Assessing streams in Germany with benthic invertebrates: Development of a multimetric invertebrate based assessment system

The main aim of the study was to develop a multimetric assessment system for macroinvertebrate communities of small and mid-sized streams in Germany in accordance with the Water Framework Directive of the European Union. The system should be applicable by water authorities, capable of distinguishing between different impacts, and specifically adapted to all types of small and mid-sized rivers in Germany. An assessment system has been developed consisting of two modules based on the established indices for saprobic degradation and acidity, and a third module covering general degradation. For the third module a new multimetric index (MMI) was developed and tested using preclassifications for stream hydromorphological degradation, land use and general impairment as impact measures. More information on sampling method, season and the type of dominating human impairment allowed to further analyse the index' capabilities and sensitivity. It performed well in all seasons and detected all types of impairment except acidity. The usefulness of the impact measures used in this study is discussed with regard to the development of a multimetric index. The comparison of the new index with other indices showed that it is especially sensitive in detecting macroinvertebrate community responses to hydromorphological degradation and pollution such as the German AQEM index, while IBI 12 and Renkonen's similarity more reflect general community shifts caused by any type of disturbance. The new assessment system will be proposed for future use by state agencies for nationwide monitoring in the context of the Water Framework Directive implementation.     

Conceptual study — An improved method to assess acidification in German streams by using benthic macroinvertebrates

The present study is based mainly upon the authors' hydrochemical and hydrobiological studies of small silicate streams in South-West Germany, principally in the Black Forest and the Odenwald.

The aim of the paper is the adaptation of a practically proven four-level biological classification system of different degrees of acidity using benthic maroinvertebrates to a five-level system of acidification of mainly upland streams with low buffer capacity. The main reason for such a five-class system is the Water Framework Directive of the European Union (EU WFD), which lays down a five-level classification system for the assessment of the ecological quality of waters.

The biological method of assessing the state of acidity for evaluation of the degree of anthropogenic acidification under the directive, and principles of the EU WFD, are also described. A list of 278 taxa of the macrozoobenthos has been reclassified from a four-level system to a five-level biological indication system, based upon the authors' scientific expertise and the latest references from literature of different acid sensitive areas in Germany.     

Origin,age, and significance of deep‐seated granulite‐facies migmatites in the Barrow zones of Scotland,Cairn Leuchan,Glen Muick area

Petrological modelling of granulite‐facies mafic and semipelitic migmatites from Cairn Leuchan, northeast Scotland, has provided new constraints on the pressure (P) and temperature (T) conditions of high‐grade metamorphism in the type‐locality Barrow zones. Phase diagrams constructed in the Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–O₂ system have constrained the P?T conditions of peak metamorphism in the Glen Muick region of the upper sillimanite zone (Sill+Kfs) to have been at least ～840°C at ～9 kbar (high‐P granulite facies). These conditions are ～120°C and ～3 kbar higher than those recorded by lower sillimanite zone (Sill+Ms) units located only a few kilometres away to the southeast at Glen Girnock, indicating the presence of a significant thermal and barometric high exposed within the Scottish Dalradian, and supporting previous suppositions of a potential tectonic break between the two regions. U–Pb zircon geochronology performed on these mafic migmatites produced ages of c. 540–470 Ma from grains with both igneous and metamorphic morphological characteristics. Their basaltic protoliths likely formed during a period of volcanism dated at c. 570 Ma, associated with passive‐margin extension prior to the onset of Iapetus Ocean closure, and high‐grade metamorphism and partial melting is interpreted to have taken place at c. 470 Ma, synchronous with sillimanite‐grade metamorphism recorded elsewhere in the Dalradian. These high‐grade Cairn Leuchan lithologies are interpreted as representing a fragment of Grampian Terrane lower crust that was exhumed via displacement along a steeply dipping tectonic discontinuity related to the Portsoy–Duchray Hill Lineament, and are not pre‐Caledonian Mesoproterozoic basement, as suggested by some previous studies. Veins within some mafic migmatites in the Cairn Leuchan area, composed almost entirely (>80%) of garnet, with minor quartz, plagioclase, amphibole, and clinopyroxene, are interconnected with leucosomes and are interpreted to represent former garnet‐bearing melt segregations that have been locally drained of almost all melt. Thus, mafic components of the lower crust, currently underlying relatively lower grade metasediments exposed to the southeast, may represent a potential source rock for widely documented, post‐orogenic felsic plutons, sills, and dykes that occur throughout the Grampian Terrane.     

Characterisation of Apatites as Potential Uranium Reference Materials for Fission‐track Dating by LA‐ICP‐MS

We report homogeneity tests on large natural apatite crystals to evaluate their potential as U reference materials for apatite fission‐track (AFT) thermochronology by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The homogeneity tests include the measurements of major element concentrations by electron probe microanalysis (EPMA), whereas for U concentration, isotope dilution (ID) ICP‐MS and laser ablation (LA) ICP‐MS were employed. Two apatite crystals are potential reference materials for LA‐ICP‐MS analysis: a 1 cm³ fraction of a Durango crystal (7.5 μg g^?1 U) and a 1 cm³ Mud Tank crystal (6.9 μg g^?1 U). The relative standard deviation (1 RSD) of the U concentration determined by ID‐ICP‐MS of both apatite crystals was ≤ 1.5%, whereas 1 RSD for the LA‐ICP‐MS results was better than 4%, providing sufficient homogeneity for fission‐track dating. The results on the U homogeneity for two different apatite samples are an important step towards establishing in situ dating routines for AFT analysis by LA‐ICP‐MS.     

Determination of Partition Coefficients of Metals in Natural Tropical Water

The values for the partition coefficient (K_d) were calculated for Ca, Mg, Cd, Cr, Cu, Fe, Mn, Pb, Ni, and Zn at 19 sites in the Capivara hydroelectric reservoir in Brazil. It was found that the relative values of K_d follow the order: Cr > Mn > Fe > Cu > Zn > Ni > Pb > Ca > Cd, differing from the values reported for K_d in aquatic systems in the northern hemisphere. A hierarchical cluster analysis and linear correlations showed that Cr is strongly associated with Fe and Cu, and that Cd is the only metal found in complexation with organic matter, explaining its higher solubility.     

GSD‐1G and MPI‐DING Reference Glasses for In Situ and Bulk Isotopic Determination

This paper contains the results of an extensive isotopic study of United States Geological Survey GSD‐1G and MPI‐DING reference glasses. Thirteen different laboratories were involved using high‐precision bulk (TIMS, MC‐ICP‐MS) and microanalytical (LA‐MC‐ICP‐MS, LA‐ICP‐MS) techniques. Detailed studies were performed to demonstrate the large‐scale and small‐scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD‐1G and the MPI‐DING glasses are suitable reference materials for microanalytical and bulk analytical purposes.     

Spectroscopic Observations of the 2011 Draconids Meteor Shower

Some past October Draconid shower meteoroids fell apart in a spray of fragments at the end of their trajectory before slowing down, from which it was concluded that these were among the most fragile meteoroids known. In those instances, the dust could not be reliably traced to a particular return of the parent comet 21P/Giaconini-Zinner. On October 8th, 2011, Earth was predicted to transverse the 1900 A.D. dust ejecta of the comet. In 1900, the comet’s perihelion distance first moved significantly inwards to the Sun and ejection conditions could have been unusual. An airborne observing campaign was organized, with several teams contributing imaging and spectrographic cameras to study the manner in which these meteoroids released the volatile element sodium during the ablation process in the Earth’s atmosphere. IMCCE, ESA, and the SETI Institute contributed spectrographic cameras based on low-light WATEC 902H2 Ultimate, low-light LCC1, and GenII XX1332 image intensified cameras. An outburst was observed, much as predicted. Despite a lack of bright meteors, a total of 15 Draconid spectra were recorded. All show evidence of an early release of sodium. The loss of sodium was observed to coincide with the formation of a distinct wake of fragments. The observations show that 21P/Giacobini-Zinner ejected fragile meteoroids during the return in 1900. Those grains may have lost some sodium even before impacting Earth.     

Millennial-scale variations in western Sierra Nevada precipitation during the last glacial cycle MIS 4/3 transition

Dansgaard–Oeschger (D–O) cycles had far-reaching effects on Northern Hemisphere and tropical climate systems during the last glacial period, yet the climatic response to D–O cycles in western North America is controversial, especially prior to 55 ka. We document changes in precipitation along the western slope of the central Sierra Nevada during early Marine Oxygen Isotope Stages (MIS) 3 and 4 (55–67 ka) from a U-series dated speleothem record from McLean's Cave. The timing of our multi-proxy geochemical dataset is coeval with D–O interstadials (15–18) and stadials, including Heinrich Event 6. The McLean's Cave stalagmite indicates warmer and drier conditions during Greenland interstadials (GISs 15–18), signified by elevated δ¹⁸O, δ¹³C, reflectance, and trace element concentrations, and less radiogenic ⁸⁷Sr/⁸⁶Sr. Our record extends evidence of a strong linkage between high-latitude warming and reduced precipitation in western North America to early MIS 3 and MIS 4. This record shows that the linkage persists in diverse global climate states, and documents the nature of the climatic response in central California to Heinrich Event 6.