ALBERT

Beschreibung: Fucus virsoides and Cystoseira barbata are important sources of sulfated polysaccharide fucoidan which shows a wide range of biological activities. These activities are significantly dependent on chemical composition which is influenced by species, anatomical part of the seaweed, growing location and conditions, extraction procedures and analytical methods. The objective of this study was to evaluate influence of various pre-treatment solvents and conventional extraction parameters (solvent, temperature and time) on polysaccharide yield and chemical composition (total sugar, fucose, sulfate group and uronic acid content) of the fucoidan from F. virsoides and C. barbata. Combination of acetone and ethanol was chosen for pre-treatment since it removed the most interfering compounds and resulted with the highest polysaccharide yield. Applying acid (0.1 M HCl and 0.1 M H2SO4) instead of water for polysaccharide extraction improved yield and resulted with fucoidan with higher sulfate group content, lower uronic acid content but lower fucose content. Extraction at higher temperatures and longer time resulted with higher polysaccharide yield, uronic acid and total sugars content. However, they had the opposite effect on fucose and sulfate group content between F. virsoides and C. barbata.

Beschreibung: Highlights: • Rheological evolution of the rock is influenced by its original and evolving structure. • Strain localizes at boundary between domains of different assemblages (qtz-, fsp-rich). • Strain localizes in original and recrystallized/precipitated finer-grained phases. • Formation of interconnected meso- and microshear zones deformed by diffusion creep. • The rheology of studied example is controlled by Newtonian flow. Abstract: Deformation microstructures of a quartzo-feldspathic pegmatite deformed at mid-crustal levels allow the study of the dynamics of strain localization in polymineralic rocks. Strain localization results from (i) difference in grain sizes between phases, both original and obtained during fluid present reactions and (ii) initial compositional banding. Due to original difference in grain size stress concentrates in the initially finer-grained phases resulting in their intense grain size reduction via subgrain rotation recrystallization (SGR). When the grain size is sufficiently reduced through either deformation or interphase coupled dissolution–precipitation replacement of the coarse grained feldspar, aggregates start to deform by dominantly diffusion accommodated grain boundary sliding (GBS). Phase mixing inhibits grain growth and sustains a grain size allowing GBS. Consequently, discontinuous microscale shear zones form locally within initially coarse grained areas. At the same time difference in strain rate between feldspar-rich and quartz-rich domains needs to be accommodated at domain boundaries. This results in the formation of continuous mesoscale shear zones deformed by GBS. Once these are formed, deformation in the coarse grained parts is arrested and strain is mainly accommodated in the mesoscale shear zones resulting in “superplastic” behaviour consistent with diffusion creep.

Beschreibung: The continental slope of the northern Gulf of Mexico seaward of the Mississippi Delta is characterized by very rapid Quaternary sedimentation. Thick sequences of underconsolidated muds and mudstones are present, which are severely overpressured. In the Ursa Basin, Site U1322 of the Integrated Ocean Drilling Program (IODP) provided an excellent coring record of interleaved fine-grained turbidites and hemipelagic sediments, in part severely affected by submarine slumping and sliding after deposition. Cores were continuously sampled and analyzed for anisotropy of magnetic susceptibility (AMS), to elucidate the effects of different transport mechanisms and degree of settling and consolidation on magnetic fabric properties. Generally AMS ellipticity increases with depth irrespective of transport mode, due to loss of porosity. Samples from slumped mass transport deposits (MTD), however, have higher AMS if compared to immediately overlying non-slumped material. MTD samples dominantly show triaxial magnetic fabrics whereas those found in non-slumped sediments are much more oblate. Long axes of the fabric ellipsoid reflect the direction of eastward to southward suspension transport in samples not overprinted by sliding or slumping. Short ellipsoid axes in non-slumped material are vertical, and thus parallel to the axis of maximum uniaxial shortening. In the MTD samples, many short ellipsoid axes are inclined, reflecting an overprint of the uniaxial shortening by bed-parallel shearing induced by the slumping. Shear and MTD transport direction deduced from the fabrics is top-to-SE, downslope along the morphological axis of Ursa Basin. Generally we show that magnetic fabrics of muds and mudstones are sensitive recorders of sedimentary and tectonic processes, and can be used to reconstruct essential parts of basin history.

Beschreibung: Highlights: • Abyssal AUV-based microstructure measurements over rough topography. • Indications for hydraulic control downstream of a sill in a Mid-Atlantic Ridge valley. • Asymmetric distribution of dissipation rate and elevated density variability. Abstract: Diapycnal mixing in the deep ocean is known to be much stronger in the vicinity of rough topography of mid-ocean ridges than above abyssal plains. In this study a horizontally profiling microstructure probe attached to an autonomous underwater vehicle (AUV) is used to infer the spatial distribution of the dissipation rate of turbulent kinetic energy (ε ) in the central valley of the Mid-Atlantic Ridge. To the authors’ knowledge, this is the first successful realization of a horizontal, deep-ocean microstructure survey. More than 22 h of horizontal, near-bottom microstructure data from the Lucky Strike segment (37 °N) are presented. The study focuses on a channel with unidirectional sill overflow. Density was found to decrease along the channel following the mean northward flow of 3 to 8 cm/s. The magnitude of the rate of turbulent kinetic energy dissipation was distributed asymmetrically relative to the position of the sill. Elevated dissipation rates were present in a segment 1-4 km downstream (north) of the sill with peak values of 1⋅10−71⋅10−7 W/kg. Large flow speeds and elevated density finestructure were observed within this segment. Lowered hydrographic measurements indicated unstable stratification in the same region. The data indicate that hydraulic control is established at least temporarily. Inside the channel at wavelengths between 1 m and 250 m the slopes of AUV-inferred horizontal temperature gradient spectra were found to be consistent with turbulence in the inertial-convective subrange. Integrated temperature gradient variance in this wavelength interval is consistent with an ε2/3 dependence. The results illustrate that deep-reaching AUVs are a useful tool to study deep ocean turbulence over complex terrain where free-falling and lowered turbulence measurements are inefficient and time-consuming.

Beschreibung: The Sibao Orogen in South China is one of the poorest known Grenville-aged orogenic belts through which the Neoproterozoic supercontinent Rodinia assembled. We report here the first UV laser spot 40Ar/39Ar mica and SHRIMP U–Pb zircon ages from a rare Grenville-aged metamorphic complex, the Tianli Schists, in the eastern Sibao Orogen. Our U–Pb zircon provenance ages indicate that the protolith of the Tianli Schists was a clastic sedimentary succession most likely derived from the Yangtze Block. The depositional age of the protolith is younger than 1530 Ma, as constrained by the youngest detrital zircon grains, but is older than 1040 Ma as constrained by the oldest 40Ar/39Ar muscovite ages. The Yangtze Block provenance for the Tianli Schists suggests that the Sibaoan ophiolitic complexes in northeastern Jiangxi, the ca. 970 Ma Xiwan adakitic granite intrusions, and the ca. 900 Ma(?) Xiwan blueschists, all to the northwest of the study region, were likely formed during the closure of a back-arc basin along the margin of the Yangtze Block. Our in situ UV laser 40Ar/39Ar results from S1 and S2 muscovites suggest that the Tianli Schists underwent metamorphism and deformation at 1042 ± 7 Ma to 1015 ± 4 Ma, the oldest known metamorphic event in the eastern Sibao Orogen. Muscovite/biotite cooling ages of ca. 968 ± 4 and 942 ± 8 Ma are recorded by deformed and recrystallised muscovite and biotite, respectively, indicating tectonic reactivation before 900 Ma, during the later stages of the Sibao Orogeny. Together with previous results from the western Sibao Orogen, our work suggests that the closure of the ocean between the Yangtze and Cathaysia Blocks during the assembly of Rodinia was diachronous: ≥1000 Ma at the western Sibao Orogen and ca. 900 Ma at the eastern Sibao Orogen.

Beschreibung: Determining the movement of marine animals is logistically difficult and is currently primarily based on VHF and satellite-tracking telemetry, GPS, acoustic telemetry, and geolocation, all of which have substantial limitations in accurately locating the fine-scale movements of these animals. A recent development—that of dead-reckoning—is being increasingly used to examine the fine-scale movement of animals underwater. The advantages and drawbacks of this approach are quite different to those incurred by the other methods. This paper considers the advances that deadreckoning can bring to the study of the often cryptic movement and behaviour of marine animals at sea. Methods used in determining position via dead-reckoning are presented and consideration is given to results derived from the use of deadreckoning on cetaceans, pinnipeds, penguins and sea turtles; these are complemented by data on cormorants and albatrosses acquired using GPS systems. Suggestions are made as to how movement data derived from these devices can be analysed using indices that allow interpretation over a large variety of temporal and spatial scales.

Beschreibung: This study investigates the controls on organic carbon and molybdenum (Mo) accumulation in sediments deposited within the Western Interior Seaway across the Cenomanian–Turonian boundary interval (94.34–93.04 Ma) including Oceanic Anoxic Event 2 (OAE2). Carbon fluxes to the sediment–water interface (reflecting changes in primary productivity) and bottom-water oxygen concentrations (reflecting preservation effects) are reconstructed from field data and used to constrain a benthic model that simulates the geochemistry of unconsolidated sediments as they were deposited. The results show that increased availability of reactive iron prevents Mo sequestration as thiomolybdate (MoS42 −) during OAE2 (O2 ~ 105 μM) by (i) inhibiting sulfate reduction, and (ii) buffering any free sulfide that becomes available. In the post-OAE2 period (O2 ~ 50 μM), Mo accumulation is favored by a large reduction in iron flux. Importantly, this occurs in parallel with oxygenated bottom waters and high rates of aerobic carbon degradation in the surface sediments, implying that elevated Mo burial fluxes in ancient marine facies do not necessarily reflect euxinic or even anoxic conditions within the water column. Our findings suggest that both an increase in production and preservation lead to enrichment in organic carbon in the Western Interior Seaway. More generally, the results demonstrate that a careful consideration of the coupling between iron, carbon and oxygen cycles during the early stages of diagenesis is critical for interpreting geochemical proxies in modern and ancient settings.

Beschreibung: Anthropogenic CO2 emissions lead to chronically elevated seawater CO2 partial pressures (hypercapnia). The induced ocean acidification will very likely be a relevant factor shaping future marine environments. CO2 exposure concomitantly challenges the animal's capacity of acid-base and ionic regulation as well as the ability to maintain energy metabolism and calcification. Under conditions of acute hypercapnia, numerous studies have revealed a broad range of tolerance levels displayed by various marine taxa. Thus, it is well known that, in contrast to many marine invertebrates, most teleost fish are able to fully compensate acid-base disturbances in short-term experiments (hours to several days). in order to determine whether marine fish are able to preserve aerobic scope following long-term incubation to elevated CO2, we exposed two groups of Atlantic Cod for 4 and 12 months to 0.3 and 0.6 kPa P-CO2, respectively. Measurements of standard and active metabolic rates, critical swimming speeds and aerobic scope of long-term incubated cod showed no deviations from control values, indicating that locomotory performance is not compromised by the different levels of chronic hypercapnia. While the maintenance of high activity levels is supported by a 2-fold increased Na+/K+-ATPase protein expression and 2-fold elevated Na+/K+-ATPase activity in the 12 month incubated fish (0.6 kPa P-CO2), no such elevation in Na+/K+-ATPase activity could be observed in the group treated with 0.3 kPa P-CO2. Owing to the relevance of Na+/K+-ATPase as a general indicator for ion regulatory capacity, these results point at an adjustment of enzymatic activity to cope with the CO2 induced acid-base load at 0.6 kPa P-CO2 while under milder hypercapnic conditions the 'standard' Na+/K+-ATPase capacity might still be sufficient to maintain acid-base status. (c) 2009 Elsevier B.V. All rights reserved.

Beschreibung: A numerical model was applied to investigate and quantify the biogeochemical processes fueled by the expulsion of barium and methane-rich fluids in the sediments of a giant cold-seep area in the Derugin Basin (Sea of Okhotsk). Geochemical profiles of dissolved Ba2+, Sr2+, Ca2+, SO42−, HS−, DIC, I− and of calcium carbonate (CaCO3) were fitted numerically to constrain the transport processes and the kinetics of biogeochemical reactions. The model results indicate that the anaerobic oxidation of methane (AOM) is the major process proceeding at a depth-integrated rate of 4.9 μmol cm−2 a−1, followed by calcium carbonate and strontian barite precipitation/dissolution processes having a total depth-integrated rate of 2.1 μmol cm−2 a−1. At the low seepage rate prevailing at our study site (0.14 cm a−1) all of the rising barium is consumed by precipitation of barite in the sedimentary column and no benthic barium flux is produced. Numerical experiments were run to investigate the response of this diagenetic environment to variations of hydrological and biogeochemical conditions. Our results show that relatively low rates of fluid flow (〈∼5 cm a−1) promote the dispersed precipitation of up to 26 wt% of barite and calcium carbonate throughout the uppermost few meters of the sedimentary column. Distinct and persistent events (several hundreds of years long) of more vigorous fluid flow (from 20–110 cm a−1), instead, result in the formation of barite-carbonate crusts near the sediment surface. Competition between barium and methane for sulfate controls the mineralogy of these sediment precipitates such that at low dissolved methane/barium ratios (〈4–11) barite precipitation dominates, while at higher methane/barium ratios sulfate availability is limited by AOM and calcium carbonate prevails. When seepage rates exceed 110 cm a−1, barite precipitation occurs at the seafloor and is so rapid that barite chimneys form in the water column. In the Derugin Basin, spectacular barite constructions up to 20 m high, which cover an area of roughly 22 km2 and contain in excess of 5 million tons of barite, are built through this process. In these conditions, our model calculates a flux of barium to the water column of at least 20 μmol cm−2 a−1. We estimate that a minimum of 0.44 × 106 mol a−1 are added to the bottom waters of the Derugin Basin by cold seep processes, likely affecting the barium cycle in the Sea of Okhotsk.

Beschreibung: The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEPmicro) and colorimetric (TEPcolor) methods, showed abundant (6.1×106–4.4×107 L−1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEPmicro and similar vertical profiles of TEPcolor. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L−1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.