Tracking the sediment plume from the 7th February 2021 Chamoli (Uttarakhand, India) hazard cascade

<p>The 7<sup>th</sup> February Chamoli hazard cascade originated from a 25 million m³ rock/ice avalanche slope failure that transformed into a destructive, far travelled debris flow / debris flood. There has a been necessarily a significant science focus on the proximal and immediate part of the hazard cascade. Here we report on the larger spatial and temporal scale: the sediment plume that progressed over the following days and weeks along the Ganga (Ganges) River. At the time of submission this was still recognisable over 900 km from the landslide site and had passed through hydro and nuclear power schemes. Beyond the initial plume, which has implications for rapid sedimentation in hydropower schemes and water / aquatic habitat quality, the subsequent (or not) mobilisation of event sediments over future years is a possible medium term chronic-threat to some hydropower projects. We show spectral ‘recipes’ and semi-automated methods for tracking the mass movement sediment plume and quantifying celerity using Sentinel 2 imagery, infilled using high-temporal repeat optical imagery from Planet Labs. data. The plume averaged ~60 km/day and, as expected has begun to slow as the river gradient decreases, as well as becoming less distinctive as some sediment is deposited, and as other sediment-rich water joins the Ganga.</p><p>The tracking of sediment plumes from these hazard cascades can be extended over inventories of similar events using both Sentinel 2 and Landsat archives. Such approaches allow us to provide insight into the possibilities of automated detection of hazard cascade sediment plumes to identify previously unknown events from remote source regions, as plumes have a far larger spatial-temporal footprint than the initial event.</p>

Roughing it: terrain is crucial in identifying novel translocation sites for the vulnerable brush-tailed rock-wallaby ( Petrogale pencillata )

Translocations—the movement of species from one place to another—are likely to become more common as conservation attempts to protect small isolated populations from threats posed by extreme events such as bushfires. The recent Australian mega-fires burnt almost 40% of the habitat of the brush-tailed rock-wallaby ( Petrogale pencillata ), a threatened species whose distribution is already restricted, primarily due to predation by invasive species. This chronic threat of over-predation, coupled with the possible extinction of the genetically distinct southern population (approx. 40 individuals in the wild), makes this species a candidate for a conservation translocation. Here, we use species distribution models to identify translocation sites for the brush-tailed rock-wallaby. Our models exhibited high predictive accuracy, and show that terrain roughness, a surrogate for predator refugia, is the most important variable. Tasmania, which currently has no rock-wallabies, showed high suitability and is fox-free, making it a promising candidate site. We outline our argument for the trial translocation of rock-wallaby to Maria Island, located off Tasmania's eastern coast. This research offers a transparent assessment of the translocation potential of a threatened species, which can be adapted to other taxa and systems.

The role of the locus coeruleus in the generation of pathological anxiety

This review aims to synthesise a large pre-clinical and clinical literature related to a hypothesised role of the locus coeruleus norepinephrine system in responses to acute and chronic threat, as well as the emergence of pathological anxiety. The locus coeruleus has widespread norepinephrine projections throughout the central nervous system, which act to globally modulate arousal states and adaptive behavior, crucially positioned to play a significant role in modulating both ascending visceral and descending cortical neurocognitive information. In response to threat or a stressor, the locus coeruleus–norepinephrine system globally modulates arousal, alerting and orienting functions and can have a powerful effect on the regulation of multiple memory systems. Chronic stress leads to amplification of locus coeruleus reactivity to subsequent stressors, which is coupled with the emergence of pathological anxiety-like behaviors in rodents. While direct in vivo evidence for locus coeruleus dysfunction in humans with pathological anxiety remains limited, recent advances in high-resolution 7-T magnetic resonance imaging and computational modeling approaches are starting to provide new insights into locus coeruleus characteristics.

Transcription-associated events affecting genomic integrity

Accurate maintenance of genomic as well as epigenomic integrity is critical for proper cell and organ function. Continuous exposure to DNA damage is, thus, often associated with malignant transformation and degenerative diseases. A significant, chronic threat to genome integrity lies in the process of transcription, which can result in the formation of potentially harmful RNA : DNA hybrid structures (R-loops) and has been linked to DNA damage accumulation as well as dynamic chromatin reorganization. In sharp contrast, recent evidence suggests that active transcription, the resulting transcripts as well as R-loop formation can play multi-faceted roles in maintaining and restoring genome integrity. Here, we will discuss the emerging contributions of transcription as both a source of DNA damage and a mediator of DNA repair. We propose that both aspects have significant implications for genome maintenance, and will speculate on possible long-term consequences for the epigenetic integrity of transcribing cells. This article is part of the themed issue ‘Chromatin modifiers and remodellers in DNA repair and signalling’.

A family of fluoride-specific ion channels with dual-topology architecture

Fluoride ion, ubiquitous in soil, water, and marine environments, is a chronic threat to microorganisms. Many prokaryotes, archea, unicellular eukaryotes, and plants use a recently discovered family of F− exporter proteins to lower cytoplasmic F− levels to counteract the anion’s toxicity. We show here that these ‘Fluc’ proteins, purified and reconstituted in liposomes and planar phospholipid bilayers, form constitutively open anion channels with extreme selectivity for F− over Cl−. The active channel is a dimer of identical or homologous subunits arranged in antiparallel transmembrane orientation. This dual-topology assembly has not previously been seen in ion channels but is known in multidrug transporters of the SMR family, and is suggestive of an evolutionary antecedent of the inverted repeats found within the subunits of many membrane transport proteins.