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Land Use and Hydrogeological Characteristics Influence Groundwater Invertebrate Communities
Abstract
We examine the influence of land use and hydrogeological characteristics on the abundance, composition and structure of groundwater invertebrate communities in a loessic aquifer from Argentina. Seven wells, selected according to surrounding land use and hydrogeological characteristics, were sampled twice. Groundwater was characterized as sodium bicarbonate, bicarbonate sulfate or sulfate type. NO3 - was detected in all samples. Land use in the area surrounding the well, unsaturated zone thickness and geochemical characteristics of groundwater influenced the abundance, composition and community structure of groundwater invertebrates. Copepoda, Oligochaeta, Cladocera, Ostracoda and Amphipoda were highly influenced by land use, particularly by point pollution sources that produced higher abundance and changes in taxonomic composition. The lowest invertebrate abundance was observed at the wells situated in areas with the thickest unsaturated zone. Groundwater salinity and geochemical type influenced the presence of certain species, particularly Stygonitocrella sp.
... In contrast to these findings, Schulz et al. (2013) detected high stygofaunal abundances of the three taxa Cyclopoida, Harpacticoida and Bathynellacaea in highly saline waters exceeding marine conductivities. Also, Tione et al. (2016) discovered exclusive copepod species (Stygonitocrella n. sp.) in a brackish well with high salinity (average 2737 mg L − 1 chloride). The authors concluded that groundwater species are able to adapt to special hydrochemical conditions and that salinity may be one main influencing factor for species to occur. ...
... This is resulting in a highly stressful environment for groundwater invertebrates. In urban areas, point source pollution, such as sewage leakage, may play an important role at a very local scale with altered faunal communities (Notenboom et al., 1995;Scarsbrook and Fenwick, 2003;Tione et al., 2016). For example, higher numbers of Oligochaeta as well as Microturbellaria and Nematodawhich are known to cope with less favourable conditions, low DO contents and higher temperatures (Hahn et al., 2013) were spotted in urban wells compared to wells in forest areas in the city of Karlsruhe, Germany . ...
... Fauna in groundwater is reported within a wide range of DO levels. Several studies indicated DO levels as well as land-use to be drivers of faunal assemblage patterns and shifts in niche occupation Dumas and Lescher-Moutoué, 2001;Hahn, 2002;Marmonier et al., 2018;Tione et al., 2016). For example, Koch et al. (2021) found a significant correlation between the number of taxa and the DO levels in the city of Karlsruhe, Germany. ...
Groundwater fauna (stygofauna) comprises organisms that have adapted to the dark subterranean environment over a course of thousands and millions of years, typically having slow metabolisms and long life cycles. They are crucial players in the groundwater of oxygenic aquifers, and contribute to various ecosystem services. Today's knowledge of their sensitivity to anthropogenic impacts is incomplete and a critical analysis of the general relevance of local findings is lacking. In this review, we focus on those areas with the highest interference between humans and stygofauna: cities. Here is where local pollution by various contaminants and heat strongly stresses the unique groundwater ecosystems. It is demonstrated that it is difficult to discern the influence of individual factors from the findings reported in field studies, and to extrapolate laboratory results to field conditions. The effects of temperature increase and chemical pollution vary strongly between tested species and test conditions. In general, previous findings indicate that heating, especially in the long-term, will increase mortality, and less adapted species are at risk of vanishing from their habitats. The same may be true for salinity caused by road de-icing in cold urban areas. Furthermore, high sensitivities were shown for ammonium, which will probably be even more pronounced with rising temperatures resulting in altered biodiversity patterns. Toxicity of heavy metals, for a variety of invertebrates, increases with time and chronic exposure. Our current knowledge reveals diverse potential impacts on groundwater fauna by urban pollution, but our insights gained so far can only be validated by standardized and long-term test concepts.
... Previous studies also showed that hydrogeological parameters strongly influence the occurrence and composition of 295 groundwater fauna (Koch et al. 2021;Stein et al. 2012). Geology and hydrological connectivity significantly influence water chemistry and habitat availability and, therefore, biotic distribution (Hahn 2006, Fuchs 2007Fuchs et al. 2006;Korbel, Chariton, and Hose 2018;Korbel and Hose 2015;Tione, Bedano, and Blarasin 2016). For instance, the abundance and species richness of crustacean fauna in the alluvial aquifers are most related to hydrological conditions, oxygen concentrations and geologic structures (Mösslacher, 1998), which is consistent with our findings. ...
Groundwater is an important source of freshwater, drinking water and service water for irrigation, industrial and geothermal uses and the largest terrestrial freshwater biome of the world. In many areas, this habitat is naturally or anthropogenically threatened. This study uses long-term groundwater data from South-West Germany to identify shifts in groundwater fauna due to natural or anthropogenic impacts. Comprehensive analysis of metazoan groundwater fauna and abiotic parameters from 16 monitoring wells over two decades revealed no overall temporal trends for fauna abundance, biodiversity in terms of number of species, as well as no significant large-scale trends in abiotic parameters. While nine wells out of 16 show stable ecological and hydro-chemical conditions at a local level, the remaining wells exhibit shifting or fluctuating faunal parameters. At some locations, these temporal changes are linked to natural causes, such as decreasing dissolved oxygen contents or fluctuating temperatures. A multivariate PHATE (Potential of Heat-diffusion for Affinity-based Trajectory Embedding)-analysis suggests that, beside the hydrogeological setting, varying contents of sediment and detritus impact faunal abundance. By examining aerial images of the surroundings of individual wells, we found that anthropogenic impacts, such as construction sites, can cause significant shifts in groundwater fauna and changes in the ecological status. However, variable faunal composition and abundances were also observed for sites with very stable abiotic conditions in anthropogenically less affected areas. These findings indicate that hydro(geo)logical changes and surface conditions, such as land use, should be assessed in line with hydro-chemical parameters to better understand changes in groundwater fauna. Accordingly, reference sites for natural conditions in ecological assessment and biomonitoring schemes for groundwater protection should be selected carefully.
Groundwater is an important global resource, providing water for irrigation, industry, geothermal uses and potable water. Moreover, groundwater contains the world's largest terrestrial freshwater biome with ecosystems, inhabited mainly by invertebrates (stygofauna) and microbes, undertaking important services including water purification, as well as nutrient and carbon cycling. Despite investigations on the spatial and temporal variations of groundwater fauna and the influence of environmental parameters on these organisms, in parts of the world, even the most basic knowledge of these ecosystems is still lacking. The aims of this study are to provide an overview on groundwater fauna (stygofauna) research, including the historical evolution of research topics and the development of sampling methods and secondly to identify the global distribution of groundwater fauna research and resulting data gaps. To achieve this, an extensive review of accessible groundwater fauna data was conducted by analysing 859 studies. It was evident that over time, there has been an exponential increase in the number of groundwater fauna studies together with changing paradigms in the research focus, particularly as sampling methods have developed from using simple nets, substrate samples and hand-pumps in the beginning to recent molecular analyses (e.g. eDNA). As application of molecular methods becomes more common, knowledge on groundwater diversity and functional ecology is expected to increase. Studies on groundwater fauna are spatially uneven and are dominated by research in Europe and Australia, with few studies in Africa, Asia and the Americas. This presently biased view on groundwater biota hinders the identification of biodiversity patterns and ecosystem functions on a wider geographic and climatic scale. In the future, a more evenly distributed stygofauna sampling effort in currently underrepresented areas of the globe is necessary to ensure a more comprehensive perspective on stygofauna biodiversity, roles and functional significances. This is increasingly important with the accumulating knowledge of the sensitivities of these ecosystems to anthropogenic activities, including climate change, and is fundamental to effective management of these ecosystems.
Groundwater is an important global resource, providing water for irrigation, industry, geothermal uses, and potable water all over the world. Moreover, groundwater contains the world’s largest terrestrial freshwater biome. Groundwater faunal communities undertake important ecosystem services including the provision of clean water. Despite this, investigations on the spatial and temporal variations and the influence of environmental parameters on these organisms, are still rare. The aim of this study is to provide a global overview on groundwater fauna (stygofauna) research, including the historical evolution of research topics and development of sampling methods. To achieve this, an extensive review of accessible groundwater fauna data was conducted. Over time, there has been an exponential increase in the number of studies together with changing paradigms in the research focus, particularly as sampling methods have developed and molecular analyses become common. Studies on groundwater fauna are spatially uneven and are dominated by studies in Europe and Australia, with few studies in Africa, Asia and the Americas. This has resulted in a potential geographic and climatically biased global view of stygofauna and groundwater ecology. In the future, a more evenly distributed sampling effort in underrepresented areas is necessary to enable global studies, thus allowing a more comprehensive perspective on stygofauna biodiversity, roles, and functional significances. This is increasingly important with the accumulating knowledge of the sensitivities of these ecosystems to anthropogenic activities, including climate change, and is fundamental to effective management of these ecosystems.
Groundwater pollution due to anthropogenic activities may impact overall groundwater quality. Organic and inorganic pollutants have been routinely detected at unsafe levels in groundwater rendering this important drinking water resource practically unusable. Vulnerability of groundwater pollution and subsequent impact has been documented in various studies across the globe. Field studies as well as mathematical models have demonstrated increasing levels of pollutants in both shallow and deep aquifer systems. New emerging pollutants such as organic micro-pollutants have also been detected in some industrialized as well as in developing countries. Increased vulnerability coupled with ever growing demand for groundwater may pose a greater threat of pollution due to induced recharge and lack of environmental safeguards to protect groundwater sources. In this review paper, comprehensive assessment of groundwater quality impact due to human activities such as improper management of organic and inorganic waste, and natural sources is documented. A detailed review of published reports and peer reviewed journal papers across the world clearly demonstrate that groundwater quality is declining over time. A proactive approach is needed to prevent human health and ecological consequences due to ingestion of contaminated groundwater.
Crustaceans were sampled in 17 groundwater wells at five locations in North and South Islands of New Zealand. Three sampling locations were associated with unconfined aquifers adjacent to gravel‐bed rivers, whereas the other two locations were distant from rivers, but associated with land‐based sewage effluent disposal sites. Crustaceans and basic physico‐chemical parameters were sampled in summer and winter. Total abundance varied from 1 to 1064 individuals/250 litre sample. Copepods dominated the fauna at four of the five locations, and were most abundant immediately downstream of a sewage effluent disposal area. Paraleptamphopus spp. (Amphipoda) was found at all five locations, and abundance was also greatest downstream of sewage effluent disposal areas. Several crustacean taxa were rare or limited in distribution, including the gammarid Paracrangonyx sp. and the anthurid isopod Cruregens sp. Syncarids were widely distributed, but found in low numbers, and no specimens were found immediately below sewage effluent disposal areas. We suggest that groundwater ecology in New Zealand is restricted by lack of knowledge of taxonomy and ecology of key groups, particularly the Copepoda.
Recent surveys of groundwater invertebrates (stygofauna) worldwide are yielding rich troves of biodiversity, with significant implications for invertebrate systematists and phylogeneticists as well as ecologists and groundwater managers. What is the ecological significance of this high biodiversity of invertebrates in some aquifers? How might it influence groundwater ecosystem services such as water purification or bioremediation? In terrestrial ecosystems, bio- diversity is typically positively correlated with rates of ecosystem functions beneficial to humans (e.g. crop pollination). Ho wever, the links between biodiversity, ecosystem function, and ecosystem services in groundwater are unknown. In some aquifers, feeding, movement and excretion by diverse assemblages of stygofauna potentially enhance groundwater ecosystem services such as water purification, bioremediation and water infiltration. Further, as specific taxa apparently play 'keystone' roles in facilitating ecosystem services, declines in abundance or even their extinction have serious repercussions. One way to assess the functional significance of biodiversity is to identify 'ecosystem service providers', characterise their functional relationships, determine how service provision is affected by community structure and environmental variables, and measure the spatio-temporal scales over which these operate. Examples from Australian and New Zealand alluvial aquifers reveal knowledge gaps in understanding the functional importance of most stygofauna, hampering effective protection of currently undervalued groundwater ecosystem services.
We studied ground-water crustacean communities by collecting samples from three sets of wells located in the Rocky Glades area of Everglades National Park (ENP), the Atlantic Coastal Ridge northeast of ENP, and along canals southeast of ENP. In each well, we sampled at different depths, monthly from June to December 2000. Copepods collected included both calanoid species, 22 of the 27 species of cyclopoids, and 2 of the 8 species of harpacticoids reported from Everglades National Park. We also collected several isopods, amphipods, and ostracods that were identified at the generic level. The numbers of copepod species and individuals varied with time, and with depth class, suggesting that surface water copepods use ground water as a refuge from predators, or as a feeding site during the wet season. Surface-dwelling taxa become more numerous when the ground-water level decreased, at the end of the wet season. We documented faunal exchange from surface to ground waters and vice versa, and for the wells along the Coastal Ridge canals, movements to and from the canals into ground water.
Changes in surface land use may threaten groundwater quality and ecosystem integrity, particularly in shallow aquifers where links between groundwater and surface activities are most intimate. In this study we examine the response of groundwater ecosystem to agricultural land uses in the shallow alluvial aquifer of the Gwydir River valley, New South Wales, Australia. We compared groundwater quality and microbial and stygofauna assemblages among sites under irrigated cropping, non-irrigated cropping and grazing land uses. Stygofauna abundance and richness was greatest at irrigated sites, with the composition of the assemblage suggestive of disturbance. Microbial assemblages and water quality also varied with land use. Our study demonstrates significant differences in the composition of groundwater ecosystems in areas with different surface land use, and highlights the utility of groundwater biota for biomonitoring, particularly in agricultural landscapes.
Ecological and socioeconomic aspects of subterranean hydrosystems have changed during the past 40–50 years. The major environmental pressures (mainly anthropogenic ones) impact the quantity and quality of groundwater resources and the state of subsurface ecosystems, and it is expected that the environmental pressures on groundwater will continue, at least until 2025, unless new environmental policies change this state of affairs. The world demographic increase and the general rise of water demand constitute one of the major environmental pressures on groundwater ecosystems especially in less developed countries in Africa, Asia and South America. Specific human activities leading to the depletion of groundwater reserves include agricultural practices, landscape alteration, urbanization demand for domestic and public drinking water, various industrial activities such as thermoelectric production and mining, and the rise of tourism in coastal areas. Climate change is contributing to the water crisis too, especially in areas with arid climate and/or in some humid monsoonal countries. The overload of aquifers with pollutants derived from agriculture (fertilizers and pesticides), from industry (release of hydrocarbon chemicals, especially spills), from waste and industrial waters, from domestic and industrial landfills, from the infiltration of pollutants from surface and from the intrusion of saline water affect groundwater quality. The dangerous increase in contaminated subsurface sites with chemicals and microbial pathogens brings with it health risks to humans. Changes of redox condition in groundwater zones, changes of biological diversity, vegetation changes with modification of agriculture practices and impacts at the biosphere scale, such as the increase in the concentration of nitrous oxides in the atmosphere, all impact groundwater ecosystems. Groundwater ecosystems must be better investigated and understood. Economic, social and ecological lines of thinking have to be combined in order to achieve meaningful policies for the sustainable development of groundwater reserves and for the protection of subsurface ecosystems. Practical measures and ideas for the development of policies up to the 2025 time-horizon should improve the sustainable usage of the world's groundwater resources.
1. With few exceptions, copepods dominate over other crustacean and non‐crustacean invertebrate groups in ground water. They have colonised a vast array of habitats in continental ground waters, where they are represented by over 1000 species in six orders: Platycopioida, Misophrioida, Calanoida, Cyclopoida, Harpacticoida, Gelyelloida. However, members of only the last four orders entered genuine fresh ground water.
2. Stygobiotic copepods show a wide range of morphological and physiological adaptations to different groundwater habitats. They frequently exhibit simplifications in body plans, including reductions in appendage morphology, which is regarded as a result of paedomorphic heterochronic events.
3. Copepod distributions at small spatial scales are most strongly affected by habitat type and heterogeneity, with sediment grain size and availability of organic matter being important habitat characteristics. Large‐scale spatial distributions (biogeographical) are mainly related to past geological, climatic and geographical processes which occurred over medium to long time scales.
4. Such processes have affected colonisation patterns and diversification of copepods in ground water, leading to a number of phylogenetic and distributional relicts and a high degree of endemism at different taxonomic levels. This is reflected in the composition of groundwater copepod communities characterised by distantly related species in the phylogenetic tree.
5. Copepods dominate the species richness of groundwater fauna in all regions and on all continents where more than cursory surveys have been carried out, i.e. in Europe, North and Latin America as well as in Australia.
6. Species‐specific microhabitat preferences, high proportions of local endemics, high proportions of phylogenetic and distributional relicts, and higher‐level taxonomic diversity are all factors suggesting that copepods are a useful indicator group of overall species richness for defining conservation priorities in ground water.
An applied groundwater study of the Plana de Castelln was performed to investigate possible impacts of pollutants on ecological characteristics of the aquifer. The area is illustrative for a western mediterranean coastal plain, densely populated, industrialized, and with intensive agricultural land-use. During one year, six wells in a subsection of the plain were monitored, simultaneously sampled for zoological and physicochemical analysis. Heavy metals and pesticides were not (or at very low levels) detected in the wells. Low correlations were found between physicochemical and biological data, but there were indications that organic pollution affects the abundance of the fauna. A logarithmic relationship between abundance and COD/BOD5-ratio is postulated. Salinization, an important threat to the groundwater of the area, was clearly reflected in the chemistry of one of the wells. Probably, this process has important consequences for abundance and diversity of the fauna.
The temporal stability of interstitial crustacean communities was investigated in relation to environmental variability in a perched aquifer, characterized by limited connection with surface waters. The author hypothesized that strong physico-chemical stability would enhance persistence and affect dominance patterns for groundwater fauna. Fifteen wells were sampled four times over a two-year period in order to assess the global stability of ground waters and to evaluate temporal changes in species assemblages. For each station, environmental patterns displayed only minor changes, while between-site differences were much larger. At the scale of the aquifer, strong temporal stability was found for groundwater physical and chemical variables. Interstitial crustaceans displayed diverse assemblages dominated by cyclopoid taxa. High persistence characterized community composition and structure (species relative abundance patterns, species richness, Shannon's diversity index) over the study period. Most well faunas were dominated numerically by a single species, whether micro- or macrocrustacean assemblages were considered. Faunal persistence observed in the aquifer was greater than that reported in many surface waters and was probably related to the strong environmental stability.
Ecological constraints in subsurface environments relate directly to groundwater flow, hydraulic conductivity, interstitial biogeochemistry, pore size, and hydrological linkages to adjacent aquifers and surface ecosystems. Groundwater ecology has evolved from a science describing the unique subterranean biota to its current form emphasising multidisciplinary studies that integrate hydrogeology and ecology. This multidisciplinary approach seeks to elucidate the function of groundwater ecosystems and their roles in maintaining subterranean and surface water quality. In aquifer-surface water ecotones, geochemical gradients and microbial biofilms mediate transformations of water chemistry. Subsurface fauna (stygofauna) graze biofilms, alter interstitial pore size through their movement, and physically transport material through the groundwater environment. Further, changes in their populations provide signals of declining water quality. Better integrating groundwater ecology, biogeochemistry, and hydrogeology will significantly advance our understanding of subterranean ecosystems, especially in terms of bioremediation of contaminated groundwaters, maintenance or improvement of surface water quality in groundwater-dependent ecosystems, and improved protection of groundwater habitats during the extraction of natural resources. Overall, this will lead to a better understanding of the implications of groundwater hydrology and aquifer geology to distributions of subsurface fauna and microbiota, ecological processes such as carbon cycling, and sustainable groundwater management.
The European Water Framework Directive (WFD) defines a framework for assessing water bodies in Europe in the future. The conditions in the Directive impose a strong demand for “new” assessment systems. The AQEM project developed an assessment system for European streams using macroinvertebrates. Almost 900 samples were taken in about 400 streams covering 29 stream types distributed over eight countries. The role of the Oligochaeta within this European database was analysed. Almost half a million specimens of oligochaetes were collected in 772 samples. Eight families, 41 genera and 69 species were recorded, although identification emphasised the families Tubificidae and Naididae. Three countries identified oligochaetes to species level, most others restricted their identifications to easy identifiable taxa. Numbers of specimens, species, genera and families differed strongly between the countries due to method, although standardised, and taxonomic knowledge. About 50% of all collected oligochaete taxa had assigned biological and ecological indicator values for metric calculation in the AQEM assessment system. A further refinement of this indication list as well as increased coverage of oligochaete taxa was advised. Weighted averaging was used to evaluate the relation between oligochaete distribution and ecological quality class. It was concluded that when higher taxonomic levels are used in assessment, the quality evaluation results become biased. Furthermore, oligochaetes can tell us much more about the ecological status of streams than is commonly assumed. Differences in ecological optima among Limnodrilus udekemianus, Ilyodrilus templetoni, Aulodrilus pluriseta, Nais communis, and Spirosperma ferox are shown.
Stream Ecology: Structure and Function of Running Waters is designed to serve as a textbook for advanced undergraduate and graduate students, and as a reference source for specialists in stream ecology and related fields. The Second Edition is thoroughly updated and expanded to incorporate significant advances in our understanding of environmental factors, biological interactions, and ecosystem processes, and how these vary with hydrological, geomorphological, and landscape setting. The broad diversity of running waters - from torrential mountain brooks, to large, lowland rivers, to great river systems whose basins occupy sub-continents - makes river ecosystems appear overwhelming complex. A central theme of this book is that although the settings are often unique, the processes at work in running waters are general and increasingly well understood. Even as our scientific understanding of stream ecosystems rapidly advances, the pressures arising from diverse human activities continue to threaten the health of rivers worldwide. This book presents vital new findings concerning human impacts, and the advances in pollution control, flow management, restoration, and conservation planning that point to practical solutions. Reviews of the first edition: ".. an unusually lucid and judicious reassessment of the state of stream ecology" Science Magazine "..provides an excellent introduction to the area for advanced undergraduates and graduate students-" Limnology & Oceanography "- a valuable reference for all those interested in the ecology of running waters." Transactions of the American Fisheries Society.
Papers reviewed herein present a general overview of groundwater quality around the world in 2009. These include groundwater quality survey and assessment in urban and rural areas, and the impacts of land uses on groundwater quality, with a focus on groundwater contamination, pollution prevention, and remediation.
Low organic matter supply and reduced spatiotemporal heterogeneity severely constrain biodiversity in groundwater. At the aquifer scale, spatial variation in the groundwater recharge rate is considered a key factor in generating groundwater patches with distinctly different food supplies and spatiotemporal heterogeneity. Our study addressed the role of groundwater recharge in sustaining biodiversity in a phreatic aquifer by testing differences in the density and species richness of invertebrate assemblages among 11 reference sites and 13 sites artificially recharged with storm water. The vertical distribution pattern of invertebrate assemblages was examined using well clusters at one shallow water-table recharge site and one nearby reference site. Groundwater recharge elevated dissolved organic C (DOC) concentrations in groundwater and increased spatiotemporal physicochemical heterogeneity. The thickness of the vadose zone (VZT) controlled DOC input to groundwater at recharge sites but did not reduce spatiotemporal heterogeneity. The higher density and richness of invertebrate assemblages at the well-cluster recharge site than at the well-cluster reference site also was controlled by VZT, suggesting that organic matter supply was a primary factor determining biodiversity patterns in groundwater. Invertebrate density increased and species composition shifted with increasing depth below the groundwater table at the shallow water-table well-cluster site. Some taxa, including several epigean species, preferentially occurred near the water table, whereas others, including several hypogean species, colonized deeper groundwater layers.
Between June 2001 and December 2002, 18 hyporheic and groundwater bores were sampled for fauna and environmental data using phreatic traps. The bores were situated in three different natural geographic regions in Palatinate, Southwestern Germany.Faunal data correlated with the relative amount of detritus, bacterial abundances and the standard deviation of temperature, while very few and weak correlations were found with physical–chemical variables. Dissolved oxygen was assumed to be a limiting factor for most metazoans with a critical concentration at around 0.5–1mgl−1.To quantify the strength of the hydrological exchange with surface water and its effects on fauna, a so-called GW-Fauna-Index was developed and calculated using the relative amount of detritus, standard deviation of temperature, and oxygen concentration. From all environmental data and on all spatial scales, this index best explained the total faunal abundance and taxonomic richness.To describe the availability of organic aliments in the groundwater, the terms of “alimonic” and “alimony” [from lat. alimonium=(food) supply] were proposed.Although stygofauna was different in the geographic regions investigated, the GW-Fauna-Index was independent from these regional particularities. Using the GW-Fauna-Index, three groups of groundwater habitats could be classified according to the alimonic conditions. From oligo-alimonic group I samples, fauna was mostly absent, while meso-alimonic group II samples were prevailingly populated by stygobites, and eu-alimonic group III samples by ubiquists and stygoxenes. Total abundances and taxonomic richness increased significantly from group I to group III. Group I samples were characterized by low index values, group II samples by intermediate and group III samples by high values.The GW-Fauna-Index provides promising perspectives for application, but needs some improvement. First of all, detritus should be analysed quantitatively and qualitatively, rather than semi-quantitatively. Also, a standard protocol for sampling has to be developed.
Short-range endemism is common in groundwater fauna (stygofauna), placing many species at risk from anthropogenic impacts such as water abstraction and pollution. Few of the alluvial aquifers in eastern Australia have been sampled for stygofauna. Fauna from two aquifers in Queensland and two in New South Wales was sampled to improve ecological knowledge of stygofauna and the potential threats posed to it by development. Our surveys found stygofauna in all four aquifers, with most taxa collected from bores with low electrical conductivity (< 1500 mu S cm(-1)). Taxon richness decreased with distance below the water table. The most taxon-rich bores in each region occurred where the water table depth was < 10 m, were associated with the alluvium of tributaries of large regulated river systems, and were near phreatophytic trees. It is possible that tree roots constitute a habitat and source of organic matter in alluvial aquifers as they do in cave streams. It is important to document the biodiversity of particular regions and aquifers so that species can be conserved in the face of increasing groundwater use. For effective resource management, future research should strive to understand the tolerances and ecological requirements of groundwater communities and the ecosystem services they provide.
(1) Relative species abundances of moths in four years' light trap samples from eighteen sites were fitted to log-series and log-normal frequency distributions. (2) Samples from stable environments were best fitted by the log-series. (3) Increased skewness in changing environments better fitted the log-normal. (4) The fit of the distributions was not a product of the light trap; suction traps gave similar distributions but with different parameters. (5) The log-series index alpha was a highly efficient site discriminant and robust, yielding reasonable values with only moderate distribution fit. (6) Neither S* nor sigma, from the log-normal, were able to discriminate between sites. (7) S*/3 sigma gives values closely similar to alpha, but was more sensitive to fit in both tails of the distribution. (8) alpha was independent of sample size.
1. The first part of this review focuses on the oxygen status of natural groundwater systems (mainly porous aquifers) and hyporheic zones of streams. The second part examines the sensitivity of groundwater organisms, especially crustaceans, to low oxygen concentrations (< 3.0 mg L−1 O2).
2. Dissolved oxygen (DO) in groundwater is spatially heterogeneous at macro- (km), meso- (m) and micro- (cm) scales. This heterogeneity, an essential feature of the groundwater environment, reflects changes in sediment composition and structure, groundwater flow velocity, organic matter content, and the abundance and activity of micro-organisms. Dissolved oxygen also exhibits strong temporal changes in the hyporheic zone of streams as well as in the recharge area of aquifers, but these fluctuations should be strongly attenuated with increasing distance from the stream and the recharge zone.
3. Dissolved oxygen gradients along flow paths in groundwater systems and hyporheic zones vary over several orders of magnitude (e.g. declines of 9 × 10−5 to 1.5 ×10−2 mg L−1 O2 m−1 in confined aquifers and 2 × 10−2 to 1 mg L−1 O2 m−1 in parafluvial water). Several factors explain this strong variation. Where the water table is close to the surface, oxygen is likely to be consumed rapidly in the first few metres below the water table because of incomplete degradation of soil-generated labile dissolved organic carbon (DOC) in the vadose zone. Where the water table is far from the surface, strong oxygen depletion in the vicinity of the water table does not occur, DO being then gradually consumed as groundwater flows down the hydraulic gradient. In unconfined groundwater systems, oxygen consumption along flow paths may be compensated by down-gradient replenishment of DO, resulting either from the ingress of atmospheric oxygen or water recharge through the vadose zone. In confined groundwater systems, where replenishment of oxygen is impossible, the removal time of DO varies from a few years to more than 10 000 years, depending mainly on the organic carbon content of the sediment. Comparison of the hyporheic zones between systems also revealed strong differences in the removal time and length of underground pathways for DO. This strong variability among systems seems related to differences in contact time of water with sediment.
4. Although groundwater macro-crustaceans are much more resistant to hypoxia than epigean species, they cannot survive severe hypoxia (DO < 0.01 mg L−1 O2) for very long (lethal time for 50% of the population ranged from 46.7 to 61.7 h). In severe hypoxia, none of the hypogean crustaceans examined utilized a high-ATP yielding metabolic pathway. High survival times are mainly a result of the combination of three mechanisms: a high storage of fermentable fuels (glycogen and phosphagen), a low metabolic rate in normoxia, and a further reduction in metabolic rate by reducing locomotion and ventilation. It is suggested here that the low metabolic rate of many hypogean species may be an adaptation to low oxygen and not necessarily result from an impoverished food supply.
5. An interesting physiological feature of hypogean crustaceans is their ability to recover from anaerobic stress and, more specifically, rapidly to resynthesize glycogen stores during post-hypoxic recovery. A high storage and rapid restoration of fermentable fuels (without feeding) allows groundwater crustaceans to exploit a moving mosaic of suboxic (< 0.3 mg L−1 O2), dysoxic (0.3–3.0 mg L−1 O2) and oxic (> 3 mg L−1 O2) patches.
6. It is concluded that although hypogean animals are probably unsuited for life in extensively or permanently suboxic groundwater, they can be found in small or temporarily suboxic patches. Indeed, their adaptations to hypoxia are clearly suited for life in groundwater characterized by spatially heterogeneous or highly dynamic DO concentrations. Their capacity to survive severe hypoxia for a few days and to recover rapidly would explain partly why ecological field studies often reveal the occurrence of interstitial taxa in groundwater with a wide range of DO.
1. Relationships between the assemblage structure of stygobionts (i.e. obligate groundwater species) and habitat conditions in aquifers were explored in the French Jura based on 16 environmental variables and presence/absence data on stygobiotic species. The two data sets were simultaneously collected at a total of 269 sites.
2. The study aimed to (i) identify the environmental factors determining the composition of stygobiotic assemblages at the regional scale; (ii) define the ecological preferences of the collected stygobiotic species along environmental gradients; and (iii) describe species assemblages occurring in similar habitats. These aims were pursued with a view to refine approaches to groundwater biodiversity assessment and sampling strategies.
3. A large number of stygobionts (62 species) were collected using a stratified sampling design. The measured environmental variables explained 72% of the overall variability in stygobiotic assemblage structure. Determining factors were primarily geology (pore size) and dissolved oxygen concentration, and secondarily altitude and distance of sampling sites from areas glaciated during the Pleistocene. Water chemistry and land‐cover variables had little influence on the composition of stygobiotic assemblages.
4. Ecological preferences of stygobiotic species were bounded along environmental gradients using Outlying Mean Index (OMI) analysis. Apart from rare species (frequency < 0.01), most stygobionts had a tolerance index >1, but residual tolerance observed in the most widespread species indicates sensitivity to other variables than those studied.
5. Biodiversity hotspots mainly occurred in highly permeable geological formations such as karst and coarse alluvial environments with well oxygenated water situated between 200 and 500 m altitude. More intensive sampling of high‐altitude sites is unlikely to yield additional species, but rare species may be found at low and mid altitudes and at sites far from the Würm glaciers.
1. This paper is a synthesis of a special issue on groundwater biodiversity with a focus on obligate subterranean species, the stygobionts. The series of papers constitutes a great leap forward in assessing and understanding biodiversity patterns because of the use of large quantitative data sets obtained over a broad geographic scale. They also represent a conceptual shift, away from a purely taxonomic and phylogenetic focus to the analysis of whole groundwater assemblages.
2. The general patterns emerging for groundwater fauna are: very high levels of endemism, low local diversity relative to regional diversity, a limited number of lineages, occurrence of many relicts, and truncated food webs with very few predators.
3. β‐Diversity is at least as important as α‐diversity in determining total richness at different scales (aquifer, basin and region) and overall taxa richness increases across spatial scales.
4. Advances in understanding groundwater biodiversity patterns further include identification of several important factors related to geology and hydrology that determine the composition of European stygobiotic assemblages.
5. Important challenges for future research include improving sampling strategies, filling gaps in sampling coverage, intensifying research on theoretical and statistical models, and including functional and genetic diversity components in biodiversity assessments.
6. Strategies are proposed for protecting groundwater biodiversity and an argument is made to integrate biodiversity in groundwater management. Applying principles such as complementarity and flexibility for groundwater biodiversity conservation is a major step toward delineating a reserve network that maximise species representation at the European scale.
Detrended correspondence analysis (DCA) is an improvement upon the reciprocal averaging (RA) ordination technique. RA has two main faults: the second axis is often an arch or horseshoe distortion of the first axis, and distances in the ordination space do not have a consistent meaning in terms of compositional change (in particular, distances at the ends of the first RA axis are compressed relative to the middle). DCA corrects these two faults. Tests with simulated and field data show DCA superior to RA and to nonmetric multidimensional sealing in giving clear, interpretable results. DCA has several advantages. (a) Its performance is the best of the ordination techniques tested, and both species and sample ordinations are produced simultaneously. (b) The axes are scaled in standard deviation units with a definite meaning, (c) As implemented in a FORTRAN program called DECORANA, computing time rises only linearly with the amount of data analyzed, and only positive entries in the data matrix are stored in memory, so very large data sets present no difficulty. However, DCA has limitations, making it best to remove extreme outliers and discontinuities prior to analysis. DCA consistently gives the most interpretable ordination results, but as always the interpretation of results remains a matter of ecological insight and is improved by field experience and by integration of supplementary environmental data for the vegetation sample sites.
In order to access the descriptive value of subterranean organisms with regard to groundwater contamination, faunal sampling was carried out at two unimpacted sites and one sewage polluted site located in the south eastern part of the Lez karst system from 1991-1993. Invertebrates were collected by means of an air lift pump in 8 deep monitoring wells which intersected Cretaceous and/or Jurrassic limestones. Wells of the unimpacted sites had faunal assemblages dominated by crustaceans and they harboured a high number of stygobite species which usually represented a major component of the total number of invertebrates. At the sewage polluted site, the wells had significant relative abundances of oligochaetes, lowstygobite richnesses and their groundwater fauna consisted mainly of stygoxene taxa whose relative abundance could be as high as 88%. The spatio temporal distribution of organisms was related to the groundwater ans sewage flow patterns. During low water periods sewage polluted water moved preferentially through the conductive fractures of the saturated zone whose faunal assemblages were dominated by stygoxenes such as the polysaprobiont oligochaete Tubifex tubifex. When floods occured, these stygoxenes were flushed out of the site and were associated with stygophiles. As the source of sewage pollution decreased in intensity with time, preliminary signs of groundwater fauna recovery were observed. Oligochaetes became less abundant but recolonization of groundwater by stygobites was not yet observed. On the basis of our results and those of other authors we emphasize the advantages which could result from the development of biomonitoring programmes for the assessment of karstic groundwater contamination.
Spatial and temporal patterns in the species abundance distribution of benthic invertebrate communities of 11 freshwater habitats (10 streams and a wind-swept lake shore) were examined with respect to habitat stability. Abundance patterns varied markedly between seasons at most sites. However, mean abundance distributions at 4 of the 5 unstable sites and the 2 most stable sites were dominated by one or two taxa with a large number of rare species, whereas sites of intermediate stability had more equitable distributions. Both the log series and log normal distributions were statistically indistinguishable, at the 5% level, from all the observed mean abundance patterns. In contrast, graphical comparisons of the observed and fitted distributions suggested the log series may be the better fit at most of the unstable sites and the two most stable sites, whereas the more equitable distribution at sites of intermediate stability suggested the log normal distribution was the better fit. If conditions at a site favoured one or two species, either through severe physical conditions, or through competitive superiority in the absence of disturbance then the log series distribution may result. However, if no species in the community was strongly advantaged over others, a log normal distribution should result. Given the discriminating power of the appropriate statistical test it may not, however, be possible to pick up these differences without graphical comparisons as well.
We examined taxonomic and geographic patterns of the obligate groundwater fauna (i.e. stygobiotic fauna) by assembling in
a distributional data base all species occurrences reported from France since 1805. A simulated annealing algorithm was used
to identify conservation targets. Until the 60s, biological surveys were restricted to caves but the proportion of sampling
sites in unconsolidated sediments increased from 1 to 16% over the last 40 years. A total of 380 species and subspecies in
40 families were collected, 70% of which being restricted to France. As observed in other temperate regions, the stygobiotic
fauna was dominated by crustaceans (65% of species) and molluscs (22%). The cumulative number of species did not level off
over time, clearly showing that biodiversity was underestimated. Temporal trends in the cumulative number of obligate groundwater
and surface water species suggested that groundwater comprised more crustaceans than surface freshwater. Endemism was high
although the geographic range size of species increased as distributional data accumulated. Of 380 species, 156 were known
from a single 400-km2 cell, among which 73% were located in the southern third of France. The distribution map of species richness changed dramatically
over time, indicating that the location of richness hotspots was sensitive to sampling effort. Less than 2% of the French
landscape was needed to capture 60% of known species. Thus, a large proportion of species could be protected by focusing habitat
conservation efforts on a few complementary species-rich aquifers located in distinct regions.
Interstitial crustaceans were collected from a grid of shallow sampling wells penetrating the alluvial floodplain aquifer (ca. 10 m 5 km 10 km) of the Flathead River, Montana, USA. Eighteen taxa were identified, which collectively encompassed a range of hypogean-epigean affinities. The subterranean amphipod Stygobromus spp., the most common crustacean, occurred in all wells but was rare in the channel well. When well data were pooled into habitat types (channel, bank, near-, central-, and far-floodplain), distinct faunal patterns were apparent. Crustaceans constituted an increasing percentage of the total interstitial fauna from the channel to the near-floodplain, then maintained similar relative abundance levels with increasing distance from the river. Stygobionts attained maximum values at near- and central-floodplain habitats where copepods and ostracods dropped to the lowest levels. Distribution and abundance patterns of Crustacea at the floodplain scale are structured by hydrogeologic and geomorphic processes reflected only in part by distance from the river channel. The flood plain appears to contain a latticework of alluvial-filled paleochannels of high hydraulic conductivity that induce spatial discontinuities within the aquifer and that may play an important role in determining crustacean distribution patterns.
Environmental policy and in particular the European water legislation, in the framework of the EU Groundwater Directive, has started to consider groundwater not only as a resource but as a living ecosystem. A precondition for comprehensive groundwater protection is thus the assessment of the biological and ecological state. The assessment of ecosystems requires consideration of ecological criteria, which so far are not available for groundwater systems. In the framework of a national project, the German Federal Environment Agency (UBA) supports a consortium of scientists and stakeholders from water boards and regional environmental authorities to develop a first concept for an ecological assessment scheme for groundwater ecosystems. The attempts towards an integrative concept include the following steps: (i) selection of appropriate biological and ecological parameters, (ii) typology of groundwater ecosystems, (iii) derivation of a reference status (Leitbild) and natural background values for biological variables, (iv) identification of potential bioindicators and definition of threshold values, and (v) development of an assessment model. These proposed steps are discussed on the basis of a data set from two groundwater landscapes in Southern Germany. Investigations considered three different spatial units, i.e. the habitat unit at the local scale, and the aquifer type unit as well as the landscape unit at the regional scale. Fauna as well as bacterial communities could provide valuable ecological information on the ecosystems status. The paper reviews ‘state of the art’ knowledge and evaluates the near future perspectives for the development and implementation of groundwater ecosystems assessment programmes.
The W statistic of Shapiro and Wilk provides the best omnibus test of normality, but its application is limited up to n= 50. This study modifies W, such that it can be extended for all sample sizes. The critical values of W, i.e. the modification of W, is given for n up to 5000. The empirical moments show that the null distribution of W is skewed to the left and is consistant for all sample sizes. Empirical powers of W are also comparable with those of W.
The diversity of a planktonic foraminiferal assemblage on the ocean floor depends on the state of preservation of that assemblage. As dissolution progresses, species diversity (number of species in the assemblage) decreases, but compound diversity (based on relative species abundance) first increases and then decreases; species dominance first decreases and then increases. The reason for these changes is that the species most susceptible to solution deliver moresediment to the ocean floor than do species with solution-resistant shells, possibly because the more soluble tests are produced in surface waters, where growth and production are greatest.
Biogeography and Ecology of Irish Groundwater Fauna. Assessment of the Distribution, Structure and Functioning of Subterranean Fauna within Irish Groundwater Systems
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Structure and Functioning of Subterranean Fauna within Irish
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The Collembola of North America North of the Rio Grande
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