234Th-derived particulate organic carbon export from an island-induced phytoplankton bloom in the Southern Ocean

Morris, Paul J.; Sanders, Richard; Turnewitsch, Robert; Thomalla, Sandy J.

doi:10.1016/j.dsr2.2007.06.002

Cited by 65 publications

(77 citation statements)

References 85 publications

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Section: Poc/ 234supporting

confidence: 76%

“…This was attributed to changes in the nature of the sinking particles (less labile or more rapidly sinking) and/or less efficient biological and physical processes responsible for particle break-up and consumption below the bloom. Th and PON/ 234 Th ratios in particles C/Th and N/Th ratios were 410 μmol C dpm À 1 (average: 15 75 μmol C dpm À 1 ) and 41 μmol N dpm À 1 (average: 2 71 μmol N dpm À 1 ), respectively, in all samples collected either with ST or ISP ( 453 μm) at 100 m. Overall, these values were higher than those reported by most studies conducted in the Southern Ocean (Buesseler et al, , 2001aCoppola et al, 2005;Jacquet et al, 2011;Martin et al, 2013;Morris et al, 2007;Planchon et al, 2013;Rutgers van der Loeff et al, 2011Savoye et al, 2008), but similar to others (Cochran et al, 2000;Puigcorbé et al, 2017;Rutgers van der Loeff et al, 2002;Smetacek et al, 2012). Multiple factors may have played a role in shaping the C/Th and N/Th ratios, such as particle source, sinking velocity, Th speciation and remineralisation of C, N and 234 Th associated with sinking particles .…”

Section: Results and Comparison With Other Studiescontrasting

confidence: 50%

“…, 1997), and the CROZEX project (average: 14 74 mmol C m À 2 d À 1 , Morris et al, 2007). Our estimates of F N are also similar to the results from KEOPS and CROZEX (Morris et al, 2007;Savoye et al, 2008). In contrast, the F C are higher than those reported in KEOPS II (average: 7 72 mmol C m À 2 d À 1 , Planchon et al, 2015) for a bloom during its growing stage.…”

Section: Poc/ 234contrasting

confidence: 54%

“…The C/N ratios averaged 8 71 and 7 71 for ST and ISP samples, respectively, and were within the range of values previously reported during bloom events (Martin et al, 2013;Morris et al, 2007;Savoye et al, 2008), with a diverse composition of the dominant particle type (diatoms: Salter et al, 2007;faecal material: Ebersbach and Trull, 2008;Ebersbach et al, 2014). , 1997), and the CROZEX project (average: 14 74 mmol C m À 2 d À 1 , Morris et al, 2007).…”

Section: Poc/ 234supporting

confidence: 51%

“…Our F Th estimates at 100 m are within the range of values for blooms during their peak and/or decline occurring in the Southern Ocean, either in land remote areas (Rutgers van der Loeff et al, 1997) or near islands (Morris et al, 2007;Savoye et al, 2008). In contrast, our estimates are higher than the F Th of r1000 dpm m À 2 d À 1 reported during the onset of a bloom by Planchon et al (2015), and during the artificial iron fertilisation experiments SOIREE (Charette and Buesseler, 2000), EisenEx (Rutgers van der Loeff and Vöge, 2001) and LOHAFEX (Martin et al, 2013).…”

Section: Results and Comparison With Other Studiesmentioning

confidence: 53%

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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: Poc/ 234supporting

confidence: 76%

Section: Results and Comparison With Other Studiescontrasting

confidence: 50%

Section: Poc/ 234contrasting

confidence: 54%

Section: Poc/ 234supporting

confidence: 51%

Section: Results and Comparison With Other Studiesmentioning

confidence: 53%

See 3 more Smart Citations

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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What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

Moigne

Henson

Cavan

et al. 2016

Geophysical Research Letters

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The ocean contributes to regulating atmospheric CO2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e., the e ratio). Southern Ocean studies have found that contrary to global‐scale analyses, an inverse relationship exists between e ratio and PP. This relationship remains unexplained, with potential hypotheses being (i) large export of dissolved organic carbon (DOC) in high PP areas, (ii) strong surface microbial recycling in high PP regions, and/or (iii) grazing‐mediated export that varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e ratio/PP relationship. However, we observed that at sites with low PP and high e ratios, zooplankton‐mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e ratio in the Southern Ocean.

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Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX

Martin

Loeff

Cassar

et al. 2013

Global Biogeochemical Cycles

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102

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[1] A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO 4 ), and the 300 km 2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yield (F V /F M ) increased from 0.33 to ≥0.40. Silicic acid (<2 μmol L À1 ) limited diatoms, which contributed <10% of phytoplankton biomass. Copepods exerted high grazing pressure. This is the first study of particle flux out of an artificially fertilized bloom with very low diatom biomass. Net community production (NCP) inside the patch, estimated from O 2 :Ar ratios, averaged 21 mmol POC m À2 d À1 , probably ±20%. 234 Th profiles implied constant export of~6.3 mmol POC m À2 d À1 in the patch, similar to unfertilized waters. The difference between NCP and 234 Th-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 m. Neutrally buoyant sediment traps at 200 and 450 m inside and outside the patch caught mostly <1.1 mmol POC m À2 d À1 , predominantly of fecal origin; flux did not increase upon fertilization. Our data thus indicate intense flux attenuation between 100 and 200 m, and probably between the mixed layer and 100 m. We attribute the lack of fertilization-induced export to silicon limitation of diatoms and reprocessing of sinking particles by detritus feeders. Our data are consistent with the view that nitrate-rich but silicate-deficient waters are not poised for enhanced particle export upon iron addition.Citation: Martin, P., et al. (2013), Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX, Global Biogeochem. Cycles, 27,[871][872][873][874][875][876][877][878][879][880][881]

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234Th-derived particulate organic carbon export from an island-induced phytoplankton bloom in the Southern Ocean

Cited by 65 publications

References 85 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

What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX

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