scholarly journals Role of zooplankton in determining the efficiency of the biological carbon pump

2016 ◽  
Author(s):  
Emma L. Cavan ◽  
Stephanie A. Henson ◽  
Anna Belcher ◽  
Richard Sanders
Keyword(s):  
Biogeochemical Model ◽  
Atlantic Sector ◽  
Mesopelagic Zone ◽  
Carbon Pump ◽  
Minimum Zone ◽  
Direct Contrast ◽  
Particle Export ◽  
Biological Carbon Pump

Abstract. The efficiency of the ocean’s biological carbon pump (BCPeff – here the product of particle export and transfer efficiencies) plays a key role in the air-sea partitioning of CO2. Despite its importance in the global carbon cycle, the biological processes that control BCPeff are poorly known. We investigate the potential role that zooplankton play in the biological carbon pump using both in situ observations and model output. Observed and modelled estimates of fast, slow and total sinking fluxes are presented from three oceanic sites: the Atlantic sector of the Southern Ocean, the temperate North Atlantic and the equatorial Pacific oxygen minimum zone (OMZ). We find that observed particle export efficiency is inversely related to primary production likely due to zooplankton grazing, in direct contrast to the model estimates. The model and observations show strongest agreement in remineralization coefficients and BCPeff at the OMZ site where zooplankton processing of particles in the mesopelagic zone is thought to be low. As the model has limited representation of zooplankton-mediated remineralization processes, we suggest that these results point to the importance of zooplankton in setting BCPeff, including particle grazing and fragmentation, and the effect of diel vertical migration. We suggest that improving parameterizations of zooplankton processes may increase the fidelity of biogeochemical model estimates of the biological carbon pump. Future changes in climate such as the expansion of OMZs may decrease the role of zooplankton in the biological carbon pump globally, hence increasing its efficiency.

scholarly journals Role of zooplankton in determining the efficiency of the biological carbon pump

2017 ◽  
Vol 14 (1) ◽  
pp. 177-186 ◽  
Author(s):  
Emma L. Cavan ◽  
Stephanie A. Henson ◽  
Anna Belcher ◽  
Richard Sanders
Keyword(s):  
Biogeochemical Model ◽  
Atlantic Sector ◽  
Mesopelagic Zone ◽  
Carbon Pump ◽  
Minimum Zone ◽  
Direct Contrast ◽  
Particle Export ◽  
Biological Carbon Pump

Abstract. The efficiency of the ocean's biological carbon pump (BCPeff – here the product of particle export and transfer efficiencies) plays a key role in the air–sea partitioning of CO2. Despite its importance in the global carbon cycle, the biological processes that control BCPeff are poorly known. We investigate the potential role that zooplankton play in the biological carbon pump using both in situ observations and model output. Observed and modelled estimates of fast, slow, and total sinking fluxes are presented from three oceanic sites: the Atlantic sector of the Southern Ocean, the temperate North Atlantic, and the equatorial Pacific oxygen minimum zone (OMZ). We find that observed particle export efficiency is inversely related to primary production likely due to zooplankton grazing, in direct contrast to the model estimates. The model and observations show strongest agreement in remineralization coefficients and BCPeff at the OMZ site where zooplankton processing of particles in the mesopelagic zone is thought to be low. As the model has limited representation of zooplankton-mediated remineralization processes, we suggest that these results point to the importance of zooplankton in setting BCPeff, including particle grazing and fragmentation, and the effect of diel vertical migration. We suggest that improving parameterizations of zooplankton processes may increase the fidelity of biogeochemical model estimates of the biological carbon pump. Future changes in climate such as the expansion of OMZs may decrease the role of zooplankton in the biological carbon pump globally, hence increasing its efficiency.

Insights into the ocean’s biological carbon pump: What makes marine snow falling into the deep ocean?

2021 ◽  
Author(s):  
Frederic Le Moigne
Keyword(s):  
Carbon Cycle ◽  
Global Analysis ◽  
Deep Ocean ◽  
Ecosystem Structure ◽  
Faecal Pellets ◽  
Surface Ocean ◽  
Mesopelagic Zone ◽  
Carbon Pump ◽  
Biological Carbon Pump

<p>The oceanic biological carbon pump (BCP) regulates the Earth carbon cycle by transporting part of the photosynthetically fixed CO<sub>2</sub> into the deep ocean. Suppressing this mechanism would result in an important increase of atmospheric CO<sub>2</sub> level. The BCP occurs mainly in the form of organic carbon particles (POC) sinking out the surface ocean. Various types of particles are produced in surface ocean. They all differ in production, sinking and decomposition rates, vertically and horizontally. The amount of POC transported to depths via these various export pathways as well as their decomposition pathways all have different ecological origins and therefore may response differently to climate change. Here I will briefly review some of the processes driving both particle export out of the euphotic zone (0-100m) as well as particles transport within the mesopelagic zone (100-1000m). In the early 2000s, strong correlations between POC and mineral (calcite an opal) fluxes observed in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. These relationships were first considered as being universal. However global analysis of POC and mineral ballast fluxes showed that mineral ballasting is important in regions like the high-latitude North Atlantic but that in most places (some of which efficiently exporting) the unballasted fraction often dominates the export flux. In such regions, we later showed that zooplankton-mediated export (presence of faecal pellets) and surface microbial abundance were important drivers of the efficiency of particles export. Similar trends were found globally by including bacteria and zooplankton abundances to a global reanalysis of the global variations of the POC export efficiency. This implies that the whole ecosystem structure from bacteria to fishes, rather than just the phytoplankton community, is important in setting the strength of the biological carbon pump. Further down in the water column (mesopelagic zone), processes impacting the transport of particles are less clear. Sinking particles experience a number of biotic and abiotic transformations during their descent. These includes solubilization, remineralisation, fragmentation, ingestion/active transport, breakdown among others. While some potential factors such as O<sub>2</sub> concentration and temperature have been proposed as powerful controls, global evidences are often inconsistent. In the award talk, I will review current challenges related to the role of particles consumption by zooplankton and fishes as well as the role of particles attached prokaryotes (bacteria and archaea) in setting the efficiency of the carbon transport in the mesopelagic zone.</p>

Controls over the export flux of marine snow into the deep ocean

2020 ◽  
Author(s):  
Frederic Le Moigne
Keyword(s):  
Carbon Cycle ◽  
Global Analysis ◽  
Deep Ocean ◽  
Ecosystem Structure ◽  
Export Flux ◽  
Surface Ocean ◽  
Mesopelagic Zone ◽  
Carbon Pump ◽  
Biological Carbon Pump

<p>The oceanic biological carbon pump (BCP) regulates the Earth carbon cycle by transporting part of the photosynthetically fixed CO<sub>2</sub> into the deep ocean. Suppressing this mechanism would result in an important increase of atmospheric CO<sub>2</sub> level. The BCP occurs mainly in the form of organic carbon particles (POC) sinking out the surface ocean. Various types of particles are produced in surface ocean. They all differ in production, sinking and decomposition rates, vertically and horizontally. The amount of POC transported to depths via these various export pathways as well as their decomposition pathways all have different ecological origins and therefore may response differently to climate change. Here I will briefly review some of the processes driving both particle export out of the euphotic zone (0-100m) as well as particles transport within the mesopelagic zone (100-1000m). In the early 2000s, strong correlations between POC and mineral (calcite an opal) fluxes observed in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. These relationships were first considered as being universal. However global analysis of POC and mineral ballast fluxes showed that mineral ballasting is important in regions like the high-latitude North Atlantic but that in most places (some of which efficiently exporting) the unballasted fraction often dominates the export flux. In such regions, we later on showed that zooplankton-mediated export (presence of faecal pellets) and surface microbial abundance were important drivers of the efficiency of particles export. Similar trends were found globally by including bacteria and zooplankton abundances to a global reanalysis of the global variations of the POC export efficiency. This implies that the whole ecosystem structure, rather than just the phytoplankton community, is important in setting the strength of the biological carbon pump. Further down in the water column (mesopelagic zone), processes impacting the transport of particles are less clear. Sinking particles experience a number of biotic and abiotic transformations during their descent. These includes solubilization, remineralisation, fragmentation, ingestion/active transport, break down among others. While some potential factors such as O<sub>2</sub> concentration and temperature have been proposed as powerful controls, globally evidences are often inconsistent. Current challenges related to the role of particles consumption by zooplankton and fishes as well as the role of particles attached prokaryotes (bacteria and archaea) in setting the efficiency of the carbon transport in the mesopelagic zone will be discussed.</p>

scholarly journals Impact of hydrothermalism on the ocean iron cycle

2016 ◽  
Vol 374 (2081) ◽  
pp. 20150291 ◽  
Author(s):  
Alessandro Tagliabue ◽  
Joseph Resing
Keyword(s):  
Southern Ocean ◽  
Oxidation Kinetics ◽  
State Of The Art ◽  
Section Data ◽  
Trace Element Chemistry ◽  
Carbon Pump ◽  
Climatic Impacts ◽  
The Impact ◽  
Biological Carbon Pump

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.

scholarly journals Cryptic role of tetrathionate in the sulfur cycle: A study from Arabian Sea oxygen minimum zone sediments

2019 ◽  
Author(s):  
Subhrangshu Mandal ◽  
Sabyasachi Bhattacharya ◽  
Chayan Roy ◽  
Moidu Jameela Rameez ◽  
Jagannath Sarkar ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Potential Role ◽  
Sediment Cores ◽  
Oxygen Minimum Zone ◽  
Sulfur Cycle ◽  
Metagenome Analysis ◽  
Minimum Zone ◽  
Oxygen Minimum

ABSTRACTTo explore the potential role of tetrathionate in the sulfur cycle of marine sediments, the population ecology of tetrathionate-forming, oxidizing, and respiring microorganisms was revealed at 15-30 cm resolution along two, ∼3-m-long, cores collected from 530- and 580-mbsl water-depths of Arabian Sea, off India’s west coast, within the oxygen minimum zone (OMZ). Metagenome analysis along the two sediment-cores revealed widespread occurrence of the structural genes that govern these metabolisms; high diversity and relative-abundance was also detected for the bacteria known to render these processes. Slurry-incubation of the sediment-samples, pure-culture isolation, and metatranscriptome analysis, corroborated thein situfunctionality of all the three metabolic-types. Geochemical analyses revealed thiosulfate (0-11.1 μM), pyrite (0.05-1.09 wt %), iron (9232-17234 ppm) and manganese (71-172 ppm) along the two sediment-cores. Pyrites (via abiotic reaction with MnO2) and thiosulfate (via oxidation by chemolithotrophic bacteria prevalentin situ) are apparently the main sources of tetrathionate in this ecosystem. Tetrathionate, in turn, can be either converted to sulfate (via oxidation by the chemolithotrophs present) or reduced back to thiosulfate (via respiration by native bacteria); 0-2.01 mM sulfide present in the sediment-cores may also reduce tetrathionate abiotically to thiosulfate and elemental sulfur. Notably tetrathionate was not detectedin situ- high microbiological and geochemical reactivity of this polythionate is apparently instrumental in the cryptic nature of its potential role as a central sulfur cycle intermediate. Biogeochemical roles of this polythionate, albeit revealed here in the context of OMZ sediments, may well extend to the sulfur cycles of other geomicrobiologically-distinct marine sediment horizons.

scholarly journals Cryptic role of tetrathionate in the sulfur cycle: A study from Arabian Sea oxygen minimum zone sediments

2019 ◽  
Author(s):  
Subhrangshu Mandal ◽  
Sabyasachi Bhattacharya ◽  
Chayan Roy ◽  
Moidu Jameela Rameez ◽  
Jagannath Sarkar ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Potential Role ◽  
Sediment Cores ◽  
Oxygen Minimum Zone ◽  
Sulfur Cycle ◽  
Metagenome Analysis ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. To explore the potential role of tetrathionate in the sulfur cycle of marine sediments, the population ecology of tetrathionate-forming, oxidizing, and respiring microorganisms was revealed at 15–30 cm resolution along two, ~ 3-m-long, cores collected from 530- and 580-mbsl water-depths of Arabian Sea, off India’s west coast, within the oxygen minimum zone (OMZ). Metagenome analysis along the two sediment-cores revealed widespread occurrence of the structural genes that govern these metabolisms; high diversity and relative-abundance was also detected for the bacteria known to render these processes. Slurry-incubation of the sediment-samples, pure-culture isolation, and metatranscriptome analysis, corroborated the in situ functionality of all the three metabolic-types. Geochemical analyses revealed thiosulfate (0–11.1 µM), pyrite (0.05–1.09 wt %), iron (9232–17234 ppm) and manganese (71–172 ppm) along the two sediment-cores. Pyrites (via abiotic reaction with MnO2) and thiosulfate (via oxidation by chemolithotrophic bacteria prevalent in situ) are apparently the main sources of tetrathionate in this ecosystem. Tetrathionate, in turn, can be either converted to sulfate (via oxidation by the chemolithotrophs present) or reduced back to thiosulfate (via respiration by native bacteria); 0–2.01 mM sulfide present in the sediment-cores may also reduce tetrathionate abiotically to thiosulfate and elemental sulfur. Notably tetrathionate was not detected in situ – high microbiological and geochemical reactivity of this polythionate is apparently instrumental in the cryptic nature of its potential role as a central sulfur cycle intermediate. Biogeochemical roles of this polythionate, albeit revealed here in the context of OMZ sediments, may well extend to the sulfur cycles of other geomicrobiologically-distinct marine sediment horizons.

scholarly journals Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing

2016 ◽  
Vol 2 (5) ◽  
pp. e1600282 ◽  
Author(s):  
François Dufois ◽  
Nick J. Hardman-Mountford ◽  
Jim Greenwood ◽  
Anthony J. Richardson ◽  
Ming Feng ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Carbon Fixation ◽  
Phytoplankton Production ◽  
Biogeochemical Model ◽  
Substantial Portion ◽  
New Paradigm ◽  
Carbon Pump ◽  
Anticyclonic Eddies ◽  
Global Carbon ◽  
Biological Carbon Pump

Mesoscale eddies are ubiquitous features of ocean circulation that modulate the supply of nutrients to the upper sunlit ocean, influencing the rates of carbon fixation and export. The popular eddy-pumping paradigm implies that nutrient fluxes are enhanced in cyclonic eddies because of upwelling inside the eddy, leading to higher phytoplankton production. We show that this view does not hold for a substantial portion of eddies within oceanic subtropical gyres, the largest ecosystems in the ocean. Using space-based measurements and a global biogeochemical model, we demonstrate that during winter when subtropical eddies are most productive, there is increased chlorophyll in anticyclones compared with cyclones in all subtropical gyres (by 3.6 to 16.7% for the five basins). The model suggests that this is a consequence of the modulation of winter mixing by eddies. These results establish a new paradigm for anticyclonic eddies in subtropical gyres and could have important implications for the biological carbon pump and the global carbon cycle.

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