ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa (1998)

Rink, S. ; Kühl, M. ; Bijma, J. ; [et al.]

Springer

Marine biology 131 (1998), S. 583-595

add to mindlist on the mindlist

Details

ISSN: 1432-1793

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminifer Orbulina universa and its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2 and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2 concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness decreased the O2 concentration at the shell surface to 〈70% of the oxygen content in the surrounding air-saturated water. The pH at the shell surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2 h−1 foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2 h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2 h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2 h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross photosynthesis versus scalar irradiance curves (P vs E o curves) showed light saturation irradiances (E k) of 75 and 137 μmol photons m−2 s−1 in two O. universa specimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2 s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2 s−1. Radial profile measurements of scalar irradiance (E o) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (E d).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002270050350

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

2

Electronic Resource

Microsensor studies of photosynthesis and respiration in larger symbiotic foraminifera. I The physico-chemical microenvironment of Marginopora vertebralis, Amphistegina lobifera and Amphisorus hemprichii (2000)

Köhler-Rink, S. ; Kühl, M.

Springer

Marine biology 137 (2000), S. 473-486

add to mindlist on the mindlist

Details

ISSN: 1432-1793

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The physico-chemical microenvironment of larger benthic foraminifera was studied with microsensors for O2, CO2, pH, Ca2+ and scalar irradiance. Under saturating light conditions, the photosynthetic activity of the endosymbiotic algae increased the O2 up to 183% air saturation and a pH of up to 8.6 was measured at the foraminiferal shell surface. The photosynthetic CO2 fixation decreased the CO2 at the shell down to 4.7 μM. In the dark, the respiration of host and symbionts decreased the O2 level to 91% air saturation and the CO2 concentration reached up to 12 μM. pH was lowered relative to the ambient seawater pH of 8.2. The endosymbionts responded immediately to changing light conditions, resulting in dynamic changes of O2, CO2 and pH at the foraminiferal shell surface during experimentally imposed light–dark cycles. The dynamic concentration changes demonstrated for the first time a fast exchange of metabolic gases through the perforate, hyaline shell of Amphistegina lobifera. A diffusive boundary layer (DBL) limited the solute exchange between the foraminifera and the surrounding water. The DBL reached a thickness of 400–700 μm in stagnant water and was reduced to 100–300 μm under flow conditions. Gross photosynthesis rates were significantly higher under flow conditions (4.7 nmol O2 cm−3 s−1) than in stagnant water (1.6 nmol O2 cm −3 s−1), whereas net photosynthesis rates were unaffected by flow conditions. The Ca2+ microprofiles demonstrated a spatial variation in sites of calcium uptake over the foraminiferal shells. Ca2+ gradients at the shell surface showed total Ca2+ uptake rates of 0.6 to 4.2 nmol cm−2 h−1 in A. lobifera and 1.7 to 3.6 nmol cm−2 h−1 in Marginopora vertebralis. The scattering and reflection of the foraminiferal calcite shell increased the scalar irradiance at the surface up to 205% of the incident irradiance. Transmittance measurements across the calcite shell suggest that the symbionts are shielded from higher light levels, receiving approximately 30% of the incident light for photosynthesis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002270000335

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

3

Electronic Resource

Irradiance and temperature regulation of oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat (Solar Lake, Egypt) (2000)

Wieland, A. ; Kühl, M.

Springer

Marine biology 137 (2000), S. 71-85

add to mindlist on the mindlist

Details

ISSN: 1432-1793

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Short-term effects of temperature and irradiance on oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat were investigated with O2 microsensors in a laboratory. The effect of temperature on O2 fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons m−2 s−1) in the temperature range from 15 to 45 °C. Areal rates of dark O2 consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol−1 and the corresponding Q 10 value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O2 consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of net photosynthesis increased with temperature up to 40 °C and exhibited a Q 10 value (20 to 30 °C) of 2.8. Both O2 dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q 10 of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m−2 s−1) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E k = 148 to 185 μmol photons m−2 s−1) estimated from P versus E d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m−2 s−1, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation irradiance increased with temperature, from 32 μmol photons m−2 s−1 at 25 °C to 77 μmol photons m−2 s−1 at 40 °C, due to increased rates of O2 consumption relative to gross photosynthesis. Areal rates of O2 consumption in the illuminated mat were higher than dark O2 consumption at corresponding temperatures, due to an increasing O2 consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O2 cycling within hypersaline cyanobacterial mats.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002270000331

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

4

Electronic Resource

A Microsensor Study of the Interaction between Purple Sulfur and Green Sulfur Bacteria in Experimental Benthic Gradients (1999)

Pringault, O. ; de Wit, R. ; Kühl, M.

Springer

Microbial ecology 37 (1999), S. 173-184

add to mindlist on the mindlist

Details

ISSN: 1432-184X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The interaction between the purple sulfur bacterium Thiocapsa roseopersicina and the green sulfur bacterium Prosthecochloris aestuarii was studied in a gradient chamber under a 16-hours light-8-hours dark regime. The effects of interaction were inferred by comparing the final outcome of a mixed culture experiment with those of the respective axenic cultures using the same inoculation densities and experimental conditions. Densities of bacteria were deduced from radiance microprofiles, and the chemical microenvironment was investigated with O2, H2S, and pH microelectrodes. P. aestuarii always formed a biofilm below the maximal oxygen penetration depth and its metabolism was strictly phototrophic. In contrast, T. roseopersicina formed a bilayer in both the mixed and the axenic culture. The top layer formed by the latter organism was exposed to oxygen, and chemotrophic sulfide oxidation took place during the dark periods, while the bottom layer grew phototrophically during the light periods only. In the mixed culture, the relative density of P. aestuarii was lower than in the axenic culture, which reflects the effects of the competition for sulfide. However, the relative density of T. roseopersicina was actually higher in the mixed culture than in the corresponding axenic culture, indicating a higher growth yield on sulfide in the mixed culture experiment. Several hypotheses are proposed to explain the effects of the interaction.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002489900141

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

5

Electronic Resource

Bio-optical Characteristics and the Vertical Distribution of Photosynthetic Pigments and Photosynthesis in an Artificial Cyanobacterial Mat (2000)

Kühl, M. ; Fenchel, T.

Springer

Microbial ecology 40 (2000), S. 94-103

add to mindlist on the mindlist

Details

ISSN: 1432-184X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Zonations of photosynthesis and photopigments in artificial cyanobacterial mats were studied with (i) oxygen and pH microsensors, (ii) fiber-optic microprobes for field radiance, scalar irradiance, and PSII fluorescence, and (iii) a light microscope equipped with a spectrometer for spectral absorbance and fluorescence measurements. Our analysis revealed the presence of several distinct 1–2 mm thick cyanobacterial layers mixed with patches of anoxygenic photosynthetic bacteria. Strong attenuation of visible light confined the euphotic zone to the uppermost 3 mm of the mat, where oxygen levels of 3–4 times air saturation and a pH peak of up to pH 8.8 were observed under saturating irradiance (413 μmol photon m−2 s−1). Oxygen penetration was 5 mm in light and decreased to 1 mm in darkness. Volumetric oxygen consumption in the photic and aphotic zones of illuminated mat was 5.5 and 2.9 times higher, respectively, than oxygen consumption in dark incubated mats. Scalar irradiance reached 100–150% of incident irradiance in the upper 0.5 mm of the mat due to intense scattering in the matrix of cells, exopolymers, and carbonate precipitates. In deeper mat layers scalar irradiance decreased nearly exponentially, and highest attenuation coefficients of 6–7 mm−1 were found in cyanobacterial layers, where photosynthesis and photopigment fluorescence also peaked. Visible light was attenuated 〉100 times more strongly than near infrared light. Microscope spectrometry on thin sections of mats allowed detailed spectral absorbance and fluorescence measurements at defined positions relative to the mat surface. Besides strong spectral signals of cyanobacterial photopigments (Chl a and phycobiliproteins), the presence of both green and purple photosynthetic bacteria was evident from spectral signals of Bchl a and Bchl c. Microprofiles of photopigment absorbance correlated well with microdistributions of phototrophs determined in an accompanying study.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002480000061

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

6

Electronic Resource

Biosynthesis and Regulation of Immunoglobulins (1983)

Wall, R ; Kuehl, M

Palo Alto, Calif. : Annual Reviews

Annual Review of Immunology 1 (1983), S. 393-422

add to mindlist on the mindlist

Details

ISSN: 0732-0582

Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff

Topics: Biology , Medicine

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1146/annurev.iy.01.040183.002141

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

7

Electronic Resource

Artificial Cyanobacterial Mats: Growth, Structure, and Vertical Zonation Patterns (2000)

Fenchel, T. ; Kühl, M.

Springer

Microbial ecology 40 (2000), S. 85-93

add to mindlist on the mindlist

Details

ISSN: 1432-184X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The formation of cyanobacterial mats (originally induced by incubation of sediment cores in which metazoans and most other eukaryotes had been removed) was followed over approximately 2.6 years. The thickness of the mats increased at a rate of 2–3 mm per year because of accumulation of empty cyanobacterial sheaths and as a result of carbonate deposition; the fraction of living biomass remained relatively constant over at least 2 years, but there was a slow accumulation of nonliving organic C (≈ 1 mmol yr−1). Biota composition (dominated by five types of filamentous cyanobacteria, unicellular cyanobacteria, diatoms, anoxygenic phototrophs, and heterotrophic bacteria) and vertical zonation patterns in the upper 2–3 mm of the mats were also almost constant over time. Using transmission electron microscopy and stereological analysis it was possible to quantify the vertical distribution of major groups of organisms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002480000062

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

8

Electronic Resource

Spatial scale and the diversity of benthic cyanobacteria and diatoms in a salina (1999)

Nübel, U. ; Garcia-Pichel, F. ; Kühl, M. ; [et al.]

Springer

Hydrobiologia 401 (1999), S. 199-206

add to mindlist on the mindlist

Details

ISSN: 1573-5117

Keywords: hypersaline ; microbial mat ; cyanobacteria ; diatom ; microbial richness ; biodiversity ; 16S rRNA

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We characterized the richness of benthic cyanobacteria and diatoms in a salina system using traditional and molecular biological methods. After determining the different morphotypes and 16S rRNA genes present in various localities within this hypersaline system, an analysis of the increase of organismal richness as a function of numbers of samples considered was carried out. We found that the spatial scales of sampling yielding significant increases in cumulative richness were those at which significant variations in environmental parameters (salinity, vertical microgradients) are known to exist, indicating that the presence of environmental gradients contributes to increased biodiversity. Additionally, we could use this type of cumulative analysis for the estimation, through asymptotic extrapolation, of the total richness of oxygenic phototrophs present in the entire salina system, and for the estimation of the average degree of dissemination of community members within the system. We found interesting differences between analyses based on morphotypes or 16S rRNA genes. The cumulative number of rRNA gene sequences exceeded that of morphotypes by more than two-fold. This indicates that many organisms possessing distinct 16S rRNA gene sequences could not be distinguished on the basis of morphology. Thus, some of the apparently widely distributed morphotypes may in fact conceal several ecologically independent genotypes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1003702814150

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

9

Electronic Resource

Application of photon activation analysis to the determination of the distribution of toxic elements in soil of a sewage farm (1984)

Segebade, C. ; Schmitt, B. -F. ; Fusban, H. -U. ; [et al.]

Springer

Fresenius' Zeitschrift für analytische Chemie 317 (1984), S. 413-421

add to mindlist on the mindlist

Details

ISSN: 1618-2650

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Summary Bore-cores, taken from waste water charged and closely neighbouring virgin soil regions within the sewage farm in Berlin-Karolinenhöhe were investigated. The distributions of numerous elements along the bore-core length (or soil depth, respectively) were analysed with particular emphasis laid upon toxic components. As many as 27 elements were analysed. By comparison of the concentration profiles the significant partition of anthropogenic pollutants becomes obvious. Instrumental photon activation analysis using an electron accelerator — being a multielement technique — has proven to be a suitable tool for the given analytical task. With this method, elements can be analysed which are not or not readily determinable with other comparable instrumental techniques (thermal neutron activation analysis in particular), e.g. Ni, Tl and Pb.

Notes: Zusammenfassung Bohrkerne aus abwasserbelasteten und dicht benachbarten unbelasteten Regionen der Rieselfeldanlage in Berlin-Karolinenhöhe wurden untersucht. Die Konzentrationsverteilungen zahlreicher Elemente über die Bohrkernlänge (bzw. Bodentiefe) wurden festgestellt, wobei besonderes Augenmerk auf toxische Komponenten gerichtet wurde. Insgesamt 27 Elemente wurden analysiert. Beim Vergleich der Konzentrationsprofile wird der hohe Anteil an anthropogenen Schadstoffen in abwasserbelasteten Böden deutlich. Die instrumenteile Photonenaktivierungsanalyse mit Hilfe eines Elektronenbeschleunigers hat sich als Multielementverfahren als gut geeignet für die gestellte Analysenaufgabe erwiesen, zumal mit diesem Verfahren umweltrelevante Elemente bestimmt werden können, die mit anderen vergleichbaren instrumentellen Methoden (insbesondere Aktivierungsanalyse mit thermischen Neutronen) nicht oder nur schlecht analysierbar sind, z. B. Ni, Tl und Pb.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00494509

Permalink