British Geological Survey, Wallingford, Oxon, United Kingdom.
PLoS One. 2013 Jul 31;8(7):e70264. doi: 10.1371/journal.pone.0070264. Print 2013.
Groundwater ecosystems remain poorly understood yet may provide ecosystem services, make a unique contribution to biodiversity and contain useful bio-indicators of water quality. Little is known about ecosystem variability, the distribution of invertebrates within aquifers, or how representative boreholes are of aquifers. We addressed these issues using borehole imaging and single borehole dilution tests to identify three potential aquifer habitats (fractures, fissures or conduits) intercepted by two Chalk boreholes at different depths beneath the surface (34 to 98 m). These habitats were characterised by sampling the invertebrates, microbiology and hydrochemistry using a packer system to isolate them. Samples were taken with progressively increasing pumped volume to assess differences between borehole and aquifer communities. The study provides a new conceptual framework to infer the origin of water, invertebrates and microbes sampled from boreholes. It demonstrates that pumping 5 m(3) at 0.4-1.8 l/sec was sufficient to entrain invertebrates from five to tens of metres into the aquifer during these packer tests. Invertebrates and bacteria were more abundant in the boreholes than in the aquifer, with associated water chemistry variations indicating that boreholes act as sites of enhanced biogeochemical cycling. There was some variability in invertebrate abundance and bacterial community structure between habitats, indicating ecological heterogeneity within the aquifer. However, invertebrates were captured in all aquifer samples, and bacterial abundance, major ion chemistry and dissolved oxygen remained similar. Therefore the study demonstrates that in the Chalk, ecosystems comprising bacteria and invertebrates extend from around the water table to 70 m below it. Hydrogeological techniques provide excellent scope for tackling outstanding questions in groundwater ecology, provided an appropriate conceptual hydrogeological understanding is applied.
地下水生态系统仍然了解甚少，但可能提供生态系统服务，对生物多样性做出独特贡献，并包含有用的水质生物指标。人们对生态系统的变异性、含水层内无脊椎动物的分布以及钻孔对含水层的代表性知之甚少。我们使用钻孔成像和单钻孔稀释测试来解决这些问题，以确定两个位于地表以下不同深度（34 至 98 米）的白垩钻孔中截获的三个潜在含水层生境（裂缝、裂隙或管道）。这些栖息地的特点是使用包装器系统对无脊椎动物、微生物学和水化学进行采样，以将它们隔离。通过逐渐增加抽提体积来评估钻孔和含水层群落之间的差异来采集样本。该研究提供了一个新的概念框架，用于推断从钻孔中采样的水、无脊椎动物和微生物的来源。它表明，在这些包装器测试中，以 0.4-1.8 l/sec 的速度抽取 5 m(3)的水足以将无脊椎动物从 5 米到数十米带入含水层。无脊椎动物和细菌在钻孔中的丰度高于含水层，相关的水化学变化表明钻孔是增强生物地球化学循环的场所。生境之间的无脊椎动物丰度和细菌群落结构存在一些差异，表明含水层内存在生态异质性。然而，在所有含水层样本中都捕获到了无脊椎动物，细菌丰度、主要离子化学和溶解氧仍然相似。因此，该研究表明，在白垩纪，由细菌和无脊椎动物组成的生态系统从地下水位延伸到地下 70 米处。水文地质技术为解决地下水生态学中的悬而未决的问题提供了极好的机会，只要应用适当的概念性水文地质理解。
