ALBERT

Description: Wissenschaftliche Untersuchungen haben gezeigt, dass einige invasive Arten bzw. Populationen gegenüber Umweltstress robuster sind als nicht invasive Arten bzw. Populationen derselben Art. Es wird vermutet, dass die Toleranz gegenüber abiotischen Stressoren wahrscheinlich eine Schlüsseleigenschaft von invasiven Arten darstellt. Während des Transports von Individuen in einen neuen Lebensraum oder durch Stressereignisse könnten widrige abiotische Bedingungen eine Selektion stresstoleranter Individuen hervorrufen, was die erhöhte Stresstoleranz von invasiven Arten bzw. Populationen erklären könnte. Um dies zu testen, habe ich in einem Laborexperiment ein Transport- bzw. Stressereignis simuliert. In zwei unabhängigen Experimenten habe ich in einer Gruppe von Individuen der Weißbeingarnele Penaeus vannamei durch erhöhte Temperaturen mindestens 50 % Mortalität erzeugt. Hierbei wurden die Individuen in unabhängigen Replikaten für 13 Tage 37°C (Langzeit-Stressexperiment) bzw. für 2 h 41°C (Kurzzeit-Stressexperiment) Wassertemperatur ausgesetzt. Nach dieser ersten Stressphase wurde ein Teil der überlebenden gleichzeitig mit einer gleichen Anzahl an bis dahin nicht vorgestressten Individuen sofort wieder denselben erhöhten Temperaturen ausgesetzt und die Überlebenskurven in beiden Gruppen verglichen. Den übrigen überlebenden der ersten Stressphase wurde vor der zweiten Stressphase eine 13 Tage (Langzeit-Stressexperiment) bzw. 6 Tage (Kurzzeit-Stressexperiment) lange Erholungsphase gewährt, damit etwaige physiologische Anpassungen an Stressbedingungen abklingen konnten. Der Vergleich der Überlebenskurven einer vorgestressten Gruppe, die nach der ersten Stressphase direkt wieder Stressbedingungen ausgesetzt wurde und einer vorgestressten Gruppe, der eine Erholungsphase gewährt wurde, sollte Aufschluss darüber geben, ob eine mögliche erhöhte Stresstoleranz der vorgestressten Gruppen auf eine Selektion stresstoleranter Individuen oder physiologischer Anpassungen an Stressbedingungen zurückzuführen war. In beiden Experimenten zeigten die vorgestressten Gruppen, unabhängig davon, ob ihnen eine Erholungsphase gewährt wurde oder nicht, stets höhere Überlebensraten als die Gruppen, die nicht vorgestresst waren. Meine Ergebnisse legen einerseits nahe, dass es durch Temperaturstress zu einer physiologischen Stressabhärtung und dadurch zu erhöhten Überlebensraten der vorgestressten Individuen kam. Da Literaturdaten darauf hinweisen, dass die Erholungsphasen wahrscheinlich lang genug waren, um die physiologische Stressabhärtung in den vorgestressten Gruppen, denen eine Erholungsphase gewährt wurden, abklingen zu lassen, kann man andererseits annehmen, dass es durch den Temperaturstress bei P. vannamei zu einer Selektion stresstoleranterer Individuen gekommen ist. Dies konnte im Rahmen meiner Diplomarbeit jedoch nicht direkt bewiesen werden.

Description: Modeling of the seepage history of DNAPLs is investigated as a new, non-invasive site investigation tool in order to elucidate the possible position of still unknown DNAPL source zone at many investigated industrial sites. Therefore, the spatio-temporal spreading behavior of the DNAPL TCE is studied with the multiphase modeling software TMVOC in small and large scale 2D multiphase scenarios with varying parameter sets concerning groundwater flow, composition of aquifers and aquitards and subsurface morphologies, as depressions and trenches. The small scale models were calibrated by laboratory experiments conducted at La Sapienza University, Rome. They exhibited that even groundwater pore velocities of vw = 0.05 m/d have a strong impact on the spreading behavior and the position of a DNAPL body. Downstream inclined percolation path ways, enhanced dissolution rates and lateral transportation in downstream direction are the most dominant impacts. Small scale layering of the subsoil with horizontal lenses of impermeable materials affects the distribution pattern only slightly at vw 〉 5 m/d, which are common flow velocities in many gravelly aquifers in Europe. Upscaling of the models to field scale problems exhibited potential transportation length in downstream direction of several hundreds of meters, assuming a moderate spill rate of ca. 3 kg/day over an area of several square meters. Investigating real subsurface morphology including real material parameters provided by the ModelPROBE reference site Chimica di Bianchi in Rho, Italy, revealed that the DNAPL TCE will be transported out of moderate depressions (slope of 2.5°) even at groundwater flow velocities of vw ≤ 1 m/d, which is in the range of documented groundwater flow velocities at the reference site. Moreover, the documented material classes, which comprise the aquitard at the site, are not in general impermeable for percolating DNAPLs. Only pure clays with a hydraulic conductivity of kf ≤ 10-9 m/s are long-term barriers for vertical DNAPL percolation. The conducted investigations deliver a reasonable explanation for the often unknown position of DNAPL source zones at former industrial sites and are, as far as it is known, the first large scale scenarios of DNAPL spreading behavior in real subsurface morphology. Based on the conducted research it can be concluded that at the reference site Chimica di Bianchi the main mass of DNAPLs was not at the assumed hot spot, which was encapsulated in the 1980s, but probably migrated considerable distances in downstream direction, passing through or following partly the topography of the aquitard. But the applicability of multiphase modeling as additional non-invasive site investigation tool is still challenging due to software restriction concerning size and resolution of the models and handling of heterogeneous permeability fields.

Description: The aragonitic skeletons of scleractinian cold-water corals can serve as valuable archives in paleoceanographic studies. The potential of δ88/86Sr, Sr/Ca, Mg/Ca, Li/Ca and Mg/Li ratios of the cold-water coral Lophelia pertusa to record intermediate water mass properties has been investigated. Here we used samples from several locations along the European continental margin spanning a large temperature range from 6 to 14 °C. Stable strontium isotope measurements were carried out with the recently developed double spike TIMS technique and our results differ from those obtained with less precise methods. In contrast to the strong positive relationship with temperature of previous studies, our results suggest that δ88/86Sr measured in scleractinian cold-water corals is not controlled by seawater temperature, but reflects the Sr isotopic composition of seawater with an offset of Δ88/86Sr = − 0.196‰. As found in previous studies, the elemental ratios Sr/Ca, Li/Ca and Mg/Li measured in corals are significantly related to water temperature and do not correlate with salinity. Moreover, Sr/Ca ratios in L. pertusa display the expected inverse correlation with temperature. However, the variance in the Sr/Ca data severely limits the accuracy of paleotemperature estimates. The Li/Ca and Mg/Ca ratios reveal other influences besides temperature such as pH and/or growth or calcification rate. However, corresponding Mg/Li ratios in L. pertusa are more tightly related to temperature as they remove these secondary effects. In particular, the Mg/Li ratio in L. pertusa may serve as a new promising paleotemperature proxy for intermediate water masses. Our dataset represents the most extensive geochemical examination of L. pertusa to date, revealing a temperature sensitivity of 0.015 mol/mmol/°C for Mg/Li. However, using this temperature dependence and the precision of 5.3% (2SD) only temperature variations larger than ~ 1.5 °C can be resolved with 95% confidence.

Description: The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp- 1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is 〈0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

Description: WOR 1 provided a panoptic overview. The following report (WOR 2), the second in the series, focuses on the future of fish and their exploitation. Fish have always been a vital source of life for mankind – not only as a food. Fish continue to be essential to the daily diet of people in most regions of the world. At the same time fisheries provide a livelihood to entire coastal regions and still have great economic clout. All this, however, is in jeopardy and is coming under close scrutiny. Fish stocks are declining worldwide, entire marine regions are overfished and some species are already red-listed.

Description: Beim ersten WOR lag das Augenmerk auf dem Umfassenden; den nun folgenden Bericht widmen wir der Zukunft der Fische und deren Nutzung durch den Menschen. Seit jeher gilt Fisch als eine der wichtigsten Lebensgrundlagen für die Menschheit. Nicht nur als Lebensmittel, das in den meisten Regionen der Welt noch wesentlicher Bestandteil der täglichen Mahlzeit ist. Auch bietet die Fischerei ganzen Küstenregionen die Basis und ist als Wirtschaftskraft immer noch von großer Bedeutung. Doch dies alles steht auf dem Prüfstand. Die Fischbestände gehen weltweit zurück, ganze Meeresregionen gelten als überfischt, einige Arten stehen auf der Roten Liste der gefährdeten Tierarten.

Description: Processes of crustal growth and crustal evolution are revealed for a time interval of more than three billion years from the oldest Archean, 3.5-2.6 Ga old crustal units in the northeastern Baltic Shield, to the youngest Palaeozoic and Mesozoic sedimentary basins in the North Sea region. This long geological time span, with a series of tectonic events, together with the availability of extensive geophysical and geological data, makes the region Northern Europe a fascinating natural laboratory for the study of lithospheric structure and evolution. Although not uniquely defined, a number of geophysical experimental techniques and modelling methods are capable of providing information of “thickness of lithosphere” or depth to “lithosphere-asthenosphere boundary”. Several studies consistently show thick lithosphere, around 200-250 km (and more?), in the older northeastern and central parts of the Baltic Shield, and thinner lithosphere, around 100 km and less, beneath the tectonically younger deep sedimentary basins to the southwest in Danish, North German and North Sea areas. Regional variations in thickness of lithosphere are found to be related to regional differences in heat flow. Surface heat flow increases by a factor of two to three across the study area, from low values around 30-40 mW/m2 in the northeast, to 70-80 mW/m2 in the southwest. Thermal modelling has shown that heat flow from the mantle (estimated at 15-20 and 35-40 mW/m2 in the northeast and the southwest, respectively) plays a dominant role in controlling thickness of lithosphere. High resolution 3-D teleseismic tomography models, covering southern Scandinavia and adjacent areas, show upper mantle with contrasting P-wave velocity. An exceptionally deep (up to more than 300 km) and narrow boundary separates shield areas of high seismic velocity to the east from deep basin areas of low velocity to the southwest, including most of southern Norway. Rather than the Sorgenfrei-Tornquist Zone (as currently defined), this deep “Shield Border Zone”, outlined further to the northeast in the northern Kattegat and eastern Skagerrak, seems to be of major significance in understanding the tectonic transition between shield and deep sedimentary basins, as well as in indicating a northward continuation into, and across, southern Norway. The near-normal incidence seismic reflection technique is a unique tool in providing high-resolution, deep-structural images and a link between surface geological observations and structures at depth. Results, in particular from two marine deep seismic experiments called BABEL (Gulf of Bothnia and Baltic Sea) and MONA LISA (central and southeastern North Sea), demonstrate how structural details are resolved over the entire crustal depth, including deep shield crust, and to great depth into mantle lithosphere. Dipping mantle reflectivity, with associated Moho offsets, found to represent characteristics of fossil subduction zones, provide key observational deep-structural constraints for tectonic reconstruction. Such features are described from Palaeoproterozoic and Mesoproterozoic shield crust and from the North Sea, where the Caledonian collision between Baltica and Avalonia is imaged at a lithosphere depth scale. These observations, together with equivalent results, in particular from the Canadian Shield (including fossil subduction as old as 2.7 Ga), have demonstrated that plate tectonic processes, quite similar to those currently observed, were operating throughout the Proterozoic and at least since the Late Archean. In addition to their tectonic significance, the recognition of old structures preserved to great depth provides accurate information on the (minimum) thickness of the coherent lithosphere plate, a measure which is otherwise very difficult to obtain. Detailed information on crustal structure is available from a large number of mainly controlled-source seismological experiments, and recently also from receiver function analysis. The Baltic Shield has a crustal thickness around 45 km, but spans a wide range from 30-35 km up to 50-60 km. Since marked crustal thickness variations in the shield do not generally result in any significant Bouguer gravity anomalies or marked variations in surface elevation, the lower high-velocity part of shield crust must be very dense, close to that of the uppermost mantle. Thick, dense and refractory lower crust, together with thick, relatively cold, depleted lithosphere, seem to constitute important elements in stabilizing and preserving old shield lithosphere. In clear contrast to shield areas, the Scandes Mountains show marked negative Bouguer gravity anomalies that strongly correlate with surface elevation and show a general correlation with crustal thickness variations. From Norwegian coastal areas to beneath areas of highest topography, crustal thickness typically increases by about 10 km (from c. 30 km to c. 40 km), correlating with a marked decrease in Bouguer gravity of about 100 mgal. Buoyancy from the thickened crust plays a dominant role in the isostatic sustainment of the mountains. Thickened buoyant crust may (largely) date back to the Caledonian orogeny resulting from continental collision processes, suggesting that present-day high topography, is (mainly) a remnant from the Caledonian mountains rather than of much younger Cenozoic age. Evolution of the Danish and central North Sea Basins is modelled by phases of deep background heating, coupled with significant lithospheric stretching. Such models explain the observed marked crustal thinning, major elements of basin subsidence history and associated distribution of sedimentary sequences, and are consistent with present-day heat flow. Lithospheric stretching is found to be the most important mechanism for basin generation. Recent and current dynamic activity in the region of study is displayed by the Fennoscandian land uplift and by modest seismic activity. The glacial isostatic nature of land uplift is now unequivocally confirmed. Updated gravity maps confirm the existence of a significant central Fennoscandian long-wavelength free-air gravity low (about -15 mgal), and much new information is currently becoming available from satellite-based observations. Previous measurements of present (relative) uplift rates are generally confirmed by accurate GPS observations that also provide information on the absolute rate of uplift. Gravity-satellite data display a clear signal of gravity increase, demonstrating the existence of deep inflow of mass into the region of uplift. The Danish area constitutes part of the southwestern peripheral area of uplift that, however, is submerged as a result of regional sea level rise. The Fennoscandian lithospheric stress field, and associated seismicity, seem to be explained mainly by a combination of the regionally dominant ridge push from the North Atlantic, together with locally important contributions from gravitational potential stresses generated by marked lithospheric density variations. Stresses associated with glacial rebound also seem to play a part. High-quality temperature and heat-flow data from deep boreholes (Danish Basin, central Sweden and eastern Finland) display a significant increase of conductive heat flow with depth. Such information is critical for determination of undisturbed surface boundary heat flow and, furthermore yields new independent information on past climate. Information may be extracted concerning a characteristic surface temperature level during the last glacial period and with the magnitude of temperature increase around the termination of glaciation. This increase of temperature seems to be of the order of 10-15 °C in much of the Fennoscandian region.

Description: Im Rahmen der Masterarbeit wurden rezente Oberflächensedimente vom Schelf und Kontinentalhang der Keltischen See auf zur Zeit der Probennahme (lebende) Benthosforaminiferen untersucht. Unser Ziel war die qualitative Analyse der Faunenzusammensetzung und der Vergleich mit früheren Literaturdaten. Auf der Ausfahrt der R/V Victor Hensen Cruise (Fahrtleiter Prof. Dr. A. Freiwald, Wilhelmshaven) wurden im April 1997 vom Schelf und Kontinentalhang in der keltischen See Proben rezenter Oberflächensedimente mit einem Backengreifer genommen und in einer Lösung aus Alkohol und Begalrosa eingefärbt. Sie wurden im weiteren Verfahren geschlämmt und in unterschiedliche Fraktionen unterteilt (63‐125 μm, 125‐250 μm, 250‐400 μm, 400‐2000 sowie 〉 2000 μm). Ihre Verbreitung und Verteilung, Lebensweise und Gehäuse wurden untersucht. Das Auftreten von lebenden benthischen Foraminiferen in diesem Gebiet wurde bislang nur von Sturrock und Murray (1981) und Murray, Sturrock und Weston (1982) beschrieben. Die Proben wurden in den Jahren 1968 bis 1979 aus Wassertiefen von 112 bis 176 m entnommen und hinsichtlich der Faunenzusammensetzung mit unseren Daten verglichen. Ziel war es, seewärtige Änderungen in der Faunenzusammensetzung zu untersuchen, wie sich diese verändert, wenn lediglich größere Korngrößen untersucht werden und inwieweit sich die Faunenzusammensetzung auf dem Schelf von der Zusammensetzung auf dem Hang unterscheidet. Es sollte geprüft werden, welche Ursachen für mögliche Gemeinsamkeiten oder Unterschiede verantwortlich sind. Die Auswertung der Faunenzusammensetzung ergab, dass auf dem Schelf Trifarina angulosa, Gavelinopsis praegeri, Trochammina pygmaea, Textularia pseudogramen, Bolivina difformis sowie Arten der Gattung Cassidulina die häufigsten Arten sind. Diese lassen sich sehr gut mit Proben von Sturrock und Murray (1981) vergleichen. Die Faunenzusammensetzung setzt sich aus ähnlichen Arten zusammen, unterscheidet sich jedoch in ihrer Häufigkeit. Auch kommen vereinzelt tief infaunal lebende Arten wie Stainfortia fusiformis und Uvigerina auberiana vor, die ausschließlich in Proben von Sturrock und Murray gefunden wurden. Auf dem Hang hingegen dominieren in den von uns untersuchten Proben Gavelinopsis praegeri, Trifarina angulosa, Siphotextularia flintii, Spiriliina vivipara, Rotaliammina concava, Lepidodeuterammina ochracaea sowie Bolivina difformis. In Proben von Schönfeld und Altenbach (2005) jedoch sind Reophax calcareous, Cibicides lobatulus, Cibicides refulgens, Textularia pseudogramen, Jacuella obtusa sowie Arten der Gattung Placopsilina und Bigenerina häufige Arten. Auch unterscheiden sich die Proben vom Hang aufgrund der unterschiedlichen Lage und Topographie hinsichtlich der Diversität, Siedlungsdichte, Lebensweise als auch der Gehäuse. Sowohl auf dem Schelf als auch auf dem Kontinentalhang sind frei lebende Arten wesentlich häufiger vertreten, als angeheftet lebende Arten. Opportunistischen Arten kommen nur untergeordnet vor. Die Anzahl der Individuen nimmt mit zunehmender Korngröße stark ab. Dabei konnte eine wesentlich größere Abnahme der Individuen von 〉63 μm zu 〉125 μm auf dem Schelf festgestellt werden. Der durchschnittliche Fisher Alpha Index in den von uns untersuchten Proben (α=10,24) ist in etwa vergleichbar mit den Proben von Sturrock und Murray (α=12,26). Gemeinsamkeiten und Unterschiede auf dem Schelf und Kontinentalhang werden hauptsächlich durch das Zusammenspiel von Primärproduktion, Sedimentationsraten und hydrodynamischen Prozessen verursacht. Auch spielen Art und Zeitpunkt der Probennahme eine nicht unerhebliche Rolle.

Description: Earth system climate models generally underestimate dissolved oxygen concentrations in the deep eastern equatorial Pacific. This problem is associated with the "nutrient trapping" problem, described by Najjar et al. [1992], and is, at least partially, caused by a deficient representation of the Equatorial Intermediate Current System (EICS). Here we emulate the unresolved EICS in the UVic earth system climate model by locally increasing the zonal isopycnal diffusivity. An anisotropic diffusivity of ∼50,000 m 2 s-1 yields an improved global representation of temperature, salinity and oxygen. In addition, it (1) resolves most of the local "nutrient trapping" and associated oxygen deficit in the eastern equatorial Pacific and (2) reduces spurious zonal temperature gradients on isopycnals without affecting other physical metrics such as meridional overturning or air-sea heat fluxes. Finally, climate projections of low-oxygenated waters and associated denitrification change sign and apparently become more plausible