Groundwater animals

Groundwater animals are adapted to live in environments with no light and limited nutrients, They can provide insights into fundamental questions of evolution, ecology and biodiversity. They also have an important role to play in informing the reconstruction of past changes in geomorphology and climate, and can be used for characterising aquifers. The BGS is undertaking a systematic survey of selected areas and lithologies in the UK where groundwater animals have not been investigated. This is important because little is known about groundwater ecosystems in the UK despite the unique contribution to biodiversity made by these animals. Groundwater organisms are also thought to provide ecosystem services by means of their role in nutrient cycling and natural remediation of pollutants in the subsurface. They may also be useful indicators of human impacts on groundwaters

Silicate determination in sea water: toward a reagentless electrochemical method

ilicate has been determined in sea water by four different electrochemical methods based on the detection of the silicomolybdic complex formed in acidic media by the reaction between silicate and molybdenum salts. The first two methods are based on the addition of molybdate and protons in a seawater sample in an electrochemical cell. Cyclic voltammetry presents two reduction and two oxidation peaks giving four values of the concentration and therefore increasing the precision. Then chronoamperometry is performed on an electrode held at a constant potential. A semi-autonomous method has been developed based on the electrochemical anodic oxidation of molybdenum, the complexation of the oxidation product with silicate and the detection of the complex by cyclic voltammetry. This method is tested and compared with the classical colorimetric one during ANT XXIII/3 cruise across Drake Passage (January–February 2006). The detection limit is 1 μM and the deviation between both methods is less than 3% for concentrations higher than 10 μM. Finally a complete reagentless method with a precision of 2.6% is described based on the simultaneous formation of the molybdenum salt and protons in a divided electrochemical cell. This latter method should be very useful for developing a reagentless sensor suitable for long term in situ deployments on oceanic biogeochemical observatories

Unexpectedly deep diving in an albatross

Albatrosses are the iconic aerial wanderers of the oceans, supremely adapted for long-distance dynamic soaring flight. Perhaps because of this they are considered poorly adapted for diving1, in contrast to many smaller shearwater and petrel relatives, despite having amphibious eyes2, and an a priori mass advantage for oxygen-storage tolerance3. Modern biologging studies have largely confirmed this view4,5, casting doubt on earlier observations using capillary tube maximum depth gauges1, which may exaggerate depths, and emphasising albatrosses’ reliance on near-surface feeding. Nevertheless, uncertainty about albatross diving remains an important knowledge gap since bycatch in human fisheries (e.g. birds becoming hooked when diving for longline bait fish) is thought to be driving many population declines in this most threatened group of birds6. Here we show, using miniature electronic depth loggers (TDRs), that black-browed albatross, Thalassarche melanophris, can dive to much greater depths (19 m) and for much longer (52 s) than previously thought — three times the maxima previously recorded for this species (6 m and 15 s), and more than twice the maxima reliably recorded previously for any albatross (from 113.7 bird-days of tracking4,5,7). Further evidence that diving may be a significant behavioural adaptation in some albatrosses comes from co-deployed 3-axis accelerometers showing that these deeper dives, which occur in most individuals we tracked, involve active under-water propulsion without detectable initial assistance from momentum, sometimes with bottom phases typical of active prey pursuit. Furthermore, we find (from co-deployed GPS) that diving occurs primarily in the distal portions of long-distance foraging trips, with deeper dives occurring exclusively during daylight or civil twilight, confirming the importance of visual guidance.Fundação para a Ciênica e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Obligate groundwater crustaceans mediate biofilm interactions in a subsurface food web

Food webs in groundwater ecosystems are dominated by only a few top-level consumers, mainly crustaceans. These obligate groundwater dwellers—or stygobites—clearly interact with groundwater biofilm, but it is uncertain whether they affect the abundance and structure of biofilm assemblages. We hypothesized that crustacean stygobites would reduce bacteria and protozoan abundance and alter biofilm assemblage structure. We also hypothesized that high densities of stygobites would remove more bacteria and protozoa than would low densities, and that this difference would become more pronounced over time. First, we established that the amphipods Niphargus fontanus and Niphargus kochianus both ingest biofilm by examining their gut contents. We then conducted 2 microcosm experiments. The 1st experiment showed that both N. fontanus and the isopod Proasellus cavaticus increased protozoan abundance but that bacterial abundance was only slightly reduced in the presence of P. cavaticus. In the 2nd experiment, we determined how zero, low, and high densities of N. kochianus affected the biofilm. The high-density treatment of N. kochianus had significantly higher protozoan abundance than the control and the low-density treatment, and high densities of N. kochianus significantly increased the relative proportions of small- and medium-sized bacteria over time compared with controls. Our controlled microcosm experiments demonstrate that macroinvertebrate stygobites can influence groundwater biofilm assemblages, although the exact mechanisms are not clear. These results support the hypothesis that stygobites influence essential ecosystem services supplied by groundwater ecosystems

Étude pilote de l’entretien motivationnel chez des personnes condamnées pour conduite avec facultés affaiblies

Dans cette étude pilote contrôlée et randomisée (N = 51), nous avons examiné l’impact d’une intervention brève, l’entretien motivationnel (EM, Motivational Interviewing), comparée à une simple séance d’information comme condition contrôle, chez des personnes condamnées pour conduite avec facultés affaiblies. Les participants devaient avoir un diagnostic actif d’abus ou de dépendance à l’alcool et devaient être recrutés en dehors des programmes officiels de traitement pour conducteurs avec facultés affaiblies de façon à tester l’EM chez des individus qui n’étaient pas nécessairement prêts à changer. Nous avons évalué le pourcentage de jours de forte consommation d’alcool (≥ 6 consommations standards d’alcool par jour), les résultats à l’AUDIT et l’utilisation de services après trois et six mois de suivi. Les résultats indiquent que l’exposition à l’EM a entraîné une réduction significativement plus grande du nombre de jours à forte consommation d’alcool et du nombre de visites à des professionnels de la santé après six mois de suivi. L’ampleur des effets observés est comparable à celle que l’on peut retrouver dans d’autres études employant l’EM avec différentes populations ayant un problème d’alcool. Quoique préliminaires, ces résultats suggèrent que l’emploi de l’EM pourrait être avantageux, même chez des individus qui ne sont pas engagés dans un processus de réhabilitation. Une étude plus approfondie du potentiel de l’EM conduisant directement à une amélioration de la conduite en état d’ébriété est clairement justifiée.A pilot randomized controlled trial (N = 51) investigated the impact of a brief intervention approach : Motivational Interviewing (MI), compared to a simple information session as a control condition, in offenders convicted of driving under the influence (DUI). Participants had a current diagnosis of alcohol abuse or dependence, and were recruited outside of mandated DUI remedial programs, in order to test MI in individuals who were not necessarily prepared to change. We evaluated the percentage of days of significant alcohol consumption (≥ 6 standard drinks a day), AUDIT scores and service utilization at three and six months follow-up. Results indicated that exposure to MI resulted in a significantly greater reduction in the number of days of significant alcohol consumption and fewer visits to health professionals at six months follow-up. Observed effect sizes were comparable to other studies of MI in different populations with alcohol problems. While preliminary, these results suggest that MI for DUI could have benefits, even in individuals who are not involved in a remedial process. A comprehensive study of MI’s potential in more directly improving drinking and driving outcomes is clearly warranted.En este estudio piloto controlado y aleatorio (N = 51), hemos examinado el impacto que produjo una breve intervención, la entrevista de motivación (EM, Motivational Interviewing), en personas condenadas por conducir con facultades debilitadas, comparándola a una simple sesión de información como condición de control. Los participantes debían tener un diagnóstico activo de abuso o de dependencia de alcohol y haber sido reclutados fuera de los programas oficiales de tratamiento para conductores con facultades debilitadas, con el objetivo de probar la entrevista de motivación en individuos que no estaban necesariamente preparados para cambiar. Hemos evaluado el porcentaje de días de fuerte consumo de alcohol (≥ 6 consumos regulares de alcohol por día), los resultados en la verificación y la utilización de los servicios luego de tres y seis meses de seguimiento. Los resultados indican que la exposición a la entrevista de motivación generó una reducción significativamente más importante de días de fuerte consumo de alcohol y de la cantidad de visitas a profesionales de la salud luego de seis meses de seguimiento. La amplitud de los efectos observados es comparable a la que se puede encontrar en otros estudios que emplean la entrevista de motivación con diferentes poblaciones que tienen un problema de alcohol. Si bien preliminares, estos resultados sugieren que el uso de las entrevistas de motivación podría ser ventajoso, incluso con individuos que no están comprometidos en un proceso de rehabilitación. Se justifica ampliamente un estudio más profundo de las posibilidades de la entrevista de motivación como medio para lograr directamente una mejoría en cuando a la conducción de vehículos en estado de ebriedad

Karst hydrogeology of the Chalk and implications for groundwater protection

The Chalk is an unusual karst aquifer with limited cave development, but extensive networks of smaller solutional conduits and fissures enabling rapid groundwater flow. Small-scale karst features (stream sinks, dolines, dissolution pipes, and springs) are common, with hundreds of stream sinks recorded. Tracer velocities from 27 connections between stream sinks and springs have median and mean velocities of 4700 and 4600 m d−1. Tests to abstraction boreholes also demonstrate very rapid velocities of thousands of metres per day. Natural gradient tests from observation boreholes have rapid velocities of hundreds of metres per day. There is strong geological control on karst with dissolution focused on stratigraphical inception horizons. Surface karst features are concentrated near the Paleogene boundary, or where thin superficial cover occurs, but rapid groundwater flow is also common in other areas. The Chalk has higher storage and contaminant attenuation than classical karst, but recharge, storage and flow are influenced by karst. Point recharge through stream sinks, dolines, losing rivers, vertical solutional fissures, and soakaways enables rapid unsaturated zone flow. Saturated zone networks of solutional fissures and conduits create vulnerability to subsurface activities, and enable long distance transport of point source and diffuse pollutants, which may be derived from outside modelled catchment areas and source protection zones

Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland

Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s�1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s�1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s�1,suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers

Regional-scale drivers of groundwater faunal distributions

Freshwater aquifers are a major source of drinking water; they also possess unique assemblages of organisms. However, little is known about the distributional drivers of obligate groundwater organisms at the regional scale. We examine the distribution and composition of stygobiont assemblages in a complex geological setting and explore the relationship between groundwater fauna, hydrogeology and water chemistry. In the study area we grouped similar geologies into five hydrogeological formations (hydro-units) within which habitats for groundwater fauna were broadly similar. We found that the occurrence of stygobionts differed significantly between hydro-units. Stygobionts were significantly less likely to be recorded in mudstone/siltstone and sandstone aquifers compared with carbonate rocks or with igneous/metamorphic rocks. Variance partitioning indicated that the hydro-units explained a greater proportion of the variance (7.52%) in the groundwater community than water chemistry (5.02%). However, much of the variation remained unexplained. The macrofaunal stygobiont species in our study area formed three groups: (1) Niphargus glenniei was recorded in a range of hydro- units but only in the west of the study area. (2) Niphargus kochianus , Niphargus fontanus, Proasellus cavaticus and Crangonyx subterraneus were predominately recorded in carbonate aquifers in the east of the study area. (3) Niphargus aquilex and Microniphargus leruthi, were found throughout the study area and in a range of hydro-units. We hypothesise that physical barriers exist that prevent some stygobiont taxa from colonizing apparently suitable geologies; the low permeability deposits dividing the western and eastern parts of the study area may partly explain the observed distributions