Evidence for reduced biogenic silica dissolution rates in diatom aggregates

Moriceau, Brivaëla; Garvey, Michael; Ragueneau, Olivier; Passow, Uta

doi:10.3354/meps333129

Cited by 46 publications

(54 citation statements)

References 58 publications

(49 reference statements)

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“…Small detritus remineralises three times faster than the large detritus in the original model (Gruber et al, 2006), which is left unchanged in this study as well. Moriceau et al (2007) points to a similar ratio of silica dissolution rates between aggregated and freely suspended diatoms.…”

Section: Modeling Particle Fluxesmentioning

confidence: 99%

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

2009

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Abstract. The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opalrich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of Correspondence to: G. Fischer (gerhard.fischer@uni-bremen.de) 0.29 Tg per year down to 3000 m off the NW African upwelling region between 5 and 35 • N. Simple parameterisations of remineralisation and sinking rates in such models, however, limit their capability in reproducing the flux variation in the water column.

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Section: Modeling Particle Fluxesmentioning

confidence: 99%

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

2009

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“…Phytoplankton cells inside aggregates stay alive longer than those that are free in the medium (Moriceau et al 2007), and a living phytoplankton cell is less subject to bacterial degradation. Moreover, in large aggregates, minerals may limit decomposition by physically protecting organic matter with which they are associated (Arnarson and Keil 2000).…”

Section: Biodegradability Of the Different Settling Velocity Classes-mentioning

confidence: 99%

“…BSiO 2 dissolved 10 times faster in NT1-C and two times faster in NT1-D than in NT1-A and NT1-B, and two times faster in NT2-D than in NT2-A, NT2-B, and NT2-C (Table 6). While the embedding of diatom cells inside aggregates or fresh fecal pellets slows down BSiO 2 dissolution (Passow et al 2003;Schultes 2004;Moriceau et al 2007), the breakdown of external cell membranes by enzymes and/or the breakage of diatom frustules in fecal pellet by coprophagy (Schultes 2004;Ragueneau et al unpubl. data) would enhance BSiO 2 dissolution rates.…”

Section: Biodegradability Of the Different Settling Velocity Classes-mentioning

confidence: 99%

“…Bacterial activity enhanced diatom frustule dissolution through ectoenzymatic hydrolysis of the protein membrane surrounding the diatom frustule (Bidle andAzam 1999, 2001); however, in the bathypelagic layers, hydrostatic pressure slows down this process through inhibition of bacterial ectohydrolase (Tamburini et al 2006). At the scale of the particle, when diatoms are embedded inside aggregates in a matrix of degraded OM, dissolution of biogenic silica (BSiO 2 ) decreases (Moriceau et al 2007). …”

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confidence: 99%

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Composition and degradation of marine particles with different settling velocities in the northwestern Mediterranean Sea

Goutx¹,

Wakeham

Lee

et al. 2007

Limnology & Oceanography

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Settling particles were collected from the Ligurian Sea in the northwestern Mediterranean Sea in May 2003 and separated by elutriation into different settling velocity classes (.230, 115-230, 58-115, and ,58 m d 21 ). Particles of the different classes were incubated for 5 d to study their biodegradability. Particulate opal content and organic compound composition (amino acids, pigments, lipids, and carbohydrates) were analyzed initially and at regular time intervals during the incubation period. Most particles (48-67% of total mass) sank at greater than 230 m d 21 and were dominated by large diatom-derived aggregates produced during the spring bloom period. The initial organic composition and the biological lability of these particles varied with settling velocity. The strong phytoplankton signal was visible in all settling velocity classes, while slower settling particles carried with them a greater zooplankton and bacterial signature. As the different class particles decomposed, their compositions changed and became more similar with time, with a dominance of compounds that suggests a more degraded state: the amino acids c-aminobutyric acid and b-alanine, the pigments pyropheophorbide and pheophytin, the deoxysugars fucose and rhamnose, and lipid metabolites (diglycerides and monoglycerides, alcohols, and free fatty acids). Biogenic opal in the particles dissolved faster in more degraded particles than in fresher particles, suggesting that loss of organic matter may expose opal to dissolution. The coupling of settling velocity and decomposition rate measurements shows quantitatively that slower settling particles are quickly degraded and AcknowledgmentsThis research was part of the MedFlux and PECHE (Production and Export of Carbon: Control by Heterotrophs at small temporal scale) programs and was supported by the U.S. National Science Foundation Chemical Oceanography Program (OCE-0136370, OCE-0136318, and OCE-0113687) and the French CNRS (Centre National de la Recherche Scientifique), respectively. Participation of B.M. was funded by ORFOIS (Origin and Fate of Biogetic Particle Fluxes in the ocean) (EVK2-CT2001-00100). We thank Michael Peterson, Lynn Abramson, Jenni Szlosek, Meaghan Askea, and Isabell Putnam for shipboard and laboratory help; David Hirschberg and Michael Peterson for CHN analysis; Claude Mante for help with statistical data treatment; and the captain and crew of the RV Seward Johnson II. We wish to acknowledge the associate editor and two anonymous reviewers for very helpful comments and suggestions on the manuscript. This is MedFlux contribution 7 and MSRC contribution 1318.

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“…Since then it has been found that nutrient concentrations in the pore water of natural aggregates are elevated compared to those of the surrounding water (Gotschalk & Alldredge 1989, Brzezinski et al 1997. Possibly higher nutrient concentrations within aggregates increase the survival time of cells (Gotschalk & Alldredge 1989, Moriceau et al 2007). The higher viability of cells enclosed within aggregates is consistent with the idea of aggregates as hot spots of activity (Azam 1998) and has far-reaching implications, not only for their life cycle and reseeding, but also for the recycling of carbon and silica.…”

Section: Changes In Viability Of Thalassiosira Weissflogii Due To Aggmentioning

confidence: 99%

Applicability of the FDA assay to determine the viability of marine phytoplankton under different environmental conditions

Garvey¹,

Moriceau²,

Passow³

2007

Mar. Ecol. Prog. Ser.

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Knowing which fraction of a phytoplankton population is viable would often be helpful in answering ecological or physiological questions. However, viability stains (1) often do not function properly, especially with diatoms, (2) are rarely used, and (3) frequently appear to give ambiguous results. Here, we investigate the performance of the FDA viability assay in detail and test its applicability for investigating 2 ecologically important questions. The functioning of the assay was tested for several diatom species, as well as for Emiliania huxleyi (coccolithophorid) and Phaeocycstis globosa (Prymnesiophyceae). Additionally, changes in the viability of Thalassiosira weissflogii (diatom) -(1) due to aggregation and (2) during a prolonged stationary phase induced by nutrient limitation -were explored. Whereas the method generated solid results with some species, including T. weissflogii, it was less trustworthy or even totally ineffective with others. Ambiguous definitions of viability and cell death, as well as temporary changes in the strength of the fluorescence signal, complicate the interpretation of viability measurements. However, exiting ecological results can be attained with this method. Experiments with T. weissflogii suggested that the vast majority of cells, rather than individual survivors remained viable for over a month in an illuminated, nutrient-devoid environment. Aggregation significantly prolonged the viability of T. weissflogii cells compared to non-aggregated cells kept under otherwise identical conditions. KEY WORDS: Viability of phytoplankton · FDA assay · Nutrient limitation · AggregationResale or republication not permitted without written consent of the publisher

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Evidence for reduced biogenic silica dissolution rates in diatom aggregates

Cited by 46 publications

References 58 publications

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

Composition and degradation of marine particles with different settling velocities in the northwestern Mediterranean Sea

Applicability of the FDA assay to determine the viability of marine phytoplankton under different environmental conditions

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