The Use of 210Po/210Pb Disequilibria in the Study of the Fate of Marine Particulate Matter

Ritchie, George D.; Shimmield, Graham

doi:10.1007/978-94-011-3686-0_15

Cited by 14 publications

(17 citation statements)

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“…The model results were then used to produce self-consistent carbon budgets and quantify the various pathways for carbon flow within the euphotic zone. Kirchman et al (1993) Kirchman et al (1993) Burkill et al (1993) Burkill et al (1993) Morales et al (1993) Morales et al (1993) Williams (1981b) Ritchie and Shimmield (1991) * Observations in which sampling was occasionally less frequent than stated.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Modeling the relative contributions of autotrophs and heterotrophs to carbon flow at a Lagrangian JGOFS station in the Northeast Atlantic: The importance of DOC

Fasham

Boyd

Savidge

1999

Limnology & Oceanography

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A size-structured ecosystem model was developed and fitted to an extensive set of observations of size-fractionated biomass, primary and heterotrophic bacterial production, respiration, particle flux, and zooplankton herbivory obtained on a cruise in the NE Atlantic during 20 days of the spring bloom. Rates of water-column-integrated primary production and heterotrophic bacterial production were used to force the model, and the model parameters were determined by optimizing the model to the remaining observations. A unique model solution was not possible in the absence of dissolved organic carbon (DOC) measurements. By setting a weak constraint on the DOC concentrations (that they should remain broadly constant), a solution was obtained that predicted a small DOC increase during the bloom period; this increase was similar in magnitude to observations in other areas and produced a good fit with the other data. Major conclusions: (1) gross primary production (GPP) was over twice the measured 14 C production estimates; (2) phytoplankton exudation was a major source of DOC, and 35% of the GPP flowed through the DOC and was utilized by the bacteria, with a low gross growth efficiency (17%); (3) 62% of the community respiration came from organisms Ͻ5 m in size; (4) the major source of food for microzooplankton was phytoplankton 1-5 m in size, but the mesozooplankton ingested more microzooplankton than phytoplankton; and (5) only 8% of the total net primary production was grazed by mesozooplankton. These results provide quantitative support to the emerging consensus on the relative roles of large and small organisms in the euphotic zone and demonstrate the necessity of measuring DOC to constrain the carbon budget within the euphotic zone.A prominent objective of biological oceanography is to determine and understand the processes controlling the fluxes of carbon in the ocean over time. The most important of these is the fate of CO 2 taken up by phytoplankton in the euphotic zone. We wish to quantify how this carbon passes through the food web to its eventual fate as carbon respired within the euphotic zone or carbon exported to the deeper ocean. An attempt to budget carbon was one of the aims of the Joint Global Ocean Flux Study (JGOFS) North Atlantic Bloom Experiment (NABE) carried out in 1989 at a number of stations along the 20ЊW meridian. The most extensive coverage was at 47ЊN, where Bender et al. (1992) calculated a carbon budget for the upper water column (0-50 m) over a 13-d period during the spring bloom. Of the total gross primary production of 1.83 mmol C m Ϫ2 , they estimated that 63% was respired, 16% was stored as particulate organic carbon (POC) within the upper 50 m, and 18% was sedimented out to depths Ͼ50 m. Bender et al. (1992) did not attempt to unravel the details 1 Corresponding author: mjf@soc.soton.ac.uk. AcknowledgmentsWe thank those colleagues in the UK BOFS Program who provided data for this study and also the staff of the British Oceanographic Data Centre for assistance with accessi...

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Section: Acknowledgmentsmentioning

confidence: 99%

Modeling the relative contributions of autotrophs and heterotrophs to carbon flow at a Lagrangian JGOFS station in the Northeast Atlantic: The importance of DOC

Fasham

Boyd

Savidge

1999

Limnology & Oceanography

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“…Fisher et al (1983) concluded that 210 Po/ 210 Pb ratios in fecal pellets of zooplankton are half those of their phytoplankton food supply in field samples. In addition, Ritchie and Shimmield (1991) and Miquel et al (1993) refer to the role of fecal pellets in transporting radionuclides from the surface water to depth.…”

Section: Affinity Of 210 Po and 210 Pb For Poc And Biogenic Silicamentioning

confidence: 99%

“…The use of 210 Po and 210 Pb as tracers for particle transport was shown by Rama et al (1961), Craig et al (1973), Turekian et al (1974) and others. 210 Po and 210 Pb export from the euphotic zone and regeneration rates within the thermocline have usually been calculated with traditional steady-state models (Bacon et al, 1976;Nozaki and Tsunogai, 1976;Ritchie and Shimmield, 1991;Shimmield et al, 1995;Sarin et al, 1999). Buesseler et al (1992), and Rutgers van der Loeff et al (1997) showed that steady-state transport models have disadvantages in the case of very rapidly varying fluxes caused by phytoplankton bloom events.…”

Section: Introductionmentioning

confidence: 99%

A two-tracer (210Po–234Th) approach to distinguish organic carbon and biogenic silica export flux in the Antarctic Circumpolar Current

Friedrich

Loeff

2002

Deep Sea Research Part I: Oceanographic Research Papers

111

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We attempt to quantify and qualify the particle export from the surface water of the Antarctic Circumpolar Current during a spring phytoplankton bloom by the simultaneous use of the tracers 210 Po and 234 Th. We present data from the Southern Ocean JGOFS expedition in 1992 at about 61W, from the marginal ice zone to the Polar Frontal region. Radionuclide export was calculated with a one-dimensional non-steady-state scavenging model. Rapidly changing activities of 210 Pb and 210 Po during the phytoplankton bloom and the application of the tracer pair 210 Po/ 210 Pb with particle-reactive parent and daughter required a new solution to the non-steady-state scavenging model. The observed fractionation of 210 Po and 234 Th on particles, dependent on particle composition (POC/biogenic silica ratio), corroborates the known preference of 210 Po for cytoplasm. A combination of these two tracers can help to characterize the nature (i.e. organic carbon and biogenic silica content) of the material settling out of the mixed layer, and thus to arrive at a more detailed interpretation of export fluxes than is possible with 234 Th alone. In the Polar Front region, where diatoms are dominant in the phytoplankton and where the highest export rates were observed, we find a preferential settling of biogenic silica when heavily silicified diatom species occur. In contrast, POC and biogenic silica are exported with comparable efficiency when diatom species with thinner frustules prevail. The export of biogenic opal and carbon is then closely coupled. In the southern Antarctic Circumpolar Current (sACC), where siliceous organisms are not dominant in the plankton, we find a preferential settling of siliceous material over POC. r

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“…In the marine environment, 210 Po is introduced mainly from the in situ production by 210 Pb decay. While, 210 Pb content in seawater is supplied from the in situ decay of 226 Ra in water column and atmospheric gaseous 222 Rn (Ritchie and Shimmield, 1991). In shallow water, the predominant source of 210 Pb is atmospheric fallout (Benninger, 1978;Yang and Lin, 1992).…”

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Activities of 210Po and 210Pb in the water column at Kuala Selangor, Malaysia

Theng

Mohamed

2005

Journal of Environmental Radioactivity

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The Use of 210Po/210Pb Disequilibria in the Study of the Fate of Marine Particulate Matter

Cited by 14 publications

References 17 publications

Modeling the relative contributions of autotrophs and heterotrophs to carbon flow at a Lagrangian JGOFS station in the Northeast Atlantic: The importance of DOC

Modeling the relative contributions of autotrophs and heterotrophs to carbon flow at a Lagrangian JGOFS station in the Northeast Atlantic: The importance of DOC

A two-tracer (210Po–234Th) approach to distinguish organic carbon and biogenic silica export flux in the Antarctic Circumpolar Current

Activities of 210Po and 210Pb in the water column at Kuala Selangor, Malaysia

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