An organic carbon budget for the Mississippi River turbidity plume and plume contributions to air-sea CO2 fluxes and bottom water hypoxia

Green, Rebecca E.; Bianchi, Thomas S.; Dagg, M.; Walker, Nan D.; Breed, Greg A.

doi:10.1007/bf02784284

Cited by 101 publications

(88 citation statements)

References 77 publications

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“…Additionally, the biological removal rates were calculated by dividing DIC by the plume water residence time (Cai, 2003). Plume water residence time was estimated as 1, 1.5, 6 and 6 days for salinities 0-18, 18-27, 27-32, and 32-34.5, respectively based on satellite-derived suspended sediment distributions collected during 1989-1997 (Green et al, 2006).…”

Section: Estimation Of Stoichiometrymentioning

confidence: 99%

“…These studies have led to an improved understanding of the relationships between nutrient availability and biogeochemical processes such as photosynthesis and remineralization in all aquatic systems. Redfield stoichiometric ratios have been applied in coastal ocean biogeochemical models in the northern Gulf of Mexico (Fennel et al, 2011;Green et al, 2006Green et al, , 2008, and used in linking river nutrient loading with sea surface partial pressure of carbon dioxide (Gypens et al, 2004) and ocean acidification (Borges and Gypens, 2010). These studies have widely assumed that the dissolved inorganic carbon (DIC) uptake and nitrogen removal ratio in the water column follows the Redfield value (i.e.…”

Section: Introductionmentioning

confidence: 99%

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The stoichiometry of inorganic carbon and nutrient removal in the Mississippi River plume and adjacent continental shelf

et al. 2012

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Abstract. The stoichiometry of dissolved inorganic carbon (DIC) and nutrients during biological uptake is widely assumed to follow the Redfield ratios (especially the C / N ratio) in large river plume ecosystems. However, this assumption has not been systematically examined and documented, because DIC and nutrients are rarely studied simultaneously in river plume areas and interpretation of ratios can be confounded by strong river-ocean mixing as well as intense biological activity. We examined stoichiometric ratios of DIC and nutrients (NO and calculated biological removal as the difference between observed concentrations and those predicted from conservative mixing, as determined from a multi-endmember mixing model and observed salinity and total alkalinity. Despite complex physical and biogeochemical influences, relationships between DIC and nutrients were strongly dependent on salinity range and geographic location, and influenced by biological removal. Lower C / Si and N / Si ratios in one nearshore area were likely due to localized input of high Si and low NO − 3 water from adjacent wetlands or preferential removal of nitrogen in the area. When net biological uptake was separated from river-ocean mixing and corrected for preferential N removal, the stoichiometric ratio of C / N / Si was similar to the Redfield ratio, thus supporting the applicability of the Redfield-type C / N / Si ratios in river-plume biogeochemical models.

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Section: Estimation Of Stoichiometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The stoichiometry of inorganic carbon and nutrient removal in the Mississippi River plume and adjacent continental shelf

et al. 2012

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“…In such coastal zones, physical processes and plankton dynamics control the storage and transformation of terrestrial materials onto continental shelves towards the open sea (Green et al, 2006;Gao and Wang, 2008;Dagg et al, 2008). Besides high organic carbon deposition that occurs on the continental shelf, physical processes also induce an organic carbon export to the open sea.…”

Section: Introductionmentioning

confidence: 99%

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

et al. 2011

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Abstract.A coupled hydrodynamic-biogeochemical modelling is developed to address main mechanisms that drive the particulate organic carbon (POC) deposition in the Gulf of Lions (NW-Mediterranean). Low-salinity water (LSW, salinity <37.5) lenses detached from the Rhone River plume under specific wind conditions tend to favour the biological productivity and provide a good opportunity for validating a planktonic ecosystem modelling. A specific calibration dedicated to river plume ecosystems is then proposed and validated using in situ measurements within such LSW lens (BIOPRHOFI cruise -May 2006) and on the Gulf of Lions. During spring 2006, the POC deposition is maximal on the prodelta area and within the coastal area in the Gulf of Lions. Organic detritus mostly contribute to the total POC deposition (82-92 %) whereas the contribution of living organisms (microphytoplankton) appears lower than 17 %. Exploring both influences of terrestrial inputs from the Rhone River and planktonic ecosystems on the POC deposition on the shelf, we estimated that the contribution of terrestrial POM inputs to the total POC deposition is lower than 17 % at the shelf scale during the study period, with maxima during peak discharges of the Rhone River. The main deposition area of terrestrial POC is found in the vicinity of the river mouth in agreement with sediment data. On the other hand, a remarkable influence of marine biological processes on the POC deposition is highlighted further on the shelf (from 60 to 80 m depth). A tight feedback between zooplankton and POM contents in the water column is proposed to explain Correspondence to: P. A. Auger (pierre-amael.auger@aero.obs-mip.fr) the control of POC deposition by zooplankton: terrestrial POM inputs would favour the development of living organisms through photosynthesis and grazing processes increasing the retention of organic matter within the food web. By favouring the development of large-sized zooplankton, LSW lenses may have paradoxically a negative impact on the carbon deposition on the shelf. In the same way, peak discharges of the Rhone River finally increase the gradient of POC deposition between the prodelta and the offshore area in the Gulf of Lions. The biogenic elements from the Rhone River are then exported further offshore through advection of zooplankton communities on the Gulf of Lions shelf.

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“…Coastal seas, estuaries and river plumes are a fundamental part of the global carbon cycle because they link terrestrial, oceanic and atmospheric carbon reservoirs. Riverdominated ocean margins are the most important class of margins in terms of their impact on carbon sequestration (Green et al, 2006). In addition, riverborn nutrients yield the highest rates of primary production in the biosphere .…”

Section: Introductionmentioning

confidence: 99%

“…While Mississippi River water entering the Gulf of Mexico has very high dissolved inorganic carbon (DIC) concentrations and is believed to be a source of atmospheric CO 2 , the region of mixing with oceanic water fosters high levels of primary productivity and inorganic carbon uptake, resulting in an area of estimated CO 2 influx to the surface ocean (Cai, 2003;Green et al, 2006;Lohrenz and Cai, 2006). Evidence indicates maximum phytoplankton biomass and primary production occurs at intermediate salinities (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) in the Mississippi River plume (MRP), while productivity is lightlimited in very low salinity water and nutrientlimited at the edges and outside the plume, where seawater CO 2 partial pressure (pCO 2 ) increases and approaches equilibrium with the atmosphere (Lohrenz et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton carbon fixation gene (RuBisCO) transcripts and air-sea CO2 flux in the Mississippi River plume

et al. 2007

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River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO 2 drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO 2 dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO 2 in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30-32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, a-Synechococcus or high-light Prochlorococcus. However, rbcL transcript abundances were similar among these groups at oligotrophic stations (salinity 34-36). Diatom cell counts and heterokont rbcL RNA showed a strong negative correlation to seawater pCO 2 . While Prochlorococcus cells did not exhibit a large difference between low and high pCO 2 water, Prochlorococcus rbcL RNA concentrations had a strong positive correlation to pCO 2 , suggesting a very low level of RuBisCO RNA transcription among Prochlorococcus in the plume waters, possibly due to their relatively poor carbon concentrating mechanisms (CCMs). These results provide molecular evidence that diatom/pelagophyte productivity is largely responsible for the large CO 2 drawdown occurring in the MRP, based on the cooccurrence of elevated RuBisCO gene transcript concentrations from this group and reduced seawater pCO 2 levels. This may partly be due to efficient CCMs that enable heterokont eukaryotes such as diatoms to continue fixing CO 2 in the face of strong CO 2 drawdown. Our work represents the first attempt to relate in situ microbial gene expression to contemporaneous CO 2 flux measurements in the ocean.

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An organic carbon budget for the Mississippi River turbidity plume and plume contributions to air-sea CO2 fluxes and bottom water hypoxia

Cited by 101 publications

References 77 publications

The stoichiometry of inorganic carbon and nutrient removal in the Mississippi River plume and adjacent continental shelf

The stoichiometry of inorganic carbon and nutrient removal in the Mississippi River plume and adjacent continental shelf

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

Phytoplankton carbon fixation gene (RuBisCO) transcripts and air-sea CO2 flux in the Mississippi River plume

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