ALBERT

Description: Many of the difficulties of staining plastic embedded tissues for light and electron microscopy derive from physical exclusion of hydrophilic staining reagents by hydrophobic embedding media. Structures which stain most intensely with hydrophilic reagents usually contain less hydrophobic plastic than do non-staining structures. Such incomplete infiltration is apparently caused by exclusion of viscous, hydrophobic monomers by physically dense and/or well hydrated tissue elements. In keeping with this, generalized staining of tissues embedded in hydrophobic media does occur when hydrophobic reagents are used. Staining of plastic-free structures with single hydrophilic reagents or with sequences of such reagents, is, however, largely rate-controlled. The surprising similarity of hydrophilic and hydrophobic plastic embedding media is discussed. Limits of this simple model are explored, with a consideration of the roles of fixative and of monomer-tissue reactions

Description: Before making a critical evaluation of the crude oil and natural gas prospects for the years to the end of the century, it is necessary to review the geology and structure of the three German hydrocarbon-producing provinces. Furthermore, past exploration, production and reserves should be discussed. The three hydrocarbon-producing provinces are: the NW German Basin, the Upper Rhine Graben and the Molasse Basin, which together make up about 41% of West German territory (Fig. 1). The NW German Basin contains a sedimentary sequence over 8,000 m thick ranging in age from Permian to Quaternary. Gas and oil, the two natural hydrocarbons, are generally confined to separate lower and higher stratigraphic levels respectively (Fig. 2). The NW German Basin is the most important prospective area in West Germany. It extends into the North Sea. The tectonic rift feature of the Upper Rhine Graben originated in the Eocene. The Tertiary fill is over 4,000 m thick. Oil is found mainly in Mesozoic, Eocene and Oligocene rocks; the Miocene and Pliocene reservoir rocks contain natural gas almost exclusively (Fig. 3). The Molasse Basin is part of the foredeep north of the Alpine and Carpathian mountain ranges. The basin is filled with Upper Eocene to Pliocene and Quaternary sediments which, near the Alpine nappes, reach a thickness of over 5,000m (Fig. 4). During this century there were peaks in annual oil-production in 1910, 1940 and 1968 (see Fig. 5). The 1910 peak was the result of drilling activity in the Wietze oilfield. During the period 1934–1945, government financial aid was made available for drilling exploration wells. The success of this collaboration is demonstrated by the oil output in 1940 of 1 × 106 t. After World War II, many different types of oil-bearing structure were found, particularly by reflection seismic techniques in conjunction with detailed stratigraphical and palaeogeographical investigations. The success achieved can be seen by the peak of 8 × 106 t oil production for 1968 (Fig. 5) and in the growth of oil reserves (Fig. 7). Intensive exploration also enabled many new gasfields to be developed, especially in the deeper horizons of the NW German Basin. In 1971, estimated gas reserves reached 360 × 109 m3 (Fig. 11), and annual gas production in 1979 was 20.7 × 109 m3 (731 Bcf) (Fig. 9). There is, no doubt, still scope for the discovery and exploitation of oil and gas in Germany, especially in the NW German Basin where the best prospects for the future lie. This is borne out by two recent offshore oil discoveries and also by the successful application of enhanced recovery methods in the oilfields. The chances of finding more gas at the lower stratigraphic levels are promising now that gas has been discovered in the deeper parts of the Permian basin. The results of massive-hydraulic-fracturing tests in low-permeability pay-horizons are also encouraging. The deeper parts of oil- and gas-producing basins contain interesting prospects and have yet to be tested by ultra-deep wells. Provided that the economic climate remains favourable, there should be no difficulty in finding and supplying German oil and gas in the future. Geologically and technically possible reserves should be converted into proven and/or probable reserves. German crude oil will be available for several years beyond the year 2000, and German natural gas for a far longer time. A production rate of 19 to 20 × 109 m3 of gas per annum is feasible over the next twenty years, and oil production will probably not sink below 3 × 106 t/a in this period.

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: Tubificid and enchytraeid oligochaetes are common members of the interstitial fauna of sandy beaches. Their abundance dynamics, life cycles and distribution patterns were investigated at two beaches on the western Baltic Sea and at a North Sea beach (Isle of Sylt). Populations of 115,000 ind./m2 were found at protected Baltic beaches. Reproduction of the tubificids, Phallodrilus monospermathecus and Spiridion insigne takes place within a well defined breeding period once a year. The market horizontal and vertical distribution patterns of various tubificid and enchytraeid species are elucidated by preference reactions to several physiographic parameters, such as oxygen and water content of the sediment, and salinity.

Description: Methods for analysing fish stomach contents are listed and critically assessed with a view to their suitability for determining dietary importance—this term is defined. Difficulties in the application of these methods are discussed and, where appropriate, alternative approaches proposed. Modifications which have practical value are also considered. The necessity of linking measurements of dietary importance to stomach capacity is emphasized and the effects of differential digestion upon interpretation of stomach contents outlined. The best measure of dietary importance is proposed as one where both the amount and bulk of a food category are recorded.

Description: At the sub-Antarctic island of South Georgia 25 of the 29 breeding species are seabirds. Fifteen of these have recently been studied in some detail. By examining the timing of their breeding seasons and their diet and feeding ecology (especially feeding techniques and potential foraging ranges), the nature of their ecological isolating mechanisms, and in particular the way in which they partition the resources of the marine environment, are reviewed. Although breeding season adaptations occur (winter breeding in Wandering Albatross and King Penguin; out of phase breeding in two species-pairs of small petrels) these are less important than dillerences in food and feeding ecology. There is a fundamental distinction between the niche of pursuit-diving species (mainly penguins) and the remainder which are basically surface-feeders. The two abundant krill-eating penguins show clear differences in feeding zones. Three albatrosses and a petrel feed mainly on squid and there are differences in both the species and size of the prey of each. The remaining seabirds chiefly take krill (although the giant petrels are extensive scavengers and some smaller petrels specialize on copepods) and utilize different feeding methods and areas to do so. Various adaptations related to inshore and offshore feeding zones are discussed. Although most species possess a combination of ecological isolating mechanisms additional evidence for the particular importance of dietary differences is presented.

Description: The diets of adult Macaroni penguins Eudyptes chrysolophus chrysolophus and Southern rockhopper penguins E. chrysocome chrysocome were analysed quantitatively at Marion Island, southern Indian Ocean, throughout two successive chick-rearing seasons. The diets were broadly similar. Crustaceans were the predominant prey type comprising, overall, 90% by mass and 98% by numbers in Macaroni penguins and 96% by mass and 99% by numbers in rockhopper penguins. Nauticaris marionis was the predominant crustacean eaten by both penguin species in 1983–84, but Euphausia vallentini and Thysanoessa vicina predominated in 1984–85. Themisto gaudichaudii was present in appreciable numbers only in Macaroni penguins. Fish was not found in measurable quantities in either species in 1983–84, but contributed 5% and 4% of the mass of the diet in Macaroni and rockhopper penguins, respectively, when calculated in terms of the original biomass of food ingested. In 1984–85, however, fish comprised 10% and 6% of observed mass and c. 25% and 14% of original biomass ingested in Macaroni and rockhopper penguins, respectively. Pelagic myctophids, predominantly Krefftichthys anderssoni, Protomyctophum tenisoni and P. normani between 0·01 and 8·3 g, were the most commonly identified fish prey, but Macaroni penguins took an appreciable number of Electrona carlsbergi in 1983–84. Cephalopods made up between 1 % and 3% of the diet by mass in both penguin species and between 5% and 13% of original biomass ingested. Predominant cephalopods eaten were Kondakovia longimana and an unidentified octopus species. The relative proportions of each prey type change throughout chick-rearing, with pelagic fish and cephalopods comprising a larger proportion later in the season when the penguins were assumed to be foraging farther from their breeding sites. Dietary segregation of the two species appears to be related to the difference in the timing of the breeding season, which begins three to four weeks earlier in Macaroni penguins.

Description: A population dynamics analysis for planktonic diatoms is presented that allows estimates of the net rate of increase (k), the death rate (δ), the sedimentation rate (σ) and, in absence of grazing, the growth rate (μ). It requires counts of live and dead cells suspended in the euphotic part of the water column and accumulated in sedimentation traps. The application of the model is demonstrated for the three dominant summe diatom species in Lake Constance. Asterionella formosa Hass, Fragilaria crotonensis Kitton and Stephanodiscus binderanus Krieger. Only during the first two weeks of the summer bloom of diatoms the loss rates were unimportant in comparison to the growth rates. Thereafter diatom population dynamics was strongly influenced by sedimentation and mortality, which sometimes led to a decrease in population density even when cell division continued at high rates. There were two periods of extraordinarily high death rates, which were associated in the case of A. formosa with silicon depletion and in the case of F crotensis with fungal parasitism.

Description: Broadband receiver functions developed from teleseismic P waveforms recorded on the midperiod passband of Regional Seismic Test Network station RSCP are inverted for vertical velocity structure beneath the Cumberland Plateau, Tennessee. The detailed broadband receiver functions are obtained by stacking source‐equalized horizontal components of teleseismic P waveforms. The resulting receiver functions are most sensitive to the shear velocity structure near the station. A time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin, flat‐lying, homogeneous layers. Lateral changes in structure are identified by examining azimuthal variations in the vertical structure. The results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the East Continent Gravity High located northeast of RSCP. The results from events arriving from the northeast show a high‐velocity midcrustal layer not present in results from the southeast azimuth. This velocity structure can be shown to support the idea that this feature is part of a Keweenawan rift system. Another interesting feature of the derived velocity models is the indication that the crust‐mantle boundary beneath the Cumberland Plateau is a thick, probably laminated transition zone between the depths of 40 and 55 km, a result consistent with interpretations of early refraction work in the area.

Description: First culture results are presented from four major experiments (lasting up to 478 days) on the commercially important squid species, Loligo forbesi Steenstrup, Details are provided on eggs, hatching, feeding, growth, survival, behaviour and sexual maturation. Best survival during the critical first 75 days was 15%. The hatchlings (up to 4.9mm mantle length, ML) are the largest among the genus Loligo, and the largest squid grown was a male 155mm ML and 124g. First schooling was observed only 40–50 days post-hatching. Spawning was not achieved although males reached maturity, females had maturing ova and mating was observed. The largest giant axon measured was 425μm in diameter (from a female 130mm ML), a size suitable for most biomedical applications. Laboratory data suggest a 2-year life cycle compared to fishery data which suggest a 1-year cycle.

Description: We have determined the centroid depths and source mechanisms of 12 large earthquakes on transform faults of the northern Mid-Atlantic Ridge from an inversion of long-period body waveforms. The earthquakes occurred on the Gibbs, Oceanographer, Hayes, Kane, 15°20′, and Vema transforms. We have also estimated the depth extent of faulting during each earthquake from the centroid depth and the fault width. For five of the transforms, earthquake centroid depths lie in the range 7–10 km beneath the seafloor, and the maximum depth of seismic faulting is 14–20 km. On the basis of a comparison with a simple thermal model for transform faults, this maximum depth of seismic behavior corresponds to a nominal temperature of 900° ± 100°C. In contrast, the nominal temperature limiting the maximum depth of faulting during oceanic intraplate earthquakes with strike-slip mechanisms is 700° ± 100°C. The difference in these limiting temperatures may be attributed to the different strain rates characterizing intraplate and transform fault environments. Three large earthquakes on the 15°20′ transform have shallower centroid depths of 4–5 km and a maximum depth of seismic faulting of 10 km, corresponding to a limiting temperature of 600°C. The shallower extent of seismic behavior along the 15°20′ transform may be related to a recent episode of extension across the transform associated with the northward migration of the triple junction among North American, South American, and African plates to its present position near the transform. The source mechanisms for all events in this study display the strike-slip motion expected for transform fault earthquakes; slip vector azimuths agree to within 2°–3° of the local strike of the zone of active faulting. The only anomalies in mechanism were for two earthquakes near the western end of the Vema transform which occurred on significantly nonvertical fault planes. Secondary faulting, occurring either precursory to or near the end of the main episode of strike-slip rupture, was observed for five of the 12 earthquakes. For three events the secondary faulting was characterized by reverse motion on fault planes striking oblique to the trend of the transform. In all three cases the site of secondary reverse faulting is near a compressional jog in the current trace of the active transform fault zone. We find no evidence to support the conclusions of Engeln, Wiens, and Stein that oceanic transform faults in general are either hotter than expected from simple thermal models or weaker than normal oceanic lithosphere.

Description: Maturing females of the octopod Japetella diaphana (Hoyle) develop a luminous oral ring. Studies of specimens of different size show that this structure develops from a muscular ring which undergoes great cellular proliferation, associated with gradual degeneration of the original muscle. The light‐producing cells (photocytes) have a relatively uniform cytoplasm whose most characteristic components are small mitochondria, granular aggregates and microtubular or microfibrillar bundles. It is concluded that the original muscle tissue is not transformed directly into luminous tissue. Possible uses of the luminescence are discussed, based on the postures adopted by live specimens in shipboard aquaria.

Description: Interrelationships between the morphological and physiological properties of selected cyanobacterial species distinguished in the laboratory are used to simulate their population dynamics against realistic scales of environmental variability. Differences in performances are shown to correlate well with the ambient conditions found in the various types of lakes in which cyanobacteria are typically distributed.

Description: High-resolution seismic reflection and Sea Beam bathymetric data provide insights into the processes of sediment offscraping and accretion in the Middle America Trench off southern Mexico. Thick terrigenous sediments that are transported down Ometepec Canyon and accumulate along the trench floor are scraped off the oceanic plate and accreted in thrust packets to the lower trench slope. The packets offscraped represent most of the trench strata. Underlying hemipelagic deposits that accumulate on the seafloor seaward of the trench are subducted landward of the toe of the slope. Horizontal displacement on the thrust is less than 1 km. Leading edge folds are the surface expressions of the thrusts and strike subparallel to the base of the trench slope. The folds are continuous for as much as 10 km and have amplitudes as high as 200 m and wavelengths of 0.5 to 2 km. Folds are best developed along sections of the trench with interbedded silty turbidite and mud deposits. Fold are absent where thick coarse-grained fan deposits occur. Thickening of the thrust packets occurs by large-scale thrust duplication, by layer-parallel shortening, and by deposition of material that slumps off the leading edge of older upslope thrust blocks.

Description: Three arrays of ocean bottom seismographs have been deployed to study the seismicity at the northern end of the Juan de Fuca ridge system off western Canada. Nearly 100 events were located with estimated accuracies generally better than ±10 km, all lying on or near the en echalon ridge-transform fault plate boundaries as defined in this area by the magnetic anomalies, the seafloor morphology and by other geophysical data. The depths of 12 events were determined to lie between 2 and 6 km below the top of the crust. The seismograms exhibit clear P and S wave arrivals along with phases that involve P to S and sometimes S to P conversion probably at the base of the sediments beneath the instruments. The event magnitudes have been estimated from signal duration using four calibration events that were well recorded by a land station. The magnitude estimates permit the determination of rough magnitude-frequency of occurrence relations over the magnitude range of 1 to 3 that are in surprisingly good agreement with the recurrence relations for the area at larger magnitudes from 75 years of land station data. The mean P wave velocity in the uppermost mantle from the earthquake data recorded by the sea floor arrays is 7.6 km s-1 and the mean Vp/Vs ratio is 1.71 or a Poisson's ratio of 0.24.