbon collected from coastal waters were used to examine the correspondence between the photochemical reactivity to the specific UV irradiation and biological reactivity. The concentration of TOC in the upper layer was higher in summer when the surface layer is well stratified and was lower in winter when the mixed layer deepened. Although the winter mixed layer is shallower in lower latitudes, the amplitude of the seasonal variations in the top 50 m weighted mean TOC concentration (19.5-27.7 mM) did not vary considerably over the subtropical zones we studied. A major fraction (51.9-89.8%) of TOC was stable against specific UV irradiation and was thought to be mainly composed of biologically stable organic compounds, but the seasonal variation of TOC at each latitude was mainly attributable to the variation of UV labile fraction. This finding suggests that the seasonal variation of TOC in the upper layer is explained by the biological production of TOC in summer surface water and its vertical mixing with low UV, labile TOC in winter. Upward advection of subsurface water due to the passage of cyclonic eddies and changes in the geostrophic current are also likely to affect the temporal TOC variation, in particular, in the lower latitudes where winter mixed layer and permanent thermocline are shallower.

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Net accumulation and flux of dissolved organic carbon and dissolved organic nitrogen in marine plankton communities

Cited by 137 publications

References 51 publications

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a ¹³C tracer experiment

Concentration and UV reactivity of total organic carbon in the upper layer in the oligotrophic subtropical western North Pacific

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Net accumulation and flux of dissolved organic carbon and dissolved organic nitrogen in marine plankton communities

Cited by 137 publications

References 51 publications

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a 13C tracer experiment

Concentration and UV reactivity of total organic carbon in the upper layer in the oligotrophic subtropical western North Pacific

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Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a ¹³C tracer experiment