Shedding light on processes that control particle export and flux attenuation in the twilight zone of the open ocean

Buesseler, Ken O.; Boyd, Philip W.

doi:10.4319/lo.2009.54.4.1210

Cited by 428 publications

(582 citation statements)

References 90 publications

(147 reference statements)

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“…First, the empirical regressions used for flux estimations are less accurate at shallow depths (Buesseler & Boyd 2009). Second, these estimations leave out the lateral organic input from coastal outflows.…”

Section: Diversity Measures: Methodological Aspectsmentioning

confidence: 99%

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

Azovsky¹,

Garlitska²,

Chertoprud³

2012

Mar. Ecol. Prog. Ser.

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The α and β diversity of benthic harpacticoids were estimated using 103 published datasets from all over the world, with depths ranging from the intertidal zone to 5600 m. α diversity (expected number of species per 100 individuals) was correlated with organic matter flux to the bottom, and this effect was depth-dependent, with the correlation being negative from the shallowest waters up to 33 m and positive in deeper waters. α diversity was also positively correlated with depth itself and depended on the sediment properties and duration of study, but showed no latitudinal trend. β diversity (estimated as the slope of the species accumulation curve) was negatively correlated with latitude and positively correlated with the spatial extent and depth range of sampling. The effect of latitude and extent was mainly pronounced for the intertidal zone, whereas the depth range was the most significant factor in the deep waters. Additionally, β diversity was higher on sands and mixed sediments than on silt or mud. Latitude explained 45% of the β diversity variation in the littoral zone, 18% in the upper sublittoral, and less than 5% in deeper zones. Thus, α and β diversity act as independent and spatially uncorrelated components of overall regional diversity, driven by different mechanisms. Variations in β diversity presumably reflect spatial heterogeneity and form the latitudinal gradient in the shallowest waters. Deeper, trophic conditions play the leading role, and thus α diversity contributes the major proportion of the total diversity variance there and is responsible for the bathymetric gradient.KEY WORDS: Harpacticoida · α diversity · β diversity · Latitude · Depth · Productivity Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 460: [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77] 2012 the equator has been observed for some groups, e.g. foraminiferans (Culver & Buzas 2000) or marine macrobenthos (Rex et al. 1993, Gray 2002. Nevertheless, comprehensive meta-analysis does not show any consistent differences between hemispheres, despite some variations among the oceans (Hillebrand 2004). The strength of the gradient varies systematically with body mass across organism groups, generally decreasing or even vanishing for the smallest organisms (Hillebrand & Azovsky 2001, Hillebrand 2004. For macrofauna, latitudinal patterns are not identical, however. Some of regional studies have failed to detect this pattern (e.g. peaks in diversity at midlatitude in both Atlantic and Pacific gastropods, Roy et al. 1998); or even showed regionally opposite trends (Renaud et al. 2009 and references therein). It is unclear whether these differences are caused by regional peculiarities or by the restricted geographical range of stations sampled (Renaud et al. 2009). Furthermore, regional diversity shows consistently stronger and steeper latitudinal gradients than local (α) diversity (Clarke & Lidgard 2000, Hillebrand 2004, thus posing the question of systematic varia...

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Section: Diversity Measures: Methodological Aspectsmentioning

confidence: 99%

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

Azovsky¹,

Garlitska²,

Chertoprud³

2012

Mar. Ecol. Prog. Ser.

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“…Mixed layer depth remained constant at ~50 m throughout the study period. This depth was subsequently used as the upper boundary of the twilight zone, following the need to normalize export measurements to dynamic upper boundaries for the twilight zone 11 .…”

mentioning

confidence: 99%

Reconciliation of the carbon budget in the ocean’s twilight zone

Giering

Sanders

Lampitt

et al. 2014

Nature

320

347

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The global carbon cycle is affected by biological processes in the oceans, which export carbon from surface waters in form of organic matter and store it at depth; a process called the 'biological carbon pump'. Most of the exported organic carbon is processed by the water column biota, which ultimately converts it into CO2 via respiration (remineralization). Variations in the resulting decrease in organic flux with depth 9 can, according to models, lead to changes in atmospheric CO 2 of up to 200 ppm 3 , indicating a strong coupling between biological activity in the ocean interior and oceanic storage of CO 2 .A key constraint in the analysis of carbon fluxes in the twilight zone is that, at steady state, the attenuation of particulate organic carbon (POC) flux with depth should be balanced by community metabolism. Published estimates of POC flux attenuation with depth are, however, up to 2 orders of magnitude lower than corresponding estimates of heterotrophic metabolism [4][5][6][7] . This discrepancy indicates that either estimates of POC flux and/or community metabolism are unreliable, or that additional, unaccounted for, sources of organic carbon to the twilight zone exist 8 .We compiled a comprehensive carbon budget of the twilight zone based on an based on the ratio between DOC concentrations and apparent oxygen utilization 15 , and on DOC gradients coupled to turbulent diffusivity measured from previous work at the study site 16 (Methods; Extended Data Fig. 2). DOC was estimated to supply 17% of total export in agreement with previous estimates of 9-20% across the North Atlantic basin 17 . Organic matter input via lateral advection was assumed to be negligible based on analyses of back-trajectories (derived from satellite-derived near-surface velocities over 3 months) of the water masses arriving at the PAP site during the study period, which suggested that the water had not passed over the continental slope (Extended Data Fig. 1b). The final source of DOC, excretion at depth by active flux, was estimated using net samples of zooplankton biomass and allometric equations 6,18 , giving a supply of 3 mg C m -2 d -1 . Defecation and mortality at depth present further sources of organic carbon to the twilight zone, but these were excluded from the budget due to large uncertainties associated with their estimation. Finally, chemolithoautotrophy has been suggested to be a significant source of organic matter in the deep ocean 19 , but without strong evidence that this poorly understood process could provide a major contribution at our study site, we chose to exclude it from our carbon budget.The remineralization of organic carbon by zooplankton and prokaryotes was estimated from zooplankton biomass and prokaryotic activity. It is crucial to note that in a steady state system, such as we assume this to be, organic carbon is lost from the system only by export or by remineralization. We focus entirely on community respiration as a measure of remineralization, a fundamental advance over previous methods to derive...

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“…While it is known that the attenuation of POC fluxes is sharpest in the upper twilight zone, i.e. 100-300 m below the euphotic zone depth, our understanding of the processes affecting sinking particles throughout this layer is still poor (Buesseler and Boyd, 2009). The vertical flux of organic matter throughout the water column is dominated by large particles such as marine snow and faecal pellets (Ebersbach et al, 2011;Fowler and Knauer, 1986;Laurenceau-Cornec et al, 2015) that can be attenuated to a large extent by zooplankton and microbial degradation (Giering et al, 2014;Iversen et al, 2010;Kiørbe, 2000;Smith et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

“…However, the strength and efficiency of the biological pump (i.e. export efficiency and transfer efficiency, respectively), as well as their controlling factors are poorly understood, especially during phytoplankton blooms (Buesseler and Boyd, 2009). …”

Section: Introductionmentioning

confidence: 99%

High particulate organic carbon export during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean

Roca‐Martí

Puigcorbé

Iversen

et al. 2017

Deep Sea Research Part II: Topical Studies in Oceanography

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a b s t r a c tCarbon fixation by phytoplankton plays a key role in the uptake of atmospheric CO 2 in the Southern Ocean. Yet, it still remains unclear how efficiently the particulate organic carbon (POC) is exported and transferred from ocean surface waters to depth during phytoplankton blooms. In addition, little is known about the processes that control the flux attenuation within the upper twilight zone. Here, we present results of downward POC and particulate organic nitrogen fluxes during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean in summer 2012. We used thorium-234 ( 234 Th) as a particle tracer in combination with drifting sediment traps (ST). Their simultaneous use evidenced a sustained high export rate of 234 Th at 100 m depth in the weeks prior to and during the sampling period. The entire study area, of approximately 8000 km 2 , showed similar vertical export fluxes in spite of the heterogeneity in phytoplankton standing stocks and productivity, indicating a decoupling between production and export. The POC fluxes at 100 m were high, averaging 26 715 mmol C m À 2 d À 1 , although the strength of the biological pump was generally low. Only o 20% of the daily primary production reached 100 m, presumably due to an active recycling of carbon and nutrients. Pigment analyses indicated that direct sinking of diatoms likely caused the high POC transfer efficiencies ( $ 60%) observed between 100 and 300 m, although faecal pellets and transport of POC linked to zooplankton vertical migration might have also contributed to downward fluxes.

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Shedding light on processes that control particle export and flux attenuation in the twilight zone of the open ocean

Cited by 428 publications

References 90 publications

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

Reconciliation of the carbon budget in the ocean’s twilight zone

High particulate organic carbon export during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean

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