ALBERT

Beschreibung: The mechanism of sulfate assimilation was investigated in Rhodopseudomonas sulfidophila, a bacterium able to grow either photoautotrophically, with sulfide as electron donor, or photoheterotrophically with sulfate as sole sulfur source. ATP sulfurylase, adenosine-5′-phosphosulfate kinase, 3′-phosphoadenosine-5′-phosphosulfate sulfotransferase, thiosulfonate reductase and cysteine synthase were present. Reduced sulfur compounds, especially sulfide and sulfite repressed all steps of sulfate activation and reduction including sulfate uptake. Adenosine-5′-phosphosulfate kinase activity in contrast to the other activities was high in the presence of cysteine or reduced glutathione in the growth medium. Sulfur was incorporated into the cellular sulfolipid from sulfate and also from reduced sulfur compounds like cysteine and thiosulfate. The activity of 3′-phosphoadenosine-5′-phosphosulfate sulfotransferase was rapidly lost during gel filtration or dialysis. From comparison with other sulfotransferases and from the specific cofactor requirement for the enzyme of R. sulfidophila it is concluded that two different low molecular weight cofactors are required in this system. A reaction sequence is proposed involving thioredoxin as the reductant of another dialysable low molecular weight cofactor, that binds to the protein.

Beschreibung: Ammonium regeneration, nutrient uptake, bacterial activity and primary production were measured from March to August 1980 in Bedford Basin, Nova Scotia, Canada, a eutrophic environment. Rates of regeneration and nutrient uptake were determined using 15N isotope dilution and tracer methodology. Although primary production, nutrient uptake and ammonium regeneration were significantly intercorrelated, no relationship was detected between these parameters and heterotrophic activity. The average contribution of ammonium to total nitrogen (ammonium+nitrate) uptake was similar in the spring and in the summer (approximately 60%). On a seasonal average basis, 36% of the phytoplankton ammonium uptake could be supplied by rapid remineralization processes. In spite of the high average contribution of NH4 regeneration to phytoplankton ammonia uptake, there is indirect evidence suggesting that other NH4 sources may occasionally be important.

Beschreibung: Anhand hundertjähriger Meßreihen wurden langfristige Salzgehaltsänderungen in der Unterweser und ihre möglichen Ursachen untersucht. Dabei wurde angestrebt, die natürlichen und die anthropogenen Einflüsse auf den Salzgehalt zu trennen. Trotz des unvollständigen Datensatzes konnten der Einfluß des Einzugsgebietes und Salzgehaltsschwankungen des angrenzenden Meeresgebietes nahezu eliminiert werden. Wegen der langzeitigen Änderungen der Gezeiten in der Nordsee waren genaue Aussagen über die Auswirkung der in den letzten hundert Jahren in der Unterweser durchgeführten Baumaßnahmen auf den Salzgehalt nicht möglich. Unsere Ergebnisse geben Hinweise für moderne Meßnetze zur Bestimmung der Wasserqualität.

Beschreibung: A suite of marble specimens from the Sierra Alhamilla (Spain), deformed to large strains under natural conditions at about 300° C shows distinct variations in microstructure and fabrics. It can be demonstrated that the development of crystallographic preferred orientations and grain shape fabrics are strongly dependent on recrystallized grain size. This is interpreted to reflect the relative importance of various deformational mechanisms. Superplasticity seems to have a sharp upper grain size limit at 10–15 /smm. Within the power law creep regime, deformation in fine grained aggregates is probably dominated by diffusional, in coarser ones by dislocation mechanisms. The transition is a gradual one, and may span a grain size range of 30 /sm.

Beschreibung: Statoliths of the short-finned squid Illex illecebrosus were chemically analyzed to define their chemical composition and surveyed by scanning electron microscope to differentiate internal structural patterns. X-ray diffraction data demonstrated that L Illecebrosus statoliths were composed principally of CaCQ in the aragonite crystal form. The crystals occurred in a protein matrix to form incremental patterns which radiated from the nucleus to the edge of the statoliths. The protein matrix comprised approximately 5% of the statolith by weight. The protein was principally composed of acidic amino acids. A high abundance of aspartic acid in the protein matrix indicated that the matrix would function as a template in the initiation and acceleration of the crystal growth of CaCO. The rhythmic microstructural patterns, constructed of aragonite crystals in the protein matrix, wer e suggested to be daily in formation and subsequent growth estimations were in agreement with known life history information. The stable isotopic composition of the carbonate of L illecebrosus statoliths suggested that oxygen may be deposited in isotopic equilibrium with the surrounding environment while carbon appeared to be related to biological processes. The information recorded in the statotiths as incremental growth and stable isotopic composition could provide valuable insights into the ecological history of squid.

Beschreibung: Seismic, lithostratigraphic, faunal, and isotopic evidence from the western and northern North Atlantic indicates that formation of northern sources for strongly circulating bottom water began in the late Eocene to early Oligocene. The widely distributed reflector R4 correlates with an unconformity eroded along basin margins at the Eocene/Oligocene boundary. This change in abyssal regime also correlates with a major benthic foraminiferal turnover in the deep southern Labrador Sea (DSDP Site 112) and with a faunal reorganization in the Bay of Biscay. The principal bottom-water source probably was of Arctic origin; it entered the Norwegian Sea following separation of Greenland and Spitsbergen and flowed south across the Greenland-Scotland Ridge through the Faeroe-Shetland Channel and possibly across a sill east of Greenland. This flow may have been supplemented by dense Arctic water entering the basin via Nares Strait and Baffin Bay, and by cooling and sinking of saline surface water south of the Greenland-Scotland Ridge and in the Labrador Sea. Current-controlled sedimentation and erosion, often of a chaotic nature, continued through the Oligocene above reflector R4, but the general intensity of abyssal circulation is thought to have decreased. Above reflector R2 (upper lower Miocene) current-controlled sedimentation became more coherently developed, and a major phase of sedimentary drift development was initiated. We interpret this to be a result of a further general reduction and especially a stabilization of the abyssal circulation, possibly linked with degeneration of numerous fracture-zone conduits that previously funnelled bottom water across the Reykjanes Ridge. The gross nature of the circulation has not changed substantially since the middle Miocene, although it has been punctuated by further climatic and tectonic events.