Revised chronology of Neogene DSDP holes from the World Ocean

After nearly 30 years of growth in geochronologic knowledge, the originally published age models for many older deep sea marine sections have become badly outdated. In this report we present newly revised age models for Neogene sediments from 94 DSDP holes. Biostratigraphic data for planktonic foraminifers, calcareous nannofossils, diatoms and radiolarians, paleomagnetic and other stratigraphic data were compiled from the original Initial Reports volumes of DSDP. The Berggren et al. (1985 doi:10.1130/0016-7606(1985)96<1407:CG>2.0.CO;2) scale was used for the age of magnetic reversals, and a variety of recent papers were used to establish a standard modern set of calibrations for marine microfossil events to the magnetic reversal scale. New age vs depth plots were made for each hole, and for each a new line of correlation was created. All tabulated stratigraphic data, new age models, and age depth plots are given as appendices to the report.

Effects of ocean acidification on the swimming ability, development and biochemical responses of sand smelt larvae

Ocean acidification, recognized as a major threat to marine ecosystems, has developed into one of the fastest growing fields of research in marine sciences. Several studies on fish larval stages point to abnormal behaviours, malformations and increased mortality rates as a result of exposure to increased levels of CO2. However, other studies fail to recognize any consequence, suggesting species-specific sensitivity to increased levels of CO2, highlighting the need of further research. In this study we investigated the effects of exposure to elevated pCO2 on behaviour, development, oxidative stress and energy metabolism of sand smelt larvae, Atherina presbyter. Larvae were caught at Arrábida Marine Park (Portugal) and exposed to different pCO2 levels (control: 600 µatm, pH = 8.03; medium: 1000 µatm, pH = 7.85; high: 1800 µatm, pH = 7.64) up to 15 days, after which critical swimming speed (Ucrit), morphometric traits and biochemical biomarkers were determined. Measured biomarkers were related with: 1) oxidative stress-superoxide dismutase and catalase enzyme activities, levels of lipid peroxidation and DNA damage, and levels of superoxide anion production; 2) energy metabolism - total carbohydrate levels, electron transport system activity, lactate dehydrogenase and isocitrate dehydrogenase enzyme activities. Swimming speed was not affected by treatment, but exposure to increasing levels of pCO2 leads to higher energetic costs and morphometric changes, with larger larvae in high pCO2 treatment and smaller larvae in medium pCO2 treatment. The efficient antioxidant response capacity and increase in energetic metabolism only registered at the medium pCO2 treatment may indicate that at higher pCO2 levels the capacity of larvae to restore their internal balance can be impaired. Our findings illustrate the need of using multiple approaches to explore the consequences of future pCO2 levels on organisms.

Mineralogy, isotopic composition of oxygen, hydrogen and carbon, and oxygen isotopic temperature of deep-sea silica and coexisting carbonates (Table 1)

Water extracted from opal-CT ("porcellanite", "cristobalite"), granular microcrystalline quartz (chert), and pure fibrous quartz (chalcedony) in cherts from the JOIDES Deep Sea Drilling Project is 56? to 87? depleted in deuterium relative to the water in which the silica formed. This large fractionation is similar in magnitude and sign to that observed for hydroxyl in clay minerals and suggests that water extracted from these forms of silica has been derived from hydroxyl groups within the silica. Delta18O-values for opal-CT at sites 61, 64, 70B and 149 vary from 34.3? to 37.2? and show no direct correlation with depth of burial. Granular microcrystaUine quartz in these cores is 0.5 ? depleted in 18O relative to coexisting opal-CT at sediment depths of 100 m and the depletion increases to 2? for sediments buried below 384 m. These relationships suggest that opal-CT forms before significant burial while granular microcrystalline quartz forms during deeper burial at warmer temperatures. The temperature at which opal-CT forms is thus probably approximately equal to the temperature of the overlying bottom water. Isotopic temperatures deduced for opal-CT formation are preliminary and very approximate, but yield Eocene deep-water temperatures of 5-13°C, and 6°C for the upper Cretaceous sample. Pure euhedral quartz crystals lining a cavity in opal-CT at 388 m in core 8-70B-4-CC have a ~delta18O value of +29.8? and probably formed near maximum burial. The isotopic temperature is approximately 32 ° C.

Core scans and lithologic analysis of Subglacial Lake Whillans sediment cores

The hydrologic system beneath the Antarctic Ice Sheet is thought to influence both the dynamics and distribution of fast flowing ice streams, which discharge most of the ice lost by the ice sheet. Despite considerable interest in understanding this subglacial network and its affect on ice flow, in situ observations from the ice sheet bed are exceedingly rare. Here we describe the first sediment cores recovered from an active subglacial lake. The lake, known as Subglacial Lake Whillans, is part of a broader, dynamic hydrologic network beneath the Whillans Ice Stream in West Antarctica. Even though "floods" pass through the lake, the lake floor shows no evidence of erosion or deposition by flowing water. By inference, these floods must have insufficient energy to erode or transport significant volumes of sediment coarser than silt. Consequently, water flow beneath the region is probably incapable of incising continuous channels into the bed and instead follows preexisting subglacial topography and surface slope. Sediment on the lake floor consists of till deposited during intermittent grounding of the ice stream following flood events. The fabrics within the till are weaker than those thought to develop in thick deforming beds suggesting subglacial sediment fluxes across the ice plain are currently low and unlikely to have a large stabilizing effect on the ice stream's grounding zone.

Seawater carbonate chemistry, calcification and shell size of hard clam Mercenaria mercenaria during experiments, 2011

Increasing atmospheric carbon dioxide threatens to decrease pH in the world's oceans. Coastal and estuarine calcifying organisms of significant ecological and economical importance are at risk; however, several biogeochemical processes drive pH in these habitats. In particular, coastal and estuarine sediments are frequently undersaturated with respect to calcium carbonate due to high rates of organic matter remineralization, even when overlying waters are saturated. As a result, the post-larval stages of infaunal marine bivalves must be able to deposit new shell material in conditions that are corrosive to shell. We measured calcification rates on the hard clam, Mercenaria spp.,in 5 post-larval size classes (0.39, 0.56, 0.78, 0.98, and 2.90 mm shell height) using the alkalinity anomaly method. Acidity of experimental water was controlled by bubbling with air-CO2 blends to obtain pH values of 8.02, 7.64, and 7.41, corresponding to pCO2 values of 424, 1120, and 1950 µatm. These pH values are typical of those found in many near-shore terrigenous marine sediments. Our results show that calcification rate decreased with lower pH in all 5 size classes measured. We also found a significant effect of size on calcification rate, with the smaller post-larval sizes unable to overcome dissolution pressure. Increased calcification rate with size allowed the larger sizes to overcome dissolution pressure and deposit new shell material under corrosive conditions. Size dependency of pH effects on calcification is likely due to organogenesis and developmental shifts in shell mineralogy occurring through the post-larval stage. Furthermore, we found significantly different calcification rates between the 2 sources of hard clams we used for these experiments, most likely due to genotypic differences. Our findings confirm the susceptibility of the early life stages of this important bivalve to decreasing pH and reveal mechanisms behind the increased mortality in post-larval juvenile hard clams related to dissolution pressure, that has been found in previous studies.