Environmental predictors of decapod species richness and turnover along an extensive Australian continental margin (13–35° S)

The use of environmental data in biogeographic studies of the deep sea is providing greater insight into the processes underlying large‐scale patterns of diversity. Recent surveys of Australia's western continental margin (~100–1100 m) provide systematic sampling of invertebrate megafauna along a gradient of 22° of latitude (13–35° S). Diversity patterns of decapod crustaceans were examined and we investigated the relative importance of environmental and spatial predictor variables on both species richness (alpha diversity) and species turnover. Distance‐based linear models (DistLM) indicated a suite of variables were important in predicting species turnover, of which temperature and oxygen were the most influential. These reflected the oceanographic features that dominate distinct depth bathomes along the slope. The numbers of species within samples were highly variable; a small but significant increase in diversity towards the tropics was evident. Replicated sampling along the margin at ~100 m and ~400 m provided an opportunity to compare latitudinal patterns of diversity at different depths. On the shallow upper slope (~400 m) temperature was disassociated from latitude and the latter proved to be the best predictor of sample species richness. The predictive power of latitude over other variables indicates that proximity to the highly diverse Indo‐West Pacific (IWP) may be important, especially considering that almost 40% of species in this study had a wide IWP distribution. In the management of Australia's marine environments, geomorphic surrogates have been emphasised when defining areas for protection. We found sea‐floor characteristics were relatively less important in predicting richness or community composition.     

High-resolution seabed imagery as a tool for biodiversity conservation planning on continental margins

Submarine canyons increase seascape diversity on continental margins and harbour diverse and abundant biota vulnerable to fishing. Because many canyons are fished, there is an increasing emphasis on including them in conservation areas on continental margins. Here we report on sponge diversity and bottom cover in three canyons of South-eastern Australia, test the performance of biological and abiotic surrogates, and evaluate how biological data from detailed seabed surveys can be used in conservation planning in these habitats. The biological data on sponge assemblage structure and species richness were obtained from 576 seafloor images taken between 148 and 472 m depth, yielding 65 morphospecies. Seafloor characteristics were similar within and between canyons, being almost exclusively composed of sediments with very few rocky substrates of higher relief. This environmental homogeneity did not, however, translate into biological uniformity of the megabenthos, and environmental factors were consequently poor predictors of biological features. By contrast, total bottom cover of sponges was highly correlated with species richness and served as a good proxy for species-level data in this situation. Design strategies that employ information on cover or richness of sponges provided a large dividend in conservation effort by dramatically reducing the number of spatial units required to achieve a specified conservation target of 50–90% of species to be included in reserves. This demonstrates that image-derived data are useful for the design of reserves in the deep sea, particularly where extractive sampling is not warranted. Using biological data on the sponge megabenthos to identify conservation units can also minimise socio-economic costs to fisheries because of a smaller geographic and bathymetric ambit of conservation areas.     

White dwarf evolution and crystallization

We present a numerical study for the evolution of non-DA white dwarfs of 0.4, 0.55, 0.8, 1.0, and 1.2M . We pay special attention to the behaviour of the crystallization front. It is shown that crystallization begins at higher luminosities the higher the white dwarf mass is. The shape of the crystal growth function is very similar, almost independent of the value of the total stellar mass. We also study the crystallization process analytically, finding that it is nicely reproduced by a very simple model that accounts for the numerical results.Member of the Carrera del Investigador Científico, Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (Argentina).Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina).     

The Equation of State for Caspian Sea Waters

The density ρ of Caspian Sea waters was measured as a function of temperature (273.15–343.15) K at conductivity salinities of 7.8 and 11.3 using the Anton-Paar Densitometer. Measurements were also made on one of the samples (S = 11.38) diluted with water as a function of temperature (T = 273.15–338.15 K) and salinity (2.5–11.3). These latter results have been used to develop an equation of state for the Caspian Sea (σ = ±0.007 kg m⁻³)

Modelling indicators of water security,water pollution and aquatic biodiversity in Europe

Abstract

The GWAVA (Global Water AVailability Assessment) model for indicating human water security has been extended with a newly developed module for calculating pollutant concentrations. This module is first described and then illustrated by being used to model nitrogen, phosphorus and organic matter concentrations. The module uses solely input variables that are likely to be available for future scenarios, making it possible to apply the module to such scenarios. The module first calculates pollutant loading from land to rivers, lakes and wetlands by considering drivers such as agriculture, industry and sewage treatment. Calculated loadings are subsequently converted to concentrations by considering aquatic processes, such as dilution, downstream transport, evaporation, human water abstraction and biophysical loss processes. Aquatic biodiversity is indicated to be at risk if modelled pollutant concentrations exceed certain water quality standards. This is indicated to be the case in about 35% of the European area, especially where lakes and wetlands are abundant. Human water security is indicated to be at risk where human water demands cannot be fulfilled during drought events. This is found to be the case in about 10% of the European area, especially in Mediterranean, arid and densely-populated areas. Modelled spatial variation in concentrations matches well with existing knowledge, and the temporal variability of concentrations is modelled reasonably well in some river basins. Therefore, we conclude that the updated GWAVA model can be used for indicating changes in human water security and aquatic biodiversity across Europe.

Editor Z.W. Kundzewicz

Citation Dumont, E., Williams, R., Keller, V., Voss, A., and Tattari, S., 2012. Modelling indicators of water security, water pollution and aquatic biodiversity in Europe. Hydrological Sciences Journal, 57 (7), 1378–1403.     

Buchbesprechung

Ohne Zusammenfassung     

Stratigraphie,Tektonik und hydrothermale Vererzung im Raume Wissen-Morsbach (Sieg)

Zusammenfassung Die Grundlage einer tektonischen Untersuchung im Raume Wissen-morsbach bildete die stratigraphische Gliederung und Kartierung von Siegener Schichten. Schwermineralanalysen erwiesen sich für eine Gliederung als bedeutungslos. Wichtigstes Ergebnis der tektonischen Kartierung ist die Feststellung von Achsenrampen, in denen kilometerlange Störungen durchlaufen. Die Erzgänge, an Diagonalscherflächen gebunden, streichen im einzelnen spitzwinklig zu den Achsenrampen. In ihrer Gesamtheit lassen sie sich zu Hauptgangzonen anordnen, die innerhalb und in Richtung der Achsenrampen verlaufen. Hohe Mangangehalte in den Grauwacken weisen auf eventuelle, nicht aufgeschlossene Erzgänge hin.     

Diffusion in helium white dwarf stars

This paper is aimed at exploring the effects of diffusion on the structure and evolution of low-mass helium white dwarfs. To this end, we solve the multicomponent flow equations describing gravitational settling and chemical and thermal diffusion. The diffusion calculations are coupled to an evolutionary code in order to follow the cooling of low-mass, helium core white dwarf models having envelopes made up of a mixture of hydrogen and helium, as recently suggested by detailed evolutionary calculations for white dwarf progenitors in binary systems. We find that diffusion causes hydrogen to float and the other elements to sink over time-scales shorter than evolutionary time-scales. This produces a noticeable change in the structure of the outer layers, making the star inflate. Thus, in order to compute accurately the mass–radius relation for low-mass helium white dwarfs we need to account for the diffusion processes during (at least) the white dwarf stages of the evolution of these objects. This should be particularly important when studying the general characteristics of binary systems containing a helium white dwarf and a pulsar.
In addition, we present an analytic, approximate model for the outer layers of the white dwarf aimed at interpreting the physical reasons for the change in the surface gravity for low-mass white dwarfs induced by diffusion.