scholarly journals Rapid carbon cycling in the oligotrophic ocean

2011 ◽  
Vol 8 (6) ◽  
pp. 11661-11687 ◽  
Author(s):  
C. M. Duarte ◽  
S. Agustí
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Time Scales ◽  
Net Primary Production ◽  
Cell Lysis ◽  
Carbon Flow ◽  
Phytoplankton Production ◽  
Carbon Production ◽  
Phytoplankton Cell ◽  
Net Phytoplankton

Abstract. The dynamics of organic carbon production, release and bacterial use was examined across a range of communities spanning from highly oligotrophic ones in the Subtropical Atlantic Ocean, mesotrophic ones in the Mediterranean Sea and productive ones in the Northern African upwelling and the Southern Ocean. A comparative analysis of experiments examining total and particulate organic carbon production across a range of time scales (15 min to 24 h) for 20 communities with contrasting phytoplankton cell status, as assessed by cell lysis rates, and the use of a simple inverse model was used to resolve patterns of carbon flow in the microbial food web. Communities in productive ocean waters accumulated organic carbon over hourly time scales, whereas only a small fraction of net primary production accumulated in communities from oligotrophic waters. These communities supported high phytoplankton cell lysis rates leading to a rapid flux of organic carbon to bacteria, which had high affinity for phytoplankton-derived carbon, much of which was rapidly respired. Conventional assessments of primary production in the oligotrophic ocean severely underestimate net phytoplankton production, as carbon flow in microbial communities from oligotrophic ocean waters occurs within short (minutes) time scales. This explains difficulties to reconcile estimates of primary production with independent estimates of carbon use by bacteria in oligotrophic marine ecosystems.

scholarly journals Reviews and syntheses: Hidden forests, the role of vegetated coastal habitats in the ocean carbon budget

2017 ◽  
Vol 14 (2) ◽  
pp. 301-310 ◽  
Author(s):  
Carlos M. Duarte
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Carbon Budget ◽  
Net Primary Production ◽  
Global Ocean ◽  
Coastal Habitats ◽  
Global Carbon Budget ◽  
Global Carbon

Abstract. Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr−1, representing between 3 % and 1∕3 of oceanic CO2 uptake. Up to 1∕2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

scholarly journals Large deep-sea zooplankton biomass mirrors primary production in the global ocean

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Hernández-León ◽  
R. Koppelmann ◽  
E. Fraile-Nuez ◽  
A. Bode ◽  
C. Mompeán ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Large Scale ◽  
Net Primary Production ◽  
Deep Ocean ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Global Coupling ◽  
Do So

AbstractThe biological pump transports organic carbon produced by photosynthesis to the meso- and bathypelagic zones, the latter removing carbon from exchanging with the atmosphere over centennial time scales. Organisms living in both zones are supported by a passive flux of particles, and carbon transported to the deep-sea through vertical zooplankton migrations. Here we report globally-coherent positive relationships between zooplankton biomass in the epi-, meso-, and bathypelagic layers and average net primary production (NPP). We do so based on a global assessment of available deep-sea zooplankton biomass data and large-scale estimates of average NPP. The relationships obtained imply that increased NPP leads to enhanced transference of organic carbon to the deep ocean. Estimated remineralization from respiration rates by deep-sea zooplankton requires a minimum supply of 0.44 Pg C y−1 transported into the bathypelagic ocean, comparable to the passive carbon sequestration. We suggest that the global coupling between NPP and bathypelagic zooplankton biomass must be also supported by an active transport mechanism associated to vertical zooplankton migration.

scholarly journals Carbon Balance in Salt Marsh and Mangrove Ecosystems: A Global Synthesis

2020 ◽  
Vol 8 (10) ◽  
pp. 767 ◽  
Author(s):  
Daniel M. Alongi
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Salt Marshes ◽  
Dissolved Inorganic Carbon ◽  
Net Primary Production ◽  
Ecosystem Respiration ◽  
Soil Depth ◽  
Gross Primary Production ◽  
Coastal Ocean ◽  
Microbial Decomposition

Mangroves and salt marshes are among the most productive ecosystems in the global coastal ocean. Mangroves store more carbon (739 Mg CORG ha−1) than salt marshes (334 Mg CORG ha−1), but the latter sequester proportionally more (24%) net primary production (NPP) than mangroves (12%). Mangroves exhibit greater rates of gross primary production (GPP), aboveground net primary production (AGNPP) and plant respiration (RC), with higher PGPP/RC ratios, but salt marshes exhibit greater rates of below-ground NPP (BGNPP). Mangroves have greater rates of subsurface DIC production and, unlike salt marshes, exhibit active microbial decomposition to a soil depth of 1 m. Salt marshes release more CH4 from soil and creek waters and export more dissolved CH4, but mangroves release more CO2 from tidal waters and export greater amounts of particulate organic carbon (POC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC), to adjacent waters. Both ecosystems contribute only a small proportion of GPP, RE (ecosystem respiration) and NEP (net ecosystem production) to the global coastal ocean due to their small global area, but contribute 72% of air–sea CO2 exchange of the world’s wetlands and estuaries and contribute 34% of DIC export and 17% of DOC + POC export to the world’s coastal ocean. Thus, both wetland ecosystems contribute disproportionately to carbon flow of the global coastal ocean.

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 Diatoms Si Uptake Capacity Drives Carbon Export In Coastal Upwelling Systems

2016 ◽  
Author(s):  
F. Abrantes ◽  
P. Cermeño ◽  
C. Lopes ◽  
O. Romero ◽  
L. Matos ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Coastal Upwelling ◽  
Net Primary Production ◽  
Regional Scale ◽  
Global Scale ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Organic Carbon Content ◽  
Organic Carbon Burial

Abstract. Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica–precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. At the global-scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

scholarly journals Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

2016 ◽  
Vol 13 (14) ◽  
pp. 4099-4109 ◽  
Author(s):  
Fatima Abrantes ◽  
Pedro Cermeno ◽  
Cristina Lopes ◽  
Oscar Romero ◽  
Lélia Matos ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Coastal Upwelling ◽  
Net Primary Production ◽  
Regional Scale ◽  
Global Scale ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Organic Carbon Content ◽  
Organic Carbon Burial

Abstract. Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia–Canary, Benguela, Peru–Humboldt, California, and Somalia–Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

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

2021 ◽  
Author(s):  
Gaël Many ◽  
Caroline Ulses ◽  
Claude Estournel ◽  
Patrick Marsaleix
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Particulate Organic Carbon ◽  
Net Primary Production ◽  
Gross Primary Production ◽  
Biogeochemical Model ◽  
Eastern Region ◽  
Gulf Of Lion ◽  
Poc Export ◽  
Nw Mediterranean

Abstract. The Gulf of Lion shelf (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) budget 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 well the time and spatial evolution of temperature, chlorophyll, and nitrate concentrations and shows a clear annual cycle of gross primary production and respiration. Knowing the physical and biogeochemical inputs and outputs terms, the annual budget of the POC in the Gulf of Lion is estimated and discussed. We estimate an annual net primary production of ~200 104 tC 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 favored 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. Besides, the EOFs decomposition highlights the role of solar radiation anomalies and continental winds that favor upwellings, and inputs of the Rhône River, on annual changes in the net primary production. Annual POC deposition (19 104 tC yr−1) represents 10 % of the net primary production. The delivery of terrestrial POC favored 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 tC 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, represented 37 % of the total POC export. Maximum values were obtained during shelf dense water cascading events and marine winds. Considering surface waters only, the POC was mainly exported in the eastern part of the shelf through shelf waters and Rhône inputs, which spread to the Northern Current during favorable continental wind conditions. The Gulf of Lion 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.

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