Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets

Cavan, Emma L.; Moigne, Frédéric A.C. Le; Poulton, Alex J.; Tarling, Geraint A.; Ward, Peter; Daniels, Chris J.; Fragoso, Glaucia Moreira; Sanders, Richard

doi:10.1002/2014gl062744

Cited by 111 publications

(175 citation statements)

References 61 publications

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“…5A and B), which may have been due to zooplankton consumption of diatoms in the euphotic zone and release of faecal pellets between 100 and 300 m. Therefore, production of faecal pellets and zooplankton vertical migration might have modulated the transfer efficiency in this study. Similar conclusions have been reached by Buesseler and Boyd (2009) and Cavan et al (2015).…”

Section: Transfer Efficiencysupporting

confidence: 88%

“…Only for one station (139), which evidenced a temporal decoupling between production and export (lowest Chl-a SW inventories and NPP rates), the export efficiency was 4 30% according to all techniques. Indeed, we found an inverse relationship between export efficiency and NPP (p o0.05; ST method: ρ¼ À0.95, n ¼8; SWST method: ρ¼ À0.89, n¼ 6) supporting recent observations (Cavan et al, 2015;Laurenceau-Cornec et al, 2015;Maiti et al, 2013). This relationship could be explained by a combination of temporal decoupling between primary production and export (Henson et al, 2015;Puigcorbé et al, 2017), and other processes such as zooplankton grazing (Cavan et al, 2015), bacterial activity and recycling efficiency (Maiti et al, 2013).…”

Section: Export Efficiencysupporting

confidence: 86%

“…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). However, packaging of slowly sinking phytoplankton cells into large faecal pellets may play a key role in increasing the export and transfer efficiencies in the Southern Ocean (Cavan et al, 2015;Le Moigne et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Transfer Efficiencysupporting

confidence: 88%

Section: Export Efficiencysupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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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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“…In spring 2011, UVP-derived estimates of POC export at 350 m were 0.1 to 0.3 mmol m −2 d −1 (Table 3) (Buesseler et al, 2007b). However, there is increasing evidence in support of much higher b values in the Southern Ocean that fall in the range of 0.9-3.9 (Lam and Bishop, 2007;Henson et al, 2012;Cavan et al, 2015). Our calculations are thus consistent with emerging observations of significant POC flux attenuation in the Southern Ocean.…”

Section: Evidence For Significant Flux Attenuation Over the Kerguelensupporting

confidence: 87%

Export fluxes in a naturally iron-fertilized area of the Southern Ocean – Part 1: Seasonal dynamics of particulate organic carbon export from a moored sediment trap

et al. 2015

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Abstract.A sediment trap moored in the naturally ironfertilized Kerguelen Plateau in the Southern Ocean provided an annual record of particulate organic carbon and nitrogen fluxes at 289 m. At the trap deployment depth, current speeds were typically low ( ∼ 10 cm s −1 ) and primarily tidaldriven (M2 tidal component). Although advection was weak, the sediment trap may have been subject to hydrodynamical and biological (swimmer feeding on trap funnel) biases. Particulate organic carbon (POC) flux was generally low (< 0.5 mmol m −2 d −1 ), although two episodic export events (< 14 days) of 1.5 mmol m −2 d −1 were recorded. These increases in flux occurred with a 1-month time lag from peaks in surface chlorophyll and together accounted for approximately 40 % of the annual flux budget. The annual POC flux of 98.2 ± 4.4 mmol m −2 yr −1 was low considering the shallow deployment depth but comparable to independent estimates made at similar depths (∼ 300 m) over the plateau, and to deep-ocean (> 2 km) fluxes measured from similarly productive iron-fertilized blooms. Although undertrapping cannot be excluded in shallow moored sediment trap deployment, we hypothesize that grazing pressure, including mesozooplankton and mesopelagic fishes, may be responsible for the low POC flux beneath the base of the winter mixed layer. The importance of plankton community structure in controlling the temporal variability of export fluxes is addressed in a companion paper.

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“…Despite strong differences in surface phytoplankton biomass, primarily mediated by iron supply (Nielsdóttir et al, 2012;Borrione and Schlitzer, 2013), the amount of POC reaching the deep-ocean differs by a factor of o2 between the two sites. This is consistent with a scenario of enhanced carbon remineralization downstream of South Georgia (Cavan et al, 2015;Le Moigne et al, 2016). The annual POC fluxes observed at South Georgia are remarkably similar (o100 mmol m À 2 yr À 1 ) to those measured at other naturally iron-fertilized sites in the Southern Ocean (Salter et al, 2012;Rembauville et al, 2015b).…”

Section: Magnitude Of Particle Fluxessupporting

confidence: 84%

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Rembauville

Manno

Tarling

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tBiogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000 m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500 m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (o 5%). From these analyses we conclude that resting spore export contributes towards the slightly higher bathypelagic (POC) flux at P3 (40.6 mmol m À 2 y À 1 ) compared to P2 (26.4 mmol m À 2 y À 1 ). We compared our sediment trap records with previously published diatom assemblage data from the mixed layer and surface sediments (3760 m) around South Georgia. The relative proportion of diatom resting spores within diatom assemblages increases as a function of depth and is explained by selective preservation of their robust frustules. Our study highlights the significance of diatom resting spore export as a carbon vector out of the mixed layer. Furthermore, the contribution or resting spores to POC flux in the bathypelagic ocean and sediments suggests they play a particularly important role in sequestering biologically fixed CO 2 over climatically relevant timescales.

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Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets

Cited by 111 publications

References 61 publications

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

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

Export fluxes in a naturally iron-fertilized area of the Southern Ocean – Part 1: Seasonal dynamics of particulate organic carbon export from a moored sediment trap

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

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