ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2017-08-29
    Description: The Arctic Ocean is a region particularly prone to ongoing ocean acidification (OA) and climate-driven changes. The influence of these changes on Arctic phytoplankton assemblages, however, remains poorly understood. In order to understand how OA and enhanced irradiances (e.g., resulting from sea–ice retreat) will alter the species composition, primary production, and ecophysiology of Arctic phytoplankton, we conducted an incubation experiment with an assemblage from Baffin Bay (71°N, 68°W) under different carbonate chemistry and irradiance regimes. Seawater was collected from just below the deep Chl a maximum, and the resident pytoplankton were exposed to 380 and 1000 latm pCO2 at both 15 and 35% incident irradiance. On-deck incubations, in which temperatures were 6°C above in situ conditions, were monitored for phytoplankton growth, biomass stoichiometry, net primary production, photo-physiology, and taxonomic composition. During the 8-day experiment, taxonomic diversity decreased and the diatom Chaetoceros socialis became increasingly dominant irrespective of light or CO2 levels. We found no statistically significant effects from either higher CO2 or light on physiological properties of phytoplankton during the experiment. We did, however, observe an initial 2-day stress response in all treatments, and slight photo-physiological responses to higher CO2 and light during the first five days of the incubation. Our results thus indicate high resistance of Arctic phytoplankton to OA and enhanced irradiance levels, challenging the commonly predicted stimulatory effects of enhanced CO2 and light availability for primary production.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2016-08-31
    Description: The Arctic Ocean is one of the regions most prone to on-going ocean acidification (OA) and climate-driven changes, including increased sea surface temperature, sea-ice melt and altered mixing regimes. However, the influence of these changes on Arctic primary productivity, phytoplankton ecology and elemental cycles remains poorly understood. To date, the impact of various environmental stressors on phytoplankton have largely been assessed in isolation, and only limited process-understanding was gained. In order to understand how OA and enhanced irradiances (resulting from sea-ice retreat and increased mixed layer stratification) will alter the species composition, productivity and ecophysiology of Arctic phytoplankton, we conducted two incubation experiments with natural plankton assemblages from Davis Strait (63°N) and Baffin Bay (71°N) during the Arctic-GEOTRACES summer 2015 campaign. Phytoplankton assemblages were exposed to 400 and 1200 µatm pCO2 at both 15% and 35% surface irradiance over two weeks. These incubations were monitored and characterised in terms of phytoplankton growth, nutrient usage, biomass stoichiometry, net primary production (NPP), photophysiology and species composition. Preliminary results indicate that the Subarctic Davis Strait assemblage exhibited light- and CO2-dependent growth rates and NPP, while there were no such differences between treatments in the Arctic Baffin Bay assemblage. The suite of physiological measurements conducted in this study will be exploited to provide a mechanistic understanding of the observed differences between phytoplankton assemblages. Results from our work will provide insight into the resilience of Arctic primary producers to climate-dependent environmental change.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2016-08-31
    Description: The Arctic Ocean is one of the regions most prone to on-going ocean acidification (OA) and climate-driven changes, including increased sea surface temperature, sea-ice melt and altered mixing regimes. However, the influence of these changes on Arctic primary productivity, phytoplankton ecology and elemental cycles remains poorly understood. To date, the impact of various environmental stressors on phytoplankton have largely been assessed in isolation, and only limited process-understanding was gained. In order to understand how OA and enhanced irradiances (resulting from sea-ice retreat and increased mixed layer stratification) will alter the species composition, productivity and ecophysiology of Arctic phytoplankton, we conducted two incubation experiments with natural plankton assemblages from Davis Strait (63°N) and Baffin Bay (71°N) during the Arctic-GEOTRACES summer 2015 campaign. Phytoplankton assemblages were exposed to 400 and 1200 µatm pCO2 at both 15% and 35% surface irradiance over two weeks. These incubations were monitored and characterised in terms of phytoplankton growth, nutrient usage, biomass stoichiometry, net primary production (NPP), photophysiology and species composition. Preliminary results indicate that the Subarctic Davis Strait assemblage exhibited light- and CO2-dependent growth rates and NPP, while there were no such differences between treatments in the Arctic Baffin Bay assemblage. The suite of measurements conducted in this study will be exploited to provide a mechanistic understanding of the observed similarities and differences between phytoplankton assemblages. Our results indicate a high level of resilience of Arctic primary producers to climate-dependent environmental change.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    facet.materialart.
    Unknown
    AMER SOC LIMNOLOGY OCEANOGRAPHY
    In:  EPIC3Limnology and Oceanography, AMER SOC LIMNOLOGY OCEANOGRAPHY, 62(3), pp. 898-921, ISSN: 0024-3590
    Publication Date: 2017-06-14
    Description: We examined the light absorption properties and light-dependent rates of photosynthetic electron transport (ETRRCII) and 14C-uptake in phytoplankton of the Canadian Subarctic and Arctic Ocean. Our results reveal high variability in the light-saturated, chlorophyll a-specific rate of 14C-uptake (PChlamax; 0.7 to 8.0 mg C mg chl a−1 h−1) , and the light-dependant efficiency of 14C-uptake (αChla; 0.01 to 0.09 mg C mg Chl a−1 h−1 [μmol quanta m−2 s−1]−1). Variability in PChlamax correlated with light availability in the stratified water-column, while both PChlamax and αChla were correlated to the degree of nitrate depletion in the mixed layer. For all samples, we observed that 14C-uptake rates reached light saturation at lower irradiances than ETRRCII, leading to significant, light-dependent de-coupling of carbon fixation and photosynthetic electron transport. For samples taken from within the mixed layer, we found that the conversion factor from ETRRCII to carbon fixation was strongly correlated to the magnitude of non-photochemical quenching, as derived from fast repetition rate fluorometry (FRRF) measurements. This correlation supports recent findings from the Subarctic Pacific Ocean, and has the potential to improve FRRF-based estimates of phytoplankton carbon fixation. Our observations reveal distinct environmental regulation of phytoplankton light absorption, electron transport and carbon fixation in phytoplankton assemblages within and below the shallow summer mixed layer, and will help to inform more robust predictions of future primary production in a rapidly changing Arctic Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2022-06-26
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
  • 7
  • 8
    Publication Date: 2015-10-19
    Description: Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation at PSII (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific, over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5 fold changes in the conversion factor coupling ETRRCII and carbon fixation (Φe:C / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light, and correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and the conversion factor Φe:C / nPSII has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2009-11-23
    Description: The observed variation in the calcification responses of coccolithophores to changes in carbonate chemistry paints a highly incoherent picture, particularly for the most commonly cultured "species", Emiliania huxleyi. The disparity between magnitude and potentially even sign of the calcification change under simulated end-of-century ocean surface chemical changes (higher pCO2, lower pH and carbonate saturation), raises challenges to quantifying future carbon cycle impacts and feedbacks because it introduces significant uncertainty in parameterizations used for global models. Here we compile the results of coccolithophore carbonate chemistry manipulation experiments and review how ocean carbon cycle models have attempted to bridge the gap from experiments to global impacts. Although we can rule out methodological differences in how carbonate chemistry is altered as introducing an experimental bias, the absence of a consistent calcification response implies that model parameterizations based on small and differing subsets of experimental observations will lead to varying estimates for the global carbon cycle impacts of ocean acidification. We highlight two pertinent observations that might help: (1) the degree of coccolith calcification varies substantially, both between species and within species across different genotypes, and (2) the calcification response across mesocosm and shipboard incubations has so-far been found to be relatively consistent. By analogy to descriptions of plankton growth rate vs. temperature, such as the "Eppley curve", which seek to encapsulate the net community response via progressive assemblage change rather than the response of any single species, we posit that progressive future ocean acidification may drive a transition in dominance from more to less heavily calcified coccolithophores. Assemblage shift may be more important to integrated community calcification response than species-specific response, highlighting the importance of whole community manipulation experiments to models in the absence of a complete physiological understanding of the underlying calcification process. However, on a century time-scale, regardless of the parameterization adopted, the atmospheric pCO2 impact of ocean acidification is minor compared to other global carbon cycle feedbacks.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2009-04-01
    Description: The variation in pH-dependent calcification responses of coccolithophores paint a highly incoherent picture, particularly for the most commonly cultured "species", Emiliania huxleyi. The disparity between magnitude and even sign of the calcification change at higher CO2 (lower pH), raises challenges to quantifying future carbon cycle changes and feedbacks, by introducing significant uncertainty in parameterizations used for global models. Putting aside the possibility of methodological differences that introduce an experimental bias, we highlight two pertinent observations that can help resolve conflicting interpretations: (1) a calcification "optimum" in environmental conditions (pH) has been observed in other coccolithophore species, and (2) there exists an unambiguous direction to the CO2-calcification response across mesocosm and shipboard incubations. We propose that an equivalence can be drawn between integrated ecosystem calcification as a function of pH (or other carbonate system parameter such as calcite saturation state) and a widely used description of plankton growth rate vs. temperature – the "Eppley curve". This provides a conceptual framework for reconciling available experimental manipulations as well as a quasi-empirical relationship for ocean acidification impacts on carbonate production that can be incorporated into models. By analogy to the Eppley curve temperature vs. growth rate relationship, progressive ocean acidification in the future may drive a relatively smooth ecosystem response through transition in dominance from more to less heavily calcified coccolithophores in addition to species-specific calcification changes. However, regardless of the model parameterization employed, on a century time-scale, the CO2-calcification effect is a minor control of atmospheric CO2 compared to other C cycle feedbacks or to fossil fuel emissions.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...