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Microsensor measurements of oxygen concentration profiles, and computer-simulated concentration profiles of oxygen, ammonium and nitrate oxygen in Trichodesmium colonies (2019)

Klawonn, Isabell ; Eichner, Meri ; Wilson, Samuel T ; [et al.]

PANGAEA

In: Supplement to: Klawonn, Isabell; Eichner, Meri J; Wilson, Samuel T; Moradi, Nasrollah; Thamdrup, Bo; Kümmel, Steffen; Gehre, Matthias; Khalili, Arzhang; Grossart, Hans-Peter; Karl, David Michael; Ploug, Helle (2020): Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies. The ISME Journal, 14(2), 399-412, https://doi.org/10.1038/s41396-019-0514-9

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Publication Date: 2023-01-13

Description: Trichodesmium is an important dinitrogen (N~2~)-fixing cyanobacterium in marine ecosystems. Recent nucleic acid analyses indicate that Trichodesmium colonies with their diverse epibionts support various nitrogen (N) transformations beyond N~2~-fixation. However, rates of these transformations and concentration gradients of N-compounds in Trichodesmium colonies remain largely unresolved. We combined isotope-tracer incubations, micro-profiling, and numeric modelling to explore carbon fixation, N-cycling processes, as well as oxygen, ammonium and nitrate concentration gradients in individual field-sampled Trichodesmium colonies. Colonies were net-autotrophic, with carbon and N~2~-fixation occurring mostly at day-time. Ten percent of the fixed N was released as ammonium after 12-hour incubations. Nitrification was not detectable but nitrate consumption was high when nitrate was added. The consumed nitrate was partly reduced to ammonium, while denitrification was insignificant. Thus, the potential N-transformation network was characterized by fixed N gain and recycling processes rather than denitrification. Oxygen concentrations within colonies were 60–200% air-saturation. Moreover, our modelling predicted steep concentration gradients, with up to 6-fold higher ammonium concentrations, and nitrate depletion in the colony centre compared to the ambient seawater. These gradients created a chemically heterogeneous microenvironment, presumably facilitating diverse microbial metabolisms in millimetre-sized Trichodesmium colonies.

Keywords: Computer-simulated concentration profiles; File format; File name; File size; Microsensor concentration profiles; Uniform resource locator/link to file

Type: Dataset

Format: text/tab-separated-values, 12 data points

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Seawater carbonate chemistry and cellular inorganic carbon fluxes in Trichodesmium (2015)

Eichner, Meri ; Thoms, Silke ; Kranz, Sven A ; [et al.]

PANGAEA

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Publication Date: 2024-03-15

Description: To predict effects of climate change on phytoplankton, it is crucial to understand how their mechanisms for carbon acquisition respond to environmental conditions. Aiming to shed light on the responses of extra- and intracellular inorganic C (Ci) fluxes, the cyanobacterium Trichodesmium erythraeum IMS101 was grown with different nitrogen sources (N2 vs NO3 –) and pCO2 levels (380 vs 1400 µatm). Cellular Ci fluxes were assessed by combining membrane inlet mass spectrometry (MIMS), 13C fractionation measurements, and modelling. Aside from a significant decrease in Ci affinity at elevated pCO2 and changes in CO2 efflux with different N sources, extracellular Ci fluxes estimated by MIMS were largely unaffected by the treatments. 13C fractionation during biomass production, however, increased with pCO2, irrespective of the N source. Strong discrepancies were observed in CO2 leakage estimates obtained by MIMS and a 13C-based approach, which further increased under elevated pCO2. These offsets could be explained by applying a model that comprises extracellular CO2 and HCO3– fluxes as well as internal Ci cycling around the carboxysome via the CO2 uptake facilitator NDH-14. Assuming unidirectional, kinetic fractionation between CO2 and HCO3– in the cytosol or enzymatic fractionation by NDH-14, both significantly improved the comparability of leakage estimates. Our results highlight the importance of internal Ci cycling for 13C composition as well as cellular energy budgets of Trichodesmium, which ought to be considered in process studies on climate change effects.

Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Bicarbonate ion; Bicarbonate uptake in chlorophyll, standard deviation; Bicarbonate uptake rate, per chlorophyll a; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon dioxide efflux, per chlorophyll a; Carbon dioxide efflux, per chlorophyll a, standard deviation; Carbon dioxide uptake, per chlorophyll, standard deviation; Carbon dioxide uptake rate, per chlorophyll a; Carbon fixation rate, per chlorophyll a; Carbon fixation rate, standard deviation; Carbon uptake rate, standard deviation; Cyanobacteria; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross carbon uptake rate, per chlorophyll a; Laboratory experiment; Laboratory strains; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; pH, standard deviation; Phytoplankton; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Ratio; Ratio, standard deviation; Salinity; Single species; Species; Temperature, water; Time point, descriptive; Treatment; Trichodesmium erythraeum; Type

Type: Dataset

Format: text/tab-separated-values, 580 data points

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Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium (2014)

Eichner, Meri ; Kranz, Sven A ; Rost, Björn

PANGAEA

In: Supplement to: Eichner, Meri; Kranz, Sven A; Rost, Björn (2014): Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium. Physiologia Plantarum, 152(2), 316-330, https://doi.org/10.1111/ppl.12172

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Publication Date: 2024-03-15

Description: To predict effects of climate change and possible feedbacks, it is crucial to understand the mechanisms behind CO2 responses of biogeochemically relevant phytoplankton species. Previous experiments on the abundant N2 fixers Trichodesmium demonstrated strong CO2 responses, which were attributed to an energy reallocation between its carbon (C) and nitrogen (N) acquisition. Pursuing this hypothesis, we manipulated the cellular energy budget by growing Trichodesmium erythraeum IMS101 under different CO2 partial pressure (pCO2) levels (180, 380, 980 and 1400?µatm) and N sources (N2 and NO3-). Subsequently, biomass production and the main energy-generating processes (photosynthesis and respiration) and energy-consuming processes (N2 fixation and C acquisition) were measured. While oxygen fluxes and chlorophyll fluorescence indicated that energy generation and its diurnal cycle was neither affected by pCO2 nor N source, cells differed in production rates and composition. Elevated pCO2 increased N2 fixation and organic C and N contents. The degree of stimulation was higher for nitrogenase activity than for cell contents, indicating a pCO2 effect on the transfer efficiency from N2 to biomass. pCO2-dependent changes in the diurnal cycle of N2 fixation correlated well with C affinities, confirming the interactions between N and C acquisition. Regarding effects of the N source, production rates were enhanced in NO3-grown cells, which we attribute to the higher N retention and lower ATP demand compared with N2 fixation. pCO2 effects on C affinity were less pronounced in NO3- users than N2 fixers. Our study illustrates the necessity to understand energy budgets and fluxes under different environmental conditions for explaining indirect effects of rising pCO2.

Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, half saturation concentration; Carbon, inorganic, dissolved, half saturation concentration, standard deviation; Carbon, inorganic, dissolved, standard deviation; Carbon, organic, particulate, standard deviation; Carbon, organic, particulate/Nitrogen, organic, particulate ratio; Carbon, organic, particulate/Nitrogen, organic, particulate ratio, standard deviation; Carbon, organic, particulate per chlorophyll a; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coulometric titration; Cyanobacteria; Effective absorbance cross-section of photosystem II; Effective absorbance cross-section of photosystem II, standard deviation; Figure; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Growth rate, standard deviation; Identification; Irradiance; Laboratory experiment; Laboratory strains; Light:Dark cycle; Macro-nutrients; Maximum photochemical quantum yield of photosystem II; Maximum photochemical quantum yield of photosystem II, standard deviation; Net oxygen evolution, per chlorophyll a; Net oxygen evolution, per chlorophyll a, standard deviation; Nitrogen, organic, particulate, standard deviation; Nitrogen, organic, particulate per chlorophyll a; Nitrogen fixation rate per chlorophyll a; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate organic carbon, production, standard deviation; Particulate organic carbon production, per chlorophyll a; Particulate organic nitrogen production, per chlorophyll a; Particulate organic nitrogen production, standard deviation; Pelagos; pH; pH, standard deviation; Phytoplankton; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Re-oxidation time of the Qa acceptor; Re-oxidation time of the Qa acceptor, standard deviation; Respiration; Salinity; Single species; Species; Temperature, water; Time in hours; Time point, descriptive; Treatment; Trichodesmium erythraeum

Type: Dataset

Format: text/tab-separated-values, 1523 data points

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Diversity of ocean acidification effects on marine N2 fixers (2014)

Eichner, Meri ; Rost, Björn ; Kranz, Sven A

PANGAEA

In: Supplement to: Eichner, Meri; Rost, Björn; Kranz, Sven A (2014): Diversity of ocean acidification effects on marine N2 fixers. Journal of Experimental Marine Biology and Ecology, 457, 199-207, https://doi.org/10.1016/j.jembe.2014.04.015

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Publication Date: 2024-03-15

Description: Considering the important role of N2 fixation for primary productivity and CO2 sequestration, it is crucial to assess the response of diazotrophs to ocean acidification. Previous studies on the genus Trichodesmium suggested a strong sensitivity towards ocean acidification. In view of the large functional diversity in N2 fixers, the objective of this study was to improve our knowledge of the CO2 responses of other diazotrophs. To this end, the single-celled Cyanothece sp. and two heterocystous species, Nodularia spumigena and the symbiotic Calothrix rhizosoleniae, were acclimated to two pCO2 levels (380 vs. 980 µatm). Growth rates, cellular composition (carbon, nitrogen and chlorophyll a) as well as carbon and N2 fixation rates (14C incorporation, acetylene reduction) were measured and compared to literature data on different N2 fixers. The three species investigated in this study responded differently to elevated pCO2, showing enhanced, decreased as well as unaltered growth and production rates. For instance, Cyanothece increased production rates with pCO2, which is in line with the general view that N2 fixers benefit from ocean acidification. Due to lowered growth and production of Nodularia, nitrogen input to the Baltic Sea might decrease in the future. In Calothrix, no significant changes in growth or production could be observed, even though N2 fixation was stimulated under elevated pCO2. Reviewing literature data confirmed a large variability in CO2 sensitivity across diazotrophs. The contrasting response patterns in our and previous studies were discussed with regard to the carbonate chemistry in the respective natural habitats, the mode of N2 fixation as well as differences in cellular energy limitation between the species. The group-specific CO2 sensitivities will impact differently on future biogeochemical cycles of open-ocean environments and systems like the Baltic Sea and should therefore be considered in models estimating climate feedback effects.

Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Calothrix rhizosoleniae; Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbon, organic, particulate/Nitrogen, organic, particulate ratio; Carbon, organic, particulate/Nitrogen, organic, particulate ratio, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon fixation rate, per chlorophyll a; Carbon fixation rate, per chlorophyll a, standard deviation; Chlorophyll a, standard deviation; Chlorophyll a per cell; Coulometric titration; Cyanobacteria; Cyanothece sp.; Ethene production, per chlorophyll a; Ethene production per cell; Ethene production standard deviation; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Growth rate, standard deviation; Irradiance; Laboratory experiment; Laboratory strains; Nodularia spumigena; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate organic carbon, per cell; Particulate organic carbon, production, standard deviation; Particulate organic carbon content per cell, standard deviation; Particulate organic carbon production, per chlorophyll a; Particulate organic nitrogen per cell; Particulate organic nitrogen per cell, standard deviation; Particulate organic nitrogen production, per chlorophyll a; Particulate organic nitrogen production, standard deviation; Pelagos; pH; pH, standard deviation; Phytoplankton; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Salinity; Single species; Species; Temperature, water; Treatment

Type: Dataset

Format: text/tab-separated-values, 241 data points

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Seawater carbonate chemistry and carbonate chemistry in the microenvironment within cyanobacterial aggregates (2021)

Eichner, Meri ; Wolf-Gladrow, Dieter A ; Ploug, Helle

PANGAEA

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Publication Date: 2024-03-15

Description: Photosynthesis and respiration cause distinct chemical microenvironments within cyanobacterial aggregates. Here, we used microsensors and a diffusion–reaction model to characterize gradients in carbonate chemistry and investigate how these are affected by ocean acidification in Baltic vs. Pacific aggregates (Nodularia and Dolichospermum vs. Trichodesmium). Microsensor measurements of O2 and pH were performed under in situ and expected future pCO2 levels on Nodularia and Dolichospermum aggregates collected in the Baltic Sea. Under in situ conditions, O2 and pH levels within the aggregates covered ranges of 80–175% air saturation and 7.7–9.4 in dark and light, respectively. Carbon uptake in the light was predicted to reduce HCO3− by 100–150 μmol/L and CO2 by 3–6 μmol/L in the aggregate center compared to outside, inducing strong CO2 depletion (down to 0.5 μmol/L CO2 remaining in the center) even when assuming that HCO3− covered 80–90% of carbon uptake. Under ocean acidification conditions, enhanced CO2 availability allowed for significantly lower activity of carbon concentrating mechanisms, including a reduction of the contribution of HCO3− to carbon uptake by up to a factor of 10. The magnification of proton gradients under elevated pCO2 that was predicted based on a lower buffer capacity was observed in measurements despite a concurrent decrease in photosynthetic activity. In summary, we provide a quantitative image of the inorganic carbon environment in cyanobacterial aggregates under present-day and expected future conditions, considering both the individual and combined effects of the chemical and biological processes that shape these environments.

Keywords: Acid-base regulation; Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Baltic Sea; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Colorimetric; Cyanobacteria; Dolichospermum sp.; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Heterotrophic prokaryotes; Hydrogen ion concentration; Hydrogen ion concentration, standard deviation; Identification; Laboratory experiment; Light mode; Nodularia spumigena; OA-ICC; Ocean Acidification International Coordination Centre; Oxygen; Oxygen, standard deviation; Oxygen evolution; Oxygen evolution, standard deviation; Oxygen evolution per individual; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; pH, standard deviation; Potentiometric; Potentiometric titration; Ratio; Registration number of species; Respiration; Salinity; Single species; Species; station_B1; Temperate; Temperature, water; Treatment; Type; Uniform resource locator/link to reference

Type: Dataset

Format: text/tab-separated-values, 1101 data points

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Carbon Transfer from the Host Diatom Enables Fast Growth and High Rate of N2 Fixation by Symbiotic Heterocystous Cyanobacteria (2020)

Inomura, Keisuke ; Follett, Christopher L. ; Masuda, Takako ; [et al.]

Molecular Diversity Preservation International

In: Plants. 2020; 9(2): 192. Published 2020 Feb 04. doi: 10.3390/plants9020192.

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Publication Date: 2020-02-04

Description: Diatom–diazotroph associations (DDAs) are symbioses where trichome-forming cyanobacteria support the host diatom with fixed nitrogen through dinitrogen (N2) fixation. It is inferred that the growth of the trichomes is also supported by the host, but the support mechanism has not been fully quantified. Here, we develop a coarse-grained, cellular model of the symbiosis between Hemiaulus and Richelia (one of the major DDAs), which shows that carbon (C) transfer from the diatom enables a faster growth and N2 fixation rate by the trichomes. The model predicts that the rate of N2 fixation is 5.5 times that of the hypothetical case without nitrogen (N) transfer to the host diatom. The model estimates that 25% of fixed C from the host diatom is transferred to the symbiotic trichomes to support the high rate of N2 fixation. In turn, 82% of N fixed by the trichomes ends up in the host. Modeled C fixation from the vegetative cells in the trichomes supports only one-third of their total C needs. Even if we ignore the C cost for N2 fixation and for N transfer to the host, the total C cost of the trichomes is higher than the C supply by their own photosynthesis. Having more trichomes in a single host diatom decreases the demand for N2 fixation per trichome and thus decreases their cost of C. However, even with five trichomes, which is about the highest observed for Hemiaulus and Richelia symbiosis, the model still predicts a significant C transfer from the diatom host. These results help quantitatively explain the observed high rates of growth and N2 fixation in symbiotic trichomes relative to other aquatic diazotrophs.

Electronic ISSN: 2223-7747

Topics: Biology

Published by Molecular Diversity Preservation International

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Hydrogen Dynamics in Trichodesmium Colonies and Their Potential Role in Mineral Iron Acquisition (2019)

Eichner, Meri ; Basu, Subhajit ; Gledhill, Martha ; [et al.]

Frontiers Media

In: Frontiers in Microbiology . 2019; 10: Published 2019 Jul 10. doi: 10.3389/fmicb.2019.01565.

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Publication Date: 2019-07-10

Electronic ISSN: 1664-302X

Topics: Biology

Published by Frontiers Media

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Mineral iron dissolution in Trichodesmium colonies: The role of O 2 and pH microenvironments (2019)

Eichner, Meri ; Basu, Subhajit ; Wang, Siyuan ; [et al.]

Wiley

In: Limnology and Oceanography. 2019; 65(6): 1149-1160. Published 2019 Oct 31. doi: 10.1002/lno.11377.

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Publication Date: 2019-10-31

Print ISSN: 0024-3590

Electronic ISSN: 1939-5590

Topics: Biology , Geosciences , Physics

Published by Wiley on behalf of Association for the Sciences of Limnology and Oceanography.

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Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies (2019)

Klawonn, Isabell ; Eichner, Meri J. ; Wilson, Samuel T. ; [et al.]

Springer Nature

In: ISME Journal. 2019; 14(2): 399-412. Published 2019 Oct 21. doi: 10.1038/s41396-019-0514-9.

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Publication Date: 2019-10-21

Description: Trichodesmium is an important dinitrogen (N2)-fixing cyanobacterium in marine ecosystems. Recent nucleic acid analyses indicate that Trichodesmium colonies with their diverse epibionts support various nitrogen (N) transformations beyond N2 fixation. However, rates of these transformations and concentration gradients of N compounds in Trichodesmium colonies remain largely unresolved. We combined isotope-tracer incubations, micro-profiling and numeric modelling to explore carbon fixation, N cycling processes as well as oxygen, ammonium and nitrate concentration gradients in individual field-sampled Trichodesmium colonies. Colonies were net-autotrophic, with carbon and N2 fixation occurring mostly during the day. Ten percent of the fixed N was released as ammonium after 12-h incubations. Nitrification was not detectable but nitrate consumption was high when nitrate was added. The consumed nitrate was partly reduced to ammonium, while denitrification was insignificant. Thus, the potential N transformation network was characterised by fixed N gain and recycling processes rather than denitrification. Oxygen concentrations within colonies were ~60–200% air-saturation. Moreover, our modelling predicted steep concentration gradients, with up to 6-fold higher ammonium concentrations, and nitrate depletion in the colony centre compared to the ambient seawater. These gradients created a chemically heterogeneous microenvironment, presumably facilitating diverse microbial metabolisms in millimetre-sized Trichodesmium colonies.

Print ISSN: 1751-7362

Electronic ISSN: 1751-7370

Topics: Biology

Published by Springer Nature

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