scholarly journals Export fluxes in a naturally fertilized area of the Southern Ocean, the Kerguelen Plateau: ecological vectors of carbon and biogenic silica to depth (Part 2)

2014 ◽  
Vol 11 (12) ◽  
pp. 17089-17150 ◽  
Author(s):  
M. Rembauville ◽  
S. Blain ◽  
L. Armand ◽  
B. Quéguiner ◽  
I. Salter
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon ◽  
Biogenic Silica ◽  
Faecal Pellet ◽  
Trophic Levels ◽  
Kerguelen Plateau ◽  
Resting Spores ◽  
Poc Export ◽  
Autumn And Winter

Abstract. The chemical (particulate organic carbon and nitrogen, biogenic silica) and biological (diatoms and faecal pellets) composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally-fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC) export (98.2 mmol m−2) at 289 m was low but annual biogenic silica export was significant (114 mmol m−2). This feature was related to the abundance of empty diatom frustules and the ratio of full : empty cell exerted a first order control in BSi : POC export stoichiometry of biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were found to be responsible for more than 60% of the annual POC that occurred during two very short export events (<14 days in spring-summer) representing the majority of captured export. Low diatom fluxes were observed over the remainder of the year. Faecal pellet contribution to annual carbon flux was low (34%) and reached it's seasonal maximum in autumn and winter (>80%). The seasonal progression of faecal pellet types revealed a clear transition from small spherical shapes (small copepods) in spring, larger cylindrical and ellipsoid shapes in summer (euphausiids and large copepods) and finally large tabular shapes (salps) in autumn and winter. We propose that in this High Biomass, Low Export (HBLE) environment, small, highly silicified, fast-sinking resting spores are able to bypass the high grazing pressure and efficient carbon transfer to higher trophic levels that are responsible for the low fluxes observed the during the remainder of the year. Our study also provides a statistical framework linking the ecological succession of diatom and zooplankton communities to the seasonality of carbon and silicon export within an iron-fertilized bloom region in the Southern Ocean.

scholarly journals Export fluxes in a naturally iron-fertilized area of the Southern Ocean – Part 2: Importance of diatom resting spores and faecal pellets for export

2015 ◽  
Vol 12 (11) ◽  
pp. 3171-3195 ◽  
Author(s):  
M. Rembauville ◽  
S. Blain ◽  
L. Armand ◽  
B. Quéguiner ◽  
I. Salter
Keyword(s):  
Southern Ocean ◽  
Faecal Pellet ◽  
Grazing Pressure ◽  
Trophic Levels ◽  
Faecal Pellets ◽  
Carbon Transfer ◽  
Resting Spores ◽  
Poc Export ◽  
Annual Carbon ◽  
Autumn And Winter

Abstract. The biological composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC) export (98.2 mmol m−2) at 289 m was low, but annual biogenic silica export was significant (114 mmol m−2). This feature was related to the abundance of empty diatom cells and the ratio of full to empty cells exerted a first-order control in BSi : POC export stoichiometry of the biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were responsible for more than 60% of the annual POC flux that occurred during two very short export events of < 14 days in spring–summer. Relatively low diatom fluxes were observed over the remainder of the year. Faecal pellet contribution to annual carbon flux was lower (34%) and reached its seasonal maximum in autumn and winter (> 80%). The seasonal progression of faecal pellet types revealed a clear transition from small spherical shapes (small copepods) in spring, to larger cylindrical and ellipsoid shapes in summer (euphausiids and large copepods) and finally to large tabular shapes (salps) in autumn and winter. We propose in this high-biomass, low-export (HBLE) environment that small but highly silicified and fast-sinking resting spores are able to bypass the intense grazing pressure and efficient carbon transfer to higher trophic levels that are responsible for the low fluxes observed the during the remainder of the year. More generally our study also provides a statistical framework linking the ecological succession of diatom and zooplankton communities to the seasonality of carbon and silicon export within an iron-fertilized bloom region in the Southern Ocean.

scholarly journals Export fluxes in a naturally fertilized area of the Southern Ocean, the Kerguelen Plateau: seasonal dynamic reveals long lags and strong attenuation of particulate organic carbon flux (Part 1)

2014 ◽  
Vol 11 (12) ◽  
pp. 17043-17087 ◽  
Author(s):  
M. Rembauville ◽  
I. Salter ◽  
N. Leblond ◽  
A. Gueneugues ◽  
S. Blain
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon ◽  
Sediment Trap ◽  
Time Lag ◽  
Deep Ocean ◽  
Biomass Accumulation ◽  
Companion Paper ◽  
Kerguelen Plateau ◽  
Poc Flux

Abstract. A sediment trap moored in the naturally iron-fertilized 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 low (∼10 cm s−1) and primarily tidal-driven (M2 tidal component) providing favorable hydrodynamic conditions for the collection of flux. 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 relatively low considering the shallow deployment depth, but similar to deep-ocean (>2 km) fluxes measured from similarly productive iron-fertilized blooms. Comparison of the sediment trap data with complementary estimates of biomass accumulation and export indicate that ∼90% of the flux was lost between 200 and 300 m. We hypothesize that grazing pressure, including mesozooplankton and mesopelagic fishes, may be responsible for rapid flux attenuation and the High Biomass Low Export regime characterizing the Kerguelen bloom. The importance of plankton community structure in controlling the temporal variability of export fluxes is addressed in a companion paper.

Upper ocean export of particulate organic carbon and biogenic silica in the Southern Ocean along 170°W

2001 ◽  
Vol 48 (19-20) ◽  
pp. 4275-4297 ◽  
Author(s):  
K.O. Buesseler ◽  
L. Ball ◽  
J. Andrews ◽  
J.K. Cochran ◽  
D.J. Hirschberg ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon ◽  
Biogenic Silica ◽  
Upper Ocean

scholarly journals The export flux of particulate organic carbon derived from <sup>210</sup>Po∕<sup>210</sup>Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise

2019 ◽  
Vol 16 (2) ◽  
pp. 309-327 ◽  
Author(s):  
Yi Tang ◽  
Nolwenn Lemaitre ◽  
Maxi Castrillejo ◽  
Montserrat Roca-Martí ◽  
Pere Masqué ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
North Atlantic ◽  
Study Region ◽  
Vertical Advection ◽  
Export Flux ◽  
The North ◽  
Iberian Basin ◽  
Poc Export ◽  
The North Atlantic

Abstract. The disequilibrium between 210Po activity and 210Pb activity in seawater samples was determined along the GEOTRACES GA01 transect in the North Atlantic during the GEOVIDE cruise (May–June 2014). A steady-state model was used to quantify vertical export of particulate 210Po. Vertical advection was incorporated into one version of the model using time-averaged vertical velocity, which had substantial variance. This resulted in large uncertainties for the 210Po export flux in this model, suggesting that those calculations of 210Po export fluxes should be used with great care. Despite the large uncertainties, there is no question that the deficits of 210Po in the Iberian Basin and at the Greenland Shelf have been strongly affected by vertical advection. Using the export flux of 210Po and the particulate organic carbon (POC) to 210Po ratio of total (> 1 µm) particles, we determined the POC export fluxes along the transect. Both the magnitude and efficiency of the estimated POC export flux from the surface ocean varied spatially within our study region. Export fluxes of POC ranged from negligible to 10 mmol C m−2 d−1, with enhanced POC export in the Labrador Sea. The cruise track was characterized by overall low POC export relative to net primary production (export efficiency < 1 %–15 %), but relatively high export efficiencies were seen in the basins where diatoms dominated the phytoplankton community. The particularly low export efficiencies in the Iberian Basin, on the other hand, were explained by the dominance of smaller phytoplankton, such as cyanobacteria or coccolithophores. POC fluxes estimated from the 210Po∕210Pb and 234Th∕238U disequilibria agreed within a factor of 3 along the transect, with higher POC estimates generally derived from 234Th. The differences were attributed to integration timescales and the history of bloom events.

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

2015 ◽  
Vol 42 (3) ◽  
pp. 821-830 ◽  
Author(s):  
E. L. Cavan ◽  
F. A. C. Le Moigne ◽  
A. J. Poulton ◽  
G. A. Tarling ◽  
P. Ward ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon ◽  
Carbon Flux ◽  
Fecal Pellets ◽  
Scotia Sea ◽  
Organic Carbon Flux ◽  
Particulate Organic Carbon Flux

Size-fractionated biomass and productivity of phytoplankton and particulate organic carbon in the southern ocean

Polar Biology ◽  
1996 ◽  
Vol 16 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Ning Xiuren ◽  
Liu Zilin ◽  
Zhu Genhai ◽  
Shi Junxian
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon

scholarly journals Particulate organic carbon dynamics in the Gulf of Lion shelf (NW Mediterranean) using a coupled hydrodynamic–biogeochemical model

2021 ◽  
Vol 18 (19) ◽  
pp. 5513-5538
Author(s):  
Gaël Many ◽  
Caroline Ulses ◽  
Claude Estournel ◽  
Patrick Marsaleix
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Particulate Organic Carbon ◽  
Chlorophyll A ◽  
Net Primary Production ◽  
Biogeochemical Model ◽  
Eastern Region ◽  
Gulf Of Lion ◽  
Poc Export ◽  
Nw Mediterranean

Abstract. The Gulf of Lion shelf (GoL, NW Mediterranean) is one of the most productive areas in the Mediterranean Sea. A 3D coupled hydrodynamic–biogeochemical model is used to study the mechanisms that drive the particulate organic carbon (POC) dynamics over the shelf. A set of observations, including temporal series from a coastal station, remote sensing of surface chlorophyll a, and a glider deployment, is used to validate the distribution of physical and biogeochemical variables from the model. The model reproduces the time and spatial evolution of temperature, chlorophyll a, and nitrate concentrations well and shows a clear annual cycle of gross primary production and respiration. We estimate an annual net primary production of ∼ 200 × 104 t C yr−1 at the scale of the shelf. The primary production is marked by a coast-slope increase with maximal values in the eastern region. Our results show that the primary production is favoured by the inputs of nutrients imported from offshore waters, representing 3 and 15 times the inputs of the Rhône in terms of nitrate and phosphate. In addition, the empirical orthogonal function (EOF) decomposition highlights the role of solar radiation anomalies and continental winds that favour upwellings, and inputs of the Rhône River, in annual changes in the net primary production. Annual POC deposition (27 × 104 t C yr−1) represents 13 % of the net primary production. The delivery of terrestrial POC favours the deposition in front of the Rhône mouth, and the mean cyclonic circulation increases the deposition between 30 and 50 m depth from the Rhône prodelta to the west. Mechanisms responsible for POC export (24 × 104 t C yr−1) to the open sea are discussed. The export off the shelf in the western part, from the Cap de Creus to the Lacaze-Duthiers canyon, represents 37 % of the total POC export. Maximum values are obtained during shelf dense water cascading events and marine winds. Considering surface waters only, the POC is mainly exported in the eastern part of the shelf through shelf waters and Rhône inputs, which spread to the Northern Current during favourable continental wind conditions. The GoL shelf appears as an autotrophic ecosystem with a positive net ecosystem production and as a source of POC for the adjacent NW Mediterranean basin. The undergoing and future increase in temperature and stratification induced by climate change could impact the trophic status of the GoL shelf and the carbon export towards the deep basin. It is crucial to develop models to predict and assess these future evolutions.

scholarly journals Late summer particulate organic carbon export and twilight zone remineralisation in the Atlantic sector of the Southern Ocean

2012 ◽  
Vol 9 (3) ◽  
pp. 3423-3477 ◽  
Author(s):  
F. Planchon ◽  
A.-J. Cavagna ◽  
D. Cardinal ◽  
L. André ◽  
F. Dehairs
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Southern Ocean ◽  
Depth Interval ◽  
Twilight Zone ◽  
Atlantic Sector ◽  
Export Production ◽  
Sinking Particles ◽  
Steady State Model ◽  
Poc Export

Abstract. During the Bonus-GoodHope (BGH) expedition (Jan–Mar 2008) we studied the water column distribution of total 234Th and biogenic particulate Ba (Baxs) in the Atlantic sector of the Southern Ocean. The objective was to assess the export flux of particulate organic carbon (POC) from the surface to the mesopelagic twilight zone along a section between the Cape Basin and Weddell Gyre. Export production of POC was estimated from steady state and non steady state export fluxes of 234Th which were converted into POC fluxes, using the POC/234Th ratio of large (>53 μm) suspended particles, collected via in-situ pumps. Deficits in 234Th activities were observed at all stations from the surface to the bottom of the mixed-layer. 234Th export fluxes from the upper 100 m ranged from 496 ± 57 dpm m−2 d−1 to 1195 ± 120 dpm m−2 d−1 for the steady state model and from 149 ± 18 dpm m−2 d−1 to 1217 ± 146 dpm m−2 d−1 for the non steady state model calculated for a time window of 15 to 22 days preceding the timing of the present cruise. The POC/234Thp ratio of large, potentially sinking particles (>53 μm), was observed to increase with latitude, from 1.9 ± 0.2 μmol dpm−1 and 1.7 ± 0.3 μmol dpm−1 in the Subtropical Zone (STZ) and Subantarctic Zone (SAZ), respectively, to 3.0 ± 0.2 μmol dpm−1 in the Polar Front Zone (PFZ), 4.8 ± 1.9 μmol dpm−1 at the Southern Antarctic Circumpolar Current Front (SACCF) to 4.1 ± 1.7 μmol dpm−1 in the northern Weddell Gyre, in line with an increasing contribution of larger cell diatoms. Steady state and non steady state POC export from the upper 100 m ranged from 0.9 ± 0.2 mmolC m−2 d−1 to 5.1 ± 2.1 mmolC m−2 d−1 and from 0.3 ± 0.0 mmolC m−2 d−1 to 4.9 ± 3.2 mmolC m−2 d−1, respectively. From the SAZ to the SACCF, non steady state POC export production represented only 15 to 54 % of the steady state POC flux, suggesting that the intensity of export had decreased over time partly due to the fact that regenerated-production based communities of small-sized phytoplankton became predominant. In contrast, for the HNLC area south of the SACCF, we found an excellent agreement between the two modeling approaches indicating that surface POC export remained rather constant there. Estimated POC export represented between 6 to 54 % of the potential export as represented by new production, indicating that export efficiency was particularly low throughout the studied area, except close to the SACCF. Below the export layer, in the mesopelagic zone, 234Th activities generally reached equilibrium with 238U, but sometimes were in large excess relative to 238U (234Th/238U ratio>1.1), reflecting intense remineralisation/disaggregation of 234Th-bearing particles. The accumulation of excess 234Th in the 100–600 m depth interval ranged from 458 ± 55 dpm m−2 d−1 to 3068 ± 368 dpm m−2 d−1. Using POC to 234Th ratio of sinking particles, we converted this 234Th flux into a POC remineralisation flux, which ranged between 0.9 to 9.2 mmolC m−2 d−1. Mesopelagic remineralisation was also evidenced by Baxs inventories which are related to bacterial degradation of sinking material and offer a means to quantify the flux of respired C. Highest biogenic particulate Ba (Baxs) contents were generally observed in the 200–400 m depth interval with values reaching up to >1000 pM in the northern PFZ. Depth weighted average mesopelagic Baxs (meso-Baxs) was high in the PFZ and low in the northernmost (STZ-SAZ) and the southernmost (SACCF-AZ-WG) parts of the BGH section; conversion into respired C flux yielded a range of –0.23 to 6.4 mmolC m−2 d−1. Excluding two outliers, we found a significant positive correlation for mesopelagic waters between POC remineralisation estimated from meso-Baxs and from 234Th excess (R2 = 0.73). Our results indicate that POC export production in this area of the Southern Ocean was strongly attenuated in the mesopelagic waters due to remineralisation, a process which thus appears to strongly impact on longer term bathypelagic zone sequestration of POC.

Studies on Phytoplankton and Particulate Organic Carbon in the Southern Ocean

2011 ◽  
Vol 137 ◽  
pp. 344-352
Author(s):  
Gen Hai Zhu ◽  
Yan Lan Liu ◽  
Li Hong Chen ◽  
Pei Song Yu ◽  
Mao Jin ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Particulate Organic Carbon ◽  
Euphotic Zone ◽  
Study Data ◽  
Phytoplankton Abundance ◽  
Average Cell ◽  
Chl A ◽  
Cell Abundance ◽  
Phytoplankton Cell

Using China Southern Ocean’s study data collected from 1989 to 2009 year, this paper analyzed the related characteristics between phytoplankton abundance, Ch1 a concentrations and particulate organic carbon. The average cell abundance of Southern Ocean phytoplankton was 7.38×104 cells/dm3. The dominant species of Southern Ocean phytoplankton were Fragilariopsis kerguelensis, Fragilariopsis curta, Pseudo-nitzschia lineola, Eucampia antarctica, Thalassiosira antarctica and Corethron criophilum and son on. In Prydz Bay of the Southern Ocean, the contribution of phytoplankton cell abundance and phytoplankton carbon toward particulate organic carbon were higher than that in the Northern Gulf Ocean Area. In the upper layer of euphotic zone, the contribution of phytoplankton abundance and phytoplankton carbon toward particulate organic carbon were higher than that in the deep water district. Through analysis of regressive statistics, phytoplankton cell abundance (y) and particulate organic carbon (POC) and chlorophyll a (Chl a) were a remarkable positive correlation.

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