ALBERT

Description: The two quotes above are representative of the controversy concerning the age of Nautilus, the last externally shelled cephalopod. If we accept the first age estimate, we would have to include Nautilus as a living fossil, the end member of a clade that has survived for a long time and undergone little morphologic change.

Description: 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.

Description: Natural phytoplankton from Lake Constance was exposed to competition experiments in continuous culture at 6 different molar rations of PratioSi as potentially limiting nutrients. As predicted by theory there was competitive exclusion of all species but one at single nutrient limitation, and coexistence of two species in steady state when P was limiting for one and Si for the other species. In one case coexistence of three species occurred. Equilibrium species composition, which stabilized after 3 to 6 weeks of cultivation, was independent of the species composition of the inoculum and only controlled by the nutrient regime. Comparability of experimental results and field observations is discussed.

Description: Ceratium hirundinella cells in Lake Constance divided during the second half of the night. Growth rates are calculated from the fraction of cells undergoing cell division. Potential growth rates are compared with observed changes in population density. The discrepancy between both is discussed as a possible function of fungal parasitism.

Description: Seasonal variations in bacterial populations (total number, biomass, biomass-spectrum, number of dividing cells) as well as in concentrations and decomposition rates of particulate organic material were followed in a sandy mud sediment of the Western Kiel Bight (Baltic Sea; FRG). The strong seasonal variations observed could be traced back to the effect of certain ecological situations and events in the sediment from which the input of the phytoplankton blooms in autumn and spring, respectively, the accumulation of organic material during winter, and the spring development of the benthic fauna turned out to be the most important. Bacterial carbon net production following the breakdown of the phytoplankton blooms ranged between 9 μg (autumn) and 16 μg (spring) per g of dry weight sediment per day. The consequences of shifts in the size composition of the bacterial populations as well as the importance of the measurement of enzymatic decomposition rates of particulate organic material in sediments are demonstrated and discussed in relation to the events mentioned above

Description: Mesozoic deep water sedimentary rocks uplifted and exposed in basement complexes on the islands of Fuerteventura (Canary Islands) and Maio (Cape Verdes) help document the early Atlantic ocean and the volcanic history of these islands. On Fuerteventura ca. 1.5 km of terrigenous quartzose clastics, black shales, and subordinate redeposited limestones of early Cretaceous age are overlain first by Albian-Cenomanian marls and clastics, showing extensive soft sediment slumping, then after a hiatus by Senonian nannofossil chalks with chert nodules. After a further break alkalic submarine volcanic rocks, largely hyaloclastics, were erupted, then overlain by redeposited bioclastic limestones and volcaniclastics of Oligocene age. A dyke complex was intruded, then the basement complex was uplifted, peneplaned, and overlain by Neogene plateau lavas. On Maio the basement complex comprises mafic pillow lavas of midocean ridge character overlain by up to 4 00 m of deep water sedimentary rocks. Upper Jurassic to lower Cretaceous radiolarianrich pelagic limestones are succeeded by middle and upper Cretaceous sequences of mudstones, redeposited limestones, chalks, tuffs, and volcaniclastics which document the onset of volcanism. During a sedimentary hiatus plutonic rocks were intruded, uplifted, then eroded to produce conglomerates of late Miocene age. These are overlain by several series of gently dipping subaerial alkaline basalt flows. Comparisons with D.S.D.P. sites, oil wells and on land geology confirm that the lower Cretaceous Fuerteventura quartzose clastics formed part of a deep water fan complex located close to the Atlantic continent-ocean boundary. Comparable flysch is known in the Moroccan basin, in the Betic-Maghrebide system and the feeding Tan-Tan-Cape Bojador delta system. The inferred disconformity between Cenomanian and Senonian is part of a widespread depositional hiatus associated with slumping on the adjacent west African continental margin. On Maio pelagic limestones comparable with the Tethyan Maiolica facies were deposited on a subsiding? middle/late Jurassic ocean ridge before uplift related to onset of volcanism probably in the late Cretaceous.

Description: 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.

Description: Sponges are diploblastic acoelomate Metazoa. They are sedentary, filter-feeding animals which utilize a layer of flagellated cells to pump a unidirectional water current through themselves. They are found in freshwater, but more abundantly in marine habitats. Sponges have been persistent throughout geological time from the Precambrian to the Recent, with special success during the Paleozoic. They are apparently the most primitive multicellular animals on a phylogenetic scale ranked by morphological complexity, although the levels of physiological and biochemical complexity found in sponges easily measure up to the degree of sophistication found in so-called higher animals. The Porifera (sponges) and Coelenterata are related as two phyla representing distinct stocks, but stemming from a presumed common although presently unknown origin (Hyman, 1940).

Description: Die Probleme, die bei Speciesuntersuchungen von Spurenelementen mit Hilfe der Differentialpuls Anodic Stripping Voltammetrie auftreten, werden zu-sammenfassend dargestellt. Neben den bei der eigentlichen Bestimmung auftretenden Problemen, werden auch solche erwähnt, die mit der Probennahme sowie der Lagerung und Vorbehandlung der Proben in Zusammenhang stehen.

Description: A program of geophysical research was carried out as a preliminary stage of study of the Santorini volcanic group. This area is of remarkable geothermal and volcanological interest, and the definition of a volcanological structural model is the starting point for an understanding of the local geodynamic processes. Gravity, magnetic and geoelectrical data proved that: (i) the core of the volcanic edifice consists of a sedimentary-metamorphic basement; (ii) the basement is tectonically disturbed and a linear tectonic system produces a graben-type structure in the middle part of the area.