Fishing for diatoms: fish gut analysis reveals water quality changes over a 75-year period

Defining the reference state of some perturbed streams and rivers is challenging since their non-altered state is undocumented. Despite the near-absence of pristine sites in highly anthropogenic areas, information about aquatic communities that existed prior to human disturbance can be obtained from historic sources. Sediment coring is commonly used in paleolimnology to estimate past environmental conditions of lakes, but this technique is often not appropriate for studies of lotic systems. An alternative is to use diatom assemblages present in the guts of fish that were captured in the streams prior to significant human disturbance. The purpose of the present study was to evaluate the biological integrity of several streams in Ontario and Québec during the early twentieth century based on “paleo” diatom assemblages extracted from the guts of fish stored in museums. The Eastern Canadian diatom index (IDEC: Indice Diatomées de l’Est du Canada) was used to evaluate the biological status of “paleo” and “modern” diatom assemblages. The IDEC shows the position of diatom assemblages on a general pollution gradient. The comparison of IDEC values calculated for the 1925–1948 and the 2003–2007 periods showed that several streams were severely polluted in the early 1900s. In general, present water quality has declined compared to the early 1900s. The biological integrity of only three of the 22 sites has increased. IDEC values were not influenced by the species of fish studied.     

Pockmarks in the inner Oslofjord,Norway

Multibeam bathymetric surveys of the Inner Oslofjord, Norway have revealed a high density of pockmarks in the 179-km² inner fjord area, which contains over 500 pockmarks of varying size, typically 20–50 m in diameter and 2–10 m deep. These pockmarks have been investigated with a variety of techniques, including acoustic subbottom profiling, sedimentological and geochemical analyses of cores, remotely operated vehicle observation, and morphometry. Both the distribution and shapes of the pockmarks suggest that they are related to structures in the bedrock underlying relatively thin (<50 m) unconsolidated glacial and postglacial sediments. The data provide no direct indication of a particular mode of pockmark formation, but release of large amounts of biogenic, shallow methane seems unlikely. Several lines of evidence point to a continuous process of pockmark formation followed by inactivity, with some pockmarks recently active whereas others have been inactive for a considerable time. Some pockmarks are characterised by coarse sediment in their centres. The density, variety and easy access make this pockmark field an ideal model area for pockmark research. John S. Gray is deceased.     

Major and trace element geochemistry of neutral and acidic thermal springs at El Chichón volcano,Mexico: Implications for monitoring of the volcanic activity

Four groups of thermal springs with temperatures from 50 to 80 °C are located on the S–SW–W slopes of El Chichón volcano, a composite dome-tephra edifice, which exploded in 1982 with a 1 km wide, 160 m deep crater left. Very dynamic thermal activity inside the crater (variations in chemistry and migration of pools and fumaroles, drastic changes in the crater lake volume and chemistry) contrasts with the stable behavior of the flank hot springs during the time of observations (1974–2005). All known groups of hot springs are located on the contact of the basement and volcanic edifice, and only on the W–SW–S slopes of the volcano at almost same elevations 600–650 m asl and less than 3 km of direct distance from the crater. Three groups of near-neutral (pH ≈ 6) springs at SW–S slopes have the total thermal water outflow rate higher than 300 l/s and are similar in composition. The fourth and farthest group on the western slope discharges acidic (pH ≈ 2) saline (10 g/kg of Cl) water with a much lower outflow rate (< 10 l/s).     

Adaptive balance of global development processes

We study the processes of global self-regulation of Earth’s biota (GAIA-theory) by applying the method of adaptive balance of causes proposed by the authors. By using, as an example, the Daisy World model constructed by this method, we reveal the phenomenon of preservation of the mean temperature of Earth’s surface due to the presence of the vegetation cover. We develop an integral model of global natural, social, and economic processes in which the World Ocean is one of the factors regulating the amount of greenhouse gases in the atmosphere. The decrease in the amount of greenhouse gases in the atmosphere caused by the GAIA-effects increases the number of hurricanes and floods on the Earth. As a result, the levels of ecological and social hazards for the mankind become much higher. To eliminate these threats, it is necessary to intensify the processes of self-organization of the society realized via the improvement of education, development of science, and global regulation of the competition for natural resources. We present the results of numerical experiments performed by using the model demonstrating possible scenarios of global development with regard for the processes of self-organization of the society. __________ Translated From Morskoi Gidrofizicheskii Zhurnal, No. 3, Pp. 62–80, May–June, 2007.     

Undamped oscillations of collisionless stellar systems: Spheres,spheroids and discs

The collisionless Boltzmann equation governing self-gravitating systems such as galaxies has recently been shown to admit exact oscillating solutions with planar and spherical symmetry. The relation of the spherically symmetric solutions to the Virial theorem, as well as generalizations to non-uniform spheres, uniform spheroids and discs form the subject of this paper. These models generalize known families of static solutions. The case of the spheroid is worked out in some detail. Quasiperiodic as well as chaotic time variation of the two axes is demonstrated by studying the surface of section for the associated Hamiltonian system with two degrees of freedom. The relation to earlier work and possible implications for the general problem of collisionless relaxation in self gravitating systems are also discussed     

Oxygen and nutrient dynamics within mats of the filamentous macroalga Chaetomorpha linum

Concentration profiles of O₂, NH₄ ⁺, NO₃ ⁻, and PO₄ ³⁻ were measured at high spatial resolution in a 12-cm thick benthic mat of the filamentous macroalga Chaetomorpha linum. Oxygen and nutrient concentration profiles varied depending on algal activity and water turbulence. High surface irradiance stimulated O₂ production in the surface layers and introduced O₂ to deeper parts of the mat while the bottom layers of the mat and the underlying sediment were anoxic. Nutrient concentrations were highest in the bottom layers of the mat directly above the sediment nutrient source and decreased towards the surface layers due to algal assimilation and enhanced mixing with the overlying water column. Increased turbulence during windy periods resulted in more homogeneous oxygen and nutrient concentration profiles and shifted the oxic-anoxic interface downward. Denitrification within the mat, as measured by the isotope pairing technique on addition of ¹⁵NO₃ ⁻, was found to take place directly below the oxic-anoxic interface. Denitrification activity was always due to coupled nitrification-denitrification, whereby nitrifiers in the mat utilize NH₄ ⁺ diffusing from below and O₂ diffusing from above. The denitrification rate in the mat ranged from 22 μmol m⁻² h⁻¹ to 28 μmol m⁻² h⁻¹, approximately equivalent to that measured in the surrounding nonvegetated sediment. Although sediment denitrification is suppressed when the sediment surface is covered by a dense macroalgal mat, the denitrification zone may migrate up into the mat. In eutrophic estuaries with a large area of macroalgal cover, the physical structure and growth stage of algal mats may thus play an important role in the regulation of nitrogen removal by denitrification.     

Thermal stability of ladderane lipids as determined by hydrous pyrolysis

Anaerobic ammonium oxidation (anammox) has been recognized as a major process resulting in loss of fixed inorganic nitrogen in the marine environment. Ladderane lipids, membrane lipids unique to anammox bacteria, have been used as markers for the detection of anammox in marine settings. However, the fate of ladderane lipids after sediment burial and maturation is unknown. In this study, anammox bacterial cell material was artificially matured by hydrous pyrolysis at constant temperatures ranging from 120 to 365 °C for 72 h to study the stability of ladderane lipids during progressive dia- and catagenesis. HPLC-MS/MS analysis revealed that structural alterations of ladderane lipids already occurred at 120 °C. At temperatures >140 °C, ladderane lipids were absent and only more thermally stable products could be detected, i.e., ladderane derivatives in which some of the cyclobutane rings were opened. These diagenetic products of ladderane lipids were still detectable up to temperatures of 260 °C using GC-MS. Thus, ladderane lipids are unlikely to occur in ancient sediments and sedimentary rocks, but specific diagenetic products of ladderane lipids will likely be present in sediments and sedimentary rocks of relatively low maturity (i.e., C₃₁ hopane 22S/(22S + 22R) ratio <0.2 or ββ/(αβ + βα + ββ) ratio of >0.5).     

Corrosion Resistance of the Nd–Ti Matrix for Actinides

Doklady Earth Sciences - Leaching of Np and Pu in water from samples composed of two titanate phases Nd2Ti3O9 (75 wt %) and Nd2Ti2O7 (25 wt %) is investigated. The rates of leaching actinides...     

Linearized Stability Analysis of Charged and Scalar Hairy Thin-shell Wormhole

Astronomy Reports - We construct a spherically symmetric charged thin-shell wormhole using the cut-and-paste technique implemented by Visser in Einstein–Maxwell gravity with a conformally...