Plutonium and210Pb distributions in northeast Atlantic sediments: subsurface anomalies caused by non-local mixing

Smith, J. N.; Boudreau, Bernard P.; Noshkin, V.E.

doi:10.1016/0012-821x(86)90097-x

Cited by 120 publications

(53 citation statements)

References 26 publications

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“…Subsurface maxima in 210 Pb excess in the SML, as evident in cores SL9, KG17 and KG37, have also been noted elsewhere, and have been ascribed to local injection of surficial material at depth, for example as infill of large burrows (e.g. Smith et al, 1987;Soetaert et al, 1996;Thomson et al, 2000). This local or impulse bioturbation contrasts with the reworking by multiple small-scale events (termed non-local mixing) that approximate diffusive mixing Radakovitch et al (1999) is shaded.…”

Section: Discussionmentioning

confidence: 62%

Indications of low macrobenthic activity in the deep sediments of the eastern Mediterranean Sea

Basso¹,

Thomson²,

Corselli³

2004

Sci. Mar.

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SUMMARY:The fluxes and budget of organic matter from the oligotrophic surface waters of the eastern Mediterranean to the deep waters are poorly known, and little information is available on past and present macrobenthic activity on the sea floor. Evidence of macrobenthic activity can be direct, through recovery of living organisms or their autochthonous skeletal remains, or indirect, through bioturbation and trace fossils. The evidence of biological activity in deep eastern Mediterranean sediments has been evaluated and compared through 210 Pb profiles from box-cores and study of dredge samples from sites on Medina Rise (1374 m water depth), the Messina Abyssal Plain (4135 m) and several sites along the Mediterranean Ridge, SW and S of Crete (1783 to 3655 m). All these sites are remote from the continental shelves, so the biological benthic activity is expected to depend primarily on primary production from surface waters. The results show that present-day macrobenthos and trace fossils are generally scarce, especially at depths >2500 m. This observation is supported by surface sediment 210 Pb excess distributions that show a surface mixed layer (SML) <6 cm deep in cores from water depths <2500 m and only 2-3 cm at greater depths, and estimated bioturbation intensities similarly fall off with water depth. These values are much lower than the average SML of ~10 cm in marine sediments elsewhere. It is unlikely that the present-day primary production in the eastern Mediterranean can sustain any structured macrobenthic activity at >2500 m. The historical layer of some box-cores and the Pleistocene hardgrounds collected in the Cleft area (Mediterranean Ridge) do, however, record a macrobenthic activity that is apparently more intense than at present, which may be related to higher primary production of the Pleistocene glacial intervals. In contrast with most areas of the present-day deep eastern Mediterranean which depend on surface primary production based on photosynthesis, a relatively dense and diversified macrobenthic community based on chemosynthesis has been recognised at depths >1100 m on the Napoli Dome mud volcano in the Olimpi area, and on the Kazan and other mud volcanoes in the Anaximander Mountains.Key words: deep macrobenthos, eastern Mediterranean, 210 Pb profiles, surface mixed layer, trace fossils, chemosynthesis, sapropels, Pleistocene. RESUMEN: INDICACIONES DE BAJA ACTIVIDAD EN EL MACROBENTOS DE SEDIMENTOS PROFUNDOS EN EL MEDITERRÁNEO ORIEN-TAL. -En el Mediterráneo oriental los flujos de materia orgánica desde las aguas superficiales oligotróficas hasta las aguas profundas son poco conocidos y en general hay poca información sobre la actividad del macrobentos en el fondo del mar. La evidencia de la actividad macrobentónica puede ser directa, a través de los organismos vivos o de los restos de esqueletos autóctonos, o indirecta, a través de la bioturbación y fósiles. La evidencia de la actividad biológica en los sedimentos profundos del Mediterráneo oriental se ha evaluado y comparado por medio de ...

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Section: Discussionmentioning

confidence: 62%

Indications of low macrobenthic activity in the deep sediments of the eastern Mediterranean Sea

Basso¹,

Thomson²,

Corselli³

2004

Sci. Mar.

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“…Sediment studies usually include Pu isotopes in combination with other radionuclides or stable isotopes (e.g. Krishnaswami et al, 1980;Santschi et al, 1980;Benninger and Krishnaswami, 1981;Cochran, 1985;Smith et al, 1986;Carpenter et al, 1987;Lapicque et al, 1987;Buffoni et al, 1992;Huh et al, 1997;Huh and Su, 1999;Smith et al, 2000b;Gascó et al, 2002;Su and Huh, 2002;Moon et al, 2003;Garcia-Orellana et al, 2009). Knowledge of particle mixing rates in sediments is essential for deconvoluting different depth-dependent sediment processes that could influence the distribution of chemical pollutants.…”

Section: Sediment Studiesmentioning

confidence: 99%

Plutonium isotopes as tracers for ocean processes: A review

Lindahl

Lee

Worsfold

et al. 2010

Marine Environmental Research

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Since the first nuclear weapons tests in the 1940s, pulsed inputs of plutonium isotopes have served as excellent tracers for understanding sources, pathways, dynamics and the fate of pollutants and particles in the marine environment. Due to the well-defined spatial and temporal inputs of Pu, the long half- Pu and its unique chemical properties, Pu is a potential tracer for various physical and biogeochemical ocean processes, including circulation, sedimentation and biological productivity, and hence a means of assessing the impacts of global climate change. Due to the source dependency of the Pu isotopic signature, plutonium isotopes are beginning to be exploited as tools for the evaluation and improvement of regional and global ocean models that will enhance understanding of past and future changes in the oceans. This paper addresses the major sources of Pu and the physical and biogeochemical behaviour in the marine environment. Finally, the use of Pu isotopes as tracers for various oceanic processes (e.g. water mass transport, particle export, and sedimentation) is considered.

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“…The current bioturbation model uses 4 different elementary components (François et al 1997) corresponding to the 4 functional groups described in the literature (e.g. Fisher et al 1980, Boudreau 1986, Smith et al 1986, Gardner et al 1987, i.e. biodiffusors, regenerators, upward-conveyors and downward-conveyors.…”

Section: Introductionmentioning

confidence: 99%

Functional approach to sediment reworking by gallery-forming macrobenthic organisms: modeling and application with the polychaete Nereis diversicolor

François¹,

Gérino²,

Stora³

et al. 2002

Mar. Ecol. Prog. Ser.

148

118

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A mechanistic model has been developed to characterize and quantify sediment-mixing due to macrobenthic organisms that construct gallery systems. The mixing model is time-and spacedependent and employs ordinary differential equations. It uses (1) biological parameters -the size of the bioturbated zone, rate of biodiffusion and rate of biotransport; (2) physical parametes -output to the water-column coefficient and rate of physical mixing due to local water currents; and (3) biogeochemical parameters -decay rate of the tracer. This gallery-diffusor model is based on a combination of 2 processes: biodiffusion in the sediment layer containing very dense gallery systems, and biotransport in the region of tube bottoms. The performance of this gallery-diffusor model is compared with that of the biodiffusor model classically used to describe mixing of such organisms. Both models are applied to conservative tracer profiles measured in laboratory experiments with the polychaete Nereis diversicolor. Our new model provides mechanisms to describe and explain the tracer-profile shapes observed in sediments. It includes rapid particle transport from the upper layer of the sediment to the tube bottom zone, which is not taken into account with the biodiffusor model but which is of great importance in understanding the processes of organic matter degradation in the sedimentary column. It also makes possible the accurate quantification of the different components of the mixing process of an organism (in this study, the polychaete N. diversicolor). The gallery-diffusor model constitutes 1 of 5 elementary components in a global bioturbation model that allows the study, quantification and prediction of sediment reworking by macrobenthic communities according to their functional group and composition and/or to the specific characteristics of the individual organisms. KEY WORDS: Bioturbation · Nereis diversicolor · Model · Functional groups · MacrobenthosResale or republication not permitted without written consent of the publisher

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Plutonium and210Pb distributions in northeast Atlantic sediments: subsurface anomalies caused by non-local mixing

Cited by 120 publications

References 26 publications

Indications of low macrobenthic activity in the deep sediments of the eastern Mediterranean Sea

Indications of low macrobenthic activity in the deep sediments of the eastern Mediterranean Sea

Plutonium isotopes as tracers for ocean processes: A review

Functional approach to sediment reworking by gallery-forming macrobenthic organisms: modeling and application with the polychaete Nereis diversicolor

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