Feeding habits of Cardinalfish Epigonus crassicaudus, using stomach contents and stable isotopes

Indexación: Scopus.El besugo, Epigonus crassicaudus, es una especie de importancia económica para la actividad pesquera que opera en el centro-sur de Chile. A pesar de ello, poco es lo que se conoce respecto a su biología. En este sentido, este trabajo estudió los hábitos alimentarios combinando análisis estomacales y de estabilidad isotópica. Los resultados del análisis dan cuenta de la importancia de los peces mesopelágicos (Myctophidae, Stomiidae) en la dieta con un aporte del 80%, seguido por crustáceos (Sergestes arcticus) alcanzando un 10%. No se detectaron diferencias en la dieta en peces con distinto grado de madurez sexual. En tanto, los valores de los isótopos de nitrógeno y carbono mostraron valores de promedio de 17,12 ± 1,1 δ15N y de -17,51 ± 0,7 δ13C, respectivamente. La constitución de valores de δ13C fue proporcional al tamaño corporal de los besugos: individuos de mayor tamaño habitan en ambientes más demersales que ejemplares de menor tamaño. De acuerdo a estos resultados, el besugo se sitúa como consumidor secundario.https://revistas.uv.cl/index.php/rbmo/article/view/125

Controls on post-seismic landslide behavior in brittle rocks

Earthquakes trigger widespread landsliding in tectonically active landscapes. The effects of strong ground shaking on hillslope stability persist into the post-seismic stage; rates of landsliding remain elevated in the years following an earthquake. The mechanisms that control the spatial pattern and rate of ongoing landsliding are poorly constrained, hindering our ability to reliably forecast how landscapes and landslide hazard evolve. To address this, we undertook a detailed geotechnical investigation in which we subjected representative rock samples to dynamic loading, simulating the effects of earthquake ground shaking on hillslopes of different configuration. Our results indicate that post-seismic hillslope strength is not an intrinsic rock property; rather, it responds to the amplitude of imposed dynamic loads and the degree of pre-existing shear surface formation within the rock. This path-dependent behavior results from differences in the character of fractures generated by dynamic loads of different amplitude, and the ways in which apertures are mobilized or degraded in subsequent (post-seismic) shearing. Sensitivity to dynamic loading amplitude is greater in shallow landslides in which shear surfaces are yet to fully form; such hillslopes can be strengthened or weakened by earthquake events, depending on their characteristics. In contrast, deeper landslides on steeper hillslopes in which shear surfaces have largely developed are less likely to display differences in behavior in response to dynamic loading because strain accumulation along pre-existing fractures is dominant. Our results demonstrate the need to consider path-dependent hillslope stability in numerical models used to forecast how landscapes respond to earthquakes and how post-seismic hazard evolves

Liquiñe-Ofqui’s fast slipping intra-volcanic arc crustal faulting above the subducted Chile Ridge

The southernmost portion of the Liquiñe-Ofqui fault zone (LOFZ) lies within the proposed slab window which formed due to oblique subduction of the Chile Ridge in Patagonia. Mapping of paleo-surface ruptures, offsets, and lithological separations along the master fault allowed us to constrain geologic slip rates for the first time with dextral rates of 11.6–24.6 mm/year (Quaternary) and 3.6–18.9 mm/year (Late-Cenozoic) respectively. We had trouble mapping the LOFZ in one local because of a partially collapsed and previously undiscovered volcanic complex, Volcan Mate Grande (VMG: 1,280 m high and thus Vesuvius-sized) that grew in a caldera also offset along the LOFZ and has distinct geochemistry from adjacent stratovolcanoes. Besides the clear seismic and volcanic hazard implications, the structural connection along the main trace of the fast slipping LOFZ and geochemistry of VMG provides evidence for the slab window and insight into interplay between fast-slipping crustal intra-arc crustal faults and volcanoes

The Effect of Dynamic Loading on the Shear Strength of Pyroclastic Ash Deposits and Implications for Landslide Hazard: The Case of Pudahuel Ignimbrite, Chile

The co-seismic and post-seismic behaviour of pyroclastic ash deposits and its influence on slope stability remains as a challenging subject in engineering geology. Case studies in volcanic areas of the world suggest that soil structural changes caused by seismic shaking results in landslide activity. It is critical to constrain how this kind of soil behaves during coseismic ground shaking, as well as the effects of dynamic loading on shear strength parameters after shaking. Direct shear tests carried out on cineritic volcanic materials from the Pudahuel Ignimbrite Formation in central Chile show a direct effect of cyclic loading on the shear strength and in a minor extent on the rheology. A high apparent cohesion found in monotonic shear tests, likely attributed to suction and cementation, is destroyed by dynamic loading. At the same time, the internal friction angle rises. This defines a differential post-dynamic behaviour depending on normal effective stress conditions, which favour the occurrence of shallow landslides. These results show how the use of shear strength parameters obtained from standard monotonic direct shear tests may produce misleading results when analyzing seismic slope stability in this type of soils

Controls on post-seismic landslide behaviour in brittle rocks

Earthquakes trigger widespread landsliding in tectonically-active landscapes. The effects of strong ground shaking on hillslope stability persist into the post-seismic stage; rates of landsliding remain elevated in the years following an earthquake. The mechanisms that control the spatial pattern and rate of ongoing landsliding are poorly constrained, hindering our ability to reliably forecast how landscapes and landslide hazard evolve. To address this, we undertook a detailed geotechnical investigation in which we subjected representative rock samples to dynamic loading, simulating the effects of earthquake ground shaking on hillslopes of different configuration. Our results indicate that post-seismic hillslope strength is not an intrinsic rock property; rather, it responds to the amplitude of imposed dynamic loads and the degree of pre-existing shear surface formation within the rock. This path-dependent behaviour results from differences in the character of fractures generated by dynamic loads of different amplitude, and the ways in which apertures are mobilised or degraded in subsequent (post-seismic) shearing. Sensitivity to dynamic loading amplitude is greater in shallow landslides in which shear surfaces are yet to fully form; such hillslopes can be strengthened or weakened by earthquake events, depending on their characteristics. In contrast, deeper landslides on steeper hillslopes in which shear surfaces have largely developed are less likely to display differences in behaviour in response to dynamic loading because strain accumulation along pre-existing fractures is dominant. Our results demonstrate the need to consider path-dependent hillslope stability in numerical models used to forecast how landscapes respond to earthquakes and how post-seismic hazard evolves

Proteomic response of the marine ammonia‐oxidising archaeon Nitrosopumilus maritimus

Dissolved iron (Fe) is vanishingly low in the oceans, with ecological success conferred to microorganisms that can restructure their biochemistry to maintain high growth rates during Fe scarcity. Chemolithoautotrophic ammonia-oxidising archaea (AOA) are highly abundant in the oceans, constituting ~30% of cells below the photic zone. Here we examine the proteomic response of the AOA isolate Nitrosopumilus maritimus to growth-limiting Fe concentrations. Under Fe limitation, we observed a significant reduction in the intensity of Fe-dense ferredoxins associated with respiratory complex I whilst complex III and IV proteins with more central roles in the electron transport chain remain unchanged. We concomitantly observed an increase in the intensity of Fe-free functional alternatives such as flavodoxin and plastocyanin, thioredoxin and alkyl hydroperoxide which are known to mediate electron transport and reactive oxygen species detoxification, respectively. Under Fe limitation, we found a marked increase in the intensity of the ABC phosphonate transport system (Phn), highlighting an intriguing link between Fe and P cycling in N. maritimus. We hypothesise that an elevated uptake of exogenous phosphonates under Fe limitation may either supplement N. maritimus' endogenous methylphosphonate biosynthesis pathway - which requires Fe - or enhance the production of phosphonate-containing exopolysaccharides known to efficiently bind environmental Fe