Geotechnical properties of sediments at DSDP Site 75-532

During Leg 75 of the Deep Sea Drilling Project (DSDP) from the D/V Glomar Challenger, a 200-m deep hole was drilled at Hole 532A on the eastern side of Walvis Ridge at a water depth of 1331 m. Sediment cores were obtained by means of a hydraulic piston corer. All of the cores from this boring were designated for geotechnical studies and were distributed among eight institutions. The results of laboratory studies on these sediment cores were compiled and analyzed. Sediment properties, including physical characteristics, strength, consolidation, and permeability were studied to evaluate changes as a function of depth of burial. It was concluded that the sediment profile to the explored depth of 200 m at Walvis Ridge consists of approximately 50 m of foram-nannofossil marl (Subunit 1a) over 64 m of diatom-nannofossil marl (Subunit 1b) over nannofossil marl (Subunit 1c) to the depth explored. All three sediment units appear to be normally consolidated, although some anomalies seem to exist to a depth of 120 m. No distinct differences were found among the sediment properties of the three subunits (1a, 1b, and 1c) identified at this site.

Species-specific consequences of ocean acidification for the calcareous tropical green algae Halimeda, 2011

Ocean acidification (OA), resulting from increasing dissolved carbon dioxide (CO2) in surface waters, is likely to affect many marine organisms, particularly those that calcify. Recent OA studies have demonstrated negative and/or differential effects of reduced pH on growth, development, calcification and physiology, but most of these have focused on taxa other than calcareous benthic macroalgae. Here we investigate the potential effects of OA on one of the most common coral reef macroalgal genera,Halimeda. Species of Halimeda produce a large proportion of the sand in the tropics and are a major contributor to framework development on reefs because of their rapid calcium carbonate production and high turnover rates. On Palmyra Atoll in the central Pacific, we conducted a manipulative bubbling experiment to investigate the potential effects of OA on growth, calcification and photophysiology of 2 species of Halimeda. Our results suggest that Halimeda is highly susceptible to reduced pH and aragonite saturation state but the magnitude of these effects is species specific. H. opuntiasuffered net dissolution and 15% reduction in photosynthetic capacity, while H. taenicola did not calcify but did not alter photophysiology in experimental treatments. The disparate responses of these species to elevated CO2 partial -pressure (pCO2) may be due to anatomical and physiological differences and could represent a shift in their relative dominance in the face of OA. The ability for a species to exert biological control over calcification and the species specific role of the carbonate skeleton may have important implications for the potential effects of OA on ecological function in the future.

Non-isoprenoidal intact polar lipids, isoprenoidal and non-isoprenoidal core lipids, isoprenoidal intact polar lipids of the Black Sea site GeoB15105 sampled during Meteor cruise M84/1 in February 2011

This PhD thesis focused on the analysis and application of microbial membrane lipids as biomarkers in marine sediments. Existing protocols for lipid extraction from marine sediments and biomass were modified. In addition, recent protocols based on high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) as well as state-of-the-art mass spectrometric analysis by quadrupole time-of-flight (MSqTOF) and the triple quadrupole (MSQQQ) mass spectrometer were used to investigate matrix effects and evaluate the reliability of quantitative analysis in marine environmental samples. The improved lipid extraction and quantification were used to analyze Black Sea water column and sediments samples to a depth of 8 meters from site GeoB 15105 taken during cruise M84/1 (DARCSEAS) with R/V Meteor to apply lipid analysis in benthic bio systems. With this component specific differentiation between planktonic and benthic lipid signature we assessed possible lipid sources. Here, this high detail lipid fingerprinting allowed us to observe changes in the head group and lipid core structures of the intact polar lipids according to the geochemical zonation.

Pliocene sediment and silicon isotope record of ODP Site 145-882

Increases in the low-field mass-specific magnetic susceptibility (chi), dropstones and the terrigenous sediment component from Ocean Drilling Program (ODP) Site 882 (~45°N) have been interpreted to indicate a major onset of ice-rafting to the sub-Arctic northwest Pacific Ocean during marine isotope stage (MIS) G6 (from ~2.75 Ma). In contrast, studies of the terrigenous content of sediments cored downwind of ODP Site 882 indicate that dust and disseminated volcanic ash deposition in the sub-Arctic Pacific increased markedly during MIS G6. To investigate the relative contribution of dust, volcanic ash and ice rafting to the Pliocene chi increase, we present new high-resolution environmental magnetic and ice-rafted debris records from ODP Sites 882 and 885. Our results demonstrate that the chi increase at both sites across MIS G6 is predominantly controlled by a previously overlooked mixture of aeolian dust and volcanic ash. Our findings call into question the reliability of chi as a proxy for ice-rafting to the North Pacific. They also highlight a previously undocumented link between iron fertilisation and biogeochemical cycling in the North Pacific at a key stage during intensification of late Pliocene northern hemisphere glaciation.