Earth Sciences

Paraleucilla magna was the first sponge recognised as alien in the Atlantic. It was first registered in Rio de Janeiro (Brazil) and soon became very abundant in the southeastern and southern coasts of Brazil and also in the Mediterranean. Its origin is still unknown but recurrent introductions seem to have occurred in the Mediterranean. In this study, we used genetic markers (microsatellites) to test if Brazilian and Adriatic populations share a single source or if multiple introductions occurred in both regions. We also compared the genetic composition of populations established almost 30 years ago (Brazil) with a recently founded population (Adriatic—less than 10 years). Populations of P. magna were sampled in four localities across 900 km in the Southwestern Atlantic (Brazilian coast) and in one locality in the Adriatic (Croatian coast). Our results suggest the presence of five genetically distinct populations possibly originated by multiple human-mediated introductions from different sources and show that the putative most recently established population is genetically more diverse.

Aliphatic (AHs) and polycyclic aromatic hydrocarbons (PAHs) concentrations were measured in marine surface sediments around the Brazilian station in Admiralty Bay, during the summers of 1997/98 and 1999/2000 using GC-FID and GC-MS. Total aliphatic hydrocarbons ranged from 0.15 to 13.28 μg·g−1 (dry weight) while n-alkanes varied between 0.10 and 9.63 μg·g−1. The highest concentrations were obtained at the sewage outfall, with decreasing levels away from the outfall. The distribution of n-alkanes showed significant quantities of long chain n-alkanes (n-C22 to n-C34) at sites near the Brazilian station that may be attributed to the station activities. A short chain n-alkanes sequence (n-C12 to n-C21) associated with diesel fuel arctic (DFA) was present in all the samples. Total PAHs varied from 9.45 to 270.5 ng·g−1. The higher PAHs level and the presence of an unresolved complex mixture only in sediment from the sewage outfall is an indication of oil contamination at this location. A s...

The Yonge Street Aquifer (YSA) in the Greater Toronto Area of south-central Ontario is a prolific municipal supply aquifer. It has been considered to be channelized sand and gravel linked to a bedrock valley. Despite considerable work, the fundamental conceptual model for the YSA is not well developed and documented. Based on high-quality data, a revised conceptual model of the aquifer is presented. Seismic profiles define the geometry of the regional stratigraphy with four distinct units: bedrock, Lower sediments, Newmarket Till, and Oak Ridges Moraine (ORM) sediment. Seismic data reveal two generations of roughly north–south channels: older sub-Newmarket Till channels within Lower sediments (termed Thorncliffe channel) and ORM-related channels (termed ORM channel) that incise both Newmarket Till and Lower sediments. The YSA is interpreted to occur within a Thorncliffe channel, with possible vertical connection to younger ORM channels and lateral connection to inter-channel Lower s...

Abstract The basal succession of the Condamine Valley, which overlays the boundary between the Surat and Clarence-Moreton basins (eastern Australia), contains a clay-rich horizon ‘the Transition Zone’ that marks a pronounced unconformity between the Jurassic Walloon Coal Measures and the Quaternary Condamine Alluvium. This paper provides insights into the tectonic and drainage evolution of the Condamine Valley through integrated analysis of U–Pb ages of detrital zircon from three samples (494 concordant analyses), stable oxygen isotope analysis on eight authigenic clay samples, X-ray fluorescence of primary and trace elements, and hyperspectral mineral analysis from two drill cores (Lone Pine 17 and Daandine 164). The Transition Zone is interpreted to consist of both weathered Jurassic sediments and Cenozoic clay deposits. Two sequential cycles of erosion, deposition and pedogenesis, related to geomorphological and climatic conditions are recognised. Distinctive oxygen isotope signatures of the two weathering fronts demonstrated an initial Early Cretaceous phase (δ18O = 11.9–15.7‰ VSMOW) associated with laterisation and possible uplift, followed by Paleogene (δ18O = 16.4–17.3‰ VSMOW) silcretisation of reworked Jurassic sediments. Detrital zircon geochronology yielded Jurassic maximum constraints for the age of deposition of three samples that are indistinguishable within error, the oldest of which (163 ± 8 Ma from the lateritic profile) corresponds to the age of the underlying Walloon Coal Measures. The two overlaying samples from a silcrete profile and granular alluvium yielded overlapping yet younger ages of 150 ± 6 Ma and 156 ± 9 Ma, respectively. Vitrinite reflectance used as a proxy for the thermal condition of the coal strata enabled an estimated 2–3 km of burial and subsequent (likely Early Cretaceous) uplift. Geochemical insights from the Condamine Valley correspond to broad-scale climatic and tectonic conditions, suggesting that ‘transition zone equivalents’ and corresponding groundwater dynamics may occur in similar sedimentary settings throughout eastern Australia.

Sensitive and reliable methods are required for the assessment of oxidative DNA damage, which can result from reactive oxygen species that are generated endogenously from cellular metabolism and inflammatory responses, or by exposure to exogenous agents. The development of a liquid chromatography/tandem mass spectrometry (LC/MS/MS) selected reaction monitoring (SRM) method is described, that utilises online column-switching valve technology for the simultaneous determination of two DNA adduct biomarkers of oxidative stress, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxodA). To allow for the accurate quantitation of both adducts the corresponding [(15)N(5)]-labelled stable isotope internal standards were synthesised and added prior to enzymatic hydrolysis of the DNA samples to 2'-deoxynucleosides. The method required between 10 and 40 microg of hydrolysed DNA on-column for the analysis and the limit of detection for both 8-oxodG and 8-oxodA was 5 fmol. The analysis of calf thymus DNA treated in vitro with methylene blue (ranging from 5 to 200 microM) plus light showed a dose-dependent increase in the levels of both 8-oxodG and 8-oxodA. The level of 8-oxodG was on average 29.4-fold higher than that of 8-oxodA and an excellent linear correlation (r = 0.999) was observed between the two adducts. The influence of different DNA extraction procedures for 8-oxodG and 8-oxodA levels was assessed in DNA extracted from rat livers following dosing with carbon tetrachloride. The levels of 8-oxodG and 8-oxodA were on average 2.9 (p = 0.018) and 1.4 (p = 0.018) times higher, respectively, in DNA samples extracted using an anion-exchange column procedure than in samples extracted using a chaotropic procedure, implying artefactual generation of the two adducts. In conclusion, the online column-switching LC/MS/MS SRM method provides the advantages of increased sample throughput with reduced matrix effects and concomitant ionisation suppression, making the method ideally suited when used in conjunction with chaotropic DNA extraction for the determination of oxidative DNA damage.