Open Access

Characterizing fluid circulation in orogens is key to understanding orogenic processes because fluid–rock interaction modifies the physical properties of rocks, hence their response to deformation and, for example, their suitability for radioactive waste storage. Fluid circulation can be dated by applying geochronological methods to fluid-precipitated minerals. Fluid sources and associated pathways can be traced using isotope data measured in the same or in other cogenetic minerals. We applied this concept to the Aar Massif (central Swiss Alps), which was part of the former European passive continental margin that was deformed and exhumed during the (Cenozoic) Alpine orogeny. Newly collected epidote from veins and from one cleft at several localities in meta-granitoids in the Aar Massif yielded U–Pb ages ranging from 27.7 ± 3.4 to 12.4 ± 1.9 Ma, which complement previously published geochronological data revealing Permian (278 ± 29, 251 ± 50, and 275 ± 18 Ma) and Miocene (19.2 ± 4.3 and 16.9 ± 3.7 Ma) epidote veins. We used Pb–Sr–O–H isotope geochemistry of epidote to evaluate fluid sources and pathways during Permian rifting and the Miocene compressional phases of Alpine orogeny. Strontium isotope data of Permian epidote are consistent with previous work suggesting meteoric water infiltration along syn-rift faults and through syn-rift sediments. A more-complex structural framework existed in the Miocene, when a sedimentary lid covered the Aar Massif. Strontium, O, and H isotope data of Miocene epidote-forming fluids indicate (1) meteoric water, mixing with (2) fluids derived from sedimentary units being compacted during orogenesis and/or (3) metamorphic water. All three fluid endmembers may have been circulating and mixing in the Aar Massif during Miocene deformation. Strontium isotope data further indicate that Miocene fluids contributed to imprinting a highly radiogenic Sr isotope composition onto Alpine shear zones or that the fluids inherited a highly radiogenic Sr isotope component by dissolving the Rb-rich, high 87Sr / 86Sr biotite therein. Both possibilities can coexist, and they imply that external fluids could modify the chemical composition of the post-Variscan granitoids hosting the studied epidote veins by fluid–rock interaction processes during deformation. Lead, Sr, and H isotopic differences among Miocene samples further suggest complexity of large-scale fluid circulation. Our work supports the fact that the reconstruction of multifaceted and multi-stage fluid circulation in highly deformed rocks benefits from extracting geochronological and isotope data from the same mineral.

Streamflow drought hazard indicators (SDHIs) are mostly lacking in large-scale drought early warning systems (DEWSs). This paper presents a new systematic approach for selecting and computing SDHIs for monitoring drought for human water supply from surface water and for river ecosystems. We recommend considering the habituation of the system at risk (e.g., a drinking water supplier or small-scale farmers in a specific region) to the streamflow regime when selecting indicators; i.e., users of the DEWSs should determine which type of deviation from normal (e.g., a certain interannual variability or a certain relative reduction of streamflow) the risk system of interest has become used to and adapted to. Distinguishing four indicator types, we classify indicators of drought magnitude (water anomaly during a predefined period) and severity (cumulated magnitude since the onset of the drought event) and specify the many relevant decisions that need to be made when computing SDHIs. Using the global hydrological model WaterGAP 2.2d, we quantify eight existing and three new SDHIs globally. For large-scale DEWSs based on the output of hydrological models, we recommend specific SDHIs that are suitable for assessing the drought hazard for (1) river ecosystems, (2) water users without access to large reservoirs, and (3) water users with access to large reservoirs, as well as being suitable for informing reservoir managers. These SDHIs include both drought magnitude and severity indicators that differ by the temporal averaging period and the habituation of the risk system to reduced water availability. Depending on the habituation of the risk system, drought magnitude is best quantified either by the relative deviation from the mean or by the return period of the streamflow value that is based on the frequency of non-exceedance. To compute the return period, we favor empirical percentiles over the standardized streamflow indicator as the former do not entail uncertainties due to the fitting of a probability distribution and can be computed for all streamflow time series. Drought severity should be assessed with indicators that imply habituation to a certain degree of interannual variability, to a certain reduction from mean streamflow, and to the ability to fulfill human water demand and environmental flows. Reservoir managers are best informed by the SDHIs of the grid cell that represents inflow into the reservoir. The DEWSs must provide comprehensive and clear explanations about the suitability of the provided indicators for specific risk systems.

Surface temperature is a fundamental parameter of Earth’s climate. Its evolution through time is commonly reconstructed using the oxygen isotope and the clumped isotope compositions of carbonate archives. However, reaction kinetics involved in the precipitation of carbonates can introduce inaccuracies in the derived temperatures. Here, we show that dual clumped isotope analyses, i.e., simultaneous ∆47 and ∆48 measurements on the single carbonate phase, can identify the origin and quantify the extent of these kinetic biases. Our results verify theoretical predictions and evidence that the isotopic disequilibrium commonly observed in speleothems and scleractinian coral skeletons is inherited from the dissolved inorganic carbon pool of their parent solutions. Further, we show that dual clumped isotope thermometry can achieve reliable palaeotemperature reconstructions, devoid of kinetic bias. Analysis of a belemnite rostrum implies that it precipitated near isotopic equilibrium and confirms the warmer-than-present temperatures during the Early Cretaceous at southern high latitudes.

It is generally recognized that large-scale whaling in the 19th and 20th century led to a substantial reduction of the size of many cetacean populations, particularly those of the baleen whales (Mysticeti). The impact of these operations on genomic diversity of one of the most hunted whales, the fin whale (Balaenoptera physalus), has remained largely unaddressed because of the paucity of adequate samples and the limitation of applicable techniques. Here, we have examined the effect of whaling on the North Atlantic fin whale based on genomes of 51 individuals from Icelandic waters, representing three temporally separated intervals, 1989, 2009 and 2018 and provide a reference genome for the species. Demographic models suggest a noticeable drop of the effective population size of the North Atlantic fin whale around a century ago. The present results suggest that the genome-wide heterozygosity is not markedly reduced and has remained comparable with other baleen whale species. Similarly, there are no signs of apparent inbreeding, as measured by the proportion of long runs of homozygosity, or of a distinctively increased mutational load, as measured by the amount of putative deleterious mutations. Compared with other baleen whales, the North Atlantic fin whale appears to be less affected by anthropogenic influences than other whales such as the North Atlantic right whale, consistent with the presence of long runs of homozygosity and higher levels of mutational load in an otherwise more heterozygous genome. Thus, genome-wide assessments of other species and populations are essential for future, more specific, conservation efforts.

This study was performed to identify Peronosclerospora species found in Indonesia based on sequence analysis of the cox2 gene. In addition, sequence data in total, 26 isolates of Peronosclerospora were investigated in this study. They were obtained from 7 provinces in Indonesia, namely Lampung, Jawa Timur, Jawa Barat, Sumatera Utara, Jawa Tengah, Yogyakarta, and Sulawesi Selatan. Sequence analysis of cox2 and phylogenetic inference were performed on all the 26 isolates. A set of primers developed in this study, PCOX2F and PCOX2R, was used for PCR amplification. Phylogenetic analyses showed that all the Indonesian isolates were divided into two groups. Group I contained 13 isolates; 9 isolates obtained from Lampung, 3 isolates from Sumatera Utara, and 1 isolate from Jawa Barat. Group II consisted of 13 isolates; 7 isolates from Jawa Timur, 2 isolates from Jawa Tengah, 1 isolate from Yogyakarta, and 3 isolates from Sulawesi Selatan. All the members of group I clustered with the ex-type sequence of P. australiensis. Meanwhile, all members of Group II formed the sister clade of isolates obtained from Timor-Leste and may represent P. maydis.