ALBERT

Description: Auszug aus einem Arbeitsbericht

Description: Clay- and silt-size mineral assemblages are described from eight piston cores from the fiords and shelf on the western margin of Baffin Bay, Arctic Canada. Radiocarbon dates indicate that all the cores extend back in time to the last local glacial/interglacial transition (i.e. 8–10 ka); four extend back to between 10 and 12 ka, and HU77-021-156, located on the Southeast Baffin Island shelf, includes the entire late Foxe glacial stage. Silt- and clay-size particles constitute ca 40 and 55%, respectively, by weight of the bulk sediment. The clay-size fraction is dominated by mica; feldspars and quartz are the main constituents of the silt fraction. The fiord sediments are mainly composed of local mineralogies, but on the shelf, and at times in the fiords, exotic mineral species occur. The most important of these are detrital carbonates, derived from erosion of the Paleozoic basins in Arctic Canada and/or northwest Greenland. Both calcite and dolomite occur; calcite is the major carbonate mineral in the “southern” cores, whereas dolomite is the most abundant in cores north of 66°N. Higher inputs of carbonate species occur during regional deglaciation, 7–10 ka, and during the last 5 ka (probably reflecting increased iceberg production from northwest Greenland). Thus variations in the precentages of the carbonate minerals indicate significant shifts in Late Quaternary glacial-sediment source areas and oceanographic regimes.

Description: Changes in composition of modern benthic ostracod faunas across the continental margin of southwestern Africa occur at boundaries between and within major water masses: a Mixed Layer-Antarctic Intermediate Water (AAIW) boundary at 200 m, an AAIW salinity minimum zone at 650 m, an AAIW bathyal thermocline at 1000 m, and the AAIW/North Atlantic Deep Water (NADW) boundary at 1500 m. In addition, two population changes occur within the NADW at 1.8–2.0 km and 2.0–3.0 km. The Antarctic Bottom Water assemblage is sparse and poorly preserved.

Description: In a midoceanic region of the northeast Atlantic, patches of freshly deposited phytodetritus were discovered on the sea floor at a 4500 m depth in July/August 1986. The color of phytodetritus was variable and was obviously related to the degree of degradation. Microscopic analyses showed the presence of planktonic organisms from the euphotic zone, e.g., cyanobacteria, small chlorophytes, diatoms, coccolithophorids, silicoflagellates, dinoflagellates, tintinnids, radiolarians, and foraminifers. Additionally, crustacean exuviae and a great number of small fecal pellets, “minipellets,” were found. Although bacteria were abundant in phytodetritus, their number was not as high as in the sediment. Phytodetrital aggregates also contained a considerable number of benthic organisms such as nematodes and special assemblages of benthic foraminifers. Pigment analyses and the high content of particulate organic carbon indicated that the phytodetritus was relatively undegraded. Concentrations of proteins, carbohydrates, chloroplastic pigments, total adenylates, and bacteria were found to be significantly higher in sediment surface samples when phytodetritus was present than in equivalent samples collected at the same stations in early spring prior to phytodetritus deposition. Only the electron transport system activity showed no significant difference between the two sets of samples, which may be caused by physiological stress during sampling (decompression, warming). The chemical data of phytodetritus samples displayed a great variability indicative of the heterogeneous nature of the detrital material. The gut contents of various megafauna (holothurians, asteroids, sipunculids, and actiniarians) included phytodetritus showing that the detrital material is utilized as a food source by a wide range of benthic organisms. Our data suggest that the detrital material is partly rapidly consumed and remineralized at the sediment surface and partly incorporated into the sediment. Incubations of phytodetritus under simulated in situ conditions and determination of the biological oxygen demand under surface water conditions showed that part of its organic matter can be biologically utilized. Based on the measured standing stock of phytodetritus, it is estimated that 0.3–3% of spring primary production sedimented to the deep-sea floor. Modes of aggregate formation in the surface waters, their sedimentation, and distribution on the seabed are discussed.

Description: Loligo forbesi Steenstrup is a commercially and biomedically important species raneing from Scotland to North Africa and from the Azores Islands in the central Atlantic east through the Mediterranean Sea and Red Sea. Eggs were collected from Plymouth. England and from the Azores and the hatchlings were reared to adult size in recirculating seawater systems. Growth data were obtained primarily from mortalities during the course of three culture experiments which lasted 360, 240 and 480 days. Loligo forbesi hatched at a size of 5–9mg (3.0–4.6mm mantle length, ML) and grew to a maximum size of 124g (155 mm ML) in 413 days. In all experiments, growth was exponential in form for at least the first 3 months at rales of 5.8, 5.1 and 3.6% body weight per day (BW/d) at mean temperatures of 14.1, 14.0 and 13.1°C respectively. In one short-term experiment, month-old squids grew at 8.0% BW/d at 17.4°C. Growth beyond 3 months was slower and either logarithmic (as described by the power function) or exponential in form. Growth rates gradually declined to 1–2% BW/d, Analyses of mantle length growth confirmed the wet weight results. There was no evidence of sexual dimorphism in the laboratory populations, which were of small size, and the length-weight (L-W) relationships were found to be similar to those of field populations. Growth rates during the exponential growth phase appeared very sensitive to temperature, with a 1°C difference changing growth rate by 2% BW/d and producing a three-fold difference in weight at 90 days post-hatching. These dramatic effects of temperature on adult size and lifespan in nature are discussed. It is hypothesized that the small size of mature laboratory-reared squids was due to low culture temperatures during the first 3 months.

Description: Measurements in the mixing zone of the Elbe estuary were performed during three consecutive tidal cycles with three types of instruments—a moored tripod with velocity and temperature/conductivity/light attenuation sensors, a profiling sonde with similar sensors lowered from an anchored vessel, and instrumented moorings. Acoustic-travel-time sensors were used for velocity measurements. Spectral analysis of 12·8 min pieces of the obtained time series gives results that are consistent with isotropic turbulence for part of the frequency space. Temporal changes of turbulent kinetic energy are correlated with tidal current velocity. A retardation is found between changes in tidal current and turbulent energy. Not all shear stress terms are in similar phase with tidal flow. Mean gradients, Reynolds stress terms, and turbulent salt flux terms are combined to determine eddy viscosity and eddy diffusion coefficients.

Description: Compressional-wave (P-wave) velocities and magnetic susceptibilities were measured on gravity (GGC) and piston cores (PC) and Ocean Drilling Program (ODP) Leg 108 advanced piston cores (APC) from the equatorial Atlantic to test our hypothesis that climatically driven changes in terrigenous and biogenic fluxes, and in carbonate dissolution control the interrelationships between the two signals. In Pleistocene sediments deposited above the calcium compensation depth (CCD) we observed changes in P-wave velocity and magnetic susceptibility that are (1) inversely correlated, and (2) coherent to changes in glacial-interglacial climate. Glacials show low P-wave velocities and relatively high magnetic susceptibilities. In contrast, interglacials show high P-wave velocities and relatively low magnetic susceptibilities. These temporal changes in P-wave velocity and magnetic susceptibility reflect the climatic history recorded in the sediments and are related to: (1) the production of biogenic carbonate, mainly planktonic foraminifera, and (2) the terrigenous sediment supply that contains magnetic minerals. Below the CCD this pattern disappears and consistently low P-wave velocities and distinctly higher magnetic susceptibilities prevail. The distinct decrease of large P-wave velocity fluctuations is due to the dissolution of carbonate sediments which cause a distinct decrease in sand grain sizes and a consistently low carbonate content (〈 10%). Dilution of magnetic material by the carbonate fraction is minor and the high magnetic susceptibility values and the relatively high amplitude variations in magnetic susceptibility are due to changes in the magnetic mineral concentration of the terrigenous (non-carbonate) fraction. In early Pliocene sediments we also observed covarying velocity and magnetic susceptibility signals that may reflect a predominatly terrigenous control on sedimentation. Our preliminary results demonstrate that a combined use of non-destructive measurements of acoustic and rock-magnetic signals provides a potential paleoceanographic tool for characterizing: (1) glacial-interglacial pelagic sedimentation, (2) pelagic sedimentation above the CCD, (3) increases in carbonate dissolution, and (4) areas below the CCD. Furthermore, rock magnetic fluctuations in sediments below the CCD may provide an important stratigraphic tool for the deep carbonate-free basins of the world's oceans.

Description: The life cycle of loliginid squids has been completed in recirculating seawater systems. Two systems were required: a 2 m diameter circular culture tank (CT) with adjoining 2 m circular filter tank (3000 liters total volume of natural seawater) for culture of hatchlings, 1–60 days old; and a 6 × 2·6 × 1 m raceway culture tank (RW) with a smaller adjoining rectangular filter tank (14 850 liters total volume of artificial seawater) for the grow-out of adults. Both systems were equipped with temperature control apparatus, modular filter units (particle filters and activated carbon), foam fractionators, biological filters (crushed oyster shell) and UV sterilizers. The systems carried low bioloads, 〈 1·0 g/m3 and as high as 0·8 kg/m3, respectively. Water quality was excellent: NH4N was below 0·01 mg/liter in the CT and 0·10 mg/liter in the RW: NO2N was below 0·01 mg/liter in the CT and 0·03 mg/liter in the RW; NO3N was below 12 mg/liter in the CT and below 50 mg/liter in the RW; and pH was above 8·0 in both systems. The design of the systems proved to be behaviorally and physiologically suitable for squids and two species grew to adult size and produced viable young. These systems are compared to other squid maintenance and rearing systems and marine recirculating seawater systems.

Description: A comparative study of isodideimnine-1 and didemnin B is presented using spcctroecopic methods, partial degradation and partial synthesis. This leads to the conclusion of the presence of a single depsipeptide, namely didemnin B, with (3S,4R,5S) isostatine instead of the previous statine residue. An attempt to determine the whole conformation in solution of didemnin B by using 2D-NMR is also described.

Description: Seismic refraction investigations along a 440-km long profije on the northern Baltic Shield have resolved the crustal structure in this area of Archaean to Early Proterozoic lithosphere formation. The profile, called the POLAR Profile, extends approximately along a SW-NE-oriented line from the Karelian Province in northern Finland across the Lapland Granulite Belt and the Kola Peninsula Province to the Varanger Peninsula in northeastern Norway. At six shotpoints, large explosions (200–1680 kg), and at three shotpoints, small explosions (80 kg) were detonated and recorded at an average station spacing of 2 km, providing high-quality record sections. A two-dimensional cross section of the crust was obtained by forward modelling using ray-tracing techniques. High-velocity bodies are found in the upper crust related to the Karasjok-Kittilä Greenstone Belt and the Lapland Granulite Belt. They extend to a depth of 6–13 km. In the Karelian Province in the southwest, a low-velocity zone was found between the depths of 8 and 14 km. The middle crust shows a slight increase in the average velocities from the southwest to the northeast, and a small velocity jump is found along a mid-crustal boundary between 18 and 21 km. The thickness of the middle crust varies between 16 and 18 km. The lower crust and the crust-mantle boundary (Moho) show considerable lateral variation. The top of the lower crust lies between 26 and 33 km, while its thickness decreases from 21 km in the southwest to 10–14 km beneath the Lapland Granulite Belt and the Inari Terrain, reaching 20 km again in the extreme northeast. The velocities also change laterally. The thin lower crust is characterized by rather low velocities (6.8–6.9 km/s), whereas in the southwest and northeast the velocities (6.9–7.3 km/s) resemble more typical shield structures. The Moho is found at 47 km in the Karelian Province, rises to 40 km beneath the Lapland Granulite Belt and descends to 46 km in the northeastern part of the Kola Peninsula Province. The upper mantle velocities at the Moho range from 8.1 km/s in the region of the thin crust, to 8.5 km/s and more beneath the Karelian Province. It is tempting to suggest that the anomalous lower crust underlying the Lapland Granulite Belt and the Inari Terrain may represent the remnants of an Early Proterozoic back-arc basin that was active prior to the 2.0 to 1.9 Ga plate convergence event, during which the Lapland Granulite Belt was thrust onto the Archaean basement of the Karelian Province. Another explanation is to assume that the velocity reduction in the anomalous lower crust was caused by a rather pronounced uplift of this region following the 1.9-Ga collision event.