Dissolved Humic Substances Can Directly Affect Freshwater Organisms

Direct effects of pure humic substance (BS1 FA) on three different aquatic organisms (Ceratophyllum demersum, Dreissena polymorpha, and Chaetogammarus ischnus) were demonstrated in this study. Exposure to environmentally relevant concentrations (0.5 mg/L) of this humic substance led to the activation of the microsomal and soluble glutathione S‐transferase (GST) in Ceratophyllum demersum. Exposure to 3‐chlorobiphenyl showed also an elevation of GST activity, which is due to the proposed detoxication metabolism of these chlorinated biphenyl. Coexposure to a mixture of 3‐chlorobiphenyl and BS1 FA showed a reduction of enzyme elevation, but still significant over an untreated control. The direct impact of humic substances seems not to be restricted to a specific class of organisms.     

A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats

We determined fluxes of oxygen and nutrients between water and sediments at 21 sites primarily in Virginia and North Carolina estuaries, over the past 15 yr. These sites represented broad ranges in salinity, tidal amplitude, hydrology, nutrient availability, turbidity, light availability, depth, sediment grain size, and anthropogenic disturbance. In general, we found that heterotrophically dominated sediments had the potential to degrade water quality, whereas photoautotrophy in the sediments ameliorated this impact. We propose a benthic trophic state index as a management tool to make general assessments of the degree to which sediments support ecological processes related to photoautotrophy. The index can be based on simple measurements of metabolic parameters. We also evaluated the relative significance of variability in the index across a number of spatial and temporal scales. Reduced photoautotrophy and/or enhanced heterotrophy tended to be associated with finer-grained, organic-rich sediments. This sediment type was common in oligohaline areas at water depths exceeding 2 m. Temporally, autotrophy declined from winter to spring particularly at sandy sites, while interannual variability was more pronounced for mud sites. *** DIRECT SUPPORT *** A01BY074 00011     

A novel ozone sensor for direct eddy flux measurements

A small, lightweight (1.5 kg) and fast-response ozone sensor for direct eddy flux measurements has been built. The basis for detection is the chemiluminescence of an organic dye adsorbed on dry silica gel in the reaction with ozone. The chemiluminescence is monitored with a cheap and small blue-sensitive photomultiplier. At a flow rate of 100 l min^-1 the ozone sensor has a 90% response time of significantly better than 0.1 s with a detection limit lower than 50 ppt at S/N=3. There are no interferences from other atmospheric trace gases like NO_x, H₂O₂ and PAN. Water vapour and SO₂ enhance the chemiluminescence efficiency of the ozone sensor. Since their response times are 22 seconds and 30 minutes, respectively, no correlation between rapid ozone fluctuations and those of these two trace gases is noticed by the ozone sensor when operating at a frequency of 10 Hz.The ozone sensor was tested for several weeks in continuous measurements of ozone fluxes and deposition velocities over different croplands using the eddy correlation technique. Good agreement was found between ozone dry deposition velocities derived from profile measurements and by eddy correlation.     

Fluid composition and evolution in coesite-bearing rocks (Dora-Maira massif,Western Alps): implications for element recycling during subduction

Fluid inclusions and F, Cl concentration of hydrous minerals were analysed in the coesite-pyrope quartzite, the interlayered jadeite quartzite and their country-rock gneiss from the Dora-Maira massif using a combination of microthermometry, Raman spectrometry, synchrotron X-ray microfiuorescence and electron microprobe analysis. Three populations of fluid inclusions were recognized texturally and can be related to distinct metamorphic stages. A low-salinity aqueous fluid occurs in the retrogressed country gneiss and as late secondary inclusions in jadeite quartzite and chloritized pyrope. An earlier secondary population is found in matrix quartz of the jadeite- and pyro-pe-quartzites. This population can be related to the early decompression and so to incipient breakdown of garnet into phlogopite-bearing assemblages. The inclusion fluid is highly saline (up to 84 wt% equivalent NaCl) and contains Na, Ca, Fe, Cu and Zn as major cations. In pyrope quartzite, additional K was found in these brines, which locally coexist with CO₂-rich inclusions. The oldest fluid inclusions are preserved in kyanite grains included in fresh pyrope and in pyrope itself. In pyrope, all inclusions have decrepitated and contain magnesite, an Mg-phosphate, sheet-silicate(s), a chloride and an opaque phase, with no fluid preser ved. In contrast, the kyanite inclusions in pyrope preserve primary H₂O-CO₂ low-salinity fluid inclusions, probably owing to the low compressibility of the kyanite inclusions and host garnet. In spite of in-situ re-equilibration, these inclusions can be interpreted as relics of the dehydration fluid that attended pyrope growth. These correlations between textural and chemical fluid inclusion data and metamorphic stages are consistent with the fluid composition calculated from the halogen content of different generations of phlogopite and biotite. The preservation of different fluid compositions, both in time and space, is evidence for local control and possibly origin of the fluids, in agreement with isotopic data. These results, in particular the absence of CO₂ in the jadeite quartzite, are best interpreted in terms of a fluid-melt system evolution. With increasing metamorphism, partitioning of H₂O, Na, Ca, Fe and heavy metals into melt (jadeite quartzite) and Mg, Na/K, F, CO₂ and P(?) into a residual aqueous fluid can account for depletion in Na, Ca and Fe of the pyrope quartzite. During the retrograde path, a _{H 2 O} rose as melt crystallized, generating the two populations of hypersaline and water-rich fluids that were highly reactive to pyrope. The process of fluid-melt interaction envisioned here coupled with models of melt extraction in subduction zones provides an attractive opportunity for the instantaneous ( < 1 Ma) and selective transport of elements between a downgoing slab and the overlying mantle wedge.     

Kontinentale und marine Senkungsbecken als Ausdruck epirogener Bewegungen

Zusammenfassung Wir unterscheiden innerhalb der Geosynklinalen langgestreckte, schmale kontinentale Stenosynklinalen (besonders der Permzeit) im Gegensatz zu den aus ihnen herauswachsenden breiten, flächenhaften Eurysynklinalen. Während bei der ersten Form keine eigentlichen Geantiklinalen zu beobachten sind, können die Flanken der Eurysynklinalen als Kippungsflächen um eine oder mehrere Achsen (bzw. Achsenbündel) mit aufsteigendem Geantiklinal-Hebelarm und absteigendem Geosynklinalarm aufgefa\t werden.Der Betrag der Senkung wird ausgedrückt durch den stets nur zu errechnenden, niemals zu messenden absoluten oder relativen Senkungswinkel. Der Höchstbetrag der Senkung wird bezeichnet durch den Trogwinkel, d. h. die Abweichung der ganzen Beckenfläche von der ursprünglichen Horizontalebene. Der Durchschnitts-Senkungswinkel ist bei den Eurysynklinalen nur durch Bogenminuten oder -Sekunden auszudrücken. Senkungs- und Trogwinkel sind in der Mitte der Senke am kleinsten, wachsen dann nach den Rändern hin etwas an, um nach den Rändern hin schlie\lich wieder abzunehmen; nur bei den Stenosynklinalen kann der Trogwinkel auf wenige Grade anwachsen.Das Wachsen der Sedimentationsräume ist bedingt durch Zunahme des Senkungswinkels. Verschiebt sich die Kippungsachse gegen das Senkentiefste, so steigt bei gleichbleibender Kippungstendenz das zwischen der alten und neuen Achse gelegene Stück wieder auf, es beginnt das Schwinden des Sedimentationsraumes, das bei den Stenosynklinalen zu einem völligem Verschwinden durch Zuschüttung wird.Im Bereich der Kippungsachse findet, sofern diese nicht gerade untermeerisch liegt, weder Ablagerung noch Abtragung statt, während mit wachsender Entfernung von ihr im sinkenden Hebelarm Vermehrung der Ablagerungen, im aufsteigenden Hebelarm Verstärkung der Abtragung eintritt.