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

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

Distribution of blood lead levels in schoolchildren in selected cape peninsula suburbs subsequent to reductions in petrol lead

Objective. To determine blood lead levels among children attending schools in selected Cape Peninsula suburbs, and to assess the impact of a reduction in the lead content of petrol.Design. A cross-sectional analytical study of children's blood lead levels and associated risk factors.Setting. Selected inner city, suburban, and peri-urban schools in the Cape Peninsula, expected to have differing levels of environmental exposure to lead.Subjects. Grade 1 schoolchildren for whom prior written parental consent had been obtained, and who were present at school on the day of the study.Outcame measures. Blood lead levels (μg / dl), associated with a wide range of potential risk factors.Results. Median blood lead levels in suburbs varied from 14 to 16 μg/ dl, the lowest levels occurring in the peri-urban suburb and the highest in the inner city suburb. Within the inner city suburb of Woodstock, variations in mean blood lead concentrations among schools were substantial, varying from 13 to 19 μg/ dl. Overall, no change occurred in blood lead levels in this suburb subsequent to the lowering of the lead content of petrol.Conclusion. Every effort should be made in South Africa to control sources of lead in the urban environment. The study will serve as a useful baseline against which to measure the impact on blood lead levels of further actions which have been taken to promote the use of lead-free petrol in South Africa

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

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.DW was supported by a joint studentship from the National Environment Research Council (NERC) and the University of Roehampton, London

Ca II Triplet Spectroscopy of Small Magellanic Cloud Red Giants. I. Abundances and Velocities for a Sample of Clusters

We have obtained near-infrared spectra covering the Ca II triplet lines for a number of stars associated with 16 SMC clusters using the VLT + FORS2. These data compose the largest available sample of SMC clusters with spectroscopically derived abundances and velocities. Our clusters span a wide range of ages and provide good areal coverage of the galaxy. Cluster members are selected using a combination of their positions relative to the cluster center as well as their abundances and radial velocities. We determine mean cluster velocities to typically 2.7 km/s and metallicities to 0.05 dex (random errors), from an average of 6.4 members per cluster. (continued in paper)Comment: 68 pages, 15 figures, Accepted to AJ Reason for the replacement: section 7 and fig. 9 have been modified according referee suggestion

Defining geo-habitats for groundwater ecosystem assessments: an example from England and Wales (UK)

Groundwater ecosystems comprising micro-organisms and metazoans provide an important contribution to global biodiversity. Their complexity depends on geology, which determines the physical habitat available, and the chemical conditions within it. Despite this, methods of classifying groundwater habitats using geological data are not well established, and researchers have called for higher resolution habitat frameworks. A novel habitat typology for England and Wales (UK) is proposed, which distinguishes 11 geological habitats (geo-habitats) on hydrogeological principles and maps their distribution. Hydrogeological and hydrochemical data are used to determine the characteristics of each geo-habitat, and demonstrate their differences. Using these abiotic parameters, a new method to determine abiotic habitat quality is then developed. The geo-habitats had significantly different characteristics validating the classification system. Karstic and porous habitats were generally of higher quality than fractured habitats. All geo-habitats were highly heterogeneous, containing both high quality habitat patches that are likely to be suitable for fauna, and areas of low quality that may limit faunal distributions. Overall, 70 % of England and Wales are covered by lower quality fractured habitats, with only 13 % covered by higher quality habitats. The main areas of high quality habitats occur in central England as north-south trending belts, possibly facilitating dispersal along this axis. They are separated by low quality geo-habitats that may prevent east-west dispersal of fauna. In south-west England and in Wales suitable geo-habitats occur as small isolated patches. Overall, this paper provides a new national-scale typology that is adaptable for studies in other geographic areas

Extensional faulting on Tinos island, Aegean sea, Greece: How many detachments?

Zircon and apatite fission track (ZFT and AFT) and (U-Th)/He, 40Ar/39Ar hornblende, and U-Pb zircon ages from the granites of Tinos Island in the Aegean Sea, Greece, suggest, together with published ZFT data, that there are three extensional detachments on Tinos. The Tinos granites crosscut the Tinos detachment. Cooling of the granites was controlled by the Livadi detachment, which occurs structurally above the Tinos detachment. Our U-Pb zircon age is 14.6 ± 0.2 Ma and two 40Ar/39Ar hornblende ages are 14.4 ± 0.4 and 13.7 ± 0.4 Ma. ZFT and AFT ages go from 14.4 ± 1.2 to 12.2 ± 1.0 Ma and 12.8 ± 2.4 to 11.9 ± 2.0 Ma. (U-Th)/He ages are from 10.4 ± 0.2 to 9.9 ± 0.2 Ma (zircon) and 11.9 ± 0.5 to 10.0 ± 0.3 Ma (apatite). All ages decrease northeastward in the direction of hanging wall transport on the Livadi detachment and age-distance relationships yield a slip rate of 2.6 (+3.3 / −1.0) km Ma−1. This rate is smaller than a published slip rate of 6.5 km Ma−1 for the Vari detachment, which is another detachment structurally above the Tinos detachment. Because of the different rates and because published ZFT ages from the footwall of the Vari detachment are ∼10 Ma, we propose that the Vari detachment has to be distinguished from the older Livadi detachment. We discuss various models of how the extensional detachments may have evolved and prefer a scenario in which the Vari detachment cut down into the footwall of the Livadi detachment successively exhuming deeper structural units. The thermochronologic ages demonstrate the importance of quantitative data for constraining localization processes during extensional deformation

Can Chatbots Help Support a Person’s Mental Health?:Perceptions and Views from Mental Healthcare Professionals and Experts

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