Surface and Hyporheic Oligochaete Assemblages in a French Suburban Stream

The Chaudanne stream received urban inputs discharged through combined sewer overflows (CSOs). The water quality was not severely impaired, with pollution mainly of organic origin. Oligochaete assemblages were studied in the coarse surface sediments and the hyporheic zone and sampled at four sites on seven occasions during 2000 and 2001. The seasonal distribution of oligochaete assemblages was analyzed by a PCA, the oligochaete species being assigned to functional traits (FTrs). Site 1, located upstream of the CSOs, was characterized by FTrs 1 and 2 (species indicating permeability and those intolerant to water pollution). Below the CSOs, high densities of oligochaetes occurred in the benthic layer of sites 3 and 4, with a predominance of FTr3 (species with tolerance to water pollution). At site 4, FTr4 species (indicative of sludge conditions) constantly predominated in the hyporheic system, but predominated in the benthos only during low stream discharges associated with peaks in CSOs. FTr3 was related to amounts of the oxidized forms of nitrogen, high stream discharges and probably to groundwater upwellings and the sludge tolerant species group (FTr4) was associated with high NH₊⁴ contents. We are now testing the relevance and generalization of this new approach.     

Oligochaete communities in the hyporheic zone of a glacial river,the Roseg River,Switzerland

We examined the composition and distribution of oligochaete communities in the hyporheic zone of the Roseg River, a glacial river in southeastern Switzerland. Ten oligochaete species were collected from 11 sites distributed along an 11-km reach of the river, downstream of the Tschierva Glacier. The most frequently encountered species were Dorydrilus michaelseni, Propappus volki, Cernosvitoviella atrata and Cernosvitoviella carpatica. Six other species were relatively scarce and exhibited a discontinuous distribution pattern only in the downstream sites. At the most downstream site, a population of eyeless Nais communis was discovered with anatomical traits apparently related to a subterranean life-adaptation of this surface-living species. The species richness and abundance of oligochaete communities were relatively constant over time, but increased at sites where groundwater entered the stream. The spatial distribution of several oligochaete species was linked to the longitudinal arrangement of groundwater upwelling areas. This observation suggested that groundwater was an important upstream migration pathway for oligochaetes during the glacial retreat.     

Transport of Algal Cells in Hyporheic Sediments of the River Elbe (Germany)

The advective transport of algal cells into the interstices of the hyporheic zone of the River Elbe was spatially and temporally heterogenous. Even deep sediment layers were reached by large phytoplankton species. Therefore, it is suggested that (i) the advective interstitial transport patterns vary between different algal sizes and morphotypes and (ii) sediment characteristics, expressed by the permeability coefficient k_f of porous media, affect retention and retardation of surface water algae during subsurface transport. The transport behaviour of different green algae (Chlorella sp., Scenedesmus acuminatus, Desmodesmus communis, and Pediastrum duplex) and algal sized microspheres was tested in flow‐through column experiments with hyporheic sediments. The algal cell transport was directly related to the permeability of the column sediments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Riparian Trees and Flow Paths between the Hyporheic Zone and Groundwater in the Oberer Seebach,Austria

We investigated lateral subsurface water exchange in a 2^nd order mountain stream with a piezometer method. At both banks the stream hyporheic zone lost water to the riparian groundwater zone. Independently, the hydraulic heads at three sites in the streambed and in the riparian zone exhibited periodic, diurnal fluctuations. We attributed them to water consumption by the riparian trees, as solar radiation explained part of this additional variation. Our results demonstrate that subsurface water exchanges take place between the hyporheic zone and lateral riparian groundwater in spatially defined small‐scale flow paths. These small‐scale interactions occur within the context of large‐scale patterns of loss and gain of channel water.     

The Effects of an Environmental Flow Release on Water Quality in the Hyporheic Zone of the Hunter River,Australia

Environmental flow releases have been advocated as a useful rehabilitation strategy for improving river condition but assessments of their success have typically focused on surface water quality and biota. In this study, we investigated the impacts of an environmental flow release on water temperature, conductivity, dissolved oxygen, and nitrate concentrations in surface and subsurface (hyporheic) water at upwelling and downwelling zones in three sites along the Hunter River, New South Wales, Australia. We hypothesised that the flow pulse would ‘flush’ the sediments with oxygenated water, stimulating hyporheic microbial activity and nitrification, enhancing nitrate concentrations over time. Surface and subsurface samples were collected before, 7 days after, and 49 days after an environmental flow release of 5000 Ml for a period of 3 days. No lasting effects on dissolved oxygen or conductivity were evident at most sites although dissolved oxygen declined over time at the downwelling site at Bowmans Crossing. At the downwelling zones at all sites, hyporheic nitrate concentrations declined initially following the release, but then rose or leveled off by Day 49. This initial drop in concentration was attributed to flushing of nitrate from the sediments. At two sites, nitrate concentrations had increased by Day 49 in the upwelling zones while at the third site, it fell significantly, associated with very low dissolved oxygen and likely reductive loss of nitrate. Electrical conductivity data indicate that potential inputs of agriculturally enriched groundwater may contribute to the nitrogen dynamics of the Hunter River. This study highlights the spatial heterogeneity that occurs in the hyporheic zone within and among sites of a regulated river, and emphasises the need for multiple-site surveys and an understanding of groundwater dynamics to assess physicochemical responses of the hyporheic zone to environmental flow releases.     

Hyporheic zone hydrology and nitrogen dynamics in relation to the streambed topography of a N-rich stream

The influence of riffle-pool units on hyporheic zone hydrology and nitrogen dynamics was investigated in Brougham Creek, a N-rich agricultural stream in Ontario, Canada. Subsurface hydraulic gradients, differences in background stream and groundwater concentrations of conservative ions, and the movement of a bromide tracer indicated the downwelling of stream water at the head of riffles and upwelling in riffle-pool transitions under base flow conditions. Channel water also flowed laterally into the floodplain at the upstream end of riffles and followed a subsurface concentric flow path for distances of up to 20 m before returning to the stream at the transition from riffles to pools. Differences in observed vs predicted concentrations based on background chloride patterns indicated that the hyporheic zone was a sink for nitrate and a source for ammonium. The removal of nitrate in the streambed was confirmed by the loss of nitrate in relation to co-injected bromide in areas of downwelling stream water in two riffles. Average stream water nitrate-N concentrations of 1.0 mg/L were often depleted to <0.005 mg/L near the sediment-water interface. Consequently, an extensive volume of the hyporheic zone in the streambed and floodplain had a large unused potential for nitrate removal. Conceptual models based mainly on studies of streams with low nutrient concentrations have emphasized the extent of surface-subsurface exchanges and water residence times in the hyporheic zone as important controls on stream nutrient retention. In contrast, we suggest that nitrate retention in N-rich streams is influenced more by the size of surface water storage zones which increase the residence time of channel water in contact with the major sites of rapid nitrate depletion adjacent to the sediment-water interface.     

Importance of transient storage zones for ammonium and phosphate retention in a sandy-bottom Mediterranean stream

1. The ability of hyporheic sediments to exchange water and retain ammonium and phosphate in the Riera Major stream ,North-East Spain, under different discharge conditions was measured by conducting short-term nutrient and chloride additions. 2. The mean exchange coefficients from free-flowing water to the storage zone (k₁) and vice versa (k₂) were 0.82 × 10–4 s^??1 and 7 × 10^??3 s^??1, respectively. The ratio of storage zone cross-sectional area to stream cross-sectional area (A_S/A) averaged 2.8 × 10–2 and was negatively correlated with discharge (r = –0.85, d.f. = 13, P < 0.001). 3. The percentage of hyporheic zone water which came from surface water varied as a function of discharge and hyporheic depth, ranging between 33% and 95% at 25 cm depth, and between 78% and 100% at 10 cm depth. 4. The nutrient retention efficiency in the hyporheic zone at 10 cm depth measured as uptake length (S_wh) was less than 3.3 cm for ammonium and 37 cm for phosphate. Higher nutrient retentions were measured in the sediments at 10 cm depth than at 25 cm, indicating that near-surface sediments were involved more actively in phosphate retention than the deeper hyporheic sediments. The lack of ammonium at any depth of the hyporheic zone showed that ammonium was very rapidly taken up in the surfacial sediments.     

Benthic insects and fish of the Doubs River system: typological traits and the development of a species continuum in a theoretically extrapolated watercourse

Using the distribution patterns of benthic insects (198 species) and fishes ( 29 species) from 11 tributaries and the main channel of the Doubs River drainage basin (French Jura), the authors have tried to establish whether there is an organization of species into discrete, identifiable communities. Principal Component Analysis (PCA) was used to identify whether a continuum existed, and also used to select 50 least-disturbed sites, which were used to define a theoretical watercourse. The density classes of each species were projected on this longitudinal gradient and each species response was characterised by two typological traits: its typological preferendum (tp) and its typological amplitude (ta),thus creating a synthesis of ecological characteristics. In the typological index given in the appendix, the 210 species which form a biological templet are listed in alphabetical order with their tp and ta values. These typological species traits are useful contributions to a database for running waters biomonitoring.     

Studies on Atmosphere Spores and Pollen and Their Influences on the Sporopollen Assemblages in the Sediments of Huanghai Sea

Totally, 321 grains of spores and pollens which consist of 23 genera and species, were collected from the atmosphere over Huanghai Sea during the survey in 1978–1979. It has been found that the amount of spores and pollen in the atmosphere was high in spring, lower in autumn and the lowest in summer and winter. The content of arboreal pollens amount to 74%, with 23% of herbaceous pollens and SM of spores. By comparing the spores and pollens in the atmosphere with those in the marine sedments it was revealed that they were well correlated but the former influences distinctly to the distribution of the latter, thus making a high content of herbaceous pollens in the sporopollen distributions in the marine sediments nearshore area and high content of arboreal pollens in area far from the coast.     

A Survey of Escherichia coli and Salmonella in the Hyporheic Zone of a Subtropical Stream: Their Bacteriological,Physicochemical and Environmental Relationships

The Hyporheic Zone is among the most important interstitial freshwater habitats, but the relationship between biotic and abiotic factors in this zone remains under-explored. Enterobacteria were expected to be present, but no specific studies had ever confirmed this prediction. The aim of this study was, therefore, to evaluate the total coliforms, Escherichia coli and Salmonella spp. in hyporheic water and to determine the relationship of the physical, chemical and environmental factors at different depths in a rainforest stream. To this end, thirty-six water samples were collected at three depths in sites located in the first, second and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmonella sp. were evaluated in terms of their CFU/ml. In the interstitial samples, coliforms were detected in 100% of the samples. The total coliform counts had higher values at intermediate depths, while E. coli and Salmonella spp. instead had higher values at intermediate and large depths, often reaching or exceeding the values of the surface samples. Our results revealed that Salmonella spp. and the coliforms have different microhabitat preferences. Salmonella spp. and coliform species prefer deposition areas, such as lateral sides of pools, curves and bars, but they have a tendency to distribute into different depths, likely due to temperature differences. Salmonella spp. prefer compact substrata, with fewer fluids passing through and with upwelling areas with lower oxygen inflow. The coliform species showed the opposite preference. Our results suggest that bacterial variation is related to environmental factors and physical-chemical parameters within the HZ and may play a key role in the microbial diversity and distribution in these ecosystems.     

Evaluation of Phosphorus Species in the Bed Sediments of an Atlantic Basin: Bioavailability and Relation with Surface Active Components of the Sediment

In this study, total phosphorus (P) concentrations and P fractions in the bed sediments of the Anllóns River (NW Spain) have been examined. The Lowest Effect Level of the Ontario Sediment Quality Guidelines was trespassed for total phosphorus (600 mg kg^?1) at three out of the five sampling sites which, in addition, showed an average of 43% of bioavailable phosphate. The inorganic P fractions (loosely bound P, redox-sensitive P, metal oxide-bound P, carbonate and apatite P, and residual P) showed that inorganic P was mostly found as metal oxide bound P. The difference between total phosphorus and the sum of the inorganic P forms determined in these extracts is attributed to P associated to organic compounds being solubilized in some of the extractants, and represented in average 58% of total phosphorus. With the exception of loosely bound P, all the P fractions showed significant positive correlations with each other and with total phosphorus.     

北方农牧交错带植被重建中适宜乔、灌、草种的生态区划

因遭受滥垦及过度放牧破坏的中国北方农牧交错带亟待进行植被的恢复和重建.本文从为该区域植被的恢复与重建提供植物物种上的支持出发,对适宜该区域生长与分布的乔、灌、草种进行了生态区划.生态区划的原则概括为4条:生态保育优先、有利生产发展、适地适树适草以及参考行政区划边界.在该原则指导下,依据限定农牧交错带植物生长和分布的主要生态因子:年最低日均温、年大于0℃积温、湿润度指数(年降水量与年大于0℃积温之比)、反映区域地表组成物质、地形及气候特征影响的土壤类型等,将农牧交错带划分为7个不同的生态区域,依次为:Ⅰ.松辽平原西部及大兴安岭山地区,Ⅱ.辽河上游风沙区,Ⅲ.蒙古高原中、东部及冀西北山地区,Ⅳ.吕梁山、太行山、燕山山地区,Ⅴ.鄂尔多斯高原风沙区,Ⅵ.陕北、陇东黄土高原区,Ⅶ.陇中及青海高原东部黄土区.在上述分区的基础上,对以往文献报道中出现的适宜该区域生长和分布的乔、灌、草,包括乡土种和人工栽培或引种的外来种,按其生态习性分别进行了细致的甄别选择,并在文中择其精要予以列出.     

北方农牧交错带植被重建中适宜乔、灌、草种的生态区划

因遭受滥垦及过度放牧破坏的中国北方农牧交错带亟待进行植被的恢复和重建。本文从为该区域植被的恢复与重建提供植物物种上的支持出发,对适宜该区域生长与分布的乔、灌、草种进行了生态区划。生态区划的原则概括为4条：生态保育优先、有利生产发展、适地适树适草以及参考行政区划边界。在该原则指导下,依据限定农牧交错带植物生长和分布的主要生态因子：年最低日均温、年大于0℃积温、湿润度指数(年降水量与年大于O℃积温之比)、反映区域地表组成物质、地形及气候特征影响的土壤类型等,将农牧交错带划分为7个不同的生态区域,依次为：I．松辽平原西部及大兴安岭山地区,II．辽河上游风沙区,In．蒙古高原中、东部及冀西北山地区,Ⅳ．吕梁山、太行山、燕山山地区,V．鄂尔多斯高原风沙区,Ⅵ．陕北、陇东黄土高原区,Ⅶ．陇中及青海高原东部黄土区。在上述分区的基础上,对以往文献报道中出现的适宜该区域生长和分布的乔、灌、草,包括乡土种和人工栽培或引种的外来种,按其生态习性分别进行了细致的甄别选择,并在文中择其精要予以列出。     

Bacterial and Archaeal Community Structure in the Surface Diatom Sediments of Deep Freshwater Lake Baikal (Eastern Siberia)

Diatom sediment records of large lakes can be used to decipher the history of ancient phytoplankton. The upper layer of the sediment is an important area of remineralization of the sedimenting phytoplankton biomass. It hosts a bacterial community different from those of both the water column and deeper sediment layers. In this work, we analyzed the structure and diversity of the communities of Bacteria and Archaea in the surface sediment core containing valves of diatoms, the major producers in Lake Baikal. Pyrosequencing of the bacterial V3–V4 region of the 16 S ribosomal RNA (rRNA) and archaeal V1–V3 16 S rRNA gene regions yielded 29,168 and 36,997 reads, respectively. In total, we have identified 33 bacterial phyla; uncultured Actinobacteria were the most abundant in the upper layers, while lower sediment was dominated by Firmicutes and Alphaproteobacteria. The composition of the archaeal community changed with depth, but was generally dominated by Crenarchaeota from the classes Marine Group I and Miscellaneous Crenarchaeotic Group, as well as Euryarchaeota from the class Thermoplasmata. These dominant bacterial and archaeal taxa are presumed to participate in the destruction of buried organic matter, which eventually leads to degradation of the diatom valves.     

Sediments in Marsh Ponds of the Gulf Coast Chenier Plain: Effects of Structural Marsh Management and Salinity

Physical characteristics of sediments in coastal marsh ponds (flooded zones of marsh associated with little vegetation) have important ecological consequences because they determine compositions of benthic invertebrate communities, which in turn influence compositions of waterbird communities. Sediments in marsh ponds of the Gulf Coast Chenier Plain potentially are affected by (1) structural marsh management (levees, water control structures and impoundments; SMM), and (2) variation in salinity. Based on available literature concerning effects of SMM on sediments in emergent plant zones (zones of marsh occasionally flooded and associated with dense vegetation) of coastal marshes, we predicted that SMM would increase sediment carbon content and sediment hardness, and decrease oxygen penetration (O₂ depth) and the silt-clay fraction in marsh pond sediments. Assuming that freshwater marshes are more productive than are saline marshes, we also predicted that sediments of impounded freshwater marsh ponds would contain more carbon than those of impounded oligohaline and mesohaline marsh ponds, whereas C:N ratio, sediment hardness, silt-clay fraction, and O₂ depth would be similar among pond types. Accordingly, we measured sediment variables within ponds of impounded and unimpounded marshes on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana. To test the above predictions, we compared sediment variables (1) between ponds of impounded (IM) and unimpounded mesohaline marshes (UM), and (2) among ponds of impounded freshwater (IF), oligohaline (IO), and mesohaline (IM) marshes. An a priori multivariate analysis of variance (MANOVA) contrast indicated that sediments differed between IM and UM marsh ponds. As predicted, the silt-clay fraction and O₂ depth were lower and carbon content, C:N ratio, and sediment hardness were higher in IM than in UM marsh ponds. An a priori MANOVA contrast also indicated that sediments differed among IF, IO, and IM marsh ponds. As predicted, carbon content was higher in IF marsh ponds than in ponds of other impounded marsh types. In contrast to our predictions, C:N ratio and sediment hardness were lowest and silt-clay fraction and O₂ depth were highest in IO and IM marsh ponds. Our results indicated that SMM has affected physical properties of sediments in coastal marsh ponds. Moreover, sediments in IF marsh ponds were affected more so than were those in IO and IM marsh ponds. Our results, in conjunction with those of previous studies, indicated that sediments of marsh ponds and emergent plant zones differed greatly. We predict that changes in pond sediments due to SMM will promote greater epifaunal macroinvertebrate biomass, which in turn should attract larger populations of wintering waterbirds. However, waterbirds that filter or probe soft sediments may be negatively affected by SMM because of the expected decrease in infaunal invertebrate biomass.     

北方农牧过渡带农户农业生产系统模式的生态评价和改良研究

农牧过渡带 (或农牧交错带、半农半牧区 )是指我国传统种植业区和传统畜牧业区的镶嵌结合地带。近世纪以来 ,由于人口剧增 ,垦草种粮面积不断扩大 ,滥垦、过牧、滥樵 ,使草地植被大面积消失 ,沙漠化和荒漠化日趋严重。据报道 ,目前我国北方农牧过渡带荒漠化土地面积已达 1 6 7×10 5ｈａ ,占土地总面积的 5 2 73% ,年增长率约为1 39% [3] 。赤峰市是我国北方农牧过渡带较典型、分布面积较大的地区。该地区资源类型丰富 ,互补优势明显 ,特别是农牧结合的潜力巨大。但长期以来这里区域生态环境恶化加剧 ,导致严重的贫困化。解决这一问题的关…     

Defining types of running waters in Germany using benthic algae: A prerequisite for monitoring according to the Water Framework Directive

The Water Framework Directive of the European Union (EU-WFD) requires the definition of different types of running water which are of relevance when assessing their ecological status. In Germany, 25 close to natural, pristine sampling sites in the Central Highlands and the Central Plains were selected which were considered to represent best conditions available at present. The abundance of benthic algae other than diatoms or Charales was investigated. Sampling was repeated in two different seasons (summer and winter). In total, 107 taxa from 12 classes could be found, of which 70 taxa from eight classes were used for statistical analysis. Multivariate statistical analysis showed that the distribution of the algae was influenced mainly by the acid capacity and hardness of water. Based on the species composition and the abundances of the species, three groups of sampling sites could be distinguished leading to the definition of three types of running water: a. siliceous sites in the Central Highlands, b. organic sites (influenced by peat) in the Central Plains, c. calcareous sites in the Central Highlands and the Central Plains. These types show a specific species composition under reference conditions and differ significantly in terms of species richness and diversity. The results presented here are fundamental for the development of a routine for monitoring the ecological status according to EU-WFD.     

Distribution,Sources Identification,and Ecological Risk of PAHs and PCBs in Coastal Surface Sediments from the Northern Persian Gulf

Hormozgan Province plays a vital role in fishery, petroleum, and industrial activities in southern Iran. However, no comprehensive studies on organic pollution have been performed. PCBs and PAHs were analyzed in surface sediments from areas receiving industrial (nine sites), river (one site), and urban (two sites) effluents. The sediment samples were collected in March and September 2010 (in dry and wet seasons) at the highest tidal time. The overall pollution level of PCBs ranged from 2.5 ± 0.8 to 462.0 ± 206.7 ng/g dry weight. CB153 congener dominated in most of the sediment samples. Congener profiles of PCBs showed close similarity with formulations of commercial products such as Aroclor 1260 and 1254 g. A wide range of 55.3 to 1231.6 ng/g dry weight was detected for ∑PAHs. Results of PCA and PCA-MLR tests confirmed both petrogenic and pyrogenic origins for PAH pollution. The higher means of ∑PAHs and ∑PCBs in industrial and urban wastewaters were found near the shore, evidencing the role of these wastewaters in the PAH and PCB contamination in Hormozgan sediment. The concentrations of PAHs and PCBs in detected hotspots exceed the U.S. NOAA sediment quality guidelines.     

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea,China

Distribution and magnitude of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the southern Bohai Sea, China, were investigated. Sediments from the estuarine and coastal areas of the Jie and Xiaoqing Rivers contained highest concentrations of arsenic, cadmium, copper, mercury, and zinc. Mean concentrations of Cu, Zn, Cr, Pb, and Cd were higher than background concentrations determined for the areas. The magnitude of both enrichment factors (EF) and geoaccumulation indices (I_geo) suggested that pollution with As and metals was occurring along estuarine and coastal areas of the southern Bohai Sea. Risk analysis also suggested that concentrations of As and metals were sufficiently elevated as to cause adverse biological effects in the study area. According to the ecological risk index (RI) values, the upstream of the Jie River has a very high ecological risk for the waterbody. The data provided in this study are considered crucial for controlling and remediation of As and metals’ pollution of the southern Bohai Sea.     

Ecological speciation in an island snail: evidence for the parallel evolution of a novel ecotype and maintenance by ecologically dependent postzygotic isolation

Speciation is the process by which reproductive isolation evolves between populations. Two general models of speciation have been proposed: ecological speciation, where reproductive barriers evolve due to ecologically based divergent selection, and mutation‐order speciation, where populations fix different mutations as they adapt to similar selection pressures. I evaluate these alternative models and determine the progress of speciation in a diverse group of land snails, genus Rhagada, inhabiting Rosemary Island. A recently derived keeled‐flat morphotype occupies two isolated rocky hills, while globose‐shelled snails inhabit the surrounding plains. The study of one hill reveals that they are separated by a narrow hybrid zone. As predicted by ecological speciation theory, there are local and landscape level associations between shell shape and habitat, and the morphological transition coincides with a narrow ecotone between the two distinct environments. Microsatellite DNA revealed a cline of hybrid index scores much wider than the morphological cline, further supporting the ecological maintenance of the morphotypes. The hybrid zone does not run through an area of low population density, as is expected for mutation‐order hybrid zones, and there is a unimodal distribution of phenotypes at the centre, suggesting that there is little or no prezygotic isolation. Instead, these data suggest that the ecotypes are maintained by ecologically dependent postzygotic isolation (i.e. ecological selection against hybrids). Mitochondrial and Microsatellite DNA indicate that the keeled‐flat form evolved recently, and without major historical disruptions to gene flow. The data also suggest that the two keeled‐flat populations, inhabiting similar rocky hills, have evolved in parallel. These snails provide a complex example of ecological speciation in its early stages.