Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone

Rigual-Hernández, Andrés S.; Flores, José-Abel; Sierro, Francisco J.; Fuertes, Miguel Ángel; Cros, Lluïsa; Trull, Thomas W.

doi:10.5194/bg-15-1843-2018

Cited by 21 publications

(21 citation statements)

References 121 publications

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“…Second, latitudinal variations in the abundance of heterotrophic calcifiers (mainly foraminifera but also pteropods) must play a major role in modulating the observed variations in CaCO 3 export. In particular, our data suggest that the fractional contribution of heterotrophic calcifiers to CaCO 3 production increases from ∼ 40 %-60 % in the Australian SAZ to up to 95 % in the AZ (Rigual Hernández et al, 2018). This pattern is consistent with previous shipboard and sediment trap studies that reported higher abundances of planktonic foraminifera at the PFZ and AZ compared to that of the SAZ in the Australian sector (King and Howard, 2003;Trull et al, 2018).…”

Section: Contribution Of Coccolithophores To Carbonatesupporting

confidence: 91%

“…Therefore, the second peak in satellite-derived PIC could have been caused by a senescent diatom bloom. This hypothesis is likely, since diatom blooms in the SAZ are known to develop early in the productive season (Rigual- Hernández et al, 2015b) and rapidly decay following the depletion of silicate and/or iron stocks in the surface layer (Lannuzel et al, 2011). However, no secondary late summer maximum was observed in biogenic silica fluxes in the SAM.…”

Section: Coccolithophore Phenology In the Saz: Satellite Versus Sedimmentioning

confidence: 99%

“…Macronutrient concentrations display pronounced seasonal changes in the SAZ, with fully replete levels during winter to substantial depletion during summer, particularly for silicate (Dugdale et al, 1995;Rintoul and Trull, 2001;Bowie et al, 2011). The phytoplankton community in the subantarctic zone is dominated by pico-and nannoplankton including cyanobacteria, coccolithophores and autotrophic flagellates, with lower abundances of diatoms than polar waters south the polar front (Chang and Gall, 1998;Kopczynska et al, 2001; de Salas et al, 2011;Rigual-Hernández et al, 2015b;Eriksen et al, 2018).…”

Section: Oceanographic Settingmentioning

confidence: 99%

“…Annual coccolith export across the major zonal systems of the Australian sector of the Southern Ocean exhibits a clear latitudinal gradient, with maximum fluxes at the SAZ (8.6×10 11 coccoliths m −2 yr −1 ) and 8-fold lower fluxes in the polar waters of the Antarctic zone (AZ; 1.0 × 10 11 coccoliths m −2 yr −1 ; Rigual Hernández et al, 2018). Coccolithophore species occurrence documented by our subantarctic sediments traps is consistent with previous reports on coccolithophore assemblage compositions in the surface layer (Findlay and Giraudeau, 2000;Saavedra-Pellitero et al, 2014;Malinverno et al, 2015;Chang and Northcote, 2016) and sediments (Findlay and Giraudeau, 2000;Saavedra-Pellitero and Baumann, 2015) and are more diverse than those found in the AZ (Rigual Hernández et al, 2018). The southward decline in coccolithophore abundance and diversity is most likely due to the decrease in sea-surface temperature (SST) and light availability moving poleward (Charalampopoulou et al, 2016;Trull et al, 2018).…”

Section: Magnitude and Composition Of Subantarctic Coccolithophore Asmentioning

confidence: 99%

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Coccolithophore biodiversity controls carbonate export in the Southern Ocean

et al. 2020

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Abstract. Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abundance of Southern Ocean coccolithophore populations are likely to alter the marine carbon cycle, with feedbacks to the rate of global climate change. However, the contribution of coccolithophores to CaCO3 export in the Southern Ocean is uncertain, particularly in the circumpolar subantarctic zone that represents about half of the areal extent of the Southern Ocean and where coccolithophores are most abundant. Here, we present measurements of annual CaCO3 flux and quantitatively partition them amongst coccolithophore species and heterotrophic calcifiers at two sites representative of a large portion of the subantarctic zone. We find that coccolithophores account for a major fraction of the annual CaCO3 export, with the highest contributions in waters with low algal biomass accumulations. Notably, our analysis reveals that although Emiliania huxleyi is an important vector for CaCO3 export to the deep sea, less abundant but larger species account for most of the annual coccolithophore CaCO3 flux. This observation contrasts with the generally accepted notion that high particulate inorganic carbon accumulations during the austral summer in the subantarctic Southern Ocean are mainly caused by E. huxleyi blooms. It appears likely that the climate-induced migration of oceanic fronts will initially result in the poleward expansion of large coccolithophore species increasing CaCO3 production. However, subantarctic coccolithophore populations will eventually diminish as acidification overwhelms those changes. Overall, our analysis emphasizes the need for species-centred studies to improve our ability to project future changes in phytoplankton communities and their influence on marine biogeochemical cycles.

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Section: Contribution Of Coccolithophores To Carbonatesupporting

confidence: 91%

Section: Coccolithophore Phenology In the Saz: Satellite Versus Sedimmentioning

confidence: 99%

Section: Oceanographic Settingmentioning

confidence: 99%

Section: Magnitude and Composition Of Subantarctic Coccolithophore Asmentioning

confidence: 99%

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Coccolithophore biodiversity controls carbonate export in the Southern Ocean

et al. 2020

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“…Ocean acidification combined with the increase in sea-surface temperature due to global warming are major concerns in polar and subpolar regions (e.g., Wassmann et al, 2011;Post et al, 2013;Freeman and Lovenduski, 2015), triggering an increasing interest in coccolithophore ecology at high latitudes (e.g., Harada et al, 2012;Dylmer et al, 2013;Balch et al, 2016;Charalampopoulou et al, 2016;Giraudeau et al, 2016;Saruwatari et al, 2016;Nissen et al, 2018;Rigual Hernández et al, 2018;Krumhardt et al, 2019). Questions remain about how coccolithophore populations will adapt to predicted changes in 25 their environment, if at all.…”

mentioning

confidence: 99%

Calcification and distribution of extant coccolithophores across the Drake Passage during late austral summer 2016

Saavedra‐Pellitero¹,

Baumann²,

Fuertes³

et al. 2019

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Abstract. Coccolithophores are globally distributed microscopic marine algae that exert a major influence on the global carbon cycle through calcification and primary productivity. There is recent interest in coccolithophore polar communities, however field observations regarding their biogeographic distribution are scarce for the Southern Ocean. This study documents the latitudinal variability in the coccolithophore assemblage composition and the coccolith mass variation of the ecologically dominant Emiliania huxleyi across the Drake Passage. Ninety-six water samples were taken between 10 and 150&#8201;m water depth from 18 stations during POLARSTERN Expedition PS97 (February&#8211;April, 2016). A minimum of 200 coccospheres per sample were classified in scanning electron microscope and coccolith mass was estimated with light microscopy, using the C-Calcita software. We find that coccolithophore abundance and diversity decrease southwards marking different oceanographic fronts as ecological boundaries. We characterize three zones: (1) the Chilean margin, where E. huxleyi type A (normal and overcalcified) and type R are present; (2) the Subantarctic Zone (SAZ), where E. huxleyi reaches maximum values of 212.5&#215;103cells/L and types B/C, C, O are dominant. (3) The Polar Front Zone (PFZ), where E. huxleyi types B/C and C dominate. We link the decreasing trend in E. huxleyi coccolith mass to the poleward latitudinal succesion from type A to type B group. Remarkably, we find that coccolith mass is strongly anticorrelated to total alkalinity, total CO2, bicarbonate ion and pH. We speculate that low temperatures are a greater limiting factor than carbonate chemistry in the Southern Ocean. However, further in situ oceanographical data is needed to verify the proposed relationships. We hypothesize that assemblage composition and calcification modes of E. huxleyi in the Drake Passage will be strongly influenced by the ongoing climate change.

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Southern Ocean calcification controls the global distribution of alkalinity

Krumhardt

Long

Lindsay

et al. 2020

Preprint

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Biological processes in Southern Ocean surface waters have widespread impacts on global productivity and oceanic CO 2 storage. Here, we demonstrate that biological calcification in the Southern Ocean exerts a strong control on the global distribution of alkalinity. The signature of Southern Ocean calcification is evident in observations as a depletion of potential alkalinity within portions of Subantarctic Mode and Intermediate Water. Experiments with an ocean general circulation model indicate that calcification and subsequent sinking of biogenic carbonate in this region effectively transfers alkalinity between the upper and lower cells of the meridional overturning circulation. Southern Ocean calcification traps alkalinity in the deep ocean; decreasing calcification permits more alkalinity to leak out from the Southern Ocean, yielding increased alkalinity in the upper cell and low-latitude surface waters. These processes have implications for atmosphere-ocean partitioning of carbon. Reductions in Southern Ocean calcification increase the buffer capacity of surface waters globally, thereby enhancing the ocean's ability to absorb carbon from the atmosphere. This study highlights the critical role of Southern Ocean calcification in determining global alkalinity distributions, demonstrating that changes in this process have the potential for widespread consequences impacting air-sea partitioning of CO 2 .Plain Language Summary Plankton living in the Southern Ocean affect the composition of seawater through biological processes. Due to the particular oceanic circulation in the Southern Ocean, these biologically driven changes in ocean chemistry can have widespread effects on the global ocean. Species of plankton that form shells of calcium carbonate remove alkalinity from surface waters through the process of calcification. The amount of alkalinity in surface waters is important because it affects how much CO 2 the ocean can absorb from the atmosphere. We show that Southern Ocean calcifying plankton affect the global distribution of alkalinity through the presence of a Southern Ocean "alkalinity trap." More Southern Ocean calcification yields a stronger alkalinity trap, with more alkalinity being retained in the Southern Ocean and in deep waters, away from the atmosphere. Reduced calcification in the Southern Ocean permits more alkalinity to escape the Southern Ocean and remain in the upper ocean globally. These changes affect oceanic CO 2 uptake from the atmosphere.

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Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone

Cited by 21 publications

References 121 publications

Coccolithophore biodiversity controls carbonate export in the Southern Ocean

Coccolithophore biodiversity controls carbonate export in the Southern Ocean

Calcification and distribution of extant coccolithophores across the Drake Passage during late austral summer 2016

Southern Ocean calcification controls the global distribution of alkalinity

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