Geochemistry and paleontology of sediment core GeoB3359-3

A geochemical and paleontological reconstruction of paleoproductivity, upwelling intensity and sea surface temperature (SST) off central Chile at 35°S (GeoB3359-3) reveals marked changes from the Last Glacial Maximum (LGM) through the Early Holocene. Surface-water productivity was determined by the interaction between the atmospheric (the Southern Westerlies) and oceanographic (the Antarctic Circumpolar Current, ACC) systems from the LGM through early Termination I (TI). The northward shift of the climate zones during the LGM brought the ACC, as the main macronutrient source, closer to the GeoB3359-3, SST lowered, and surface water productivity and accumulation rates of biogenic components enhanced. With the poleward return of the Southern Westerlies and the ACC, the subtropical high-pressure system became the dominant atmospheric component southward till 35°S during the late TI and Early Holocene and caused surface water productivity to increase through enhanced upwelling.

Evaluation of the attack rates and level of damages by the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), affecting corn-crops in the northeast of Argentina

The fall armyworm (FAW) is the most important threat to corn crops in Argentina, and there exists very little up-to-date information on its actual pest status because the available literature was published more than 20 years ago. Therefore, field surveys were carried out in the northeast of Argentina, in order to establish the attack rates and injury levels of the pest in relation to the crop phenology. The study was carried out at two localities: Colonia Benítez, an agricultural region, and Tapenagá, a cattle-raising area. At each site two 1-ha plots were sown either with a Bt-corn expressing Cry 1F protein or with an untransformed corn germplasm. Optimal and late sowing was assayed and FAW larval abundance, relative age composition, attack rates and level of damage to corn were recorded. At the moment of the field experiments, Bt-corn was not affected by FAW larvae. However, untransformed germplasms were severely affected by FAW larvae, with an average of attacked plants of 18% or more. In contrast to data obtained 30 years ago, higher values of FAW density were registered. Levels of damage to corn plants were higher after the V4 stage. It was found that the sowing date affected the infestation levels and early seeding avoided high armyworm densities that develop later in the season; in northern Argentina, this was only relevant in agricultural areas.

Effect of compost and slow-release fertilizers addition on soil biochemistry and yield of maize (Zea mays L.) in Oaxaca, Mexico

The effect of Bokashi (B, a fermented compost), slow-release fertilizers (SRFs) and their combined application on mycorrhizal colonization (MC), soil invertase, cellulase, acid (AcP) and alkaline (AlP) phosphatases activities and maize (Zea mays L.) yield was investigated in terrace (TS) and valley (VS) soils in Oaxaca, Mexico. A complete randomized design, seven fertilizer treatments and four replications were used: unamended control (C); conventional fertilization (90-46-00 NPK) (CF); B; SRF1 (Multigro 6®, 21-14-10 NPK); SRF2 (Multigro 3®, 24-05-14 NPK); B+SRF1; B+SRF2. Highest root colonization percentage: CF in VS, and SRF2 in TS. Highest extraradical mycelium length: B, B+SRF1, CF in VS, and B+SRF1 in TS. In both soils, B increased the spore number. Highest AcP activity: B, SRF2 in VS, and B+SRF1, B+SRF2 in TS. Highest AlP activity: B+SRF1, CF in VS, and C in TS. Highest invertase activity: B+SRF1, SRF2, CF in VS, and B in TS. Grain yield only increased with B in VS. The significant interaction soil type × fertilizer treatment for the majority of the biological soil properties analyzed suggests that MC and soil enzyme activity response to fertilization was influenced by soil type. Bokashi, alone or combined with SRFs improves biological soil fertility in maize fields.

Physical properties and minerals of Leg 65 Holes basalts

Velocities and densities of submarine basalts obtained during Leg 65 are distinguished by their relatively high values (about 6.3 km/s and 2.9 g/cm/**3, respectively). This is consistent with their low degree of alteration. The range of velocities covered by these samples correlates well with porosity, and a comparison with in situ velocities from refraction data suggests maximum porosities ih the upper 100 meters of the crust of about 10%.

Chlorophyll a and carbon fluxes, and characteristics of the water column during summer 2008 in the Beaufort Sea

Following the extreme low ice year of 2007, primary production and the sinking export of particulate and gel-like organic material, using short-term particle interceptor traps deployed at 100 m, were measured in the southeastern Beaufort Sea during summer 2008. The combined influence of early ice retreat and coastal upwelling contributed to exceptionally high primary production (500 ± 312 mg C/m**2/day, n = 7), dominated by large cells (>5 µm, 73% ± 15%, n = 7). However, except for one station located north of Cape Bathurst, the sinking export of particulate organic carbon (POC) was relatively low (range: 38-104 mg C/m**2/day, n = 12) compared to other productive Arctic shelves. Estimates indicate that 80% ± 20% of the primary production was cycled through large copepods or the microbial food web. Exopolymeric substances were abundant in the sinking material but did not appear to accelerate POC sinking export. The use of isotopic signatures (d13C, d15N) and carbon/nitrogen ratios to identify sources of the sinking material was successful only at two stations with a strong marine or terrestrial signature, indicating the limitations of this approach in hydrographically and biologically complex Arctic coastal waters such as in the Beaufort Sea. At these two stations influenced by either coastal upwelling or erosion, the composition and magnitude of particulate sinking fluxes were markedly different from other stations visited during the study. These observations underscore the fundamental role of mesoscale circulation patterns and hydrodynamic singularities on the export of particulate organic material on Arctic shelves.

Magnetic mineralogy and geochemistry of ODP Holes 137-504B and 140-504B samples

Leg 140 of the Ocean Drilling Program deepened Hole 504B to a total depth of 2000.4 m below seafloor (mbsf), making it the deepest hole drilled into ocean crust. Site 504, south of the Costa Rica Rift, is considered the most important in-situ reference section for the structure of shallow ocean crust. We present the results of studies of magnetic mineralogy and magnetic properties of Hole 504B upper crustal rocks recovered during Legs 137 and 140. Results from this sample set are consistent with those discussed in Pariso et al. (this volume) from Legs 111, 137, and 140. Coercivity (Hc) ranges from 5.3 to 27.7 mT (mean 12 mT), coercivity of remanence (HCR) ranges from 13.3 to 50.6 mT (mean 26 mT), and the ratio HCR/HC ranges from 1.6 to 3.19 (mean 2.13). Saturation magnetization (JS) ranges from 0.03 to 5.94 * 10**-6 Am**2, (mean 2.52 * 10**-6 Am**2), saturation remanence (JR) ranges from 0.01 to 0.58 * 10**-6 Am2 (mean 0.37 * 10**-6 Am**2), and the ratio JR/JS ranges from 0.08 to 0.29 (mean 0.16), consistent with pseudo-single-domain behavior. Natural remanent magnetization (NRM) intensity ranges from 0.029 to 7.18 A/m (mean 2.95 A/m), whereas RM10 intensity varies only from 0.006 to 4.8 A/m and has a mean of only 1.02 A/m. Anhysteretic remanent magnetization (ARM) intensity ranges from 0.04 to 6.0 A/m, with a mean of 2.46 A/m, and isothermal remanent magnetization (IRM) intensity ranges from 0.5 to 1683 A/m, with a mean of 430.7 A/m. Volume susceptibility ranges from 0.0003 to 0.043 SI (mean 0.011 SI). In all samples examined, high-temperature oxidation of primary titanomagnetite has produced lamellae or pods of magnetite and ilmenite. Hydrothermal alteration has further altered the minerals in some samples to a mixture of magnetite, ilmenite, titanite, and a high-titanium mineral (either rutile or anatase). Electron microprobe analyses show that magnetite lamellae are enriched in the trivalent oxides Cr2O3, Al2O3, and V2O5, whereas divalent oxides (MnO and MgO) are concentrated in ilmenite lamellae.

(Table 1) Frequency of wind direction reportings and duration of wave action in Mittelgrund, Eckernfoerder Bay, Germany

A detailed survey of the Mittelgrund in Eckernförde Bay shows slope breaks at 10-12 m and 15-16 m water depth. They are thought to be mainly the result of marine abrasion. Utilizing records from the Edgerton mud-penetrator, a map of holocene sediment thickness has been drawn. From the pattern of bottom echos 4 types of stratification can be recognized. An interpretation of them is attempted, as they are supposed to serve as models for other transgression contacts.

Geochemistry and mineralogy of Eocene-Oligocene sediments of IODP Hole 302-M0002A

In 2004, Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition, ACEX) to the Lomonosov Ridge drilled the first Central Arctic Ocean sediment record reaching the uppermost Cretaceous (~430 m composite depth). While the Neogene part of the record is characterized by grayish-yellowish siliciclastic material, the Paleogene part is dominated by biosiliceous black shale-type sediments. The lithological transition between Paleogene and Neogene deposits was initially interpreted as a single sedimentological unconformity (hiatus) of ~26 Ma duration, separating Eocene from Miocene strata. More recently, however, continuous sedimentation on Lomonosov Ridge throughout the Cenozoic was proclaimed, questioning the existence of a hiatus. In this context, we studied the elemental and mineralogical sediment composition around the Paleogene-Neogene transition at high resolution to reconstruct variations in the depositional regime (e.g. wave/current activity, detrital provenance, and bottom water redox conditions). Already below the hiatus, mineralogical and geochemical proxies imply drastic changes in sediment provenance and/or weathering intensity in the hinterland, and point to the existence of another, earlier gap in the sediment record. The sediments directly overlying the hiatus (the Zebra interval) are characterized by pronounced and abrupt compositional changes that suggest repeated erosion and re-deposition of material. Regarding redox conditions, euxinic bottom waters prevailed at the Eocene Lomonosov Ridge, and became even more severe directly before the hiatus. With detrital sedimentation rates decreasing, authigenic trace metals were highly enriched in the sediment. This continuous authigenic trace metal enrichment under persistent euxinia implies that the Arctic trace metal pool was renewed continuously by water mass exchange with the world ocean, so the Eocene Arctic Ocean was not fully restricted. Above the hiatus, extreme positive Ce anomalies are clear signs of a periodically well-oxygenated water column, but redox conditions were highly variable during deposition of the Zebra interval. Significant Mn enrichments only occur above the Zebra interval, documenting the Miocene establishment of stable oxic conditions in the Arctic Ocean. In summary, extreme and abrupt changes in geochemistry and mineralogy across the studied sediment section do not suggest continuous sedimentation at the Lomonosov Ridge around the Eocene-Miocene transition, but imply repeated periods of very low sedimentation rates and/or erosion.

Experiment: Growth rates and percentages of normal versus malformed versus incomplete versus incomplete and malformed coccoliths

The coccolithophore Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was cultured in natural seawater with the addition of either the microtubule-inhibitor colchicine, the actin-inhibitor cytochalasin B, or the photosynthesis inhibitor 3-(3,4 dichlorophenyl)-1,1-dimethyl-urea (DCMU). Additionally, E. huxleyi was cultured at different light intensities and temperatures. Growth rate was monitored, and coccolith morphology analyzed. While every treatment affected growth rate, the percentage of malformed coccoliths increased with colchicine, cytochalasin B, and at higher than optimal temperature. These results represent the first experimental evidence for the role of microtubules and actin microfilaments in coccolith morphogenesis.

Geochemical composition and granulometry of ODP Hole 167-1017E sediments

Intensification of North Pacific Intermediate Water during the Younger Dryas and stadials of the last glacial episode has been advocated by Kennett and his colleagues based on studies of ventilation history in Santa Barbara Basin. Because Santa Barbara Basin is a semi-isolated marginal basin, this hypothesis requires testing in sequences on the upper continental margin facing the open-ocean of the Pacific. Ocean Drilling Program Site 1017 is located on the upper slope of southern California off Point Conception close to the entrance of Santa Barbara Basin, an ideal location to test the hypothesis of late Quaternary switching in intermediate waters. We examined chemical and mineral composition, sedimentary structures, and grain size of hemipelagic sediments representing the last 80 k.y. at this site to detect changes in behavior of intermediate waters. We describe distinct compositional and textual variations that appear to reflect changes in grain size in response to flow velocity fluctuations of bottom waters. Qualitative estimates of changes in degree of pyritization indicate better ventilation of bottom water during intervals of stronger bottom-water flow. Comparison between variations in the sediment parameters and the planktonic d18O record indicates intensified bottom-current activity during the Younger Dryas and stadials of marine isotope Stage 3. This result strongly supports the hypothesis of Kennett and his colleagues. Our investigation also suggests strong grain-size control on organic carbon content (and to less extent carbonate carbon content). This, in turn, suggests the possibility that organic carbon content of sediments, which is commonly used as an indicator of surface productivity, can be influenced by bottom currents.

Stable isotopes of foraminifers, mineralogy and ages of sediment core GeoB1523-1

Today the western tropical Atlantic is the most important passage for cross-equatorial transfer of heat in the form of warm surface water flowing from the South into the North Atlantic. Circulation changes north of South America may thus have influenced the global thermohaline circulation system and high northern latitude climate. Here we reconstruct late Quaternary variations of western equatorial Atlantic surface circulation and Amazon lowland climate obtained from a multiproxy sediment record from Ceará Rise. Variations in the illite/smectite ratio suggest drier climatic conditions in the Amazon Basin during glacials relative to interglacials. The 230Thex-normalized fluxes and the 13C/12C record of organic carbon indicate that sea level fluctuations, shelf topography, and changes of the surface circulation pattern controlled variations and amplitude of terrigenous sediment supply to the Ceará Rise. We attribute variations in thermocline depth, reconstructed from vertical planktic foraminiferal oxygen isotope gradients and abundances of the phytoplankton species Florisphaera profunda, to changes in southeast trade wind intensity. Strong trade winds during ice volume maxima are associated with a deep western tropical Atlantic thermocline, strengthening of the North Brazil Current retroflection, and more vigorous eastward flow of surface waters.