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7 Research products, page 1 of 1

  • Canada
  • Research data
  • Other dataset type
  • European Commission
  • PANGAEA
  • PANGAEA - Data Publisher for Earth and Environmental Science

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  • Open Access English
    Authors: 
    Callbeck, Cameron; Lavik, Gaute; Ferdelman, Timothy G; Kuypers, Marcel MM;
    Publisher: PANGAEA
    Project: NSERC , EC | NITROX (704272)

    Supplement to: Callbeck, Cameron; Lavik, Gaute; Ferdelman, Timothy G; Fuchs, Bernhard M; Gruber-Vodicka, Harald R; Hach, Philipp F; Littmann, Sten; Schoffelen, Niels J; Kalvelage, Tim; Thomsen, Soeren; Schunck, Harald; Löscher, Carolin R; Schmitz, Ruth A; Kuypers, Marcel MM (2018): Oxygen minimum zone cryptic sulfur cycling sustained by offshore transport of key sulfur oxidizing bacteria. The data set includes, sulfide and sulfur concentrations, SUP05 cell densities, as well as denitrification and carbon fixation rates (based on 15N- and 13C-labelled in situ incubation experiments). The transect extends from the sulfidic upper shelf into the sulfide-free offshore oxygen minimum zone.

  • Open Access English
    Authors: 
    Gibbin, Emma M; Chakravarti, Leela Jackie; Jarrold, Michael; Christen, Felix; Turpin, Vincent; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero;
    Publisher: PANGAEA
    Project: NSERC , EC | EVOLMARIN (659359)

    Ocean warming and acidification are concomitant global drivers that are currently threatening the survival of marine organisms. How species will respond to these changes depends on their capacity for plastic and adaptive responses. Little is known about the mechanisms that govern plasticity and adaptability or how global changes will influence these relationships across multiple generations. Here, we exposed the emerging model marine polychaete Ophryotrocha labronica to conditions simulating ocean warming and acidification, in isolation and in combination over five generations to identify: (i) how multiple versus single global change drivers alter both juvenile and adult life-traits; (ii) the mechanistic link between adult physiological and fitness-related life-history traits; (iii) whether observed phenotypic changes observed over multiple generations are of plastic and/or adaptive origin. Two juvenile (developmental rate; survival to sexual maturity) and two adult (average reproductive body size; fecundity) life-history traits were measured in each generation, in addition to three physiological (cellular reactive oxygen species content, mitochondrial density; mitochondrial capacity) traits. We found that multi-generational exposure to warming alone caused an increase in: juvenile developmental rate, reactive oxygen species production and mitochondrial density and decreases in: average reproductive body size, fecundity and fluctuations in mitochondrial capacity, relative to control conditions. While exposure to ocean acidification alone, had only minor effects on juvenile developmental rate. Remarkably, when both drivers of global change were present, only mitochondrial capacity was significantly affected, suggesting that ocean warming and acidification act as opposing vectors of stress across multiple generations. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2016-11-29. Supplement to: Gibbin, Emma M; Chakravarti, Leela Jackie; Jarrold, Michael; Christen, Felix; Turpin, Vincent; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero (2017): Can multi-generational exposure to ocean warming and acidification lead to the adaptation of life history and physiology in a marine metazoan? Journal of Experimental Biology, 220(4), 551-563

  • Research data . Other dataset type . 2014
    Open Access English
    Authors: 
    Vuichard, Nicolas; Papale, Dario;
    Publisher: PANGAEA
    Project: NSERC , EC | GEOCARBON (283080)

    (preliminary) Exchanges of carbon, water and energy between the land surface and the atmosphere are monitored by eddy covariance technique at the ecosystem level. Currently, the FLUXNET database contains more than 500 sites registered and up to 250 of them sharing data (Free Fair Use dataset). Many modelling groups use the FLUXNET dataset for evaluating ecosystem model's performances but it requires uninterrupted time series for the meteorological variables used as input. Because original in-situ data often contain gaps, from very short (few hours) up to relatively long (some months), we develop a new and robust method for filling the gaps in meteorological data measured at site level. Our approach has the benefit of making use of continuous data available globally (ERA-interim) and high temporal resolution spanning from 1989 to today. These data are however not measured at site level and for this reason a method to downscale and correct the ERA-interim data is needed. We apply this method on the level 4 data (L4) from the LaThuile collection, freely available after registration under a Fair-Use policy. The performances of the developed method vary across sites and are also function of the meteorological variable. On average overall sites, the bias correction leads to cancel from 10% to 36% of the initial mismatch between in-situ and ERA-interim data, depending of the meteorological variable considered. In comparison to the internal variability of the in-situ data, the root mean square error (RMSE) between the in-situ data and the un-biased ERA-I data remains relatively large (on average overall sites, from 27% to 76% of the standard deviation of in-situ data, depending of the meteorological variable considered). The performance of the method remains low for the Wind Speed field, in particular regarding its capacity to conserve a standard deviation similar to the one measured at FLUXNET stations. The dataset contains meteorological fields retrieved from ERA-interim climate reanalysis and debiased making use of in-situ data at FLUXNET stations. Data are interpolated from the original 3-hour time resolution of ERA-interim product to the time resolution of measurements at FLUXNET stations (half-hourly) and distributed under the same format than in-situ data, in local time. Data are provided for the 153 sites from the LaThuile collection based on Fair-Use policy, as available in August 2013. This meteorological data can be used to fill the gaps in original in-situ data in order to get uninterrupted time series for the meteorological fields needed for running most of ecosystem models.Data are provided in csv-files, sorted in folder by site and zipped.The meteorological fields contained in the dataset are the Air Temperature (Ta_era, °C), the Vapour Pressure Deficit (VPD_era, hPa), the Wind horizontal speed (WS_era, m s-1), the Precipitation (Precip_era, mm tstep-1), the Global Radiation (Rg_era, W m-2) and the Incoming Longwave Radiation (LWin_era, W m-2). Supplement to: Vuichard, Nicolas; Papale, Dario (2015): Filling the gaps in meteorological continuous data measured at FLUXNET sites with ERA-Interim reanalysis. Earth System Science Data, 7(2), 157-171

  • Open Access English
    Authors: 
    Chakravarti, Leela Jackie; Jarrold, Michael; Gibbin, Emma M; Christen, Felix; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero;
    Publisher: PANGAEA
    Project: NSERC , EC | EVOLMARIN (659359)

    Human-assisted, trans-generational exposure to ocean warming and acidification has been proposed as a conservation and/or restoration tool to produce resilient offspring. To improve our understanding of the need for and the efficacy of this approach, we characterised life history and physiological responses in offspring of the marine polychaete Ophryotrocha labronica exposed to predicted ocean warming (OW: + 3 °C), ocean acidification (OA: pH -0.5) and their combination (OWA: + 3 °C, pH -0.5), following the exposure of their parents to either control conditions (within-generational exposure) or the same conditions (trans-generational exposure). Trans-generational exposure to OW fully alleviated the negative effects of within-generational exposure to OW on fecundity and egg volume and was accompanied by increased metabolic activity. While within-generational exposure to OA reduced juvenile growth rates and egg volume, trans-generational exposure alleviated the former but could not restore the latter. Surprisingly, exposure to OWA had no negative impacts within- or trans-generationally. Our results highlight the potential for trans-generational laboratory experiments in producing offspring that are resilient to OW and OA. However, trans-generational exposure does not always appear to improve traits, and therefore may not be a universally useful tool for all species in the face of global change. Supplement to: (2016): Can trans-generational experiments be used to enhance species resilience to ocean warming and acidification? Evolutionary Applications

  • Open Access English
    Authors: 
    Couture, Nicole; Irrgang, Anna Maria; Pollard, Wayne H; Lantuit, Hugues; Fritz, Michael;
    Publisher: PANGAEA
    Project: NSERC , EC | Nunataryuk (773421)

    Narrowing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from erosion. Different terrain units are assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, sample SOC contents are reduced by 19% and sediment contents by 16%. The SOC content in a 1 m**2 column of soil varies according to the height of the bluff, ranging from 30 to 662 kg, with a mean value of 183 kg. Forty-four per cent of the SOC is within the top 1 m of soil and values vary based on surficial materials, ranging from 30 to 53 kg C/m**3, with a mean of 41 kg. Eighty per cent of the shoreline is erosive with a mean annual rate of change is 0.7 m/a. This results in a SOC flux per meter of shoreline of 131 kg C/m/a, and a total flux for the entire Yukon coast of 35.5 10**6 kg C/a (0.036 Tg C/a). The mean flux of sediment per meter of shoreline is 5.3 10**3 kg/m/a, with a total flux of 1,832.0 10**6 kg/a (1.832 Tg/a). Sedimentation rates indicate that approximately 13% of the eroded carbon is sequestered in nearshore sediments, where the overwhelming majority of organic carbon is of terrestrial origin. Supplement to: Couture, Nicole; Irrgang, Anna Maria; Pollard, Wayne H; Lantuit, Hugues; Fritz, Michael (2018): Coastal Erosion of Permafrost Soils Along the Yukon Coastal Plain and Fluxes of Organic Carbon to the Canadian Beaufort Sea. Journal of Geophysical Research: Biogeosciences

  • Open Access English
    Authors: 
    Hoppe, Clara Jule Marie; Hassler, Christel S; Payne, Christopher D; Tortell, Philippe Daniel; Rost, Björn; Trimborn, Scarlett;
    Publisher: PANGAEA
    Project: ARC | Novel technologies to res... (DP1092892), NSERC , EC | PHYTOCHANGE (205150)

    The potential interactive effects of iron (Fe) limitation and Ocean Acidification in the Southern Ocean (SO) are largely unknown. Here we present results of a long-term incubation experiment investigating the combined effects of CO2 and Fe availability on natural phytoplankton assemblages from the Weddell Sea, Antarctica. Active Chl a fluorescence measurements revealed that we successfully cultured phytoplankton under both Fe-depleted and Fe-enriched conditions. Fe treatments had significant effects on photosynthetic efficiency (Fv/Fm; 0.3 for Fe-depleted and 0.5 for Fe-enriched conditions), non-photochemical quenching (NPQ), and relative electron transport rates (rETR). pCO2 treatments significantly affected NPQ and rETR, but had no effect on Fv/Fm. Under Fe limitation, increased pCO2 had no influence on C fixation whereas under Fe enrichment, primary production increased with increasing pCO2 levels. These CO2-dependent changes in productivity under Fe-enriched conditions were accompanied by a pronounced taxonomic shift from weakly to heavily silicified diatoms (i.e. from Pseudo-nitzschia sp. to Fragilariopsis sp.). Under Fe-depleted conditions, this functional shift was absent and thinly silicified species dominated all pCO2 treatments (Pseudo-nitzschia sp. and Synedropsis sp. for low and high pCO2, respectively). Our results suggest that Ocean Acidification could increase primary productivity and the abundance of heavily silicified, fast sinking diatoms in Fe-enriched areas, both potentially leading to a stimulation of the biological pump. Over much of the SO, however, Fe limitation could restrict this possible CO2 fertilization effect. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne et al, 2014) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2014-09-16. Supplement to: Hoppe, Clara Jule Marie; Hassler, Christel S; Payne, Christopher D; Tortell, Philippe Daniel; Rost, Björn; Trimborn, Scarlett (2013): Iron limitation modulates ocean acidification effects in Southern Ocean phytoplankton communities. PLoS ONE, 8(11), e79890

  • Open Access English
    Authors: 
    Tortell, Philippe Daniel; Trimborn, Scarlett; Li, Y; Rost, Björn; Payne, Christopher D;
    Publisher: PANGAEA
    Project: NSERC , NSF | Collaborative Research: I... (0338097), EC | PHYTOCHANGE (205150)

    We present results from a field study of inorganic carbon (C) acquisition by Ross Sea phytoplankton during Phaeocystis-dominated early season blooms. Isotope disequilibrium experiments revealed that HCO3- was the primary inorganic C source for photosynthesis in all phytoplankton assemblages. From these experiments, we also derived relative enhancement factors for HCO3-/CO2 interconversion as a measure of extracellular carbonic anhydrase activity (eCA). The enhancement factors ranged from 1.0 (no apparent eCA activity) to 6.4, with an overall mean of 2.9. Additional eCA measurements, made using membrane inlet mass spectrometry (MIMS), yielded activities ranging from 2.4 to 6.9 U/[mg chl a] (mean 4.1). Measurements of short-term C-fixation parameters revealed saturation kinetics with respect to external inorganic carbon, with a mean half-saturation constant for inorganic carbon uptake (K1/2) of ~380 mM. Comparison of our early springtime results with published data from late-season Ross Sea assemblages showed that neither HCO3- utilization nor eCA activity was significantly correlated to ambient CO2 levels or phytoplankton taxonomic composition. We did, however, observe a strong negative relationship between surface water pCO2 and short-term 14C-fixation rates for the early season survey. Direct incubation experiments showed no statistically significant effects of pCO2 (10 to 80 Pa) on relative HCO3- utilization or eCA activity. Our results provide insight into the seasonal regulation of C uptake by Ross Sea phytoplankton across a range of pCO2 and phytoplankton taxonomic composition. Supplement to: Tortell, Philippe Daniel; Trimborn, Scarlett; Li, Y; Rost, Björn; Payne, Christopher D (2010): Inorganic carbon utilization by Ross Sea phytoplankton across natural and experimental CO2 gradients. Journal of Phycology, 46(3), 433-443

search
Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
7 Research products, page 1 of 1
  • Open Access English
    Authors: 
    Callbeck, Cameron; Lavik, Gaute; Ferdelman, Timothy G; Kuypers, Marcel MM;
    Publisher: PANGAEA
    Project: NSERC , EC | NITROX (704272)

    Supplement to: Callbeck, Cameron; Lavik, Gaute; Ferdelman, Timothy G; Fuchs, Bernhard M; Gruber-Vodicka, Harald R; Hach, Philipp F; Littmann, Sten; Schoffelen, Niels J; Kalvelage, Tim; Thomsen, Soeren; Schunck, Harald; Löscher, Carolin R; Schmitz, Ruth A; Kuypers, Marcel MM (2018): Oxygen minimum zone cryptic sulfur cycling sustained by offshore transport of key sulfur oxidizing bacteria. The data set includes, sulfide and sulfur concentrations, SUP05 cell densities, as well as denitrification and carbon fixation rates (based on 15N- and 13C-labelled in situ incubation experiments). The transect extends from the sulfidic upper shelf into the sulfide-free offshore oxygen minimum zone.

  • Open Access English
    Authors: 
    Gibbin, Emma M; Chakravarti, Leela Jackie; Jarrold, Michael; Christen, Felix; Turpin, Vincent; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero;
    Publisher: PANGAEA
    Project: NSERC , EC | EVOLMARIN (659359)

    Ocean warming and acidification are concomitant global drivers that are currently threatening the survival of marine organisms. How species will respond to these changes depends on their capacity for plastic and adaptive responses. Little is known about the mechanisms that govern plasticity and adaptability or how global changes will influence these relationships across multiple generations. Here, we exposed the emerging model marine polychaete Ophryotrocha labronica to conditions simulating ocean warming and acidification, in isolation and in combination over five generations to identify: (i) how multiple versus single global change drivers alter both juvenile and adult life-traits; (ii) the mechanistic link between adult physiological and fitness-related life-history traits; (iii) whether observed phenotypic changes observed over multiple generations are of plastic and/or adaptive origin. Two juvenile (developmental rate; survival to sexual maturity) and two adult (average reproductive body size; fecundity) life-history traits were measured in each generation, in addition to three physiological (cellular reactive oxygen species content, mitochondrial density; mitochondrial capacity) traits. We found that multi-generational exposure to warming alone caused an increase in: juvenile developmental rate, reactive oxygen species production and mitochondrial density and decreases in: average reproductive body size, fecundity and fluctuations in mitochondrial capacity, relative to control conditions. While exposure to ocean acidification alone, had only minor effects on juvenile developmental rate. Remarkably, when both drivers of global change were present, only mitochondrial capacity was significantly affected, suggesting that ocean warming and acidification act as opposing vectors of stress across multiple generations. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2016-11-29. Supplement to: Gibbin, Emma M; Chakravarti, Leela Jackie; Jarrold, Michael; Christen, Felix; Turpin, Vincent; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero (2017): Can multi-generational exposure to ocean warming and acidification lead to the adaptation of life history and physiology in a marine metazoan? Journal of Experimental Biology, 220(4), 551-563

  • Research data . Other dataset type . 2014
    Open Access English
    Authors: 
    Vuichard, Nicolas; Papale, Dario;
    Publisher: PANGAEA
    Project: NSERC , EC | GEOCARBON (283080)

    (preliminary) Exchanges of carbon, water and energy between the land surface and the atmosphere are monitored by eddy covariance technique at the ecosystem level. Currently, the FLUXNET database contains more than 500 sites registered and up to 250 of them sharing data (Free Fair Use dataset). Many modelling groups use the FLUXNET dataset for evaluating ecosystem model's performances but it requires uninterrupted time series for the meteorological variables used as input. Because original in-situ data often contain gaps, from very short (few hours) up to relatively long (some months), we develop a new and robust method for filling the gaps in meteorological data measured at site level. Our approach has the benefit of making use of continuous data available globally (ERA-interim) and high temporal resolution spanning from 1989 to today. These data are however not measured at site level and for this reason a method to downscale and correct the ERA-interim data is needed. We apply this method on the level 4 data (L4) from the LaThuile collection, freely available after registration under a Fair-Use policy. The performances of the developed method vary across sites and are also function of the meteorological variable. On average overall sites, the bias correction leads to cancel from 10% to 36% of the initial mismatch between in-situ and ERA-interim data, depending of the meteorological variable considered. In comparison to the internal variability of the in-situ data, the root mean square error (RMSE) between the in-situ data and the un-biased ERA-I data remains relatively large (on average overall sites, from 27% to 76% of the standard deviation of in-situ data, depending of the meteorological variable considered). The performance of the method remains low for the Wind Speed field, in particular regarding its capacity to conserve a standard deviation similar to the one measured at FLUXNET stations. The dataset contains meteorological fields retrieved from ERA-interim climate reanalysis and debiased making use of in-situ data at FLUXNET stations. Data are interpolated from the original 3-hour time resolution of ERA-interim product to the time resolution of measurements at FLUXNET stations (half-hourly) and distributed under the same format than in-situ data, in local time. Data are provided for the 153 sites from the LaThuile collection based on Fair-Use policy, as available in August 2013. This meteorological data can be used to fill the gaps in original in-situ data in order to get uninterrupted time series for the meteorological fields needed for running most of ecosystem models.Data are provided in csv-files, sorted in folder by site and zipped.The meteorological fields contained in the dataset are the Air Temperature (Ta_era, °C), the Vapour Pressure Deficit (VPD_era, hPa), the Wind horizontal speed (WS_era, m s-1), the Precipitation (Precip_era, mm tstep-1), the Global Radiation (Rg_era, W m-2) and the Incoming Longwave Radiation (LWin_era, W m-2). Supplement to: Vuichard, Nicolas; Papale, Dario (2015): Filling the gaps in meteorological continuous data measured at FLUXNET sites with ERA-Interim reanalysis. Earth System Science Data, 7(2), 157-171

  • Open Access English
    Authors: 
    Chakravarti, Leela Jackie; Jarrold, Michael; Gibbin, Emma M; Christen, Felix; Massamba-N'siala, Gloria; Blier, Pierre; Calosi, Piero;
    Publisher: PANGAEA
    Project: NSERC , EC | EVOLMARIN (659359)

    Human-assisted, trans-generational exposure to ocean warming and acidification has been proposed as a conservation and/or restoration tool to produce resilient offspring. To improve our understanding of the need for and the efficacy of this approach, we characterised life history and physiological responses in offspring of the marine polychaete Ophryotrocha labronica exposed to predicted ocean warming (OW: + 3 °C), ocean acidification (OA: pH -0.5) and their combination (OWA: + 3 °C, pH -0.5), following the exposure of their parents to either control conditions (within-generational exposure) or the same conditions (trans-generational exposure). Trans-generational exposure to OW fully alleviated the negative effects of within-generational exposure to OW on fecundity and egg volume and was accompanied by increased metabolic activity. While within-generational exposure to OA reduced juvenile growth rates and egg volume, trans-generational exposure alleviated the former but could not restore the latter. Surprisingly, exposure to OWA had no negative impacts within- or trans-generationally. Our results highlight the potential for trans-generational laboratory experiments in producing offspring that are resilient to OW and OA. However, trans-generational exposure does not always appear to improve traits, and therefore may not be a universally useful tool for all species in the face of global change. Supplement to: (2016): Can trans-generational experiments be used to enhance species resilience to ocean warming and acidification? Evolutionary Applications

  • Open Access English
    Authors: 
    Couture, Nicole; Irrgang, Anna Maria; Pollard, Wayne H; Lantuit, Hugues; Fritz, Michael;
    Publisher: PANGAEA
    Project: NSERC , EC | Nunataryuk (773421)

    Narrowing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from erosion. Different terrain units are assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, sample SOC contents are reduced by 19% and sediment contents by 16%. The SOC content in a 1 m**2 column of soil varies according to the height of the bluff, ranging from 30 to 662 kg, with a mean value of 183 kg. Forty-four per cent of the SOC is within the top 1 m of soil and values vary based on surficial materials, ranging from 30 to 53 kg C/m**3, with a mean of 41 kg. Eighty per cent of the shoreline is erosive with a mean annual rate of change is 0.7 m/a. This results in a SOC flux per meter of shoreline of 131 kg C/m/a, and a total flux for the entire Yukon coast of 35.5 10**6 kg C/a (0.036 Tg C/a). The mean flux of sediment per meter of shoreline is 5.3 10**3 kg/m/a, with a total flux of 1,832.0 10**6 kg/a (1.832 Tg/a). Sedimentation rates indicate that approximately 13% of the eroded carbon is sequestered in nearshore sediments, where the overwhelming majority of organic carbon is of terrestrial origin. Supplement to: Couture, Nicole; Irrgang, Anna Maria; Pollard, Wayne H; Lantuit, Hugues; Fritz, Michael (2018): Coastal Erosion of Permafrost Soils Along the Yukon Coastal Plain and Fluxes of Organic Carbon to the Canadian Beaufort Sea. Journal of Geophysical Research: Biogeosciences

  • Open Access English
    Authors: 
    Hoppe, Clara Jule Marie; Hassler, Christel S; Payne, Christopher D; Tortell, Philippe Daniel; Rost, Björn; Trimborn, Scarlett;
    Publisher: PANGAEA
    Project: ARC | Novel technologies to res... (DP1092892), NSERC , EC | PHYTOCHANGE (205150)

    The potential interactive effects of iron (Fe) limitation and Ocean Acidification in the Southern Ocean (SO) are largely unknown. Here we present results of a long-term incubation experiment investigating the combined effects of CO2 and Fe availability on natural phytoplankton assemblages from the Weddell Sea, Antarctica. Active Chl a fluorescence measurements revealed that we successfully cultured phytoplankton under both Fe-depleted and Fe-enriched conditions. Fe treatments had significant effects on photosynthetic efficiency (Fv/Fm; 0.3 for Fe-depleted and 0.5 for Fe-enriched conditions), non-photochemical quenching (NPQ), and relative electron transport rates (rETR). pCO2 treatments significantly affected NPQ and rETR, but had no effect on Fv/Fm. Under Fe limitation, increased pCO2 had no influence on C fixation whereas under Fe enrichment, primary production increased with increasing pCO2 levels. These CO2-dependent changes in productivity under Fe-enriched conditions were accompanied by a pronounced taxonomic shift from weakly to heavily silicified diatoms (i.e. from Pseudo-nitzschia sp. to Fragilariopsis sp.). Under Fe-depleted conditions, this functional shift was absent and thinly silicified species dominated all pCO2 treatments (Pseudo-nitzschia sp. and Synedropsis sp. for low and high pCO2, respectively). Our results suggest that Ocean Acidification could increase primary productivity and the abundance of heavily silicified, fast sinking diatoms in Fe-enriched areas, both potentially leading to a stimulation of the biological pump. Over much of the SO, however, Fe limitation could restrict this possible CO2 fertilization effect. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne et al, 2014) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2014-09-16. Supplement to: Hoppe, Clara Jule Marie; Hassler, Christel S; Payne, Christopher D; Tortell, Philippe Daniel; Rost, Björn; Trimborn, Scarlett (2013): Iron limitation modulates ocean acidification effects in Southern Ocean phytoplankton communities. PLoS ONE, 8(11), e79890

  • Open Access English
    Authors: 
    Tortell, Philippe Daniel; Trimborn, Scarlett; Li, Y; Rost, Björn; Payne, Christopher D;
    Publisher: PANGAEA
    Project: NSERC , NSF | Collaborative Research: I... (0338097), EC | PHYTOCHANGE (205150)

    We present results from a field study of inorganic carbon (C) acquisition by Ross Sea phytoplankton during Phaeocystis-dominated early season blooms. Isotope disequilibrium experiments revealed that HCO3- was the primary inorganic C source for photosynthesis in all phytoplankton assemblages. From these experiments, we also derived relative enhancement factors for HCO3-/CO2 interconversion as a measure of extracellular carbonic anhydrase activity (eCA). The enhancement factors ranged from 1.0 (no apparent eCA activity) to 6.4, with an overall mean of 2.9. Additional eCA measurements, made using membrane inlet mass spectrometry (MIMS), yielded activities ranging from 2.4 to 6.9 U/[mg chl a] (mean 4.1). Measurements of short-term C-fixation parameters revealed saturation kinetics with respect to external inorganic carbon, with a mean half-saturation constant for inorganic carbon uptake (K1/2) of ~380 mM. Comparison of our early springtime results with published data from late-season Ross Sea assemblages showed that neither HCO3- utilization nor eCA activity was significantly correlated to ambient CO2 levels or phytoplankton taxonomic composition. We did, however, observe a strong negative relationship between surface water pCO2 and short-term 14C-fixation rates for the early season survey. Direct incubation experiments showed no statistically significant effects of pCO2 (10 to 80 Pa) on relative HCO3- utilization or eCA activity. Our results provide insight into the seasonal regulation of C uptake by Ross Sea phytoplankton across a range of pCO2 and phytoplankton taxonomic composition. Supplement to: Tortell, Philippe Daniel; Trimborn, Scarlett; Li, Y; Rost, Björn; Payne, Christopher D (2010): Inorganic carbon utilization by Ross Sea phytoplankton across natural and experimental CO2 gradients. Journal of Phycology, 46(3), 433-443