ALBERT

Description: Petrographic, mineralogic, and geochemical data are reported for lavas from two of the major shield volcanoes of the Santorini volcanic complex (Skaros and Micro Profitis Ilias), both of which were active prior to the well-known Minoan eruption with associated caldera collapse. Field work and whole-rock chemical analyses indicate four cycles of eruptive activity within the Skaros sequence and three within the Micro Profitis Ilias (M P1) sequence. SiO2 and LIL-element contents decrease from the base to the top of all cycles except for the uppermost cycle of Skaros. Chemical variations within cycles are interpreted to result from eruption from compositionally and thermally zoned magma chambers. Major oxide data and the results of least-squares, mass balance modeling indicate that fractional crystallization played an important role in the development of the observed chemical variations. However, observed systematic variations in groundmass compositions within each cycle, observed irregular variations in total phenocryst content and the results of density calculations require that generation of the chemical zonation did not involve crystal settling but reflects unstable density stratification, probably resulting from sidewall crystallization. Some of the primitive lavas erupted on Santorini preserve phenocryst and xenocryst evidence for a stage of high-pressure fractional crystallization (involving removal of olivine, clinopyroxene, orthopyroxene, and Cr-spinel). Trace element data combined with petrographic data (i.e. the occurrence of abundant phenocrysts with resorption textures) is taken as evidence that magma mixing was also important in the development of cyclic variations. Most basaltic andesites from Skaros appear to be hybrids derived by mixing of basalt and andesite/dacite. Mineralogic data demonstrate that mixing was also important in the development of zonation in the chambers beneath MPI, but trace element data cannot be explained by combined fractionation and mixing alone. Specifically, incompatible, and compatible element abundances are lower than predicted if fractionation and mixing occurred and it is suggested that the anomalous trace element behaviour of especially LIL elements reflects the simultaneous operation of assimilation, for which there is support from isotopic studies. It is concluded that inter- cyclic chemical variations are explicable in terms of fractionation, mixing and assimilation. The LIL element and highly compatible element concentrations in the most primitive lavas erupted in each cycle of Skaros and MPI increase with time, indicating that mixing became more important with time.

Description: The kinetics of methane hydrate decomposition was studied using a semibatch stirred-tank reactor. The decomposition was accomplished by reducing the pressure on a hydrate slurry in water to a value below the three-phase equilibrium pressure at the reactor temperature. The data were obtained at temperatures from 274 to 283 K and pressures from 0.17 to 6.97 MPa. The stirring rates were high enough to eliminate mass-transfer effects. Analysis of the data indicated that the decomposition rate was proportional to the particle surface area and to the difference in the fugacity of methane at the equilibrium pressure and the decomposition pressure. The proportionality constant showed an Arrhenius temperature dependence. An estimate of the hydrate particle diameters in the experiments permitted the development of an intrinsic model for the kinetics of hydrate decomposition.

Description: 1. Effects of noradrenaline and the related compounds adrenaline, dopamine, octopamine, tryamine, clonidine and isoprenaline were studied in isolated heart preparations from the cuttlefish Sepia officinalis L. 2. All analogues produced a positive inotropic affect, with noradrenaline being the most potent substance. The chronotropic effects of the tested compounds differed widely. 3. The action of substances of the phenylethanolamine group were not antagonized by propanolol but were partly antagonized by phentolamine. 4. Serotonin and its analogues also produced cardio-excitation. These effects were blocked by cyproheptadine but not by methysergide. 5. These results indicate the presence of two different receptors in the Sepia myocardium: one type reacting with noradrenaline most effectively and a second type being stimulated by serotonin.

Description: The octopus Eledone cirrhosa (Lamarck 1798), enclosed in a small chamber of flowing sea water, was tested for responses to water-borne chemicals. Incidence of body movements and change in ventilation rate were recorded by a non-invasive technique- At concentrations no more than 1x10 -4M at the animal, the octopuses responded to betaine, proline, alanine, lactic acid, and serine (order of decreasing sensitivity)- Glutamic acid and trimethylamine oxide were considerably less stimulatory, arginine and taurine were hardly more effective than sea-water controls.

Description: Pore fluids extracted from near-surface sediments of the deformation front along the Oregon subduction zone have, in general, the dissolved nutrient pattern characteristic of bacterial sulfate reduction. However, in certain locations there are peculiar ammonium distributions and anomalously 13C-depleted dissolved ΣCO2. These carbon isotope and nutrient patterns are attributed to the concurrent microbially-mediated oxidation of sedimentary organic matter (POC) and methane (CH4) originating from depth. In contrast to the oxidation of sedimentary organic matter in the sulfate zone, utilization of methane as the carbon source by sulfate-reducing bacteria would generate only half as much total carbon dioxide for each mole of sulfate consumed and would not generate any dissolved ammonium. The isotopically light ΣCO2 released from methane oxidation depletes the total metabolic carbon dioxide pool. Therefore, NH4+, ΣCO2 and δ13C of interstitial carbon dioxide in these pore fluids distintcly reflect the combined contributions of each of the two carbon substrates undergoing mineralization; i.e. methane and sedimentary organic matter. By appropriately partitioning the nutrient and substrate relationships, we calculate that in the area of the marginal ridge of the Oregon subduction zone as much as 30% of the ΣCO2 in pore fluids may result from methane oxidation. The calculation also predicts that the carbon isotope signature of the carbon dioxide derived from methane is between −35‰ and −63‰ PDB. Such an isotopically light gas generated from within the accretionary complex could be the residue of a biogenic methane pool. Fluid advection is required to carry such methane from depth to the present near-surface sediments. This mechanism is consistent with large-scale, tectonically-induced fluid transport envisioned for accreted sediments of the world's convergent plate boundaries.

Description: The potential vorticity profile in the seasonal pycnocline can be predicted from the surface buoyancy and momentum fluxes by means of the Lagrangian correlation of seasonally varying mixed-layer depth and density. Water flows geostrophically from the seasonal pycnocline into the permanent pycnocline, through the sloping surface of depth D defined by the annual maximum depth of the mixed layer. Potential vorticity flows into the permanent pycnocline where U(D)· ∇D ≤W(D) and vice versa. A theory is given for the regional variation of D, and methods of determining D from hydrographic data are reviewed. This physical understanding of potential vorticity sources and sinks makes it possible to reformulate ventilated thermocline models in terms of flux rather than density boundary conditions, and guides the design of coupled models of ocean—atmosphere circulation. It leads to formulae for water-mass formation and the nutrient balance in the seasonal boundary layer.

Description: Of about 20,000 modern fish species, only about 200 are found south of the Antarctic Convergence. The ichthyofauna is dominated by small species up to 40 cm long. The majority are bottom dwelling forms which belong mostly to the suborder Notothenioidei. Antarctic pelagic fishes are descendants from several faunal groups of different origins: bathypelagic and mesopelagic species, and species originating from demersal families which are secondarily adapted to temporary or permanent midwater life. More than 30 species of squid are so far known from the Southern Ocean. The majority are obviously meso-and bathy-pelagic dwellers. Several adaptations, including stenothermy, freezing resistance, aglomerular kidneys, and neutral buoyancy, enable Antarctic coastal fish to live successfully in the harsh environment. Growth rates of coastal fish are comparable to those found in Newfoundland cod. Most coastal fish do not spawn until they are 5 year old. Three reproductive strategies occur in coastal fish: autumn/early winter spawners with few, but yolky, eggs of 3–6 mm diameter; late winter/spring spawners with many, but smaller, eggs of 1.5–2 mm diameter; and species which guard their nests. Based on their food spectra, fish species can roughly be divided into three groups: fish and krill feeders, plankton feeders, and benthos feeders. Krill consumption by coastal fish around South Georgia and in West Antarctic waters was probably in the order of 5–6 × 106 tonnes before the onset of exploitation. Overall euphausiid consumption may have been about 20 × 106 tonnes. Fish, particularly mesopelagic fish, appear to be more important krill predators than squid. The role of squid as krill predators may have been overestimated in the past. Squid seem to be more important as a food resource for top level predators, particularly sperm whales and birds, than fish appear to be. All estimates of food consumption—krill as well as fish—are still subject to many uncertainties, and so it can be expected that increasing knowledge in the future may alter the given figures quite substantially. Exploitation of Antarctic finfish started at the end of the 1960s. The main fishing grounds are South Georgia and Kerguelen Islands. So far about 2.3 × 106 tonnes have been harvested from the Southern Ocean and the stocks particularly around South Georgia are heavily depleted. Conservation measures adopted by the Commission for the Conservation of Antarctic Marine Living Resources in 1984 and 1985 are probably not sufficient to support the recovery of the stocks.

Description: Osmotic adaption by halophilic and halotolerant bacteria is generally achieved by the accumulation or synthesis of several organic solutes. Accumulation by uptake from the medium is preferred over biosynthesis. The chemical nature of the major solute is important in determining the degree of osmotolerance of the organism. Glycine betaine accumulation confers a greater degree of osmotolerance than proline, which in turn confers more osmotolerance than glutamate accumulation. The occurrence and uptake of these solutes in a variety of eubacteria is reviewed.

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.