scholarly journals Diel quenching of Southern Ocean phytoplankton fluorescence is related to iron limitation

2019 ◽  
Author(s):  
Christina Schallenberg ◽  
Robert F. Strzepek ◽  
Nina Schuback ◽  
Lesley A. Clementson ◽  
Philip W. Boyd ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Chlorophyll A ◽  
Photosynthetic Efficiency ◽  
Physiological State ◽  
Water Masses ◽  
Photochemical Quenching ◽  
Physiological Status ◽  
Phytoplankton Productivity ◽  
Significant Difference ◽  
Fe Addition

Abstract. Evaluation of photosynthetic competency in time and space is critical for better estimates and models of oceanic primary productivity. This is especially true for areas where the lack of iron limits phytoplankton productivity, such as the Southern Ocean. Assessment of photosynthetic competency on large scales remains challenging, but phytoplankton chlorophyll-a fluorescence (ChlF) is a signal that holds promise in this respect as it is affected by, and consequently provides information about, the photosynthetic efficiency of the organism. A second process affecting the ChlF signal is heat dissipation of absorbed light energy, referred to as non-photochemical quenching (NPQ). NPQ is triggered when excess energy is absorbed; i.e., when more light is absorbed than can be used directly for photosynthetic carbon fixation. The effect of NPQ on the ChlF signal complicates its interpretation in terms of photosynthetic efficiency, and therefore most approaches relating ChlF parameters to photosynthetic efficiency seek to minimize the influence of NPQ by working under conditions of sub-saturating irradiance. Here, we propose that NPQ itself holds potential as an easily acquired optical signal indicative of phytoplankton physiological state with respect to iron (Fe) limitation. We present data from a research voyage to the Subantarctic Zone south of Australia. Incubation experiments confirmed that resident phytoplankton were Fe-limited, as the maximum quantum yield of primary photochemistry, Fv/Fm, measured with a Fast Repetition Rate fluorometer (FRRf), increased significantly with Fe addition. The NPQ capacity of the phytoplankton also showed sensitivity to Fe addition, decreasing with increased Fe availability, confirming previous work. The fortuitous presence of a remnant warm-core eddy in the vicinity of the study area allowed comparison of fluorescence behaviour between two distinct water masses, with the colder water showing significantly lower Fv/Fm than the warmer eddy waters, suggesting a difference in Fe limitation status between the two water masses. Again, NPQ capacity measured with the FRRf mirrored the behaviour observed in Fv/Fm, decreasing as Fv/Fm increased in the warmer water mass. We also analysed the diel quenching of underway fluorescence measured with a standard fluorometer, such as is frequently used to monitor ambient chlorophyll-a concentrations, and found a significant difference in behaviour between the two water masses. This difference was quantified by defining an NPQ parameter akin to the Stern-Volmer parameterization of NPQ, exploiting the fluorescence quenching induced by diel fluctuations in incident irradiance. We propose that monitoring of this novel NPQ parameter may enable assessment of phytoplankton physiological status (related to Fe availability) based on measurements made with standard fluorometers, as ubiquitously used on moorings, ships, floats and gliders.

scholarly journals Diel quenching of Southern Ocean phytoplankton fluorescence is related to iron limitation

2020 ◽  
Vol 17 (3) ◽  
pp. 793-812 ◽  
Author(s):  
Christina Schallenberg ◽  
Robert F. Strzepek ◽  
Nina Schuback ◽  
Lesley A. Clementson ◽  
Philip W. Boyd ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Chlorophyll A ◽  
Photosynthetic Efficiency ◽  
Physiological State ◽  
Water Masses ◽  
Photochemical Quenching ◽  
Physiological Status ◽  
Phytoplankton Productivity ◽  
Significant Difference ◽  
Fe Addition

Abstract. Evaluation of photosynthetic competency in time and space is critical for better estimates and models of oceanic primary productivity. This is especially true for areas where the lack of iron (Fe) limits phytoplankton productivity, such as the Southern Ocean. Assessment of photosynthetic competency on large scales remains challenging, but phytoplankton chlorophyll a fluorescence (ChlF) is a signal that holds promise in this respect as it is affected by, and consequently provides information about, the photosynthetic efficiency of the organism. A second process affecting the ChlF signal is heat dissipation of absorbed light energy, referred to as non-photochemical quenching (NPQ). NPQ is triggered when excess energy is absorbed, i.e. when more light is absorbed than can be used directly for photosynthetic carbon fixation. The effect of NPQ on the ChlF signal complicates its interpretation in terms of photosynthetic efficiency, and therefore most approaches relating ChlF parameters to photosynthetic efficiency seek to minimize the influence of NPQ by working under conditions of sub-saturating irradiance. Here, we propose that NPQ itself holds potential as an easily acquired optical signal indicative of phytoplankton physiological state with respect to Fe limitation. We present data from a research voyage to the Subantarctic Zone south of Australia. Incubation experiments confirmed that resident phytoplankton were Fe-limited, as the maximum quantum yield of primary photochemistry, Fv∕Fm, measured with a fast repetition rate fluorometer (FRRf), increased significantly with Fe addition. The NPQ “capacity” of the phytoplankton also showed sensitivity to Fe addition, decreasing with increased Fe availability, confirming previous work. The fortuitous presence of a remnant warm-core eddy in the vicinity of the study area allowed comparison of fluorescence behaviour between two distinct water masses, with the colder water showing significantly lower Fv∕Fm than the warmer eddy waters, suggesting a difference in Fe limitation status between the two water masses. Again, NPQ capacity measured with the FRRf mirrored the behaviour observed in Fv∕Fm, decreasing as Fv∕Fm increased in the warmer water mass. We also analysed the diel quenching of underway fluorescence measured with a standard fluorometer, such as is frequently used to monitor ambient chlorophyll a concentrations, and found a significant difference in behaviour between the two water masses. This difference was quantified by defining an NPQ parameter akin to the Stern–Volmer parameterization of NPQ, exploiting the fluorescence quenching induced by diel fluctuations in incident irradiance. We propose that monitoring of this novel NPQ parameter may enable assessment of phytoplankton physiological status (related to Fe availability) based on measurements made with standard fluorometers, as ubiquitously used on moorings, ships, floats and gliders.

ABOUT SOME PECULIARITIES OF THE PHYSIOLOGICAL HETEROGENEITY OF THE POPULATION OF SCENEDESMUS QUADRICAUDA (TURP.) BREB. IN THE PRESENCE OF LOW CONCENTRATIONS OF METALS

2018 ◽  
pp. 34-43
Author(s):  
V. I. Ipatova ◽  
A. G. Dmitrieva ◽  
О. F. Filenko ◽  
T. V. Drozdenko
Keyword(s):  
Cell Division ◽  
Toxic Effect ◽  
Copper Chloride ◽  
Single Cells ◽  
Physiological State ◽  
Scenedesmus Quadricauda ◽  
Physiological Status ◽  
Lag Phase ◽  
Protective Mechanism ◽  
Low Concentrations

The structure of the laboratory population of green microalgae Scenedesmus quadricauda (Turp.) Breb (=Desmodesmus communis E. Hegew.) was studied at different stages of its growth (lag-phase, log-phase and stationary phase) at low concentrations of copper chloride and silver nitrate by the method microculture, allowing to monitor the state and development of single cells having different physiological status. The response of the culture of S. quadricauda - the change in the number of cells and the fractional composition (the fraction of dividing, «dormant» and dying cells) depended not only on the concentration of the toxicant in the medium, but also on the physiological state of the culture: the level of synchronization and the growth phase. Silver ions at low concentrations had a more pronounced toxic effect on the culture than copper ions at different phases of its development, especially at a concentration of 0.001 mg/l (10-9 M). The main mechanism of the toxic effect of metals is to inhibit the process of cell division. At low concentrations of toxicants, especially at a concentration of 0.001 mg/l, a «paradoxical» effect expressed in the predominance of the fraction of «dormant» cells was revealed. The temporary inhibition of the process of cell division can be regarded as a protective mechanism that allows preserving the integrity of the population and its ability to survive in a changing environment. The obtained data explain the effect of action of low concentrations of substances due to their inclusion in the cell, the subsequent accumulation in the cell and their low excretion.

Efficacy of prayer in inducing immediate physiological changes: a systematic analysis of objective experiments

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Felix Chin ◽  
Ryan Chou ◽  
Muhammad Waqas ◽  
Kunal Vakharia ◽  
Hamid Rai ◽  
...  
Keyword(s):  
Physiological State ◽  
Experimental Studies ◽  
Peripheral Resistance ◽  
Pain Tolerance ◽  
Physiological Status ◽  
Physiological Changes ◽  
Mental Functioning ◽  
Baroreceptor Sensitivity ◽  
Systematic Analysis ◽  
Blood Marker

Abstract Objectives To assess the immediate impact of prayer on physiological state by systematically reviewing objective, controlled experimental studies in the literature. Content Experimental studies measuring objective physiological changes induced by prayer. Studies containing the keyword, “Prayer” anywhere in the title or abstract were curated from the following databases: Public/Publisher Medline (PubMed), Excerpta Medica Database (EMBASE) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) in May 2019. Titles and abstracts were screened with the remaining 30 articles analyzed for inclusion. Only experimental studies were included. Summary Eight experimental studies were identified of which five investigated neurocognitive changes and three investigated systemic physiological changes during prayer. The five studies focusing on neuroactivity used functional MRI (fMRI), electroencephalography or SPECT imaging to obtain measurements. The remaining three studies analyzed an array of systemic physiological metrics, including blood pressure, heart rate, respiratory rate, peripheral resistance, baroreceptor sensitivity and/or cardiovascular rhythm variability during prayer. All studies aside from one saw objective changes during prayer. Neurocognitive changes were mainly associated with improved mental functioning, control and pain tolerance. Prayer was found to slow down physiological functions in two of the three vital-based studies, with the third reporting no change in physiological status. None of the studies measured blood marker changes. Outlook Experimental studies show prayer to induce healthy neurocognitive and physiological changes. Additional studies exploring objective measures from prayer are encouraged to provide practitioners with a more nuanced, scientific perspective when it comes to prescribing prayer as a complementary and alternative medicine (CAM) therapy.

Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

2006 ◽  
Vol 63 (1-2) ◽  
pp. 20-34 ◽  
Author(s):  
N. Anilkumar ◽  
Alvarinho J. Luis ◽  
Y.K. Somayajulu ◽  
V. Ramesh Babu ◽  
M.K. Dash ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Heat Content ◽  
Austral Summer ◽  
Water Masses ◽  
Indian Sector

The role of tides on the carbonate chemistry of a coastal polynya in the south-eastern Weddell Sea

2021 ◽  
Author(s):  
Elise Droste ◽  
Melchor González Dávila ◽  
Juana Magdalena Santana Casiano ◽  
Mario Hoppema ◽  
Gerd Rohardt ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Weddell Sea ◽  
Water Masses ◽  
Total Alkalinity ◽  
The South ◽  
Carbonate Chemistry ◽  
Large Variability ◽  
South Eastern ◽  
Coastal Polynya ◽  
Eastern Weddell Sea

<p>Tides have a large impact on coastal polynyas around Antarctica. We investigate the effect of semi-diurnal tidal cycles on the seawater carbonate chemistry in a coastal polynya hugging the Ekström Ice Shelf in the south-eastern Weddell Sea. This region experiences some of the strongest tides in the Southern Ocean. We assess the implications for the contribution of coastal polynyas to the carbon dioxide (CO<sub>2</sub>) air-sea flux of the Weddell Sea.</p><p>Two site visits, in January 2015 and January 2019, are intercompared in terms of the dissolved inorganic carbon (DIC) concentration, total alkalinity, pH, and CO<sub>2</sub> partial pressure (pCO<sub>2</sub>). The tides induce large variability in the carbonate chemistry of the coastal polynya in the austral summer: DIC concentrations vary between 2174 and 2223 umol kg<sup>-1</sup>.</p><p>The tidal fluctuation in the DIC concentration can swing the polynya from a sink to a source of atmospheric CO<sub>2 </sub>on a semi-diurnal timescale. We attribute these changes to the mixing of different water masses. The amount of variability induced by tides depends on – and is associated with – large scale oceanographic and biogeochemical processes that affect the characteristics and presence of the water masses being mixed, such as the rate of sea ice melt.</p><p>Sampling strategies in Antarctic coastal polynyas should always take tidal influences into account. This would help to reduce biases in our understanding of how coastal polynyas contribute to the CO<sub>2</sub> uptake by the Southern Ocean.</p>

scholarly journals Influence of different water masses and biological activity on dimethylsulphide and dimethylsulphoniopropionate in the subantarctic zone of the Southern Ocean during ACE 1

1998 ◽  
Vol 103 (D13) ◽  
pp. 16691-16701 ◽  
Author(s):  
Graham B. Jones ◽  
Mark A. J. Curran ◽  
Hilton B. Swan ◽  
Richard M. Greene ◽  
F. Brian Griffiths ◽  
...  
Keyword(s):  
Biological Activity ◽  
Southern Ocean ◽  
Water Masses

The impact of nanoplastic on embryonic development of Antarctic krill in current and future acidified conditions of the Southern Ocean 

2021 ◽  
Author(s):  
Emily Rowlands ◽  
Tamara Galloway ◽  
Matthew Cole ◽  
Ceri Lewis ◽  
Victoria Peck ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Southern Ocean ◽  
Antarctic Krill ◽  
Multiple Stressors ◽  
Combined Treatment ◽  
Limb Bud ◽  
Atlantic Sector ◽  
Antarctic Species ◽  
Significant Difference ◽  
The Impact

<p>Antarctic krill (<em>Euphausia superba</em>), hereafter krill, are pivotal to the Antarctic marine ecosystem, forming the base of a highly productive system and contributing significantly to the biogeochemical cycle. The negative effects of anthropogenic climate stressors amplified in the Southern Ocean such as rapid warming and ocean acidification (OA) have been acknowledged for krill. Less explored is the impact of increasing plastic pollution, particularly in conditions that reflect the likely future Southern Ocean environment. We hypothesise that krill have heightened vulnerability to multi-stressor scenarios due to their physiological and behavioural traits coupled with rapid environmental changes of their Antarctic habitats. Here, we investigate the single and combined effects of nanoplastic (NP; spherical, aminated (NP-NH<sub>2</sub>), yellow-green, fluorescent polystyrene nanoparticles) and OA (pCO<sub>2</sub>-manipulated seawater, pH 7.7) on the embryonic development of krill eggs. Krill were collected in the Scotia Sea within the Atlantic sector of the Southern Ocean in austral summer 2019. Eggs from a single female were incubated in seawater at 0.5 °C for 6 days with three treatments: (i) with 0.16 μm NP, (ii) in acidified conditions, and (iii) with a combined treatment of NP (0.16μm) and acidification. All NP treatments were at a concentration of 2.5μg/ml. We found that exposure to the NP-OA multi-stress treatment negatively impacted the development of embryos, decreasing the probability of reaching the limb bud stage by 9% compared with the control, whilst no significant difference was observed for the singular NP or OA treatments. This preliminary study supports our hypothesis regarding the potential impacts of multiple stressors on vulnerable embryonic stages of this ecologically critical Antarctic species.</p>

Grain yield, dry matter remobilization and chlorophyll content in maize (Zea mays L.) as influenced by nitrogen and water deficit

2018 ◽  
Vol 44 (3) ◽  
pp. 359-356
Author(s):  
Mahta Haghjoo ◽  
Abdollah Bahrani
Keyword(s):  
Zea Mays ◽  
Grain Yield ◽  
Chlorophyll Content ◽  
Water Deficit ◽  
Chlorophyll A ◽  
Dry Matter ◽  
Zea Mays L ◽  
Nitrogen Application ◽  
Significant Difference ◽  
Biological Yield

Out of 20, 40, 60 and 80 per cent moisture depletion 20% showed significantly higher grain yields, biological yield, chlorophyll a, b than the others. However, the highest contribution of stem and leaf dry matter remobilization in grain yield were obtained in 80% moisture depletion and 300 kg N/ha and the lowest one was found in the 20% moisture depletion and 150 kg N/ha. Nitrogen application increased all traits, however there were no significant difference between 250 and 300 kg N/ha.

scholarly journals Effects of Different Shading Rates on the Photosynthesis and Corm Weight of Konjac Plant

2019 ◽  
Vol 47 (3) ◽  
Author(s):  
Yaoguo QIN ◽  
Zesheng YAN ◽  
Honghui GU ◽  
Zhengxiang WANG ◽  
Xiong JIANG ◽  
...  
Keyword(s):  
Photosynthetic Efficiency ◽  
Daily Variation ◽  
Photochemical Efficiency ◽  
High Yield ◽  
Photochemical Quenching ◽  
Digital Object Identifier ◽  
Chlorophyll Fluorescence Parameters ◽  
Relative Electron ◽  
Comprehensive Comparison ◽  
Non Photochemical Quenching

To study the effects of shading level on the photosynthesis and corm weight of konjac plant, the chlorophyll fluorescence parameters, daily variation of relative electron transport rate (rETR), net photosynthetic rate (Pn), and corm weight of konjac plants under different treatments were measured and comparatively analyzed through covered cultivation of biennial seed corms with shade nets at different shading rates (0%, 50%, 70%, and 90%). The results showed that with the increase in shading rate, the maximum photochemical efficiency, potential activity, and non-photochemical quenching of photosystem Ⅱ (PSⅡ) of konjac leaves constantly increased, whereas the actual photosynthetic efficiency, rETR, and photochemical quenching of PSⅡ initially increased and then decreased. This result indicated that moderate shading could enhance the photosynthetic efficiency of konjac leaves. The daily variation of rETR in konjac plants under unshaded treatment showed a bimodal curve, whereas that under shaded treatment displayed a unimodal curve. The rETR of plants with 50% treatment and 70% treatment was gradually higher than that under unshaded treatment around noon. The moderate shading could increase the Pn of konjac leaves. The stomatal conductance and transpiration rate of the leaves under shaded treatment were significantly higher than those of the leaves under unshaded treatment. Shading could promote the growth of plants and increase corm weight. The comprehensive comparison shows that the konjac plants had strong photosynthetic capacity and high yield when the shading rate was 50%-70% for the area.   ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

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