Assimilation efficiency in herbivorous aquatic organisms—The potential of the ratio method using <sup>14</sup>C and biogenic silica as markers1

Tande, Kurt S.; Slagstad, Dag

doi:10.4319/lo.1985.30.5.1093

Cited by 76 publications

(55 citation statements)

References 7 publications

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“…Literature data suggest that diatoms are more difficult to digest than flagellated microalgae (Conover 1966 as recalculated by Paffenhö fer and Kö ster 2005; Thor and Wendt 2010). One can speculate that the copepod gut produced more acidic fluid to aid the digestion of diatoms, although this is not necessarily related to the siliceous frustules because silica dissolution tends to occur faster in alkaline, not acidic, pH (Lewin 1961;Schlü ter and Rickert 1998), and biogenic silica is often used as inert tracer in copepod feeding studies (Tande and Slagstad 1985;Cowie and Hedges 1996).…”

Section: Discussionmentioning

confidence: 99%

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Tang¹,

Glud²,

Glud³

et al. 2011

Limnology & Oceanography

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The environmental conditions inside the gut of Calanus hyperboreus and C. glacialis were measured with microelectrodes. An acidic potential hydrogen (pH) gradient was present in the gut of C. hyperboreus, and the lowest pH recorded was 5.40. The gut pH of a starved copepod decreased by 0.53 after the copepod resumed feeding for a few hours, indicating the secretion of acidic digestive fluid. A copepod feeding on Thalassiosira weissflogii (diatom) had slightly lower pH than that feeding on Rhodomonas salina (cryptophyte). Oxygen was undersaturated in the gut of both C. hyperboreus and C. glacialis, with a steep gradient from the anal opening to the metasome region. The central metasome region was completely anoxic. Food remains in the gut led to a lower oxygen level, and a diatom diet induced a stronger oxygen gradient than a cryptophyte diet. The acidic and suboxic-anoxic environments of the copepod gut may support iron dissolution and anaerobic microbial activities that otherwise are not favored in the well-buffered and oxygenated ambient ocean.

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Section: Discussionmentioning

confidence: 99%

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Tang¹,

Glud²,

Glud³

et al. 2011

Limnology & Oceanography

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“…These BSiO 2 : OC ratios were close to the ratio of 0.13 measured by Brzezinski (1985) on diatoms cultured in silica-replete conditions. The presence of either degraded material, fecal pellets (Tande and Slagstad 1985;Cowie and Hedges 1996), or more silicified species (in response to Claquin et al 2002) is known to increase this ratio. All samples contained biomarkers indicating the presence of phytoplankton, zooplankton, and bacterial organic matter, but faster settling particles were dominated by phytoplankton aggregate indicators, particles of intermediate settling velocity had more zooplankton and fecal pellet indicators, and slower settling particles were more associated with bacterial indicators (Figs.…”

Section: Discussionmentioning

confidence: 99%

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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“…It is unlikely that the flux of either silica or carbon is dominated by the sinking of intact cells, as copepods and other larger zooplankters have been observed to produce fecal pellets enriched in silica (i.e. with Si: C ratios greater than those of their food; Tande and Slagstad 1985). Nonetheless a diatom-derived flux of anything approaching 3.6 g C m-* yr-' would be -30% of the carbon export measured with sediment traps at the BATS site (Michaels et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Diatom growth and productivity in an oligo-trophic midocean gyre: A 3-yr record from the Sargasso Sea near Bermuda

1997

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We measured the rate of biogenic silica production in the upper 160 m at the Bermuda Atlantic Time-series Study (BATS) site in the western Sargasso Sea on 12 cruises between August 1991 and May 1994 using a 30Si tracer method. Previously initiated time series of particulate silica concentrations and the gravitational flux of siliceous particles were extended to produce an October 1988-December 1994 time series for biogenic silica concentrations and August 1991-December 1994 time series for lithogenic silica concentrations and fluxes of biogenic and lithogenie silica. Specific rates of biogenic silica production during nonbloom periods indicate active diatom growth, with a mean doubling time of 4.5 d for biogenic silica. The annual silica production rate is conservatively estimated to be 240 mmol Si m-2, which corresponds to a diatom productivity of -20-45 g C m-2 yr-I, -15-25% of the mean annual primary productivity. Comparison of silica production rates with sinking fluxes from the upper 150 m (26-53 mmol Si m-2 yr-I) indicates that -80% of the silica produced in the euphotic zone dissolves in the upper 150 m. Sinking of diatoms and their remains can account for -30% of the particulate organic carbon export at the BATS site on an annual basis and nearly 100% during the annual winter/spring diatom bloom. Atmospheric dust inputs each summer, indicated by July-August maxima in the concentration and vertical flux of lithogenic silica, do not stimulate either biogenic silica production or primary productivity, implying that iron availability limits neither diatom growth nor total primary production in the western' Sargasso Sea.Most of the primary production in the oceans occurs in midocean gyres and other oligotrophic systems-a seemingly contradictory situation that results from those systems' enormous spatial extent (e.g. Ryther 1969). The phytoplankton in the midocean gyres is comprised mostly of small, nonsiliceous forms, with

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Assimilation efficiency in herbivorous aquatic organisms—The potential of the ratio method using ¹⁴C and biogenic silica as markers1

Cited by 76 publications

References 7 publications

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

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

Diatom growth and productivity in an oligo-trophic midocean gyre: A 3-yr record from the Sargasso Sea near Bermuda

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Assimilation efficiency in herbivorous aquatic organisms—The potential of the ratio method using 14C and biogenic silica as markers1

Cited by 76 publications

References 7 publications

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

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

Diatom growth and productivity in an oligo-trophic midocean gyre: A 3-yr record from the Sargasso Sea near Bermuda

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Assimilation efficiency in herbivorous aquatic organisms—The potential of the ratio method using ¹⁴C and biogenic silica as markers1