New guidelines for the application of Stokes' models to the sinking velocity of marine aggregates

Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density and porosity of aggregates and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with (i) linearly increasing sinking velocity with depth and (ii) temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency, as recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of ≈0.25±0.04, and the subtropical gyres show lower values of about 0.10±0.03. In addition to temperature as a driving factor for remineralization, diatom frustule size co-determines POC fluxes in silicifier-dominated ocean regions, while calcium carbonate enhances the aggregate excess density and thus sinking velocity in subtropical gyres. Prescribing rising carbon dioxide (CO2) concentrations in stand-alone runs (without climate feedback), M4AGO alters the regional ocean atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run, while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a test bed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles and, in particular, on the biological carbon pump.

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Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates

Biogeosciences ◽

10.5194/bg-7-2613-2010 ◽

2010 ◽

Vol 7 (9) ◽

pp. 2613-2624 ◽

Cited By ~ 174

Author(s):

M. H. Iversen ◽

H. Ploug

Keyword(s):

Respiration Rate ◽

Skeletonema Costatum ◽

Aggregate Size ◽

Respiration Rates ◽

Marine Aggregates ◽

Organic Carbon Fluxes ◽

Ocean Carbon ◽

Sinking Velocities ◽

Sinking Velocity ◽

Combined Data

Abstract. Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted), Skeletonema costatum aggregates (opal ballasted), and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted). Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than those of aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregates of different composition and sources. Compiled carbon-specific respiration rates (including this study) vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The carbon-specific respiration rate per meter settled varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size. It was lower for calcite ballasted aggregates as compared to that of similar sized opal ballasted aggregates.

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Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocities of macroscopic organic aggregates (marine snow)

Biogeosciences Discussions ◽

10.5194/bgd-7-3335-2010 ◽

2010 ◽

Vol 7 (3) ◽

pp. 3335-3364 ◽

Cited By ~ 8

Author(s):

M. H. Iversen ◽

H. Ploug

Keyword(s):

Respiration Rate ◽

Skeletonema Costatum ◽

Aggregate Size ◽

Respiration Rates ◽

Carbon Remineralization ◽

Marine Aggregates ◽

Organic Carbon Fluxes ◽

Ocean Carbon ◽

Sinking Velocities ◽

Sinking Velocity

Abstract. Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted), Skeletonema costatum aggregates (opal ballasted), and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted). Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregate of different composition and sources. Compiled carbon-specific respiration rates (including this study) vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The calculated carbon remineralization length scale due to microbial respiration and sinking velocity of mm-large marine aggregates was higher for calcite ballasted aggregates as compared to opal-ballasted aggregates. It varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size.

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Influence of plankton community structure on the sinking velocity of marine aggregates

Global Biogeochemical Cycles ◽

10.1002/2016gb005372 ◽

2016 ◽

Vol 30 (8) ◽

pp. 1145-1165 ◽

Cited By ~ 39

Author(s):

L. T. Bach ◽

T. Boxhammer ◽

A. Larsen ◽

N. Hildebrandt ◽

K. G. Schulz ◽

...

Keyword(s):

Community Structure ◽

Plankton Community ◽

Marine Aggregates ◽

Plankton Community Structure ◽

Sinking Velocity

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Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

10.5194/bg-2019-378 ◽

2019 ◽

Author(s):

Joeran Maerz ◽

Katharina D. Six ◽

Irene Stemmler ◽

Soeren Ahmerkamp ◽

Tatiana Ilyina

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

Global Ocean ◽

Co2 Uptake ◽

Diatom Frustule ◽

Marine Aggregates ◽

Carbon Pump ◽

The Impact ◽

Biological Carbon Pump ◽

Sinking Velocity

Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density, and porosity of aggregates, and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with linearly increasing sinking velocity with depth, and temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency which has been recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of &approx; 0.25 ± 0.04 and the subtropical gyres show lower values of about 0.10 ± 0.03. In addition to temperature as a driving factor, diatom frustule size co-determines POC fluxes in silicifiers-dominated ocean regions while calcium carbonate enhances the aggregate excess density, and thus sinking velocity in subtropical gyres. In ocean standalone runs and rising carbon dioxide (CO2) without CO2 climate feedback, M4AGO alters the regional ocean-atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a testbed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles, and, in particular, on the biological carbon pump.

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New Guidelines Urge PAD Screening

Internal Medicine News ◽

10.1016/s1097-8690(06)72665-8 ◽

2006 ◽

Vol 39 (2) ◽

pp. 2

Author(s):

ALICIA AULT

Keyword(s):

New Guidelines

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New Guidelines Issued to Aid Management of CAP

Internal Medicine News ◽

10.1016/s1097-8690(07)70471-7 ◽

2007 ◽

Vol 40 (8) ◽

pp. 40

Author(s):

BARBARA J. RUTLEDGE

Keyword(s):

New Guidelines

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Glycemic Control Targets Relaxed in New Guidelines

Hospitalist News ◽

10.1016/s1875-9122(09)70126-9 ◽

2009 ◽

Vol 2 (6) ◽

pp. 1-3

Author(s):

MIRIAM E. TUCKER

Keyword(s):

Glycemic Control ◽

New Guidelines

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Vitamin D Deficiency/Insufficiency and Challenges in Developing Global Vitamin D Fortification and Supplementation Policy in Adults

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000117 ◽

2012 ◽

Vol 82 (4) ◽

pp. 237-259 ◽

Cited By ~ 9

Author(s):

Moshe Ben-Shoshan

Keyword(s):

Vitamin D ◽

Vitamin D Deficiency ◽

Search Strategy ◽

Epidemiologic Studies ◽

Vitamin D Supplementation ◽

Vitamin D Status ◽

Societal Burden ◽

Time Period ◽

New Guidelines ◽

In Cis

This review summarizes studies discussing vitamin D status in adults and reveals that vitamin D deficiency/insufficiency is highly prevalent in adults and that current fortification and supplementation policies are inadequate. Background and aims: Studies suggest a crucial role for adequate vitamin D status in various health conditions including bone metabolism, cancer, cardiovascular diseases, and allergies. However, relatively little is known about poor vitamin D status and unmet needs in adults. This report aims to highlight the contribution of epidemiologic studies (through the identification of health effects and societal burden) to the development of vitamin D fortification and supplementation policies and reveal unmet global challenges in adults. Methods: In order to assess worldwide vitamin D status in adults, the search strategy combined the medical literature database MEDLINE (using PubMed) for the time period between January 1, 1980 and February 28, 2011, using the key words vitamin D deficiency and insufficiency, and included articles in which access to full text was possible and in which healthy adults were assessed according to one of four commonly used vitamin D threshold classifications. Results: This report reveals that vitamin D deficiency occurs in 4.10 % [95 % CI (confidence interval), 3.93 %, 4.27 %] to 55.05 % (54.07 %, 56.03 %) of adults, while insufficiency occurs in 26.07 % (24.82 %, 27.33 %) to 78.50 % (77.85 %, 79.16 %), depending on the classification used. However, lack of overlap in CIs and high value of I2 statistics indicate considerable heterogeneity between studies. Further, certain populations (i. e. dark-skinned individuals, immigrants, and pregnant women) may be at higher risk for poor vitamin D status. Conclusion: Current policies for vitamin D supplementation and fortification are inadequate and new guidelines are required to improve vitamin D status in adults.

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