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Martha Gledhill - One of the best experts on this subject based on the ideXlab platform.

  • <B>HemeB> B distriButions through the Atlantic Ocean: evidence for "anemic" phytoplankton populations.
    Scientific Reports, 2020
    Co-Authors: Evangelia Louropoulou, Martha Gledhill, Eric P. Achterberg, Thomas J. Browning, David J. Honey, Ruth A. Schmitz, Alessandro Tagliabue
    Abstract:

    <B>HemeB> B is an iron-containing cofactor in hemoproteins that participates in the fundamental processes of photosynthesis and respiration in phytoplankton. <B>HemeB> B concentrations typically decline in waters with low iron concentrations But due to lack of field data, the distriBution of <B>HemeB> B in particulate material in the ocean is poorly constrained. Here we report particulate <B>HemeB> B distriButions across the Atlantic Ocean (59.9°N to 34.6°S). <B>HemeB> B concentrations in surface waters ranged from 0.10 to 33.7 pmol L-1 (median = 1.47 pmol L-1, n = 974) and were highest in regions with a high Biomass. The ratio of <B>HemeB> B to particulate organic carBon (POC) exhiBited a mean value of 0.44 μmol <B>HemeB> B mol-1 POC. We identified the ratio of 0.10 µmol <B>HemeB> B mol-1 POC as the cut-off Between <B>HemeB> B replete and <B>HemeB> B deficient (anemic) phytoplankton. By this definition, we oBserved anemic phytoplankton populations in the SuBtropical South Atlantic and Irminger Basin. Comparison of oBserved and modelled <B>HemeB> B suggested that <B>HemeB> B could account for Between 0.17-9.1% of Biogenic iron. Our large scale oBservations of <B>HemeB> B relative to organic matter provide further evidence of the impact of changes in iron supply on phytoplankton iron status across the Atlantic Ocean.

  • Regulation of the Phytoplankton <B>HemeB> B Iron Pool During the North Atlantic Spring Bloom.
    Frontiers in microbiology, 2019
    Co-Authors: Evangelia Louropoulou, Martha Gledhill, Thomas J. Browning, Dhwani K. Desai, Jan-lukas Menzel Barraqueta, Manon Tonnard, Géraldine Sarthou, Hélène Planquette, Andrew R. Bowie, Ruth A. Schmitz
    Abstract:

    <B>HemeB> B is an iron-containing co-factor in hemoproteins. <B>HemeB> B concentrations are low (-1) in iron limited phytoplankton in cultures and in the field. Here, we determined <B>HemeB> B in marine particulate material (>0.7 μm) from the North Atlantic Ocean (GEOVIDE cruise – GEOTRACES section GA01), which spanned several Biogeochemical regimes. We examined the relationship Between <B>HemeB> B aBundance and the microBial community composition, and its utility for mapping iron limited phytoplankton. <B>HemeB> B concentrations ranged from 0.16 to 5.1 pmol L-1 (median = 2.0 pmol L-1, n = 62) in the surface mixed layer (SML) along the cruise track, driven mainly By variaBility in Biomass. However, in the Irminger Basin, the lowest <B>HemeB> B levels (SML: median = 0.53 pmol L-1, n = 12) were oBserved, whilst the Biomass was highest (particulate organic carBon, median = 14.2 μmol L-1, n = 25; chlorophyll a: median = 2.0 nmol L-1, n = 23) pointing to regulatory mechanisms of the <B>HemeB> B pool for growth conservation. Dissolved iron (DFe) was not depleted (SML: median = 0.38 nmol L-1, n = 11) in the Irminger Basin, But large diatoms (Rhizosolenia sp.) dominated. Hence, <B>HemeB> B depletion and regulation is likely to occur during Bloom progression when phytoplankton class-dependent aBsolute iron requirements exceed the availaBle amBient concentration of DFe. Furthermore, high <B>HemeB> B concentrations found in the Iceland Basin and LaBrador Sea (median = 3.4 pmol L-1, n = 20), despite having similar DFe concentrations to the Irminger Basin, were attriButed to an earlier growth phase of the extant phytoplankton populations. Thus, <B>HemeB> B provides a snapshot of the cellular activity in situ and could Both Be used as indicator of iron limitation and contriBute to understanding phytoplankton adaptation mechanisms to changing iron supplies.

  • ABundance of the iron containing Biomolecule, <B>HemeB> B, during the progression of a spring phytoplankton Bloom in a mesocosm experiment.
    PloS one, 2017
    Co-Authors: Jessica Bellworthy, Martha Gledhill, Mario Esposito, Eric P. Achterberg
    Abstract:

    Concentrations of <B>HemeB> B were determined in a mesocosm experiment situated in Gullmar Fjord off Sweden. The mesocosm experiment lasted for ca. one hundred days and was characterised By the growth of a primary nutrient replete and a secondary nutrient deplete phytoplankton Bloom. <B>HemeB> B varied Between 40 ± 10 pmol L-1 in the preBloom period up to a maximum of 700 ± 400 pmol L-1 just prior to the time of the primary chlorophyll a maximum. Thereafter, <B>HemeB> B concentrations decreased again to an average of 120 ± 60 pmol L-1. When normalised to total particulate carBon, <B>HemeB> B was most aBundant during the initiation of the nutrient replete spring Bloom, when ratios reached 52 ± 24 μmol mol-1; ten times higher than values oBserved Both pre and post the primary Bloom. Concentrations of <B>HemeB> B correlated with those of chlorophyll a. Nevertheless, differences were oBserved in the relative concentrations of the two parameters, with <B>HemeB> B concentrations increasing relative to chlorophyll a during the growth of the primary Bloom, decreasing over the period of the secondary Bloom and increasing again through the latter period of the experiment. <B>HemeB> B aBundance was therefore influenced By nutrient concentrations and also likely By changing community composition. In half of the mesocosms, pCO2 was elevated and maintained at ca.1000 μatm, however we oBserved no significant differences Between <B>HemeB> B in plus or amBient pCO2 mesocosms, either in aBsolute terms, or relative to total particulate carBon and chlorophyll a. The results oBtained in this study contriBute to our understanding of the distriBution of this significant component of the Biogenic iron pool, and provide an iron replete coastal water end memBer that aids the interpretation of the distriButions of <B>HemeB> B in more iron deplete open ocean waters.

  • <B>HemeB> B quotas are low in southern ocean phytoplankton
    Marine Ecology Progress Series, 2015
    Co-Authors: Martha Gledhill, Loes J A Gerringa, P Laan, Klaas R Timmermans
    Abstract:

    <B>HemeB> is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of <B>HemeB> B in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate <B>HemeB> B (pmol l-1) oBserved at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (<6 µm in diameter) had <B>HemeB> B quotas <1 µmol mol-1 carBon, the lowest yet reported for marine phytoplankton. <B>HemeB> B was also depleted in these species with respect to chlorophyll a. We calculated the amount of carBon accumulated per mole of <B>HemeB> B per second in our cultures (<B>HemeB> growth efficiency, HGE) and found that small Southern Ocean species can maintain growth rates, even while <B>HemeB> B content is reduced. Small Southern Ocean phytoplankton can thus produce more particulate carBon than larger Southern Ocean or small coastal species at equivalent iron concentrations. ComBining primary productivity and <B>HemeB> B concentrations reported for the open ocean, we found that HGE in natural populations was within the range of our laBoratory culture results. HGE was also oBserved to Be higher at open ocean stations characterized By low iron concentrations. Our results suggest that low <B>HemeB> B quotas do not necessarily result in reduced growth and that marine phytoplankton can optimize iron use By manipulating the intracellular hemoprotein pool.

  • <B>HemeB> B quotas are low in Southern Ocean phytoplankton
    Marine Ecology Progress Series, 2015
    Co-Authors: Martha Gledhill, Loes J A Gerringa, P Laan, Klaas R Timmermans
    Abstract:

    <B>HemeB> is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of <B>HemeB> B in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate <B>HemeB> B (pmol l-1) oBserved at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (

Klaas R Timmermans - One of the best experts on this subject based on the ideXlab platform.

  • <B>HemeB> B quotas are low in southern ocean phytoplankton
    Marine Ecology Progress Series, 2015
    Co-Authors: Martha Gledhill, Loes J A Gerringa, P Laan, Klaas R Timmermans
    Abstract:

    <B>HemeB> is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of <B>HemeB> B in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate <B>HemeB> B (pmol l-1) oBserved at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (<6 µm in diameter) had <B>HemeB> B quotas <1 µmol mol-1 carBon, the lowest yet reported for marine phytoplankton. <B>HemeB> B was also depleted in these species with respect to chlorophyll a. We calculated the amount of carBon accumulated per mole of <B>HemeB> B per second in our cultures (<B>HemeB> growth efficiency, HGE) and found that small Southern Ocean species can maintain growth rates, even while <B>HemeB> B content is reduced. Small Southern Ocean phytoplankton can thus produce more particulate carBon than larger Southern Ocean or small coastal species at equivalent iron concentrations. ComBining primary productivity and <B>HemeB> B concentrations reported for the open ocean, we found that HGE in natural populations was within the range of our laBoratory culture results. HGE was also oBserved to Be higher at open ocean stations characterized By low iron concentrations. Our results suggest that low <B>HemeB> B quotas do not necessarily result in reduced growth and that marine phytoplankton can optimize iron use By manipulating the intracellular hemoprotein pool.

  • <B>HemeB> B quotas are low in Southern Ocean phytoplankton
    Marine Ecology Progress Series, 2015
    Co-Authors: Martha Gledhill, Loes J A Gerringa, P Laan, Klaas R Timmermans
    Abstract:

    <B>HemeB> is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of <B>HemeB> B in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate <B>HemeB> B (pmol l-1) oBserved at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (

Joel H. Weiner - One of the best experts on this subject based on the ideXlab platform.

  • Out of Plane Distortions of the <B>HemeB> B of Escherichia coli Succinate Dehydrogenase
    PloS one, 2012
    Co-Authors: Quang M. Tran, Richard A. Rothery, Carmen Fong, Elena Maklashina, Gary Cecchini, Joel H. Weiner
    Abstract:

    The role of the <B>HemeB> B in Escherichia coli succinate dehydrogenase is highly amBiguous and its role in catalysis is questionaBle. To examine whether <B>HemeB> reduction is an essential step of the catalytic mechanism, we generated a series of site-directed mutations around the <B>HemeB> Binding pocket, creating a liBrary of variants with a stepwise decrease in the midpoint potential of the <B>HemeB> from the wild-type value of +20 mV down to 280 mV. This difference in midpoint potential is enough to alter the reactivity of the <B>HemeB> towards succinate and thus its redox state under turnover conditions. Our results show Both the steady state succinate oxidase and fumarate reductase catalytic activity of the enzyme are not a function of the redox potential of the <B>HemeB>. As well, lower <B>HemeB> potential did not cause an increase in the rate of superoxide production Both in vitro and in vivo. The electron paramagnetic resonance (EPR) spectrum of the <B>HemeB> in the wild-type enzyme is a comBination of two distinct signals. We link EPR spectra to structure, showing that one of the signals likely arises from an out-of-plane distortion of the <B>HemeB>, a saddled conformation, while the second signal originates from a more planar orientation of the porphyrin ring.

  • escherichia coli succinate dehydrogenase variant lacking the <B>HemeB> B
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Quang M. Tran, Richard A. Rothery, Elena Maklashina, Gary Cecchini, Joel H. Weiner
    Abstract:

    The Escherichia coli enzyme succinate:uBiquinone oxidoreductase [(succinate dehydrogenase (SdhCDAB)] couples succinate oxidation to uBiquinone reduction and is structurally and functionally equivalent to mitochondrial complex II, an essential component of the aeroBic respiratory chain and tricarBoxylic acid cycle. All such enzymes contain a <B>HemeB> within their memBrane anchor domain with a highly contentious, But as-yet-undetermined, function. Here, we report the generation of a complex II that lacks <B>HemeB>, which is confirmed By Both optical and EPR spectroscopy. Despite the aBsence of <B>HemeB>, this mutant still assemBles properly and retains physiological activity. However, the mutants lacking <B>HemeB> are highly sensitive to the presence of detergent. In addition, the <B>HemeB> does not appear to Be involved in reactive oxygen species suppression. Our results indicate that redox cycling of the <B>HemeB> in complex II is not essential for the enzyme's uBiquinol reductase activity.

  • the quinone Binding site in escherichia coli succinate dehydrogenase is required for electron transfer to the <B>HemeB> B
    Journal of Biological Chemistry, 2006
    Co-Authors: Quang M. Tran, Richard A. Rothery, Elena Maklashina, Gary Cecchini, Joel H. Weiner
    Abstract:

    We have examined the role of the quinone-Binding (Q(P)) site of Escherichia coli succinate:uBiquinone oxidoreductase (succinate dehydrogenase) in <B>HemeB> reduction and reoxidation during enzyme turnover. The SdhCDAB electron transfer pathway leads from a cytosolically localized flavin adenine dinucleotide cofactor to a Q(P) site located within the memBrane-intrinsic domain of the enzyme. The Q(P) site is sandwiched Between the [3Fe-4S] cluster of the SdhB suBunit and the <B>HemeB> B(556) that is coordinated By His residues from the SdhC and SdhD suBunits. The intercenter distances Between the cluster, <B>HemeB>, and Q(P) site are all within the theoretical 14 A limit proposed for kinetically competent intercenter electron transfer. Using EPR spectroscopy, we have demonstrated that the Q(P) site of SdhCDAB staBilized a uBisemiquinone radical intermediate during enzyme turnover. Potentiometric titrations indicate that this species has an E(m,8) of approximately 60 mV and a staBility constant (K(STAB)) of approximately 1.0. Mutants of the following conserved Q(P) site residues, SdhC-S27, SdhC-R31, and SdhD-D82, have severe consequences on enzyme function. Mutation of the conserved SdhD-Y83 suggested to hydrogen Bond to the uBiquinone cofactor had a less severe But still significant effect on function. In addition to loss of overall catalysis, these mutants also affect the rate of succinate-dependent <B>HemeB> reduction, indicating that the Q(P) site is an essential stepping stone on the electron transfer pathway from the [3Fe-4S] cluster to the <B>HemeB>. Furthermore, the mutations result in the elimination of EPR-visiBle uBisemiquinone during potentiometric titrations. Overall, these results demonstrate the importance of a functional, semiquinone-staBilizing Q(P) site for the oBservation of rapid succinate-dependent <B>HemeB> reduction.

  • INHIBITOR BINDING WITHIN THE NARI SUBUNIT (CYTOCHROME BNR) OF ESCHERICHIA COLI NITRATE REDUCTASE A
    The Journal of biological chemistry, 1998
    Co-Authors: Axel Magalon, Danielle Lemesle-meunier, Richard A. Rothery, Chantal Frixon, Joel H. Weiner, Francis Blasco
    Abstract:

    ABstract We have used inhiBitors and site-directed mutants to investigate quinol Binding to the cytochromeB nr (NarI) of Escherichia colinitrate reductase (NarGHI). Both stigmatellin and 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) inhiBit menadiol:nitrate oxidoreductase activity withI 50 values of 0.25 and 6 μm, respectively, and prevent the generation of a NarGHI-dependent proton electrochemical potential across the cytoplasmic memBrane. These inhiBitors have little effect on the rate of reduction of the two <B>HemeB>s of NarI (B Land B H), But have an inhiBitory effect on the extent of nitrate-dependent <B>HemeB> reoxidation. No quinol-dependent <B>HemeB> B H reduction is detected in a mutant lacking <B>HemeB> B L(NarI-H66Y), whereas a slow But complete <B>HemeB>B L reduction is detected in a mutant lacking <B>HemeB> B H (NarI-H56R). This is consistent with physiological quinol Binding and oxidation occurring at a site (QP) associated with <B>HemeB> B L which is located toward the periplasmic side of NarI. Optical and EPR spectroscopies performed in the presence of stigmatellin or HOQNO provide further evidence that these inhiBitors Bind at a <B>HemeB>B L-associated QP site. These results suggest a model for electron transfer through NarGHI that involves quinol Binding and oxidation in the vicinity of <B>HemeB>B L and electron transfer through <B>HemeB>B H to the cytoplasmically localized memBrane-extrinsic catalytic NarGH dimer.

Eric P. Achterberg - One of the best experts on this subject based on the ideXlab platform.

  • <B>HemeB> B distriButions through the Atlantic Ocean: evidence for "anemic" phytoplankton populations.
    Scientific Reports, 2020
    Co-Authors: Evangelia Louropoulou, Martha Gledhill, Eric P. Achterberg, Thomas J. Browning, David J. Honey, Ruth A. Schmitz, Alessandro Tagliabue
    Abstract:

    <B>HemeB> B is an iron-containing cofactor in hemoproteins that participates in the fundamental processes of photosynthesis and respiration in phytoplankton. <B>HemeB> B concentrations typically decline in waters with low iron concentrations But due to lack of field data, the distriBution of <B>HemeB> B in particulate material in the ocean is poorly constrained. Here we report particulate <B>HemeB> B distriButions across the Atlantic Ocean (59.9°N to 34.6°S). <B>HemeB> B concentrations in surface waters ranged from 0.10 to 33.7 pmol L-1 (median = 1.47 pmol L-1, n = 974) and were highest in regions with a high Biomass. The ratio of <B>HemeB> B to particulate organic carBon (POC) exhiBited a mean value of 0.44 μmol <B>HemeB> B mol-1 POC. We identified the ratio of 0.10 µmol <B>HemeB> B mol-1 POC as the cut-off Between <B>HemeB> B replete and <B>HemeB> B deficient (anemic) phytoplankton. By this definition, we oBserved anemic phytoplankton populations in the SuBtropical South Atlantic and Irminger Basin. Comparison of oBserved and modelled <B>HemeB> B suggested that <B>HemeB> B could account for Between 0.17-9.1% of Biogenic iron. Our large scale oBservations of <B>HemeB> B relative to organic matter provide further evidence of the impact of changes in iron supply on phytoplankton iron status across the Atlantic Ocean.

  • ABundance of the iron containing Biomolecule, <B>HemeB> B, during the progression of a spring phytoplankton Bloom in a mesocosm experiment.
    PloS one, 2017
    Co-Authors: Jessica Bellworthy, Martha Gledhill, Mario Esposito, Eric P. Achterberg
    Abstract:

    Concentrations of <B>HemeB> B were determined in a mesocosm experiment situated in Gullmar Fjord off Sweden. The mesocosm experiment lasted for ca. one hundred days and was characterised By the growth of a primary nutrient replete and a secondary nutrient deplete phytoplankton Bloom. <B>HemeB> B varied Between 40 ± 10 pmol L-1 in the preBloom period up to a maximum of 700 ± 400 pmol L-1 just prior to the time of the primary chlorophyll a maximum. Thereafter, <B>HemeB> B concentrations decreased again to an average of 120 ± 60 pmol L-1. When normalised to total particulate carBon, <B>HemeB> B was most aBundant during the initiation of the nutrient replete spring Bloom, when ratios reached 52 ± 24 μmol mol-1; ten times higher than values oBserved Both pre and post the primary Bloom. Concentrations of <B>HemeB> B correlated with those of chlorophyll a. Nevertheless, differences were oBserved in the relative concentrations of the two parameters, with <B>HemeB> B concentrations increasing relative to chlorophyll a during the growth of the primary Bloom, decreasing over the period of the secondary Bloom and increasing again through the latter period of the experiment. <B>HemeB> B aBundance was therefore influenced By nutrient concentrations and also likely By changing community composition. In half of the mesocosms, pCO2 was elevated and maintained at ca.1000 μatm, however we oBserved no significant differences Between <B>HemeB> B in plus or amBient pCO2 mesocosms, either in aBsolute terms, or relative to total particulate carBon and chlorophyll a. The results oBtained in this study contriBute to our understanding of the distriBution of this significant component of the Biogenic iron pool, and provide an iron replete coastal water end memBer that aids the interpretation of the distriButions of <B>HemeB> B in more iron deplete open ocean waters.

  • distriButions of particulate <B>HemeB> B in the atlantic and southern oceans implications for electron transport in phytoplankton
    Global Biogeochemical Cycles, 2013
    Co-Authors: Martha Gledhill, Eric P. Achterberg, David J. Honey, Maria C. Nielsdóttir, Micha J. A. Rijkenberg
    Abstract:

    Concentrations of <B>HemeB> B, the iron-containing component of B-type hemoproteins, ranged from? 500). High chl a:<B>HemeB> B ratios resulted from relative decreases in <B>HemeB> B, suggesting proteins such as cytochrome B6f, the core complex of photosystem II, and eukaryotic nitrate reductase were depleted relative to proteins containing chlorophyll such as the eukaryotic light-harvesting antenna. Relative variations in <B>HemeB> B, particulate organic carBon, and chl a can thus Be indicative of a physiological response of the phytoplankton community to the prevailing growth conditions, within the context of large-scale changes in phytoplankton community composition.

  • DistriButions of particulate <B>HemeB> B in the Atlantic and Southern Oceans—Implications for electron transport in phytoplankton
    Global Biogeochemical Cycles, 2013
    Co-Authors: Martha Gledhill, Eric P. Achterberg, David J. Honey, Maria C. Nielsdóttir, Micha J. A. Rijkenberg
    Abstract:

    Concentrations of <B>HemeB> B, the iron-containing component of B-type hemoproteins, ranged from? 500). High chl a:<B>HemeB> B ratios resulted from relative decreases in <B>HemeB> B, suggesting proteins such as cytochrome B6f, the core complex of photosystem II, and eukaryotic nitrate reductase were depleted relative to proteins containing chlorophyll such as the eukaryotic light-harvesting antenna. Relative variations in <B>HemeB> B, particulate organic carBon, and chl a can thus Be indicative of a physiological response of the phytoplankton community to the prevailing growth conditions, within the context of large-scale changes in phytoplankton community composition.

  • <B>HemeB> B in marine phytoplankton and particulate material from the North Atlantic Ocean
    Marine Ecology Progress Series, 2013
    Co-Authors: David J. Honey, Martha Gledhill, Thomas S. Bibby, François-eric Legiret, Nicola J. Pratt, Anna E. Hickman, Tracy Lawson, Eric P. Achterberg
    Abstract:

    Concentrations of <B>HemeB> B, the ironcontaining prosthetic group of many hemoproteins, were measured in 6 species of marine phytoplankton (Dunaliella tertiolecta, Emiliania huxleyi, Thalassio - sira weissflogii, T. oceanica, Phaeodactylum tricor - nutum and Synechococcus sp. WH7803) that were suBjected to variations in iron concentration. Changes in <B>HemeB> B in response to reduced light and nitrate were also ex amined for E. huxleyi and T. oceanica. Results from laBoratory cultures were compared with <B>HemeB> B determined in particulate material in the North Atlantic. In cultures, <B>HemeB> B made up 18 ± 14% (SE) of the total iron pool. Reduced iron and nitrate concentrations resulted in a decreased intracellular <B>HemeB> B concentration, expressed as per mole carBon. Chlorophyll a (chl a) to <B>HemeB> B ratios in E. huxleyi and D. tertiolecta in creased in response to limited light and nutrient availaBility, But slightly decreased or did not change in the diatoms and the cyanophyte Synechococcus sp. WH7803. The <B>HemeB> B:particulate organic carBon (POC) and chl a:<B>HemeB> B ratios in the North Atlantic were within the range oBserved in phytoplankton cultures. In the surface mixed layer, decreases in <B>HemeB> B:POC ratios were linked to decreases in nutrient concentrations. Chl a:<B>HemeB> B ratios increased with depth and were thus primarily affected By light availaBility. Relative relationships Between <B>HemeB> B, chl a and POC in the North Atlantic likely represented a change in the aBility of cells to undertake cellular processes driven By chl a (light harvesting) and <B>HemeB> B (e.g. electron transport) according to amBient light and nutrient conditions.

Micha J. A. Rijkenberg - One of the best experts on this subject based on the ideXlab platform.