C1-C8 hydrocarbons in DSDP Leg 64 Holes sediments

Sediments from the Baja California Continental Margin Transect - Sites 474 and 476 - showed small amounts of C2-C8 hydrocarbons and functionalized compounds (alkenes) typical of organic-rich, Recent, cold (<30°C) marine sediments. In contrast, some samples from Sites 477, 478, 479, and Hole 481A in the Guaymas Basin, an active spreading center, showed the characteristics of thermally generated hydrocarbons. These include an increase (sometimes exponential) in amount and diversity of C2-C8 hydrocarbons and a decrease in alkenes in more thermally mature sediments. The results indicate that the injection of basaltic sills has minimal effect on C2-C8 hydrocarbon generation except in the immediate vicinity of the sill. The absence of light hydrocarbons close to the hottest sills suggests that the compounds distill away as they are formed in these areas of very active hydrothermal circulation. A sample of young sediment exposed to very high temperatures (>300°C) from deeper thermal sources at the hottest site, 477, showed a very limited hydrocarbon distribution, including primarily ethane, benzene, and toluene, together with smaller amounts of propane and butane.

Age determination and age tie-points of sediment cores from the Timor Sea

The evolution of the Australian monsoon in relation to high-latitude temperature fluctuations over the last termination remains highly enigmatic. Here we integrate high-resolution riverine runoff and dust proxy data from X-ray fluorescence scanner measurements in four well-dated sediment cores, forming a NE-SW transect across the Timor Sea. Our records reveal that the development of the Australian monsoon closely followed the deglacial warming history of Antarctica. A minimum in riverine runoff documents dry conditions throughout the region during the Antarctic Cold Reversal (15-12.9 ka). Massive intensification of the monsoon coincided with Southern Hemisphere warming and intensified greenhouse forcing over Australia during the atmospheric CO2 rise at 12.9-10 ka. We relate the earlier onset of the monsoon in the Timor Strait (13.4 ka) to regional changes in landmass exposure during deglacial sea-level rise. A return to dryer conditions occurred between 8.1 and 7.3 ka following the early Holocene runoff maximum.

Methane concentrations in the central North Sea

We investigated dissolved methane distributions along a 6 km transect crossing active seep sites at 40 m water depth in the central North Sea. These investigations were done under conditions of thermal stratification in summer (July 2013) and homogenous water column in winter (January 2014). Dissolved methane accumulated below the seasonal thermocline in summer with a median concentration of 390 nM, whereas during winter, methane concentrations were typically much lower (median concentration of 22 nM). High-resolution methane analysis using an underwater mass-spectrometer confirmed our summer results and was used to document prevailing stratification over the tidal cycle. We contrast estimates of methane oxidation rates (from 0.1 to 4.0 nM day**-1) using the traditional approach scaled to methane concentrations with microbial turnover time values and suggest that the scaling to concentration may obscure the ecosystem microbial activity when comparing systems with different methane concentrations. Our measured and averaged rate constants (k') were on the order of 0.01 day**-1, equivalent to a turnover time of 100 days, even when summer stratification led to enhanced methane concentrations in the bottom water. Consistent with these observations, we could not detect known methanotrophs and pmoA genes in water samples collected during both seasons. Estimated methane fluxes indicate that horizontal transport is the dominant process dispersing the methane plume. During periods of high wind speed (winter), more methane is lost to the atmosphere than oxidized in the water. Microbial oxidation seems of minor importance throughout the year.

Middle Eocene to Pleistocene calcareous nannofossils of ODP Leg 113 holes

Long sequences of Upper Cretaceous through Quaternary sediments rich in calcareous and siliceous microfossils were recovered at Ocean Drilling Program Sites 689 and 690 on Maud Rise off East Antarctica. These sites have become the southernmost anchor in the Atlantic Basin for bio-, magneto-, chemostratigraphic, and paleobiogeographic studies. ODP Sites 692 and 693 on the Weddell Sea margin of East Antarctica and Site 696 on the South Orkney microcontinent of West Antarctica yielded calcareous nannofossils within some stratigraphic intervals. Sites 691, 692, 694, 695, and 697 did not recover Cenozoic calcareous nannofossils. Calcareous nannofossil biostratigraphy suggests a major hiatus across the Paleogene/Neogene boundary at Sites 689 and 690, and two additional hiatuses in the middle Eocene-lower Oligocene section at Site 690. Correlation with magnetostratigraphy reveals: the last occurrence (LO) of Reticulofenestra umbilica at Maud Rise is over 1 m.y. younger than that at the middle-latitude sites; the LO of Isthmolithus recurvus is synchronous in the middle-latitude and high-latitude areas (about 34.8 Ma); Reticulofenestra oamaruensis ranges from 38.0 to 36.0 Ma at Maud Rise; Reticulofenestra reticulata has a shorter range at Maud Rise (42.1 to 38.9 Ma) than at the middle-latitude DSDP Site 516; the range of Chiasmolithus oamaruensis is diachronous over different latitudes; and the LO of Chiasmolithus solitus is a good datum at 41.3 Ma from 30°S to 65°S in the South Atlantic Ocean. Comparison of calcareous nannofossil abundances in a latitudinal transect shows: Reticulofenestra bisecta is a temperate-water species and its LO, which crosses below that of Chiasmolithus altus at Maud Rise, is not applicable for the Paleogene/Neogene boundary in high southern latitude areas; Clausicoccus fenestratus is rare or absent at Maud Rise and can not be used as a marker; Coccolithus formosus is a warm-water species which disappeared earlier toward higher latitudes. Calcareous nannofossil assemblages indicate that by at least the middle Eocene, surface water temperatures became considerably lower in the high southern latitudes than in the middle-latitude areas and that there have been more extreme cold events in the high latitudes during the Neogene. Bicolumnus ovatus n. gen., n. sp. is proposed in this paper.

Oxygen and carbon isotope composition of Globoquadrina venezuelana and Oridorsalis umbonatus at DSDP Leg 85 Holes

Oxygen and carbon isotope stratigraphies are given for the planktonic foraminifer Globoquadrina venezuelana (a deep-dwelling species) at three DSDP sites located along a north-south transect at approximately 133°W across the Pacific equatorial high-productivity zone. The records obtained at Sites 573 and 574 encompass the lower Miocene. At Site 575 the record includes the middle Miocene and extends into the lowermost lower Miocene. The time resolution of the planktonic foraminifer isotope record varies from 50,000 to 500,000 yr. The benthic foraminifer Oridorsalis umbonatus was analyzed for isotope composition at a few levels of Site 575. Isotope stratigraphies for all three sites are compared with carbonate, foraminifer preservation, and grain size records. We identified a number of chemostratigraphic signals that appear to be synchronous with previously recognized signals in the western equatorial Pacific and the tropical Indian Ocean, and thus provide useful tools for chronostratigraphic correlations. The sedimentary sequence at Site 573 is incomplete and condensed, whereas the sequences from Sites 574 and 575 together provide a complete lower Miocene record. The expanded nature of this record, which was recovered with minimum disturbance and provides excellent calcareous and siliceous biostratigraphic control, offers a unique opportunity to determine the precise timing of early Miocene events. Paleomagnetic data from the hydraulic piston cores at Site 575 for the first time allow late early Miocene paleoceanographic events to be tied directly to the paleomagnetic time scale. The multiple-signal stratigraphies provide clues for paleoceanographic reconstruction during the period of preconditioning before the major middle Miocene cooling. In the lowermost lower Miocene there is a pronounced shift toward greater d13C values (by -1%) within magnetic Chron 16 (between approximately 17.5 and 16.5 Ma). The "Chron 16 Carbon Shift" coincides with the cessation of an early Miocene warming trend visible in the d18O signals. Values of d13C remain high until approximately 15 Ma, then decrease toward initial (early Miocene) values near 13.5 Ma. The broad lower to middle Miocene d13C maximum appears to correlate with the deposition of organic-carbon-rich sediments around the margin of the northern Pacific in the Monterey Formation of California and its lateral equivalents. The sediments rimming the Pacific were probably deposited under coastal upwelling conditions that may have resulted from the development of a strong permanent thermocline. Deposition in the upwelling areas occurred partly under anaerobic conditions, which led to the excess extraction of organic carbon from the ocean. The timing of the middle Miocene cooling, which began after the Chron 16 Carbon Shift, suggests that the extraction of organic carbon preconditioned the ocean-atmosphere system for subsequent cooling. A major carbonate dissolution event in the late early Miocene, starting at approximately 18.7 Ma, is associated with the enrichment in 13C. The maximum dissolution is coeval with the Chron 16 Carbon Shift. It corresponds to a prominent acoustic horizon that can be traced throughout the equatorial Pacific.

Macrobenthos from the Novaya Zemlya Trough, Kara Sea

During Cruise 54 of R/V Akademik Mstislav Keldysh macrobenthos of the Novaya Zemlya Trough was studied with use of a Sigsby trawl along a submeridional transect near 75°30'N at depth range from 68 to 362 m. In total 140 species of bottom animals were found. Relative role of taxons was assessed using three parameters: abundance, biomass, and energy flow. Similarity of the parameters was used for comparison of samples. New material greatly contributes to data on composition of fauna and structure of communities of the studied region. It was revealed that small scyphozoid polyps and sipunculoids play an important role in the trough's community. Presence of a community dominated by Ophiocten sericeum (with important role of small bivalves) was revealed for the first time not only at the eastern by also at the western slope of the Novaya Zemlya Trough. The sharpest changes in composition and structure of the bottom community were confined to a zone of transition from the trough floor to the slope. These changes are determined by specificity of the macrorelief (of the floor and slope), composition of ground (soft brown silts abound in rhizopods and dense gray silts with admixture of pebbles), and possibly by hydrodynamic processes near the bottom.

Abundance and sizes of European oak species (Quercus petraea (Matt.) Liebl., Quercus robur L.) in dependence of neighborhood and environmental factors

Quercus robur L. (pedunculate oak) and Quercus petraea (Matt.) Liebl. (sessile oak) are two European oak species of great economic and ecological importance. Even though both oaks have wide ecological amplitudes of suitable growing conditions, forests dominated by oaks often fail to regenerate naturally. The regeneration performance of both oak species is assumed to be subject to a variety of variables that interact with one another in complex ways. The novel approach of this research was to study the effect of many ecological variables on the regeneration performance of both oak species together and identify key variables and interactions for different development stages of the oak regeneration on a large scale in the field. For this purpose, overstory and regeneration inventories were conducted in oak dominated forests throughout southern Germany and paired with data on browsing, soil, and light availability. The study was able to verify the assumption that the occurrence of oak regeneration depends on a set of variables and their interactions. Specifically, combinations of site and stand specific variables such as light availability, soil pH and iron content on the one hand, and basal area and species composition of the overstory on the other hand. Also browsing pressure was related to oak abundance. The results also show that the importance of variables and their combinations differs among the development stages of the regeneration. Light availability becomes more important during later development stages, whereas the number of oaks in the overstory is important during early development stages. We conclude that successful natural oak regeneration is more likely to be achieved on sites with lower fertility and requires constantly controlling overstory density. Initially sufficient mature oaks in the overstory should be ensured. In later stages, overstory density should be reduced continuously to meet the increasing light demand of oak seedlings and saplings.

Seal census raw data during POLARSTERN expedition ANT-XV/3 (PS48)

The density, species composition, and possible change in the status of pack ice seals within the Weddell Sea were investigated during the 1997/1998 summer cruise of the RV "Polarstern" (ANT-XV/3, PS48). Comparisons were made with previous surveys in the Weddell Sea where it was assumed that all seals were counted in a narrow strip on either side oft he ship or aircraft. A total of 15 aerial censuses were flown during the period 23 January - 7 March 1998 in the area bounded by 07°08' and 45°33' West longitude. The censused area in the eastern Weddell Sea was largely devoid of pack ice while a well circumscribed pack ice field remained in the western Weddell Sea. A total of 3,636 (95.4 %) crabeater seals, 21 (0.5 %) Ross seals, 45 (1.2 %) leopard seals and 111 (2.9 %) Weddell seals were observed on the pack ice during a total of 1,356.57 linear nautical miles (244.2 nm) of transect line censused. At a mean density of 21.16 1/nm**2 over an area of 244.2 nm, it is the highest densities on record for crabeater seals, density of up to 411.7 1/nm**2 being found in small areas. The overall high densities of seals (30.18 1/nm**2) recorded for the eastern Weddell Sea (27.46 1/nm**2, 0.27 1/nm**2, and 0.66 1/nm**2 for crabeater, leopard and Weddell seals respectively) is a consequence of the drastically reduced ice cover and the inverse relationship that exists between cover and seal densities. Ross seal densities (0.08 1/nm**2) were the lowest on record fort the area. It is suggested that seals largely remain within the confines of the pack ice despite seasonal and annual changes in its distribution. Indications are that in 1998 the El Niño has manifested itself in the Weddell Sea, markedly influencing the density and distribution of pack ice seals.

(Table 1) Mean sea-ice properties from moored upward looking sonars along the Greenwich meridian

Sea-ice ocean interaction processes are of significant influence on the water mass formation in the Weddell gyre. On the basis of data obtained between 1984 and 2008 from eight repeat hydrographic sections, moored instruments and profiling floats in the Weddell gyre on the Greenwich meridian - almost all of them collected with R.V. Polarstern - we identified variations in the properties of the Winter Water and the sea ice draft. In the Winter Water the salinity was relatively low throughout the 1990s (with a minimum in 1992) and a maximum was observed in 2003. Observations of sea ice draft by moored upward looking sonars are available from 1996 onwards. In the southern part of the transect they display variations on a decadal time scale with a minimum in sea-ice thickness in 1998 and an increase since then. Salinity variations in the Winter Water layer cannot be explained only by variations in sea-ice formation and variable entrainment of underlying Warm Deep Water, but lateral advection of water and sea ice needs to be taken into account as well. Potential sources are melt water from the ice shelves in the western Weddell Sea or transport of water of low salinity entering the Weddell gyre from the east. Accompanying variations of the properties of Warm Deep Water are discussed in detail in a companion paper (Fahrbach et al., 2011, doi:10.1016/j.dsr2.2011.06.007).

Biogenic and terrigeneous components in ODP Leg 108 holes

Five Ocean Drilling Program sites (657-661), which form a north-south transect off the western periphery of the Sahara, were selected to measure the long-term history of Saharan/Sahelian dust flux and fluvial sediment discharge and the fluxes of marine CaCO3 and opal over the last 8 m.y. Sites 658 and 659 served for high-resolution studies, and Sites 657, 660, and 661 for insights into the spatial patterns of dust flux. The nearshore mean flux of opal off Cap Blanc (21 °N) showed an abrupt increase about 3 Ma that appears to reflect the main onset of coastal upwelling fertility and enhanced trade winds. At the same time, the input of river-borne clay strongly decreased, suggesting a dry up of the central Saharan rivers. Later, marked short-lived spikes of clay and opal may indicate ongoing ephemeral pulses of fluvial runoff linked to peak interglacial stages. Given the zonal dust discharge centered near 18 °N at Site 659, the aridification of the south Sahara and Sahel increased in several steps: at 4.6, 4.3, and especially at 4.0, 3.6, and 2.1 Ma, and again, at 0.8 Ma. The late Miocene and earliest Pliocene were humid. Although the central and north Saharan climate appears to be linked to the glaciation history of the Northern Hemisphere, the long-term aridification further south followed a different schedule. The spatial distribution of quartz accumulation suggests that the dust outbreaks linked to the Intertropical Convergence Zone during summer did not shift in latitude back to 4.0 Ma, at least. The short-term variations of dust output over the last 0.5 m.y. followed orbital scale pulses with a strong precessional signal, showing a link of Sahelian humidity changes to the variation of sea-surface temperature and evaporation in the tropical Atlantic.