Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site

Stewart, Gillian; Moran, S. Bradley; Lomas, Michael W.; Kelly, Roger

doi:10.1016/j.jenvrad.2010.09.011

Cited by 26 publications

(24 citation statements)

References 89 publications

(135 reference statements)

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“…When examined on a global perspective, our results further suggest that the phenomenon is not unique to our study region but may apply broadly to ecosystems dominated by smaller taxa, agreeing with previous work from oligotrophic regions [e.g., Richardson and Jackson , ; Durkin et al ., ]. While others have shown that choosing a single particle fraction to estimate vertical export may be misleading [ Dunne et al ., ; Burd et al ., ; Stewart et al ., ], sampling uniquely large particles (>50 µm) is still the dominant approach used to estimate elemental fluxes derived from the 234 Th method. Our data again support further discussion of particle size, providing results that indicate the importance of the ecosystem and biological state of the region under interest.…”

Section: Discussionmentioning

confidence: 99%

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Puigcorbé

Benitez-Nelson

Masqué

et al. 2015

Global Biogeochemical Cycles

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Summertime carbon, nitrogen, and biogenic silica export was examined using 234 Th:238 U disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps (ISP) within the Eastern Tropical North Pacific and the Gulf of California. Fine scale ISP sampling provides evidence that in this system, particulate carbon (PC) and particulate nitrogen (PN) concentrations were more rapidly attenuated relative to 234 Th activities in small particles compared to large particles, converging to 1-5 μmol dpm À1 by 100 m. Comparison of elemental particle composition, coupled with particle size distribution analysis, suggests that small particles are major contributors to particle flux. While absolute PC and PN export rates were dependent on the method used to obtain the element/ 234 Th ratio, regional trends were consistent across measurement techniques. The highest C fixation rates were associated with diatom-dominated surface waters. Yet, the highest export efficiencies occurred in picoplankton-dominated surface waters, where relative concentrations of diazotrophs were also elevated. Our results add to the increasing body of literature that picoplankton-and diazotroph-dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton, e.g., diatoms, in low productivity pico/nanoplankton-dominated regions, where small particles are major contributors to particle export. Findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate. Therefore, we argue the necessity of collecting multiple particle sizes used to convert 234 Th fluxes into carbon or other elemental fluxes, including <50 μm, since they can play an important role in vertical fluxes, especially in oligotrophic environments. Our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method.

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Section: Discussionmentioning

confidence: 99%

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Puigcorbé

Benitez-Nelson

Masqué

et al. 2015

Global Biogeochemical Cycles

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“…In contrast using sediment traps, Antia et al (2001) Mediterranean Sea (MedFlux project) and Sargasso Sea (BATS) respectively. Le Moigne et al 94 (2013b) and Stewart et al (2011) found that 234 Th-derived POC fluxes were systematically higher 95 than 210 Po-derived fluxes during low flux periods, and higher or similar to those measured in traps 96 within the euphotic zone (E z ), while Stewart et al (2007a) found the same behaviour below the E z 97 through three seasons (early spring, late spring, summer). In contrast Buesseler et al (2008a) 98 reported higher 210 Po-derived fluxes than 234 Th-derived POC fluxes and traps (which were in good 99 agreement).…”

Section: Introduction 42mentioning

confidence: 88%

“…Two particle size classes were sampled by SAPS to determine the POC:R ratio. We estimate POC 346 export using only POC:R from >53 μm particles in order to allow comparison to other studies that 347 follow the same approach (Le Moigne et al, 2013b;Stewart et al, 2011), among many others, see 348 for review on POC:Th ratios). Nonetheless, in section 4.1 we assess the 349 effect of the exclusion of small particles on the accuracy of our results.…”

Section: Saps-derived Carbon Fluxes 345mentioning

confidence: 99%

Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps

et al. 2016

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“…The radionuclide pairs 234 Th/ 238 U and, to a lesser extent, 210 Po/ 210 Pb have been used as proxies for POC export since the 1990s [ Buesseler et al ., ; Shimmield et al ., ], but very few studies have used both pairs together [ Verdeny et al ., ; Stewart et al ., ; Wei et al ., ; Le Moigne et al ., ]. Several authors have recommended the simultaneous use of 234 Th/ 238 U and 210 Po/ 210 Pb since they cover different time scales, from weeks to months, respectively, and 234 Th and 210 Po have different biogeochemical behaviors, providing complementary information on POC export fluxes [ Friedrich and Rutgers van der Loeff , ; Verdeny et al ., ; Stewart et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint ²³⁴Th/²³⁸U and ²¹⁰Po/²¹⁰Pb study

et al. 2016

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The Arctic sea‐ice extent reached a record minimum in September 2012. Sea‐ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234Th/238U and 210Po/210Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234Th/238U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m−2 d−1) in late summer. Relationships obtained between the 234Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea‐ice algal aggregates and zooplankton‐derived material. The magnitude of the depletion of 210Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210Po fluxes and 210Po‐derived POC fluxes correlated positively with sea‐ice concentration, showing that particle sinking was greater under heavy sea‐ice conditions than under partially ice‐covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.

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Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site

Cited by 26 publications

References 89 publications

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps

Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint ²³⁴Th/²³⁸U and ²¹⁰Po/²¹⁰Pb study

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Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site

Cited by 26 publications

References 89 publications

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific

Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps

Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint 234Th/238U and 210Po/210Pb study

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Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint ²³⁴Th/²³⁸U and ²¹⁰Po/²¹⁰Pb study