scholarly journals Factors controlling the competition between <i>Phaeocystis</i> and diatoms in the Southern Ocean and implications for carbon export fluxes

2021 ◽  
Vol 18 (1) ◽  
pp. 251-283
Author(s):  
Cara Nissen ◽  
Meike Vogt
Keyword(s):  
Southern Ocean ◽  
High Latitude ◽  
Ecological Model ◽  
Ross Sea ◽  
Net Primary Production ◽  
Light Sensitivity ◽  
Spatiotemporal Variability ◽  
Carbon Export ◽  
Poc Export ◽  
Biomass Loss

Abstract. The high-latitude Southern Ocean phytoplankton community is shaped by the competition between Phaeocystis and silicifying diatoms, with the relative abundance of these two groups controlling primary and export production, the production of dimethylsulfide, the ratio of silicic acid and nitrate available in the water column, and the structure of the food web. Here, we investigate this competition using a regional physical–biogeochemical–ecological model (ROMS-BEC) configured at eddy-permitting resolution for the Southern Ocean south of 35∘ S. We improved ROMS-BEC by adding an explicit parameterization of Phaeocystis colonies so that the model, together with the previous addition of an explicit coccolithophore type, now includes all biogeochemically relevant Southern Ocean phytoplankton types. We find that Phaeocystis contribute 46±21 % (1σ in space) and 40±20 % to annual net primary production (NPP) and particulate organic carbon (POC) export south of 60∘ S, respectively, making them an important contributor to high-latitude carbon cycling. In our simulation, the relative importance of Phaeocystis and diatoms is mainly controlled by spatiotemporal variability in temperature and iron availability. In addition, in more coastal areas, such as the Ross Sea, the higher light sensitivity of Phaeocystis at low irradiances promotes the succession from Phaeocystis to diatoms. Differences in the biomass loss rates, such as aggregation or grazing by zooplankton, need to be considered to explain the simulated seasonal biomass evolution and carbon export fluxes.

scholarly journals Factors controlling the competition between <i>Phaeocystis</i> and diatoms in the Southern Ocean

2020 ◽  
Author(s):  
Cara Nissen ◽  
Meike Vogt
Keyword(s):  
Southern Ocean ◽  
High Latitude ◽  
Phytoplankton Community ◽  
Ecological Model ◽  
Ross Sea ◽  
Light Sensitivity ◽  
Relative Importance ◽  
Iron Availability ◽  
Poc Export ◽  
Biomass Loss

Abstract. The high-latitude Southern Ocean phytoplankton community is shaped by the competition between Phaeocystis and silicifying diatoms, with the relative abundance of these two groups controlling primary and export production, the production of dimethylsulfide, the ratio of silicic acid and nitrate available in the water column, and the structure of the food web. Here, we investigate this competition using a regional physical-biogeochemical-ecological model (ROMS-BEC) configured at eddy-permitting resolution for the Southern Ocean south of 35° S. We extended ROMS-BEC by an explicit parameterization of Phaeocystis colonies, so that the model, together with the previous addition of an explicit coccolithophore type, now includes all biogeochemically relevant Southern Ocean phytoplankton types. We find that Phaeocystis contribute 46 % and 40 % to annual NPP and POC export south of 60° S, respectively, making them an important contributor to high-latitude carbon cycling. In our simulation, the relative importance of Phaeocystis and diatoms is mainly controlled by the temporal variability in temperature and iron availability. The higher light sensitivity of Phaeocystis at low irradiances promotes the succession from Phaeocystis to diatoms in more coastal areas, such as the Ross Sea. Still, differences in the biomass loss rates, such as aggregation or grazing by zooplankton, need to be considered to explain the simulated seasonal biomass evolution.

scholarly journals A circumpolar dust conveyor in the glacial Southern Ocean

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Torben Struve ◽  
Katharina Pahnke ◽  
Frank Lamy ◽  
Marc Wengler ◽  
Philipp Böning ◽  
...  
Keyword(s):  
South America ◽  
Southern Ocean ◽  
Net Primary Production ◽  
South Pacific ◽  
Dust Deposition ◽  
Carbon Export ◽  
Transport Pathways ◽  
Dust Transport ◽  
Glacial Periods ◽  
Central South

Abstract The increased flux of soluble iron (Fe) to the Fe-deficient Southern Ocean by atmospheric dust is considered to have stimulated the net primary production and carbon export, thus promoting atmospheric CO2 drawdown during glacial periods. Yet, little is known about the sources and transport pathways of Southern Hemisphere dust during the Last Glacial Maximum (LGM). Here we show that Central South America (~24‒32°S) contributed up to ~80% of the dust deposition in the South Pacific Subantarctic Zone via efficient circum-Antarctic dust transport during the LGM, whereas the Antarctic Zone was dominated by dust from Australia. This pattern is in contrast to the modern/Holocene pattern, when South Pacific dust fluxes are thought to be primarily supported by Australian sources. Our findings reveal that in the glacial Southern Ocean, Fe fertilization critically relies on the dynamic interaction of changes in dust-Fe sources in Central South America with the circumpolar westerly wind system.

Short-lived thorium isotopes (, ) as indicators of POC export and particle cycling in the Ross Sea, Southern Ocean

2000 ◽  
Vol 47 (15-16) ◽  
pp. 3451-3490 ◽  
Author(s):  
J.K. Cochran ◽  
K.O. Buesseler ◽  
M.P. Bacon ◽  
H.W. Wang ◽  
D.J. Hirschberg ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ross Sea ◽  
Poc Export ◽  
Thorium Isotopes

scholarly journals Carbon export and transfer to depth across the Southern Ocean Great Calcite Belt

2015 ◽  
Vol 12 (13) ◽  
pp. 3953-3971 ◽  
Author(s):  
S. Z. Rosengard ◽  
P. J. Lam ◽  
W. M. Balch ◽  
M. E. Auro ◽  
S. Pike ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Deep Ocean ◽  
Euphotic Zone ◽  
Biological Pump ◽  
Carbon Export ◽  
Mesopelagic Zone ◽  
Poc Flux ◽  
Phytoplankton Communities ◽  
Poc Export ◽  
Particulate Inorganic Carbon

Abstract. Sequestration of carbon by the marine biological pump depends on the processes that alter, remineralize, and preserve particulate organic carbon (POC) during transit to the deep ocean. Here, we present data collected from the Great Calcite Belt, a calcite-rich band across the Southern Ocean surface, to compare the transformation of POC in the euphotic and mesopelagic zones of the water column. The 234Th-derived export fluxes and size-fractionated concentrations of POC, particulate inorganic carbon (PIC), and biogenic silica (BSi) were measured from the upper 1000 m of 27 stations across the Atlantic and Indian sectors of the Great Calcite Belt. POC export out of the euphotic zone was correlated with BSi export. PIC export was not, but did correlate positively with POC flux transfer efficiency. Moreover, regions of high BSi concentrations, which corresponded to regions with proportionally larger particles, exhibited higher attenuation of > 51 μm POC concentrations in the mesopelagic zone. The interplay among POC size partitioning, mineral composition, and POC attenuation suggests a more fundamental driver of POC transfer through both depth regimes in the Great Calcite Belt. In particular, we argue that diatom-rich communities produce large and labile POC aggregates, which not only generate high export fluxes but also drive more remineralization in the mesopelagic zone. We observe the opposite in communities with smaller calcifying phytoplankton, such as coccolithophores. We hypothesize that these differences are influenced by inherent differences in the lability of POC exported by different phytoplankton communities.

scholarly journals Carbon export and transfer to depth across the Southern Ocean Great Calcite Belt

2015 ◽  
Vol 12 (3) ◽  
pp. 2843-2896
Author(s):  
S. Z. Rosengard ◽  
P. J. Lam ◽  
W. M. Balch ◽  
M. E. Auro ◽  
S. Pike ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Deep Ocean ◽  
Euphotic Zone ◽  
Biological Pump ◽  
Carbon Export ◽  
Mesopelagic Zone ◽  
Poc Flux ◽  
Phytoplankton Communities ◽  
Poc Export ◽  
Particulate Inorganic Carbon

Abstract. Sequestration of carbon by the marine biological pump depends on the processes that alter, remineralize and preserve particulate organic carbon (POC) during transit to the deep ocean. Here, we present data collected from the Great Calcite Belt, a calcite-rich band across the Southern Ocean surface, to compare the transformation of POC in the euphotic and mesopelagic zones of the water column. The 234Th-derived export fluxes and size-fractionated concentrations of POC, particulate inorganic carbon (PIC), and biogenic silica (BSi) were measured from the upper 1000 m of 27 stations across the Atlantic and Indian sectors of the Great Calcite Belt. POC export out of the euphotic zone was correlated with BSi export. PIC export was not, but did correlate positively with POC flux transfer efficiency. Moreover, regions of high BSi concentrations, which corresponded to regions with proportionally larger particles, exhibited higher attenuation of >51 μm POC concentrations in the mesopelagic zone. The interplay among POC size partitioning, mineral composition and POC attenuation suggests a more fundamental driver of POC transfer through both depth regimes in the Great Calcite Belt. In particular, we argue that diatom-dominated communities produce large and labile POC aggregates, which generate high export fluxes but also drive more remineralization in the mesopelagic zone. We observe the opposite in communities with smaller calcifying phytoplankton, such as coccolithophores. We hypothesize that these differences are influenced by inherent differences in the lability of POC exported by different phytoplankton communities.

scholarly journals Dissolved oxygen dynamics during a phytoplankton bloom in the Ross Sea polynya

2015 ◽  
Vol 27 (4) ◽  
pp. 362-372 ◽  
Author(s):  
Bastien Y. Queste ◽  
Karen J. Heywood ◽  
Walker O. Smith ◽  
Daniel E. Kaufman ◽  
Timothy D. Jickells ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Primary Productivity ◽  
Ross Sea ◽  
Phytoplankton Bloom ◽  
Net Primary Production ◽  
Biological Processes ◽  
Carbon Export ◽  
Net Community Production ◽  
Spatio Temporal ◽  
The Difference

AbstractThe Ross Sea polynya is one of the most productive regions in the Southern Ocean. However, limited access and high spatio-temporal variability of physical and biological processes limit the use of conventional oceanographic methods to measure early season primary productivity. High-resolution observations from two Seagliders provide insights into the timing of a bloom in the southern Ross Sea polynya in December 2010. Changes in chlorophyll and oxygen concentrations are used to assess bloom dynamics. Using a ratio of dissolved oxygen to carbon, net primary production is estimated over the duration of the bloom showing a sensitive balance between net autotrophy and heterotrophy. The two gliders, observing spatially distinct regions during the same period, found net community production rates of -0.9±0.7 and 0.7±0.4 g C m-2 d-1. The difference highlights the spatial variability of biological processes and is probably caused by observing different stages of the bloom. The challenge of obtaining accurate primary productivity estimates highlights the need for increased observational efforts, particularly focusing on subsurface processes not resolved using surface or remote observations. Without an increased observational effort and the involvement of emerging technologies, it will not be possible to determine the seasonal trophic balance of the Ross Sea polynya and quantify the shelf’s importance in carbon export.

Carbon export associated with free-drifting icebergs in the Southern Ocean

2011 ◽  
Vol 58 (11-12) ◽  
pp. 1485-1496 ◽  
Author(s):  
K.L. Smith ◽  
A.D. Sherman ◽  
T.J. Shaw ◽  
A.E. Murray ◽  
M. Vernet ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Carbon Export

MPAs in the Southern Ocean under CCAMLR

2021 ◽  
Vol 9 (1) ◽  
pp. 84-107
Author(s):  
Karen N. Scott
Keyword(s):  
Southern Ocean ◽  
Protected Area ◽  
Marine Protected Area ◽  
Ross Sea ◽  
Coastal Areas ◽  
Antarctic Marine ◽  
National Jurisdiction

Abstract In 2016, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) designated the largest marine protected area (MPA) in the Ross Sea. Hailed as both a precedent and a prototype for MPAs in both Antarctica and in areas beyond national jurisdiction more generally, it is nevertheless proving challenging to implement. Moreover, further MPAs have yet to be designated in the region although a number are under negotiation. This article will evaluate the contribution made by CCAMLR to the implementation of SDG 14.5 (the conservation of at least 20 per cent of marine and coastal areas by 2020), its relationship to area-based protection under the 1991 Environmental Protocol, and highlight the challenges of establishing MPAs beyond the jurisdiction of states.

scholarly journals Modeling the effect of Ross Ice Shelf melting on the Southern Ocean in quasi-equilibrium

2018 ◽  
Vol 12 (9) ◽  
pp. 3033-3044 ◽  
Author(s):  
Xiying Liu
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ross Sea ◽  
Global Ocean ◽  
Freshwater Flux ◽  
Quasi Equilibrium ◽  
Ice Shelf ◽  
Sea Ice Concentration ◽  
Ross Ice Shelf ◽  
Ice Concentration

Abstract. To study the influence of basal melting of the Ross Ice Shelf (BMRIS) on the Southern Ocean (ocean southward of 35∘ S) in quasi-equilibrium, numerical experiments with and without the BMRIS effect were performed using a global ocean–sea ice–ice shelf coupled model. In both experiments, the model started from a state of quasi-equilibrium ocean and was integrated for 500 years forced by CORE (Coordinated Ocean-ice Reference Experiment) normal-year atmospheric fields. The simulation results of the last 100 years were analyzed. The melt rate averaged over the entire Ross Ice Shelf is 0.25 m a−1, which is associated with a freshwater flux of 3.15 mSv (1 mSv = 103 m3 s−1). The extra freshwater flux decreases the salinity in the region from 1500 m depth to the sea floor in the southern Pacific and Indian oceans, with a maximum difference of nearly 0.005 PSU in the Pacific Ocean. Conversely, the effect of concurrent heat flux is mainly confined to the middle depth layer (approximately 1500 to 3000 m). The decreased density due to the BMRIS effect, together with the influence of ocean topography, creates local differences in circulation in the Ross Sea and nearby waters. Through advection by the Antarctic Circumpolar Current, the flux difference from BMRIS gives rise to an increase of sea ice thickness and sea ice concentration in the Ross Sea adjacent to the coast and ocean water to the east. Warm advection and accumulation of warm water associated with differences in local circulation decrease sea ice concentration on the margins of sea ice cover adjacent to open water in the Ross Sea in September. The decreased water density weakens the subpolar cell as well as the lower cell in the global residual meridional overturning circulation (MOC). Moreover, we observe accompanying reduced southward meridional heat transport at most latitudes of the Southern Ocean.

Holodentata gen. nov. (Isopoda: Asellota: Paramunnidae) with a description of two new species: H. caeca and H. triangulata from the Southern Ocean

Zootaxa ◽  
2009 ◽  
Vol 2096 (1) ◽  
pp. 395-412 ◽  
Author(s):  
BRENDA LÍA DOTI ◽  
MADHUMITA CHOUDHURY ◽  
ANGELIKA BRANDT
Keyword(s):  
New Species ◽  
Southern Ocean ◽  
Dorsal View ◽  
Type Species ◽  
New Genus ◽  
Ross Sea ◽  
Weddell Sea ◽  
Two New Species

A new genus of Paramunnidae, Holodentata (type species: Paramunna gaussi Vanhöffen, 1914) is erected. The new genus comprises two new species: H. caeca, from the deep Weddell Sea and H. triangulata, from the Ross Sea. The new genus is distinguished by the following characters: article 3 of the antenna short and with strong denticles, mandible palp absent, article 2 of maxilliped palp longest, coxal plates visible in dorsal view in all pereonites, pleotelson broad and laterally denticulated.

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