Anthropogenic disturbance on nursery function of estuarine areas for marine species

Estuaries serve as nursery grounds for many marine fish species. However increasing human activities within estuaries and surrounding areas lead to significant habitat loss for the juveniles and decrease the quality of the remaining habitats. This study is based on the data of 470 beam trawls from surveys that were conducted in 13 French estuaries for the purpose of the European Water Framework Directive. It aimed at testing the effects of anthropogenic disturbances on the nursery function of estuaries. With a multispecific approach based on ecological guilds, two fish metrics, abundance and species richness of Marine Juvenile migrant fishes, were used as proxies for the estuarine nursery function. Indices of heavy metal and organic contaminations were used to estimate anthropogenic disturbances impacting these estuaries. Fish metrics were described with statistical models that took into account: (a) sampling protocol, (b) estuarine features and (c) contamination. The results of these models showed that the fish metrics highly depend on the sampling protocol, and especially type of gear, depth and salinity, which highlights the necessity of considering such metrics at the sampling (trawl haul) scale. Densities and species richness of Marine Juvenile fishes appeared to be strongly and negatively correlated to contamination indices. These results are consistent with the hypothesis that human disturbances impact the nursery function of estuaries. Finally, the densities of Marine Juvenile migrant species appeared as a potential robust and useful fish indicator for the assessment of the ecological status of estuaries within the Water Framework Directive.     

Evolution of the Peak Hill high-sulfidation epithermal Au–Cu deposit,eastern Australia

The early Palaeozoic Macquarie Arc, southeastern Australia, hosts a variety of major late Ordovician to earliest Silurian subduction-related deposits (e.g., Cadia East, Ridgeway, Cadia Hill, Cowal and Northparkes). However, there is uncertainty about whether coeval high-sulfidation epithermal deposits, which occur in intra-oceanic metallogenic belts elsewhere in the West Pacific, (e.g., Lepanto and Chinkuashih), are also present in the Macquarie Arc. This has led to suggestions that their absence may be due to the poor preservation potential of deposits that form at relatively shallow crustal levels in ancient rocks. We present here an interpretation for evolution of the Peak Hill Au–Cu deposit based on the distribution of alteration facies, sulfur isotope data from several textural forms of pyrite and barite, and an assessment of the regional volcanic and sedimentary facies architecture. These data show that the Peak Hill deposit displays a distinct sub-vertical zoning with a pyrophyllite and vuggy-quartz core, that today extends about 350 m east–west and at least 550 m north–south, which grades out through paragonite+muscovite, kaolinite to a chlorite+epidote alteration zone at the margin. The alteration zoning reflects both lower temperatures and neutralisation of acid fluids with increasing distance from the core, which represents the conduit along which hot acidic hydrothermal fluids were channelled. Several temporally overlapping events of silicification, bladed-quartz-pyrite veining, brecciation and pyrite veining occurred during the last stages of hydrothermal alteration, although most appear to predate mineralisation. Au–Cu mineralisation was associated with late quartz-pyrite-barite veins, and the highest gold grades occur mainly in microcrystalline-quartz-altered rocks in the paragonite+muscovite alteration zone, generally within 50 m outward from the boundary of the pyrophyllite and vuggy-quartz core. Sulfur- and lead-isotope data, and the characteristic zoning of ore minerals and alteration assemblages support a magmatic source for the hydrothermal fluids. Similarities in many of the isotopic signatures between Peak Hill and deposits such as Northparkes support generation of the high-sulfidation mineralisation during the Late Ordovician to earliest Silurian (possibly ca. 440 Ma) metallogenic event. The Late Ordovician to Early Silurian volcanic and sedimentary facies associations at Peak Hill are consistent with alteration and mineralisation occurring in rocks deposited in a submarine setting.     

Two distinct Miocene age ranges of basaltic rocks from the Rhön and Heldburg areas (Germany) based on Ar/Ar step heating data

New ⁴⁰Ar/³⁹Ar age data are determined for Cenozoic basaltic rocks from the Thuringian Rhön and Heldburg Gangschar (area also referred to as Grabfeld), integral parts of the Central European Volcanic Province. Applying the incremental heating technique on groundmass and plagioclase separates provided data which considerably specify our knowledge on the eruption ages in these volcanic fields and narrow down the duration of volcanic activity compared to earlier studies. All data but one outlier range between 20 and 14 Ma, being thus similar to those of the neighbouring Vogelsberg volcanic complex. The spectrum of ages is clearly divided into two distinct subsets: the Rhön ages are between 20 and 18 Ma, those of the Heldburg Gangschar are between 16 and 14 Ma. Thus, the present data clearly indicate a striking regional and temporal division of the Thuringian Miocene volcanism. The composition of the volcanic rocks in the two volcanic fields is remarkably diverse, ranging from tholeiitic basalts over alkali basalts and basanites to nephelinites. However, radiometric ages do not correlate with geochemical or petrological characteristics of the volcanics within each volcanic field, indicating that the different magma types erupted broadly contemporaneously.The outlier in age (29 Ma) is from a volcanic dyke of the NE Rhön area close to the NW end of the Thuringian Forest. However, more data are required to approve the significance of this age value, in particular since the rock showed isotopic age disturbance.     

Spatial concentration and variability of rainfall in the Iguaçu River Basin,State of Paraná−Brazil

The analysis of rainfall as an environmental factor that influences landscape dynamics is an important and ongoing topic of discussion. This discussion can be centred on the discovery of impacts caused by the increase or decrease in rainfall frequency and intensity. From this perspective, this study sought to analyse the rainfall variability in the Iguaçu River basin, located in the State of Paraná, southern Brazil. The main objective was focused on the temporal-spatial rainfall distribution in the study area and its interaction with landscape dynamics (different land uses). Precipitation data for the period 1988−2018 were obtained from the ‘Águas Paraná’ Institute. To calculate the Concentration Index−CI values of the study area, data analysis was performed using the ‘R’ software with Climatol and Precindicon subroutines of the software, and analysis of Landsat 8 satellite images through ArcGIS. The results indicated that there was a well-defined spatial variability in the study area, as the CIs defined higher rainfall concentrations upstream from the river basin and lower rainfall concentrations downstream—implying that these processes may be strongly associated with land use.     

Effect of mid-oceanic ballast water exchange on virus-like particle abundance during two trans-Pacific voyages

Ballast water is a potential source of invasive species, including viruses that target a variety of hosts. We sampled ballast during two trans-Pacific voyages and analyzed the efficacy of mid-oceanic exchange in reducing virus-like particle (VLP) abundance. Exchange did not significantly reduce virus abundance during the first voyage (P = 0.874), whereas it reduced viral abundance 3.9-fold from 1.8 × 10⁷ to 0.47 × 10⁷ VLP mL⁻¹ during the second voyage (P < 0.0001). Despite the impact of exchange during the second voyage, virus abundances were not significantly different between exchanged and unexchanged tanks upon arrival in Canada (P = 0.363) and Canadian port water samples (P = 0.502). Regressions between environmental parameters and VLP abundance uncovered negative correlations between salinity and viral abundance during one, and dissolved oxygen and viral abundance during the second voyage. In summary, ballast tanks are highly variable with respect to total virus abundance, and the efficacy of exchange requires investigation into the dynamics of specific viruses.     

Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea

Four seep sites located within an ∼20 km² area offshore Georgia (Batumi seep area, Pechori Mound, Iberia Mound, and Colkheti Seep) show characteristic differences with respect to element concentrations, and oxygen, hydrogen, strontium, and chlorine isotope signatures in pore waters, as well as impregnation of sediments with petroleum and hydrocarbon potential. All seep sites have active gas seepage, near surface authigenic carbonates and gas hydrates. Cokheti Seep, Iberia Mound, and Pechori Mound are characterized by oil-stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release. Pechori Mound is further characterized by deep fluid advection of lower salinity pore fluids. The Pechori Mound pore fluids are altered by mineral/water reactions at elevated temperatures (between 60 and 110 °C) indicated by heavier oxygen and lighter chlorine isotope values, distinct Li and B enrichment, and K depletion. Strontium isotope ratios indicate that fluids originate from late Oligocene strata. This finding is supported by the occurrence of hydrocarbon impregnations within the sediments. Furthermore, light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at Pechori Mound, Iberia Mound, and Colkheti Seep. C₁₅₊ hydrocarbons at the oil seeps are allochtonous, whereas those at the Batumi seep area are autochthonous. The presence of oleanane, an angiosperm biomarker, suggests that the hydrocarbon source rocks belong to the Maikopian Formation. In summary, all investigated seep sites show a high hydrocarbon potential and hydrocarbons of Iberia Mound, Colkheti Seep, and Pechori Mound are predominantly of thermogenic origin. However, only at the latter seep site advection of deep pore fluids is indicated.     

Political ecology and habitat conservation for endangered species planning in Southern California: Region, places, and ecological governance

The county of Riverside California has a long history of land conservation. In this comparative case study between Western Riverside County and the Coachella Valley area in the county we show how governance institutions that encompass regions that have very different ecologies, are governed by rules and regulations that are undifferentiated relative to those differences. The study argues, however, that what may differ are the workings of the local urban regimes and the metabolic appropriation of ecosystems for economic growth. In this close investigation of the sprawling county of Riverside we find very different approaches to habitat preservation and the enrollment of nature for wealth production by the local urban regimes.     

Climate change effects on snow melt and discharge of a partly glacierized watershed in Central Switzerland (SoilTrec Critical Zone Observatory)

A comprehensive hydrological modeling study in the drainage area of a hydropower reservoir in central Switzerland is presented. Two models were tested to reproduce the measured discharge dynamics: (1) a detailed energy-balance model (ALPINE3D) primarily designed for snow simulations; (2) a conceptual runoff model system (PREVAH), including a distributed temperature-index snow and ice melt model. Considerable effort was put into distributing available meteorological station data to the model grids as forcing data. The recent EU regional climate modeling initiative ENSEMBLES provided up-to-date climate predictions for two 30-a periods in mid and late 21st century. These were used to estimate evolutions in the water supply of the hydropower reservoir in response to expected climate changes. The simulations suggest a shift of spring peak-flow by almost two months for the end of the century. Warmer winter temperatures will cause higher winter base-flow. Due to glacier retreat, late-summer flow will decrease at the end of the century.