Glycerol dialkyl glycerol tetraethers (GDGT) abundance of sediment core GeoB15103-1

Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and utilized in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single sub-mm sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional LC/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (~4-year temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the 200-yr de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and hydrological factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments.

Table 1 Microorganisms, identified with DOGE analysis. 16S rDNA sequences, obtained from sequencing of DOGE bands, were assigned to the corresponding microorganisms

Microorganisms play an important role in the transformation of material within the earth's crust. The storage of CO2 could affect the composition of inorganic and organic components in the reservoir, consequently influencing microbial activities. To study the microbial induced processes together with geochemical, petrophysical and mineralogical changes, occurring during CO2 storage, long-term laboratory experiments under simulated reservoir P-T conditions were carried out. Clean inner core sections, obtained from the reservoir region at the CO2 storage site in Ketzin (Germany) from a depth of about 650 m, were incubated in high pressure vessels together with sterile synthetic formation brine under in situ P-T conditions of 5.5 MPa and 40°C. A 16S rDNA based fingerprinting method was used to identify the dominant species in DNA extracts of pristine sandstone samples. Members of the alpha- and beta-subdivisions of Proteobacteria and the Actinobacteria were identified. So far sequences belonging to facultative anaerobic, chemoheterotrophic bacteria (Burkholderia fungorum, Agrobacterium tumefaciens) gaining their energy from the oxidation of organic molecules and a genus also capable of chemolithoautotrophic growth (Hydrogenophaga) was identified. During CO2 incubation minor changes in the microbial community composition were observed. The majority of microbes were able to adapt to the changed conditions. During CO2 exposure increased concentrations of Ca**2+, K**+, Mg**2+ and SO4**2- were observed. Partially, concentration rises are (i) due to equilibration between rock pore water and synthetic brine, and (ii) between rock and brine, and are thus independent on CO2 exposure. However, observed concentrations of Ca**2+, K**+, Mg**2+ are even higher than in the original reservoir fluid and therefore indicate mineral dissolution due to CO2 exposure.

Marine barite in sediments of DSDP Site 54-424

The distribution of barite in sediments from D.S.D.P. sites 424 and 424A at the Galapagos hydrothermal mounds field is determined and the process of its formation is deduced. Barite in these deposits is associated with calcareous sediments and is completely absent from the hydrothermal material (manganese crusts and nontronite). Its concentrations tend to increase in the deeper sediments. Since manganese crusts contain significant amounts of Ba, a lack of barite in them is probably due to low concentrations of [SO4]2 in the sediment-seawater interface where they form. The formation of barite occurs within buried sediments, the interstitial waters of which are saturated with [SO4]2. The most probable source of [SO4]2- is the oxidation of H2S which is released from the hydrothermal fluids percolating upwards through the sediments. Although nontronite is formed within buried sediments the environmental conditions occurring during its formation (reducing) prevent barite formation. The association of barite with calcareous sediments is due to the release of Ba by calcareous microorganisms and/or to high concentrations of Ca in the pore waters which maintain a high pH and hence [SO4]2- is stable.

Bioturbation determines the response of benthic ammonia-oxidizing microorganisms to ocean acidification

Ocean acidification (OA), caused by the dissolution of increasing concentrations of atmospheric carbon dioxide (CO2) in seawater, is projected to cause significant changes to marine ecology and biogeochemistry. Potential impacts on the microbially driven cycling of nitrogen are of particular concern. Specifically, under seawater pH levels approximating future OA scenarios, rates of ammonia oxidation (the rate-limiting first step of the nitrification pathway) have been shown to dramatically decrease in seawater, but not in underlying sediments. However, no prior study has considered the interactive effects of microbial ammonia oxidation and macrofaunal bioturbation activity, which can enhance nitrogen transformation rates. Using experimental mesocosms, we investigated the responses to OA of ammonia oxidizing microorganisms inhabiting surface sediments and sediments within burrow walls of the mud shrimp Upogebia deltaura. Seawater was acidified to one of four target pH values (pHT 7.90, 7.70, 7.35 and 6.80) in comparison with a control (pHT 8.10). At pHT 8.10, ammonia oxidation rates in burrow wall sediments were, on average, fivefold greater than in surface sediments. However, at all acidified pH values (pH < = 7.90), ammonia oxidation rates in burrow sediments were significantly inhibited (by 79-97%; p < 0.01), whereas rates in surface sediments were unaffected. Both bacterial and archaeal abundances increased significantly as pHT declined; by contrast, relative abundances of bacterial and archaeal ammonia oxidation (amoA) genes did not vary. This research suggests that OA could cause substantial reductions in total benthic ammonia oxidation rates in coastal bioturbated sediments, leading to corresponding changes in coupled nitrogen cycling between the benthic and pelagic realms.

Distribution of microorganisms in recent sediments of Kiel Bay

Die angewandte Mikropaläontologie bestimmt heute im wesentlichen das Alter eines Gesteins mit Hilfe von Faunenvergesellschaftungen. Aus der Zusammensetzung der Fauna, aus dem Einsatz oder Fehlen bestimmter Gattungen und Arten, aus den Mineralien, die das Gestein aufbauen, aus dem ganzen Bild, das eine aus einem Gestein herausgeschlämmte Fauna dem Bearbeiter gibt, läßt sich das Alter dieses Gesteins festlegen. Will man aber verschiedene Bohrungen, vor allem auch räumlich weit voneinander getrennter Gebiete, miteinander parallelisieren, so liegt das Kernproblem der Mikropaläontologie in der Frage, ob es sich bei verschiedenen Faunen tatsächlich um Alters- oder nur um Faziesunterschiede handelt. Da die Grundlagen der mikropaläontologischen Arbeitsweise zum weitaus größten Teil auf den Ergebnissen von Untersuchungen fossiler Faunen beruhen, müssen zu ihrer Unterbauung Untersuchungen an recentem Material folgen. Besonders spielt das Ineinandergreifen mariner und brackischer Sedimente in der angewandten Mikropaläontologie eine große Rolle. Auf Grund der Tatsache, daß ein großer Teil von Gattungen und Arten der Foraminiferen an der Wende Kreide/Tertiär ausstirbt und neue an ihre Stelle treten, stellt Glässner (1948) die Behauptung auf, daß die aktualistisch gewonnenen Ergebnisse für vortertiäre Faunen nur eine geringe Bedeutung besitzen. Auch seien vortertiäre, brackische Foraminiferen nicht bekannt (Glässner 1948, S. 191). Hiltermann (1948) konnte aber bereits im nordwestdeutschen Malm brackische, d. h. in Brackwasser eindringende Foraminiferen nachweisen. Auf jeden Fall behalten aktualistische Unterlagen ihren Wert für das Tertiär und Quartär. Die Faunen, die in recenten, brackischen Sedimenten nebeneinander auftreten, sind in einem Bohrprofil in einem Gestein übereinander zu erwarten. Gelingt es, die Beziehungen einer recenten Fauna zu ihrer Umwelt zu klären, dann können umgekehrt aus fossilen, ihnen gleichen oder ähnlichen Faunen Rückschlüsse auf die Entstehungsbedingungen von Gesteinen gezogen werden. Unter Umständen können der Verlauf einer Transgression, Küstennähe, die Höhe des Salzgehaltes des Meerwassers, die vorherrschenden Temperaturen u. a., aus ihnen abgelesen werden. Die Ostsee ist ein klassisches Brackwassergebiet der Erde. Ihr westlicher Teil, die Kieler Bucht, wurde erst in jüngster geologischer Zeit vom Meer überflutet. Nach Tapfer (1940) begann hier die flandrische Transgression erst etwa um 7500 v. d. Zw. mit dem Erreichen des heutigen Meeresniveaus. Seit dieser Zeit erst entstehen neue Küstenformen, wird der Meeresboden umgelagert und bilden sich marine und brackische Absätze in diesem Gebiet.