1. Wochenbericht POS408/3

Leg 3, 23 – 28 February 2011, chief scientist: Dr. Anton Eisenhauer Within the project Nutrient Gradients (project 3) the coastal interaction between corals and macroalgae under different stress states (eutrophied versus non-eutrophied, with versus without heavy fishing pressure) was assessed. In addition, work is planned on cold water coral occurrences (azooxanthellate deep-water corals). - CTD/RO casts and net sample

The influence of increased pCO2 on the calcification of Mytilus edulis

One of the most important and abundant calcifying organisms in several marine ecosystems is the blue mussel, Mytilus edulis. It has a wide geographic distribution (Gosling 1992 Developm. Aquacult. Fish. Sci. 25, 1-20) and tolerates a broad range of environmental conditions (Seed and Suchanek 1992 Developm. Aquacult. Fish. Sci. 25, 87-170). Blue mussel beds are also common features in the Kiel Fjord (Baltic Sea), a habitat dominated by low salinity (10-20 PSU), low alkalinity (1900-2150 μmol kg-1), low pH (minimum values < 7.5) and high pCO2 (maximum value of 2340 ppm). The resulting calcium carbonate saturation state (min. values: Ωarag = 0.34 and Ωcalc = 0.58) is significantly lower than in the open ocean (Thomsen et al. submitted). Therefore, pCO2 in Kiel Fjord during summer is already higher than what is predicted for the future (e.g., Caldeira and Wickett 2003 Nature 425, 365). Additionally, Meier (2006 Clim. Dyn. 27, 39-68) projected an increase of temperature (2.6 to 5.0 °C) in the next 100 years for the Baltic Sea. To contribute to the understanding of the ability of calcifying organisms to live under ocean acidification conditions and of biomineralization mechanisms, M. edulis from this naturally CO2-enriched habitat were cultured in a flow-through system. Experiments were conducted using CO2 concentrations ranging from 380 ppm to 4000 ppm and temperatures ranging from 5° to 25°C. At the end of the experiments, hemolymph and extrapallial fluid (EPF) were taken and analyzed for pH, pCO2, bicarbonate and elemental ratios. Fluids showed decreased pH and increased CO2 with increasing water pCO2. Elemental ratios (Mg/Ca and Sr/Ca) in the fluids did not show pCO2 or temperature-related systematic changes. Furthermore, boron isotopes ([Delta]11B), used in isotope geochemistry as a pH proxy, were investigated by LA-MC-ICP-MS in shell portions precipitated during the experimental treatment. We observed high [Delta]11B variability between different individuals, but also within single shells. Average [Delta]11B values showed a weak positive correlation with pH. When comparing our results to published studies, boron isotopes appeared to represent internal pH conditions (EPF) instead of ambient water pH (Kasemann et al. 2009 Chem. Geol. 260, 138-147; Reynaud et al. 2004 Coral Reefs 23, 539-546; Sanyal et al. 2000 Geochim. Cosmochim. Acta 64, 1551-1555)

Verfahren zur Verifikation von Alters-Tiefen-Beziehungen von Gesteinen in Sedimentbecken = Method for verifying age-depth relationships of rock in sedimentary basins

Verfahren zur Verifikation von Alters-Tiefen-Beziehungen von Gestein in Sedimentbecken durch Rekonstruktion der Absenkungsrate von Proben, bei dem durch Bestimmung der Ausfalltiefe und Ausfällungstemperatur einer Karbonatausfällung die geologische Geschichte bestimmten Sedimentgesteins, aus dem Proben genommen werden, in einem Fixpunkt festgelegt wird

Calcium and strontium isotope fractionation in aqueous solutions as a function of temperature and reaction rate; I. Calcite

In order to study Strontium (Sr) partitioning and isotope fractionation of Sr and Calcium (Ca) in calcite we performed precipitation (T) experiments decoupling temperature and precipitation rate (R*). Calcite was precipitated at 12.5, 25.0 and 37.5 C by diffusingNH3 andCO2 gases into aqueous solutions closely following the experimental setup of Lemarchand et al. (2004). The precipitation rate (R*) for every sample was determined applying the initial rate method and from the specific surface area of almost all samples for each reaction. The order of reaction with respect to Ca2+ ions was determined to be one and independent of T. However, the order of reaction with respect to HCO3 changed from three to one as temperature increases from 12.5, 25 C and 37.5 C. Strontium incorporated into calcite (expressed as DSr = [Sr/Ca]calcite/[Sr/Ca]solution) was found to be R* and T dependent. As a function of increasing R* the D88/86Sr-values become more negative and as temperature increases the D88/86Sr values also increase at constant R*. The DSr and D88/86Sr-values are correlated to a high degree and depend only on R* being independent of temperature, complexation and varying initial ratios. Latter observation may have important implications for the study of diagenesis, the paleo-sciences and the reconstruction of past environmental conditions. Calcium isotope fractionation (D44/40Ca) was also found to be R* and T dependent. For 12.5 and 25.0 C we observe a general increase of the D44/40Ca values as a function ofR* (Lemarchand et al. type behavior, Lemarchand et al. (2004)). Whereas at 37.5 C a significant decreasing D44/40Ca is observed relative to increasing R* (Tang et al. type behavior, Tang et al. (2008)). In order to reconcile the discrepant observations we suggest that the temperature triggered change from a Ca2+-NH3-aquacomplex covalent controlled bonding to a Ca2+-H2O-aquacomplex van-der-Waals controlled bonding caused the change in sign of the R* D44/40Ca slope due to the switch of an equilibrium type of isotope fractionation related to the covalent bonding during lower temperatures to a kinetic type of isotope fractionation at higher temperatures. This is supported by the observation that the D44/40Ca ratios tend to depend on the [Ca]:[DIC] ratio at 12.5 and 25 C but is highly independent at 37.5 C. Our observations imply the chemical fluid composition and temperature dependent complexation controls the amount and direction of Ca isotope fractionation in contrast to the Sr isotopes which do not show any change of its fractionation behavior as a function of complexation in the liquid phase. 2016 Elsevier Ltd. All rights reserved.Three anonymous reviewers are acknowledged for their detailed reviews which significantly helped to improve the manuscript. This study is part of the TRION project in the frame of the ‘‘Trilateral Programm der Deutschen Forschungsgemeinschaft, DFG (Ei272/30-2)”. Ana Kolevica is acknowledged for Laboratory help and support in the design of the experiment. For fruitful discussions, Florian Bo¨hm, Volker Liebetrau and Jan Fietzke are acknowledged. Prof. Dr. Mutaz AlQutob from the AlQuds University in AbuDis, Palestinian Authority, is acknowledged for his general support of the work of MA

Calcium isotopic composition of high-latitude proxy carrier Neogloboquadrina pachyderma (sin.)

The accurate reconstruction of sea surface temperature (SST) history in climate-sensitive regions (e.g. tropical and polar oceans) became a challenging task in palaeoceanographic research. Biogenic shell carbonate SST proxies successfully developed for tropical regions often fail in cool water environments. Their major regional shortcomings and the cryptic diversity now found within the major high latitude proxy carrier Neogloboquadrina pachyderma (sin.) highlight an urgent need to explore complementary SST proxies for these cool-water regions. Here we incorporate the genetic component into a calibration study of a new SST proxy for the high latitudes. We found that the calcium isotopic composition (δ44/40Ca) of calcite from genotyped net catches and core-top samples of the planktonic foraminifera Neogloboquadrina pachyderma (sin.) is related to temperature and unaffected by genetic variations. The temperature sensitivity has been found to be 0.17 (±0.02)‰ per 1°C, highlighting its potential for downcore applications in open marine cool-water environments. Our results further indicate that in extreme polar environments, below a critical threshold temperature of 2.0 (±0.5)°C associated with salinities below 33.0 (±0.5)‰, a prominent shift in biomineralization affects the δ44/40Ca of genotyped and core-top N. pachyderma (sin.), becoming insensitive to temperature. These findings highlight the need of more systematic calibration studies on single planktonic foraminiferal species in order to unravel species-specific factors influencing the temperature sensitivity of Ca isotope fractionation and to validate the proxies' applicability

Cold seep carbonates and associated cold-water corals at the Hikurangi Margin, New Zealand: New insights into fluid pathways, growth structures and geochronology

The aim of this study is to provide combined new insights into the geochronological framework, isotope geochemical signatures and structural observations of methane related authigenic carbonate settings and associated cold-water corals from offshore New Zealand. The analysed samples are obtained from calcified sediments of three different cold seep areas at the Hikurangi Margin: Opouawe Bank, Uruti and Omakere Ridge. We focused the sub-sampling on aragonitic precipitates in vein like structures, partly still open fluid channel systems and related chemoherm structures in order to identify the timing and signature of focused marine methane emanation. The presented initial U/Th age data set indicates different generations of intensified seep activity and related carbonate precipitation between 12,400 ± 160 and 2090 ± 850 years BP. The youngest stage so far, was identified as contemporaneous cold seep activity at the southernmost (North Tower, Opouawe Bank) and northernmost (Bear's Paw, Omakere Ridge) sampling sites around 2300 years BP. Sharing the same water depth (1050 to 1100 m) these sites imply regional margin-wide tectonic or hydrological changes as controlling process. An intermediate phase of vein and channel structures within the sediment was detected for a time interval between approximately 5000 and 4000 years BP with contemporaneous settings of focused seep activity around 4300 years BP at Uruti Ridge (LM-10) and Opouawe Bank. δ13CPDB data reflect site and carbonate type specific signatures, clustering around − 52‰ (Uruti and Omakere Ridge) and − 47‰ for the fluid pathway system and the uppermost surface at North Tower site (Opouawe Bank). Late stage precipitates in chemoherm cavities of the latter reflect significantly heavier values of about − 38‰. Porous precipitates within open fluid channel systems are characterized by decreased δ234U(T) values, exceptional high Th and U concentrations and slightly lighter δ13CPDB signatures when compared to adjacent rim-like and dense cements. This specific kind of precipitate is interpreted as indicator for phases of less vigorous fluid seepage. The observed occurrence of cold-water corals seems to be mostly depending on the abundance of authigenic carbonates as a substrate exposed to erosive bottom water currents. But, seafloor observations combined with preliminary age data indicate a significant time gap between the inferred end of cold seep activity and coral colonization. U–Th analyses of recent reef-forming coral provided an initial δ234U(0) value of 146.3 ± 3.9‰ and 0.0013 ± 0.0002 as starting 230Th/234U activity ratio for coral growth in the bottom water

A spike of CO2 in the atmosphere at glacial-interglacial boundaries induced by rapid deposition of manganese in the oceans

The model presented here provides an explanation of the rapid response of atmospheric CO2 to increasing solar insolation. In the glacial ocean, during periods of slow, deep water renewal, when less oxygen is supplied to the deep ocean and into sediments, manganese oxide in the sediments is reduced and forms soluble MnCO3 and stays in the water column. The dissolved Mn-carbonate should then reach a concentration of ≥ 10µMol/liter, approximately 5,000 to 104 times larger than it is at present. This is the mode prevailing until deep water formation at high latitudes starts again. As soon as the balance between oxygen and organic matter becomes oxidizing once more, the deposition of MnO2 recommences. Oxidation of dissolved Mn2+CO3 to Mn4+O2 which is a spike of acidity to the ocean, rapidly lowers the CO3−− concentration in the water column and enhances release of CO2 to the atmosphere, producing the observed events of CO2 increase at the transitions from glacials to interglacials. The surprising conclusion is that the oceanic (redox-) cycle of a minor element may have had a major impact on Earth's climate

Von der Ozeanforschung zur Humanmedizin – Wie der Brückenschlag gelingt

Die Entwicklung eines Biomarkers im Rahmen des von der Helmholtz-Gemeinschaft und dem GEOMAR geförderten Projekts ID&S zur frühen Diagnose von Osteoporose und anderen Kalzium bezogenen Krankheiten ist das klassische Beispiel für einen gelungenen Technologie-Transfer zweier weit auseinanderliegender Wissenschaften der Ozeanwissenschaften und der Medizin. Gleichwohl ist trans-disziplinärer Technologietransfer nicht ein Prozess der von selbst abläuft sondern das Überwinden sehr vieler Hindernisse bedeutet. Der Technologietransfer, die Entwicklung des Biomarkers und die medizinischen Hintergründe werden in einem dreiteiligen Vortrag aus verschiedenen Perspektiven beleuchtet