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Freshwater in sediment pore fluids and methane seepage from the seafloor have often been observed concurrently in Arctic regions where submarine groundwater discharge (SGD) occurs, with advective flows potentially reintroducing ancient carbon into the modern ocean. It is hypothesized that hydraulic loading by ice sheets enhances submarine groundwater discharge, and subsequently methane transport. In the presence of microbial communities, large amounts of methane can be consumed by the anaerobic oxidation of methane (AOM), inducing precipitation of authigenic carbonates that inherit unique carbon isotopic signatures from methane. At an SGD site offshore Lofoten Islands, northern Norway (ca. 800 meters water depth), in the vicinity of the maximum extent of the Fennoscandian Ice Sheet, we observed a downcore decreasing chlorinity profile and a linear relation between δ18O and δ2H of the porewater, known as the local meteoric water line. This demonstrates a meteoric water contribution to the porewater. We also found methane-derived authigenic carbonates (MDACs) with depleted δ13C values (< -30 ‰ VPDB), suggesting that microbial (or thermogenic) methane was incorporated during MDAC precipitation. Moreover, δ18O values (> 2.5 ‰ VPDB) of MDACs indicate precipitation in the presence of 18O-enriched water, possibly a result of past hydrate dissociation. To assess the carbon cycle and timing of the methane seepage at the Lofoten SGD site, we investigated the radiocarbon contents of Total Organic and Inorganic Carbon in sediments (TOC, TIC), as well as Dissolved Inorganic Carbon (DIC) in porewater from multiple sediment horizons. The radiocarbon contents of DIC have the lowest values among the three carbon pools, in the order of 10-30 percent modern carbon. Their radiocarbon ages (~ 17,000 years BP) are in the order of the Last Glacial Maximum. Consequently, the DIC must have been closed off from the atmosphere due to long groundwater retention times. Alternatively, a methane source low in radiocarbon could have contributed to the DIC pool through AOM. The TIC pool showed radiocarbon content half of that of the TOC in the same sediment horizons, which can be explained by carbonate precipitation from the radiocarbon-depleted DIC pool. To further constrain in situ carbon cycling and advection velocities, a reaction-transport model using mass balance calculations of 12C, 13C and 14C has been applied. Radiocarbon content profiles of the DIC indeed imply the advection of old groundwater into the marine sediment porous media.

From the morning of October 28th to the evening of October 28th 2020, fieldwork was performed comprising retrieval of live siboglinid worms for genetic and environmental studies hereunder pore water content of sulphate, sulphide and methane and sediment TOC, TC and isotopes. The working area was a basin located in outer Kvalsund, Troms, northern Norway. A total of 2 box core stations and 2 gravity core stations were obtained and two CTD casts. Echosounding and chirp data were recorded on stations and on transits. The cruise may be known as: CAGE20_WORM

From the evening of June 29th to the evening of July 10th 2018, CAGE at the Department of Geology Uit, the Arctic University of Norway, arranged a scientific cruise aimed at investigating methane seep sites by surface sediment sampling, sediment core sampling, plankton sampling and water sampling. The areas for investigation were the Barents Sea (Crater area), Storfjorden Trough (Pingo area),East Greenland Ridge (non-seep, for IODP-proposal) (Leg 1 and 2) and the western Svalbard margin, Vestnesa Ridge, Arctic Ocean and Prins Karls Forland (Leg 3) on R/V “Helmer Hanssen”. The scientific sampling was done within the framework of several ongoing projects at the Department of Geology, University of Tromsø: “CAGE -Centre for Arctic Gas Hydrate, Environment and Climate”-WP6: “Methane Release, Ocean Acidification and CO2” hereunder ocean acidification impact on marine calcifiers (planktic foraminifera and pteropods, methane seeping impact on ocean acidification and productivity, the state of the inorganic and organic biological pump from foraminifera, bottom water temperature change and impact on release of methane, living benthic microfauna studies from seep sites for geochemical investigations for calibrations for paleostudies. A total of 15 gravity cores (c. 60 m),and 31 CTD (conductivity-temperature-depth) casts were performed, 11 plankton net (no. 12 failed because the net was torn completely), 22 boxcore samples x 6 surface samples for each. A total of 137 lines of acoustics and seismics together were performed. Chirp profiles and multi-beam lines were acquired during transits and in surveys mapping of new seep sites northeast of “Crater” area, seep sites in Storfjorden Trough, East Greenland Ridge, seeps in Hinlopen trough and Norske Banken, the east slope of Yermak Plateau, active and inactive pockmarks at Vestnesa Ridge and a small patch off PKF for WP4. All acoustic and seismic investigations were performed with soft-start of all instruments (Echo-sounders, deep-penetrating echosounder (‘Chirp’), Multi-beam echosounder and mini-air gun). The cruise may be known as: CAGE18_3_leg1 CAGE18_3_leg2 CAGE18_3_leg3

Taking a bird's eye's view across the globe to understand the different methods to look at vaccine safety surveillance, one thing becomes clear. The commitment to monitor the safety of a vaccine does not stop at the clinical development stage. Rather, awareness, reporting, and research need to be bolstered after the vast population gets exposed to the vaccine. Global collaboration, understanding, and embracing the global best practices will go a long way to ensure safer vaccinations. With the COVID-19 pandemic already creating havoc in minds of all, the panic or unacceptance about the vaccination side effects in the population is undesirable. Adverse events are the unfortunate yet unavoidable element in the journey of a new drug or a vaccine. But since it is a healthy population who are recipients of vaccines, the researchers and PV professionals need to be more mindful of the risk-benefit profile of the vaccine.

Permafrost is defined as perennially frozen ground (soil or rock and included ice and organic material) with a temperature near or below 0°C that remains for at least two consecutive years. Permafrost occurs mainly in high latitudes of the Southern and Northern Hemispheres, but significant area can also be found in the middle- and low-latitude regions. In these areas, the groundwater cycle is mainly controlled by the permafrost layer that may act as an aquiclude and hence block or retard the groundwater flow. However, rapid climate changes which are observed during the last decades, markedly contribute to permafrost degradation. New connections between permafrost and groundwater are expected to form during the permafrost thawing process. This will contribute to enhance permafrost and groundwater interaction and reinforce groundwater discharge. In general, groundwater discharge is a groundwater movement from the saturated ground to the surface water bodies or submarine groundwater inflow into the sea. Increased groundwater discharge may transport a significant amount of nutrients, metals, and gases to land and ocean waters and hence may change their physicochemical parameters. Unfortunately, due to the limited number of studies, understanding the significance of groundwater discharge in the Arctic regions is limited.The study aims to provide a comprehensive review of the present literature data that contribute to better understanding interaction between permafrost and groundwater in the Arctic regions, which are particularly vulnerable to climate changes. This review is focused on permafrost thawing, groundwater discharge, and recharge processes and their implication on the environment. We attempt to answer the following questions: How does permafrost affect groundwater discharge and recharge? Does permafrost act as a hindrance for groundwater? How does progressive global warming and thereby permafrost thawing impact the groundwater discharge? How significant is groundwater discharge? How important is the transport of different solutes to the environment by groundwater discharge?Based on the literature, we can conclude that the degradation of permafrost greatly influences hydrological systems in cold zones. Permafrost has a strong impact on fluid dynamics caused by negligible hydraulic conductivity. This relationship, beyond all physical, chemical, and biogeochemical responses, contributes to the formation of complex permafrost–groundwater interactions. Permafrost degradation strongly affects the ecosystem through direct and indirect impacts on the transport and cycles of different compounds, elements, and ions. Moreover, all processes are dependent on topography, geomorphology, tectonics, and surface hydrology. Research conducted in other than Arctic permafrost areas also indicated that permafrost thawing is the cause of enhanced groundwater recharge and discharge rates, which resulted in deeper water tables and groundwater flow paths. However, comprehensible and systematic studies are still needed for global assessment also in terms of searching for interdependencies between different regions.This belongs to Project No. 2019/34/H/ST10/00645 "Submarine Groundwater Discharge in a Changing Arctic Region: Scale and Biogeochemical impact", which is supported by the Norwegian Financial Mechanism and Polish national Basic Research Program.

Sclerolinum annulatus n. sp. (Annelida: Siboglinidae) is described based on specimens collected from soft sediment of the Haima cold seep in the South China Sea. Morphologically, S. annulatus n. sp. is distinct in having a tube with transverse rings and a forepart (i.e., anterior region) containing one arched row of elongated plaques on both sides of the dorsal furrow. Genome skimming, assembly, and annotation produced a nearly complete mitogenome of S. annulatus n. sp. with 15,553 bp nucleotides that encodes 13 protein-coding genes, two rRNA, and 22 tRNA. Phylogenetic analyses based on the mitochondrial cytochrome c oxidase I (cox1) gene and a concatenated dataset comprising the mitochondrial cox1 and 16S rRNA genes along with the nuclear 18S rRNA gene both strongly support the placement of S. annulatus n. sp. in the genus SclerolinumSouthward, 1961. Based on cox1, S. annulatus n. sp. is most closely related to an undescribed siboglinid from off Kushiro in Japan (“Pogonophora” sp. Kushiro-SK-2003). Transmission electron microscopy, microbial 16S rRNA amplicon sequencing, phylogenetic reconstruction, and stable isotope analyses together indicate that S. annulatus n. sp. hosts a single phylotype of sulfur-oxidizing endosymbionts.

Vaccine hesitancy is of considerable concern as it threatens the great potential of a vaccine against COVID-19. This study aims to determine factors associated with community health workers' willingness to participate in clinical trials of COVID-19 vaccine, and their vaccination intention, in India.A cross-sectional study was conducted among 377 community health workers using self-administered anonymous questionnaire during the lockdown periods in India. Participant's socio-demographics, willingness-to-participate in COVID-19 vaccine trials, intention to accept COVID-19 vaccine were recorded in a Likert scale. Data were analysed descriptively, and a multivariate logistic regression model was used to investigate factors associated with willingness to participate and accept the vaccine.Among 377 CHWs, 70 (19%) intended to participate in COVID-19 vaccine trial, 151 (40%) responded positively regarding their intention to get vaccinated. Those with knowledge on development of COVID-19 vaccine [aOR 3.05 (95% CI: 1.18-7.88), p = 0.021], and men [aOR 3.69 (95% CI: 1.51-8.97), p = 0.004] were more willing to participate in clinical-trial, while an undergraduate degree, and trust in domestic vaccines were identified as deterrents for the same. Perceiving COVID-19 as risk [aOR 2.31 (95% CI: 1.24-4.31), p = 0.009], and male gender [aOR 2.39 (95% CI: 1.17-4.88), p = 0.017] were factors associated with intention to get vaccinated. Respondents who had knowledge about COVID-19 virus were less likely to uptake the hypothetical vaccine [aOR 0.32 (95% CI: 0.12-0.88), p = 0.027].Increasing knowledge regarding COVID-19 is not enough to improve vaccine acceptance rates. Targeted interventions addressing socio-demographic determinants related to COVID-19 vaccination should help improve acceptance.

Background: Vaccine hesitancy is of considerable concern as it threatens the great potential of a vaccine against COVID-19. Community health workers (CHWs) bridge the gap between the community and the health care system. Their intention to get vaccinated will not only affect them but will also affect the community’s perception of the vaccine. This study aims to understand the intention to get vaccinated against COVID-19 among community health care workers in India and its determinants.Methods: A web-based, cross-sectional study was conducted among 357 community health workers using snowball sampling. A self-administered anonymous questionnaire was shared with study participants across major geographical regions in India through social media during the first wave (November-December 2020).Results: Among 357 community health workers, 208 (58%) responded positively regarding their intention to get a COVID-19 vaccine. Graduate [aOR 2.26 (95% CI: 1.27-4.01), p=0.006] and post-graduate participants [aOR 2.85 (95% CI: 1.43-5.68), p=0.003], those with lower risk perception [aOR 1.86 (95% CI: 1.03-3.35), p=0.038] and respondents who trusted the healthcare system [aOR 2.60 (95% CI:1.59-4.26), pConclusions: Increasing knowledge regarding the COVID-19 vaccine might not be enough to improve vaccine acceptance rates. Enhancing trust among community health workers in the healthcare system and regarding the available vaccines seem necessary. In addition, targeted interventions addressing socio-demographic determinants related to COVID-19 vaccination should help improve acceptance of the vaccine.

Cold seeps can support unique faunal communities via chemosynthetic interactions fueled by seabed emissions of hydrocarbons. Additionally, cold seeps can enhance habitat complexity at the deep seafloor through the accretion of methane derived authigenic carbonates (MDAC). We examined infaunal and megafaunal community structure at high-Arctic cold seeps through analyses of benthic samples and seafloor photographs from pockmarks exhibiting highly elevated methane concentrations in sediments and the water column at Vestnesa Ridge (VR), Svalbard (79° N). Infaunal biomass and abundance were five times higher, species richness was 2.5 times higher and diversity was 1.5 times higher at methane-rich Vestnesa compared to a nearby control region. Seabed photos reveal different faunal associations inside, at the edge, and outside Vestnesa pockmarks. Brittle stars were the most common megafauna occurring on the soft bottom plains outside pockmarks. Microbial mats, chemosymbiotic siboglinid worms, and carbonate outcrops were prominent features inside the pockmarks, and high trophic-level predators aggregated around these features. Our faunal data, visual observations, and measurements of sediment characteristics indicate that methane is a key environmental driver of the biological system at VR. We suggest that chemoautotrophic production enhances infaunal diversity, abundance, and biomass at the seep while MDAC create a heterogeneous deep-sea habitat leading to aggregation of heterotrophic, conventional megafauna. Through this combination of rich infaunal and megafaunal associations, the cold seeps of VR are benthic oases compared to the surrounding high-Arctic deep sea.

Background High primary productivity in the midst of high toxicity defines hydrocarbon seeps; this feature usually results in significantly higher biomass, but in lower diversity communities at seeps rather than in the surrounding non-seep benthos. Qualitative estimates indicate that this dichotomy does not necessarily hold true in high latitude regions with respect to megafauna. Instead, high latitude seeps appear to function as local hotspots of both megafaunal diversity and abundance, although quantitative studies do not exist. In this study, we tested this hypothesis quantitatively by comparing georeferenced seafloor mosaics of a seep in the southwestern Barents Sea with the adjacent non-seep seafloor. Methods Seafloor images of the Svanefjell seep site and the adjacent non seep-influenced background seabed in the southwestern Barents Sea were used to construct georeferenced mosaics. All megafauna were enumerated and mapped on these mosaics and comparisons of the communities at the seep site and the non-seep background site were compared. Sediment push cores were taken in order to assess the sediment geochemical environment. Results Taxonomic richness and abundance were both considerably higher at the seep site than the non-seep location. However, taxa were fewer at the seep site compared to other seeps in the Barents Sea or the Arctic, which is likely due to the Svanefjell seep site exhibiting relatively low seepage rates (and correspondingly less chemosynthesis based primary production). Crusts of seep carbonates account for the higher diversity of the seep site compared to the background site, since most animals were either colonizing crust surfaces or using them for shelter or coverage. Our results indicate that seeps in northern latitudes can enhance local benthic diversity and this effect can take place even with weak seepage. Since crusts of seep carbonates account for most of the aggregating effect of sites experiencing moderate/weak seepage such as the study site, this means that the ability of seep sites to attract benthic species extends well beyond the life cycle of the seep itself, which has important implications for the larger marine ecosystem and its management policies.

International audience; Western Pacific hydrothermal vents will soon be subjected to deep-sea mining and peripheral sites are considered the most practical targets. The limited information on community dynamics and temporal change in these communities makes it difficult to anticipate the impact of mining activities and recovery trajectories. We studied community composition of peripheral communities along a cline in hydrothermal chemistry on the Eastern Lau Spreading Center and Valu Fa Ridge (ELSC-VFR) and also studied patterns of temporal change. Peripheral communities located in the northern vent fields of the ELSC-VFR are significantly different from those in the southern vent fields. Higher abundances of zoanthids and anemones were found in northern peripheral sites and the symbiont-containing mussel Bathymodiolus brevior, brisingid seastars and polynoids were only present in the northern peripheral sites. By contrast, certain faunal groups were seen only in the southern peripheral sites, such as lollipop sponges, pycnogonids and ophiuroids. Taxonomic richness of the peripheral communities was similar to that of active vent communities, due to the presence of non-vent endemic species that balanced the absence of species found in areas of active venting. The communities present at waning active sites resemble those of peripheral sites, indicating that peripheral species can colonize previously active vent sites in addition to settling in the periphery of areas of venting. Growth and mortality were observed in a number of the normally slow-growing cladorhizid stick sponges, indicating that these animals may exhibit life history strategies in the vicinity of vents that differ from those previously recorded. A novel facultative association between polynoids and anemones is proposed based on their correlated distributions.

Deep-sea ecosystems have attracted considerable commercial interest in recent years because of their potential to sustain a diverse range of mankind's industrial needs. If these systems are to be preserved or exploited in a sustainable manner, mapping habitats and species distributions is critical. As biodiversity at cold-seeps or other deep-sea ecosystems is driven by habitat heterogeneity, imagery is the obvious choice for characterizing these systems and has indeed proven extremely valuable towards mapping biogenic habitats formed by dense aggregations of large sized species, such as coral reefs, tubeworm bushes or bivalve beds. However, the acquisition of detailed images with resolution sufficient for reliable identification is extremely time consuming, labor intensive and highly susceptible to logistical issues. We developed a novel method for quickly mapping cold seep fauna and habitats over large areas, at the scale of squares of kilometers. Our method uses multibeam echosounder bathymetry and acoustic backscatter data, both segmented and reclassified based on topographical features and then combined to obtain a raster containing unique values incorporating both backscatter and bathymetry data. Two datasets, obtained from 30 m and 8 m above the seafloor were used and the results from the two datasets were compared. The method was applied to a cold seep community located in a pockmark in the deep Congo channel and we were able to ground truth the accuracy of our method against images of the area. The two datasets, obtained from different altitudes gave varying results: the 8 m altitude dataset reliably predicted tubeworms and carbonate rock, while the 30 m altitude dataset predicted tubeworms and vesicomyid clams. The 30 m dataset was more accurate than the 8 m altitude dataset in predicting distributions of tubeworms. Overall, all the predictions were quite accurate, with at least 90% of predictions being within 5 m of real distributions.

Background: In line with WHO’s END TB strategy and Sustainable Development Goal’s vision, India has set a goal to eliminate tuberculosis by 2025. To meet this goal, intensified case finding is a strategy adopted by India’s national tuberculosis program. This study aimed to determine the proportion of presumptive pulmonary tuberculosis (PPTB) patients among outpatients of a tertiary care center and its association with socio-demographic and behavioral factors.Methods: A hospital based cross-sectional analytical study was done in a tertiary care center during November 2017 among outpatients aged 18 years or above. Known cases of tuberculosis (TB) were excluded. Information on socio-demographic characteristics and TB symptoms was collected using a structured questionnaire. A person with any symptom suggestive of TB, including, cough of any duration, subjective weight loss, and fever at present was considered to have PPTB. Presence of PPTB was reported as proportion with 95% confidence intervals. Association between variables and presumptive pulmonary TB was assessed using chi square test and prevalence ratio with 95% CI.Results: Among 2638 outpatients, 907 (34%) had PPTB. Cough was the most reported symptom (22.9%); followed by fever (10.0%), weight loss (13.9%) and hemoptysis (0.9%). PPTB was found to be significantly higher among males, smokers, alcohol users and patients having a history of contact with any TB patient.Conclusions: One-third of the outpatients had PPTB and this was high. A screening procedure could be incorporated within the hospital policy to identify outpatients with symptoms of TB.

Background: The concept of emotional intelligence has gained great popularity in the last few decades. With significant rise in stress and other emotional disturbances among students, it becomes necessary to determine whether high emotional intelligence could help manage perceived stress better. This study aims to assess emotional intelligence and perceived stress among undergraduate students of Arts and Science colleges, to determine the association of emotional intelligence with perceived stress, academic performance, and selected socio-demographic factors. Methods and Material: Using multistage sampling, 720 students aged 18 years and above were selected from four colleges in Puducherry. Emotional intelligence and perceived stress were assessed using standard self-administered questionnaires “The Schutte Self-Report Emotional Intelligence Test (SEIT)” and “Perceived Stress Scale (PSS-14),” respectively. Results: The median (IQR) Emotional Intelligence score and Perceived Stress score were 127 (114–137) and 43 (39–47), respectively. The study was not able to establish a significant association between emotional intelligence and perceived stress. A weak significant correlation existed between emotional intelligence and academic performance. Multiple variable analysis revealed gender, year of study, volunteering with youth organizations, and mother's occupation to be significantly associated with emotional intelligence (p < 0.05). Conclusions: Women, final year students and those who volunteered with youth organizations had higher emotional intelligence. Children of mothers who were employed in knowledge-intensive occupations were more emotionally intelligent. Academic performance had a weak positive significant correlation with emotional intelligence.

Bioavailable iron is an important micro-nutrient for marine phytoplankton and therefore critical to global biogeochemical cycles. Anoxic marine sediment is a significant source of Fe(II) to the ocean. Here, we investigate how the fluxes of Fe(II), both towards the sedimentary oxic layer and across the sediment-water interface, are impacted by the high concentration and flux of porewater sulfide in cold seep environments. We present new porewater data from four recently documented cold seeps around Svalbard as well as from continental shelves and fjords in northern Norway. We quantitatively investigated porewater data first by calculating the Fe(II) fluxes towards oxidized surface sediments and bottom water and, second, applied a transport-reaction model to estimate the mass balance of several key chemical species. Sedimentary sulfur speciation data from two of the sites were used to constrain Fe(II) consumption in the shallow sediments. We showed that the iron reduction zone is usually confined to the top 10 cm of the sediments from our studied sites due to high sulfate turnover and therefore high sulfide flux. Such a thin iron reduction zone allows proportionally more Fe(II) to reach the bottom water. Rapid precipitation of pyrite occurs at the base of the iron reduction zone, where the downward diffusing Fe(II) meets upward migrating hydrogen sulfide. Dissolved H2 released during pyrite formation stimulates a small but significant rate of sulfate reduction in the same horizon, which results in faster production of hydrogen sulfide and a positive feedback for iron reduction in the shallow sediment. Deeper in the sediment, where sulfate is actively consumed due to anaerobic methane oxidation, no apparent formation of pyrite is observed from the available measurements and our modeling results. This is mostly due to the relatively low availability of Fe(II) as a result of slower turnover of the less active iron mineral phases. Such an observation may contradict the use of pyrite abundance to deduce the sulfate-methane-transition-zone in past sedimentary records. A series of model sensitivity tests were performed to systematically investigate how the Fe(II) dynamics is impacted by higher deposition rate of iron (oxyhydr)oxides minerals on the seafloor and intensifying methane supply. We showed that the increases in iron reduction rate, pyrite formation rate, and Fe(II) flux are expected with higher seafloor iron (oxyhydr)oxides deposition initially. However, complicated feedbacks between Fe(II) production and sulfate reduction pose negative feedbacks to pyrite formation in the sediments. With a larger supply of methane, Fe(II) flux towards the oxic surface sediments is initially intensified by the higher production of hydrogen sulfide until such an interplay is too fast that essentially all reactive iron minerals settled on the seafloor dissolve immediately and dissolved iron is fixed through pyrite precipitation. Such an interplay between Fe(II) and sulfide determines the distribution of animals with chemoautotrophic symbionts which rely on sulfide as their energy source.

Foraging army ants face a problem general to many animals—how best to confront resource depletion and environmental heterogeneity. Army ants have presumably evolved a nomadic lifestyle as a way to minimize re-exploitation of previously foraged areas. However, this solution creates a challenge for an army ant colony: foraging by this colony and others creates a shifting landscape of food resources, where colonies should theoretically avoid their own previous foraging paths as well as those of other colonies. Here, we examine how colonies exploit this resource mosaic, using some of the optimality arguments first proposed and tested by Franks and Fletcher (1983), but with much larger data sets in a new location in SW Amazonia. Our data supported Franks and Fletcher’s (1983) model for systematic avoidance of raided areas during the statary phase, as well as a hypothesis of distance optimization between successive statary bivouacs. We also test and find significant evidence that foraging raids turn in opposite directions from the previous day’s directional angles more frequently than what would be expected if turning angles were distributed at random, which acts to move a colony away from recently exploited areas. This implies that colonies follow a straighter line path during the nomadic phase as opposed to a curved one, which acts to maximize distance between statary bivouacs. In addition to intra-colony movement optimization, we examine evidence for inter-colony avoidance from more than 330 colony emigrations and suggest that colony-specific pheromones are not necessarily repulsive to other colonies. Lastly, we compare our results with those of similar studies carried out at Barro Colorado Island (BCI), Panama. Despite a higher density of army ants in the SW Amazon region, colonies spend less time emigrating than their counterparts at BCI, which suggests a higher prey density in SW Amazonia.

Army ant colonies do not have permanent nests but frequently move to new patches. Local food depletion is considered the ultimate cause of this nomadic behaviour, but the proximate causes are not well understood. We tested if and how patch departure time of the aboveground-hunting army ant Dorylus molestus under field conditions is influenced by food availability and nest attacks by predators. In the first food supplement experiment, colonies receiving additional food throughout an entire nest stay did not reside in their nests for longer periods than control colonies. However, the distances travelled by colonies after nest stays during which colonies obtained food were shorter than those before these nest stays, indicating that colonies do assess food availability and avoid moving too far away from patches of high food availability. In the second food supplement experiment, in which colonies were given even larger amounts of food in the second half of their nest stay to mimic a rich unpredictable food source that these highly polyphagous predators are likely to encounter sometimes, patch departure times likewise did not differ between treated and control colonies. Either patch departure time is independent of food availability or there is another, as yet unappreciated proximate cause of colony movements in this species which we were unable to control for in our field experiments. One possibility is that encounters between neighbouring colonies influence patch departure time. In the experiment on the effect of predation, colonies responded to simulated nest attacks by mammals by leaving nests almost instantaneously and thus much earlier than control colonies. Rapid nest evacuation is likely a response to minimize the probability of repeat attacks by predators which cannot be repelled in other ways. Future studies will be necessary to definitively determine whether food availability influences patch departure times and to elucidate the consequences of colony encounters.

International audience; Patterns of succession in Lau Basin hydrothermal vent communities determined with high-resolution imagery and in situ physico-chemical data collected over 4 yr and analyzed within a Geographic Information System show that Alviniconcha snails are a pioneering group, the snail Ifremeria nautilei is a mid-successional species, and the heat-intolerant mussel Bathymodiolus brevior dominates when venting declines. The associated fauna also changes as communities progress through the successional stages, and eventually non-vent-endemic deep-sea species appear when venting has mostly subsided. This is a unique example of primary succession in which the primary producers form symbiotic associations with mobile animals, resulting in successional patterns not observed in other systems. I. nautilei dominates newly formed substrates or venting sources where both I. nautilei and Alviniconcha spp. are already established (e.g., by migration), while Alviniconcha spp. seem to be better at colonizing newly active vents (e.g., by settlement) that are remote from colonized vents. Thus, on the scale of a 5-39 m(2) diffuse flow area or a single edifice, the mid-successional species dominates new substrates instead of the pioneering group. These communities are remarkably stable over long time periods relative to other hydrothermal vent regions. In addition to the sequential replacements of species as sites age and overall conditions change, Lau vent animals track changes in vent fluids and relocate themselves when local hydrothermal plumbing changes over small spatial scales.