Groundwater Macrocrustaceans as Natural Indicators of the Ariège Alluvial Aquifer

The macrocrustacean fauna from an alluvial aquifer in the French Pyrénées was investigated using 15 wells scattered over the floodplain. Wells were sampled at three contrasting periods for faunal, phy‐sical and chemical variables to investigate relationships between amphipod, isopod distributions and environmental factors. The assemblages, dominated by stygobite amphipod species, showed an overall persistence between the sampling dates. Groundwater quality exhibited between‐site variations related to agriculturally‐induced pollution. Low correlations existed between water quality and fauna distribution patterns. At the scale of the aquifer, groundwater contamination did not influence the macrocrustacean distribution. The spatial distribution of amphipods and isopods was clearly related to hydrogeology and hydrodynamics: strong relationships were found between the assemblages composition and the hydrological context of the stations (wells from the alluvial plain and from the alluvial terrace). With respect to spatial and temporal scales and providing adequate sampling methods, macrocrustaceans then constitute natural indicators of groundwater hydrodynamics in the Ariège aquifer.     

Subsurface Dwelling Crustaceans as Indicators of Hydrological Conditions,Oxygen Concentrations,and Sediment Structure in an Alluvial Aquifer

The relation between environmental conditions and the species composition and individual abundance of crustaceans was investigated in a shallow alluvial aquifer, located in the Danube wetlands (Lobau, Austria). Samples, consisting of groundwater, sediment, and fauna, were taken from permanent installed wells by means of a piston pump five times in a year cycle. The results show that the spatial and temporal distribution, individual abundance, and species richness of crustacean fauna is related to hydrological conditions, oxygen concentrations, and geologic structures in the alluvial aquifer. Therefore, crustaceans, divided in stygoxene, stygophile, and stygobite species, can be used as bioindicators of these environmental conditions in an aquifer. It is suggested that beside physicochemical analyses also the crustacean fauna should be considered to characterise a groundwater ecosystem.     

The Impact of Water Table Drawdown and Drying on Subterranean Aquatic Fauna in In-Vitro Experiments

The abstraction of groundwater is a global phenomenon that directly threatens groundwater ecosystems. Despite the global significance of this issue, the impact of groundwater abstraction and the lowering of groundwater tables on biota is poorly known. The aim of this study is to determine the impacts of groundwater drawdown in unconfined aquifers on the distribution of fauna close to the water table, and the tolerance of groundwater fauna to sediment drying once water levels have declined. A series of column experiments were conducted to investigate the depth distribution of different stygofauna (Syncarida and Copepoda) under saturated conditions and after fast and slow water table declines. Further, the survival of stygofauna under conditions of reduced sediment water content was tested. The distribution and response of stygofauna to water drawdown was taxon specific, but with the common response of some fauna being stranded by water level decline. So too, the survival of stygofauna under different levels of sediment saturation was variable. Syncarida were better able to tolerate drying conditions than the Copepoda, but mortality of all groups increased with decreasing sediment water content. The results of this work provide new understanding of the response of fauna to water table drawdown. Such improved understanding is necessary for sustainable use of groundwater, and allows for targeted strategies to better manage groundwater abstraction and maintain groundwater biodiversity.     

Biotic and abiotic interactions between surface and interstitial systems in rivers

Water chemistry and community assemblages of surface and interstitial invertebrates were studied at seven sues on the French Rivers Rhône and Am at surface and at 50 cm depth into the bed sediments Chemical factors allowed differentiation of surface water from groundwater and detection of water exchanges defining clear downwelling and upwelling zones At some sites, interstitial water showed both surface and phreatic conditions, characterizing the underflows of the Rhone or of the Am In the interstitial area, most taxa showed no significant correlations with water chemistry Some epigean and hypogean fauna showed correlations with certain factors Clear relationships appeared between the water exchanges and the distribution of surface and interstitial faunas In interstitial samples, epigean and some hypogean species characterized the downwelling zones while others seemed to be strictly linked to the upwelling zones In surface samples, the presence of hypogean species was associated with regions of groundwater upwelling     

Longitudinal variation in the composition of the benthic macroinvertebrate fauna of a typical North coast Jamaican river

Benthic macroinvertebrate fauna plays a major role in river ecosystems, especially those of tropical islands. Since there is no information on the distribution of benthic invertebrates along a Jamaican river, we report here on the composition of the benthic fauna of the Buff Bay river, on the Northern coast of Jamaica. A total of 14 samples were collected from five sites, using kick nets and a Surber sampler, between May 1997 and October 1998. We also examined the applicability of the rhithron/potamon model, and some of the premises of the River Continuum Concept (RCC) in relation to the distribution of invertebrate taxa. The results showed a total of 38 taxa of identified invertebrates. A group of dominant taxa, composed mainly of immature stages of insects, occurred at all sites. Two notable characteristics of the river were the absence of a true potamonic fauna and the low representation of the shredder functional feeding group in the community We conclude that, while there was minor variation in the composition of the benthic macroinvertebrate fauna among the sites, this was a response to local conditions within the river system. The characteristics of the community did not conform to either of the models.     

High diversity and local endemism in Aotearoa New Zealand's groundwater crustacean fauna

We used DNA barcoding to assess the diversity and distribution of New Zealand''s groundwater amphipods and isopods (Crustacea) and to determine whether biodiversity and endemism within tectonically active New Zealand are similar to those of more tectonically stable continents. Sixty‐five wells were sampled in seven aquifers across four regions within the North and South islands of New Zealand, and resident invertebrates were morphologically identified and then assessed using sequencing of the mitochondrial DNA cytochrome c oxidase subunit one (COI) gene. Invertebrates were found in 54 wells. Of the 228 individual amphipods and isopods found in 36 of the wells, 154 individuals were successfully sequenced for COI (68% success rate) from 25 wells, with at least one well in each aquifer containing sequenced individuals. Of the 45 putative species identified using Barcode Index Numbers (BINs), 30 BINs (78% of all taxa and 83% of amphipods) were previously unrecorded. Substantial morphologically cryptic, species‐level diversity was revealed, particularly within the amphipod Family Paraleptamphopidae. Similarly, one isopod taxon morphologically identified as Cruregens fontanus was assigned to five well‐separated BINs based on COI sequences. Endemism appeared high, with all taxa regionally endemic; 87% of species were restricted to one aquifer and more than 50% restricted to one well. Non‐saturated species accumulation curves indicated that, while additional sampling may increase the range of some currently identified taxa, additional range‐restricted taxa are also likely to be discovered. Patterns of diversity and short‐range endemism were similar to those found elsewhere, including locations which are more tectonically stable. The predominance of local endemism within New Zealand''s groundwater fauna suggests that land‐use activities and groundwater extraction require careful evaluation to minimize threats to groundwater biodiversity.     

宁夏银北盐碱地油葵田土壤动物多样性及群落结构

【目的】调查宁夏银北盐碱地油葵田的土壤动物多样性及群落结构,探讨不同改良时间盐碱地土壤动物多样性及群落结构与环境因子之间的相关性。【方法】生物与环境因子之间的关系研究一直是生态学研究的热点,尤其是恢复生态学中如何设计环境因子来恢复生物群落的结构和功能最近引起了国内外学者的关注。以宁夏银北盐碱地油葵田为对象,研究了不同改良时间盐碱地中油葵田土壤动物与环境因子的相互关系,采用野外调查和室内试验相结合。【结果】共采集12个土壤动物类群,优势类群为弹尾目(60.67%)、蜱螨亚纲(23.24%)和鞘翅目(6.45%);土壤动物物种多样性、丰富度指数和均匀度在未改良盐碱地中较高。【结论】土壤pH值、碱化度和全盐质量分数是土壤动物分布的限制因素,土壤动物的数量随土壤pH值、碱化度和全盐质量分数的降低而增加。这些结果为盐碱地改良的恢复与评价提供了重要的数据支持和基础资料。     

Longitudinal patterns of invertebrates in the hyporheic zone of a glacial river

1. Longitudinal changes in physicochemical factors and the composition of the invertebrate community were examined in the hyporheic zone of a glacial river (Val Roseg, Switzerland) over a distance of 11 km from the glacier terminus. Multivariate analysis was used to determine the habitat preferences of taxa along an upstream‐downstream gradient of increasing temperature and groundwater contribution to river flow. 2. The hyporheos conformed to the longitudinal distribution model described for zoobenthic communities of glacial rivers in that taxonomic richness increased with distance from the glacier terminus. Spatial variation in taxonomic richness was best explained by temperature, the influence of groundwater, and the amount of organic matter. The overriding importance of these variables on the distribution of taxa was confirmed by the multivariate analysis. 3. The hyporheic zone contributed significantly to the overall biodiversity of the Roseg River. Whereas insect larvae were predominant in the benthos, hyporheic invertebrates were dominated by taxa belonging to the true groundwater fauna and the permanent hyporheos. Several permanently aquatic taxa (e.g. Nematoda, Ostracoda, Cyclopoida, Harpacticoida, Oligochaeta) appeared exclusively in the hyporheic zone or they extended farther upstream in the hyporheic layer than in the benthic layer. Leuctridae, Nemouridae, and Heptageniidae colonised hyporheic sediments where maximum water temperature was only 4 °C. 4. Despite strong seasonal changes in river discharge and physicochemistry in hyporheic water, the density and distribution of the hyporheos varied little over time. 5. Taxonomic richness increased markedly in the downstream part of a floodplain reach with an extensive upwelling zone. Upwelling groundwater not only maintained a permanent flow of water but also created several species‐rich habitats that added many species to the community of the main channel.     

The phreatic aquifer of the ‘Plana de Castellón’ (Spain):relationships between animal assemblages and groundwater pollution

An applied groundwater study of the Plana de Castellón 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.     

Skink and invertebrate abundance in relation to vegetation, rabbits and predators in a New Zealand dryland ecosystem

We explored the relationships between ground vegetation, ground fauna (native skinks and invertebrates), rabbits, and predators in a modified New Zealand dryland ecosystem. We hypothesised that vegetation cover would provide habitat for ground fauna. We also hypothesised that rabbits (Oryctolagus cuniculus) would reduce the abundance of these fauna by reducing vegetation, and by providing prey for mammalian predators (cats Felis catus and ferrets Mustela putorius) that consume ground fauna as secondary prey. We measured these variables at 30 sites across three pastoral properties in the South Island in 1996 and 2002. There were mostly positive relationships between vegetation ground cover and fauna captures in pitfall traps. Relatively few beetles and caterpillars were caught where cover was less than 80%, no millipedes were caught where cover was less than 70%, and few spiders and mostly no skinks, crickets, flies or slugs were caught where vegetation cover was less than 50%. Most grasshoppers were caught where cover ranged from 30 to 80%. Faunal species richness was also positively related to cover. This supports our hypothesis that ground vegetation provides habitat for skinks and invertebrates in this ecosystem. The introduction of rabbit haemorrhagic disease in 1997 provided a natural experiment to test the hypothesised indirect effects of rabbits on ground fauna. Declines in rabbits varied between properties, and vegetation cover and predator abundance changed according to the magnitude of these declines. However, skink and invertebrate abundance did not track these changes as expected, but instead varied more or less consistently between properties. Some fauna increased (skink captures quadrupled and cricket captures nearly doubled), others declined (flies, caterpillars and spiders), and some did not change (beetles, millipedes, slugs and grasshoppers, and faunal species richness and diversity). Therefore, rabbits, predators and vegetation did not affect changes in skinks and invertebrates in consistent ways. The dynamics of ground fauna are likely to be more influenced by factors other than those we measured.     

高原鼢鼠干扰下高寒草甸大型土壤动物多样性对环境因子的响应

为研究高寒草甸大型土壤动物群落组成和分布对环境因子的响应,选取祁连山东段的甘肃省天祝县高原鼢鼠典型分布区域,以鼠丘密度代表干扰强度设置4个干扰区。调查各干扰区植被群落特征、土壤理化性质、大型土壤动物类群组成及其数量,采用约束性排序方法分析环境因子对大型土壤动物类群组成和分布的影响。结果表明：高原鼢鼠干扰下高寒草甸大型土壤动物优势类群为瓦娄蜗牛科、象甲科和短角亚目幼虫;极重度干扰区大型土壤动物类群的丰度、丰富度、Shannon指数显著高于重度干扰区（P<0.05）;多元回归分析表明大型土壤动物类群丰度、丰富度和Shannon指数与土壤温度呈显著负相关（P<0.05）,丰富度与土壤含水量呈显著负相关（P<0.05）,丰度与土壤紧实度呈显著负相关（P<0.05）,丰富度和Shannon指数与植物Shannon指数呈显著负相关（P<0.05）;冗余分析和偏冗余分析表明,土壤温度、紧实度和含水量是影响高寒草甸大型土壤动物类群组成和分布的主要环境因子。     

Invertebrates and urban runoff in a small northern stream,Edmonton, Alberta,Canada

The invertebrate fauna of a small northern stream was examined within Edmonton, Alberta. Many invertebrates that were common upstream of the city were absent or rare within the city. In contrast, some tubificids and chironomids were very abundant within the city. Diversity and richness (number of taxa) of the fauna were much lower within Edmonton than upstream, while the total density was much higher within the city. These changes in the urban invertebrate fauna were apparently caused by the discharge of organic materials and silt from storm sewer runoff.Chemical analysis of routinely-collected water samples did not show significant differences between urban and non-urban sites. This was probably due to the sporadic nature of storm sewer runoff. Peak levels of contaminants in the stream were usually missed because of the routine nature of sampling. Aquatic invertebrates, which exhibit long-term responses to sporadic runoff incidents, provided a better indication of stream water quality than did routine chemical monitoring.     

Velvet worm (Phylum Onychophora) on a sand island,in a wetland: Flushed from a Pleistocene refuge by recent rainfall?

Velvet worms (Onychophora) are restricted to moist, humid microclimates, but are poorly known from south‐east Queensland, Australia, where they are typically rainforest fauna. We made the unlikely observation of one of these invertebrates clinging to floating debris in a wetland on North Stradbroke Island. Palaeoecology of this wetland reveals that it once was within rainforest and has remained moist for at least the past 80 000 years, thus potentially harbouring an onychophoran population as a relic of a past broader, rainforest distribution. The presence of this animal, floating in the wetland, can be explained by recent climate, since the wetland filled following heavy rainfall shortly before the observation. This highlights the importance of groundwater‐fed wetlands as evolutionary refugia for moisture‐dependent biota.     

Assessment of the spatial variability of intertidal benthic communities by axial tomodensitometry: importance of fine-scale heterogeneity

At the water-sediment interface of aquatic ecosystems, the presence of biogenic structures produced by benthic invertebrates strongly affects biogeochemical processes. The quantification of these structures and the assessment of the vertical distribution of fauna are essential for determining the impact of communities in sediments. In the present study, computer axial tomodensitometry (CAT-scan) was used to measure the space occupied by an intertidal community of the St. Lawrence estuary. Three cores were sampled at a site that was considered homogeneous according to surface sediments. The vertical distribution of biogenic structures and gravel were measured in the three cores using CAT-scan; the vertical distribution of fauna was also analysed for each core. The biogenic structures were highest at the water-sediment interface and decreased with depth in the three cores. The number of invertebrates also decreased with depth. We observed similar distributions of biogenic structures in cores 1 and 2. However, fewer biogenic structures were observed below 90 mm in core 3. This result was correlated with a high quantity of gravel from 90 to 140 mm in core 3 whereas the other cores had lower quantities of coarse material. We found relationships among the distributions of biogenic structures, fauna, and sediment characteristics (gravel quantity) that can affect species distribution. The vertical distributions of Macoma balthica, Mya arenaria, Nereis virens, and small-sized gallery-producing species (nematodes and oligochaetes) could also be recorded with the CAT-scan method. Thus, CAT-scan is an excellent tool to determine the fine-scale heterogeneity in the space occupied by benthic invertebrates in sediments.     

Lacustrine sediment/groundwater nutrient dynamics

A small pond in southwestern peninsular Florida was sampled to determine the areal and depth distribution of total phosphorus, total nitrogen, and organic matter. Concentrations of these constituents decreased from the center to the edge of the pond and from the top to the bottom of the sediments. At the center of the pond total phosphorus showed a secondary concentration peak at a depth of 20 to 40 cm in the sediments indicative of the downward transfer of soluble phosphorus during times of low water.A system of monitoring wells was installed at the pond to measure groundwater input and output nutrient concentrations. There was no difference in total groundwater nitrogen concentration across the pond but the mean increase in total phosphorus concentration between input and output wells, ca. 200 g1^–1, was statistically highly significant. The results suggest that whereas nitrogen is recycled from sediments to the pond and the atmosphere, the pond-sediment system loses some phosphorus to groundwater throughflow.     

Responses of benthic invertebrates in an experimental channel to artificial flushes

A large experimental channel was used to examine the responses of benthic invertebrate communities to artificial flushes. Two artificial flushes were done at a 20-day interval with a 2-fold difference in peak discharge and duration between them. The effects of the flushes on macroinvertebrates were monitored by comparing the abundance of individual taxa, taxon richness, diversity measures, and similarity indices. Taxon richness and abundances of invertebrates were drastically reduced by every flush. However, the diversity of invertebrates was not significantly reduced by the flushes, and the composition was similar before and after each flush. The fast recruitment of some taxa, having short life cycles, reduced the diversity of invertebrates in the interval between the two flushes. The flushes caused significant reductions in the abundance of epiphytes and fauna living in the streambed. The fauna more resistant to flushes were invertebrates that fasten their cases or retreats by silk threads to substrata. Taxa living in sediment under stones and having a sucking apparatus were also resistant to flushes. Handling editor: R. Bailey     

Benthic invertebrates of streams on the Alburz Mountain range near Tehran,Iran

Samples of benthic invertebrates were collected from riffle sites on two river systems in the southern Alburz Mountains in the neighbourhood of Tehran. Iran. Main river channels had a fauna of Oligochaeta, Plecoptera, Ephemeroptera, Trichoptera, Coleoptera, Diptera and Potamonidae and downstream changes in community structure were observed. Tributary streams had few or no benthic invertebrates. The main factors determining fauna appeared to be frequent flooding and high levels of suspended solids caused by quick run-off of rain and melting snow from the bare, eroded and degraded mountain sides.     

Benthic and hyporheic macroinvertebrate distribution within the heads and tails of riffles during baseflow conditions

The distribution of lotic fauna is widely acknowledged to be patchy reflecting the interaction between biotic and abiotic factors. In an in situ field study, the distribution of benthic and hyporheic invertebrates in the heads (downwelling) and tails (upwelling) of riffles were examined during stable baseflow conditions. Riffle heads were found to contain a greater proportion of interstitial fine sediment than riffle tails. Significant differences in the composition of benthic communities were associated with the amount of fine sediment. Riffle tail habitats supported a greater abundance and diversity of invertebrates sensitive to fine sediment such as EPT taxa. Shredder feeding taxa were more abundant in riffle heads suggesting greater availability of organic matter. In contrast, no significant differences in the hyporheic community were recorded between riffle heads and tails. We hypothesise that clogging of hyporheic interstices with fine sediments may have resulted in the homogenisation of the invertebrate community by limiting faunal movement into the hyporheic zone at both the riffle heads and tails. The results suggest that vertical hydrological exchange significantly influences the distribution of fine sediment and macroinvertebrate communities at the riffle scale.     

黄河三角洲莱州湾湿地柽柳种群分布特征及其影响因素

为探明黄河三角洲莱州湾柽柳(Tamarix chinensis Lour)灌丛环境因子的基本特征及其对柽柳灌丛空间分布类型的影响,采用样地与样方相结合的测定方法,对柽柳灌丛样地距海远近、地下水水位、土壤盐碱含量、土壤容重和孔隙度等基本物理参数以及土壤有机质、速效氮、磷养分等13个环境因子参数进行相关性和主成分分析。结果表明:莱州湾柽柳种群空间分布表现为聚集型分布,林分密度与距海距离和地下水水位呈极显著正相关,与土壤含水量呈极显著负相关;土壤含盐量与土壤含水量呈极显著正相关,与地下水水位和土壤孔隙度呈极显著负相关;土壤含水量与地下水位呈极显著负相关。莱州湾柽柳灌丛13个环境因子的变异系数在0.060—1.296之间,土壤K+含量、土壤含盐量和林分密度变化幅度较大;其次为土壤有机质和有效磷,地下水水位的空间变异性高于至海距离,而土壤p H值、土壤容重和总孔隙度等基本物理性状变化幅度较小。土壤盐碱含量分别为0.47%和p H为8.48,呈重盐土和偏碱性特征。主成分分析表明,土壤盐碱含量是影响黄河三角洲莱州湾湿地柽柳灌丛分布的主导因素,其次是距海距离,土壤速效磷和地下水位次之。     

Macroconsumers are more important than specialist macroinvertebrate shredders in leaf processing in urban forest streams of Rio de Janeiro,Brazil

Coarse particulate organic matter is often broken down by specialist shredder invertebrates in temperate streams. In some tropical streams, larger, non-specialist, omnivorous fauna, (macroconsumers), particularly decapod shrimps and crabs, have been found to process coarse particulate matter. Larger shrimps and fish may also prey on or inhibit smaller invertebrates. Depending on the relative importance of larger and smaller fauna in leaf processing and in predatory interactions, we could expect that exclusion of larger fauna could either result in a decrease in leaf processing (if they were important in shredding or bioturbation) or increase in leaf processing if they negatively affected smaller shredders. We tested this by excluding fauna of different sizes from leaf peaks using bags with different sizes of mesh –0.2 mm (exclusion of most fauna), 2 mm (exclusion of larger fauna), and 10 mm (access to most fauna). Bag effect on leaf processing was minimized by constructing the bags of the same, fine, material, and sewing a relatively small window of the required mesh size. The experiment was conducted on two occasions in three streams of the urban forest of Parque Estadual da Pedra Branca, city of Rio de Janeiro. The three streams differed in larger fauna of shrimps (Macrobrachium potiuna), crabs, tadpoles, and fish. Packs were incubated for six time intervals and the rate of leaf processing calculated as the exponential rate of loss of leaf material. Rate of leaf processing was faster in bags with the largest mesh size; the rates in the other two mesh sizes were not statistically different. Rates varied between experiments and among streams. We could not attribute the faster leaf processing to any particular component of the larger fauna; the patterns of differences among streams and between experiments were not associated with particular taxa. There was no general trend of fewer smaller fauna in the presence of macroconsumers; the few smaller taxa that were different between mesh sizes were variously less and more abundant in the 10-mm mesh bags compared to the 2-mm. Known shredders were rare in the smaller fauna; the mining chironomid Stenochironomus was common, but was apparently not affected by larger fauna and apparently did not increase leaf processing. We conclude that macroconsumers and not smaller fauna had a positive effect on leaf processing, and this confirms a pattern observed in some other coastal Neotropical streams.