Influence of streambed sediment clogging on microbial processes in the hyporheic zone

1. The hyporheic zone plays a key role in hydrological exchange and biogeochemical processes in streambed sediments. The clogging of sediments caused by the deposition of particles in the bed of streams and rivers can decrease sediment permeability and hence greatly affect hyporheic microbial processes. 2. The main objective of this study was to determine the influence of sediment clogging on hyporheic microbial processes in three French rivers (the Usses, Drôme and Isère). In each river, microbial abundance and activity were studied at three depths (10, 30 and 50 cm) in the sediment at one unclogged (high porosity) and one clogged site (low porosity). 3. The results showed that the sediment clogging had inconsistent effects on microbial processes in the three rivers. Increases (Usses) or decreases (Drôme and Isère) in both aerobic and anaerobic processes were detected at the clogged sites compared to unclogged sites. These results suggest that microbial changes because of the sediment clogging are mainly mediated by the residence time of water within the hyporheic sediments. 4. A single model predicting the effect of clogging on hyporheic microbial processes cannot be applied generally to all rivers because the degree of clogging creates heterogeneous effects on flow rates between surface and interstitial waters. As a consequence, the influence of heterogeneous clogging on surface water–hyporheic exchanges needs to be evaluated by water tracing and hydraulic modelling to determine the links between microbial processes and hydraulic heterogeneity induced by clogging in hyporheic sediments.     

The rates of sediment-water exchange of oxygen and sediment bioturbation in Lough Neagh,Northern Ireland

Oxygen is transported 30 mm into the sediment at an 8 m depth site in eutrophic Lough Neagh by the irrigational activities of the benthic fauna. Faunal activity also mixes the upper 20 mm of sediment. Sediment oxygen uptake rate, redox potential-depth profile and the chlorophylla concentration were measured in the upper sediment layers from February to November 1979. Chlorophylla input to the sediment, following the Spring phytoplankton maximum, remained in the 0–1 cm sediment layer but did cause the redox potential profile to change from one with potentials around 400 mV in the upper 50 mm to one with a strong gradient over the 0–30 mm region. The start of benthic faunal activity in May caused the chlorophylla to be mixed into the 1–2 cm layer and also caused oxygen to be transported into the sediment at a rate sufficient to change the redox potential back to its initial state. The biodiffusion coefficient for solids in the upper 20 mm was estimated to be 6 × 10⁻⁸ cm² s⁻¹. Oxygen transport in the pore, waters of the upper sediment layers was considered to be best described as advection, caused by the irrigational activities of the benthic fauna.     

The clogging of coarse gravel river beds by fine sediment

Laboratory investigations were carried out to examine the clogging process in coarse gravel river beds. Field samples taken from the Langeten river in Switzerland show that the intruded fine particles of the flow are deposited in the top layer of the river bed. For lower discharges the decrease of the hydraulic conductivity depends mainly on the dimensionless shear stress of the flow, the concentration of the suspended load, the hydraulic gradient between river and groundwater and the grain-size distribution of the river bed. However, when the armour layer breaks up during high discharges and the whole river bed is mobilized, the deposited fines are flushed downstream and a new layer with an initial maximum hydraulic conductivity is formed. The relationship between the dimensionless shear stress and the hydraulics conductivity is discussed. Changes in the nature of the catchment area or in the river itself which can accelerate the clogging process in the affected river are also discussed.     

水丝蚓对太湖沉积物有机磷组成及垂向分布的影响

以太湖常见底栖动物——水丝蚓为研究对象,借助室内流动培养装置和31P核磁共振技术(phosphorus-31 nuclearmagnetic resonance spectroscopy)(31P-NMR),研究生物扰动对太湖沉积物有机磷组成及垂向分布的影响。结果表明:短时间内水丝蚓扰动对沉积物有机磷化合物种类组成影响并不显著,但会引起上层沉积物中稳定性较差的有机磷化合物磷脂和DNA含量出现显著降低,同时沉积物中总磷和有机磷的垂向分布亦发生明显改变。此外,水丝蚓扰动下沉积物含水率、孔隙率和碱性磷酸酶活性显著增加,使活性较高的有机磷化合物分解加速,最终导致表层沉积物中的磷脂与DNA含量降低。     

生物扰动对沉积物中污染物环境行为的影响研究进展

生物扰动由于显著改变沉积物结构和性质,进而影响沉积物中污染物的环境行为。综述生物扰动对沉积物中氮、磷、重金属和疏水性有机污染物环境行为的影响。生物扰动促进这些污染物从沉积物向水体释放。生物扰动还对不同的污染物产生其它不同的影响。对于氮,生物扰动还影响其硝化与反硝化作用;对于磷,生物扰动不仅改变其化学形态,还提高有机磷降解。对于重金属,生物扰动还能改变其在沉积物中的分布及化学形态。对于疏水性有机污染物,生物扰动主要增强生物富集和代谢,以及提高生物降解。     

Effect of bioturbation on denitrification in a marine sediment from the West Mediterranean littoral

Thein vitro effect ofNereis diversicolor on denitrification has been studied in PVC tubes filled with a coastal marine sediment defaunated by sieving. The first aim of the experiment was to determine the effect of sediment defaunation on denitrification (denitrifying population and Denitrifying Enzyme Assays). Sieving induced a loss of 70% of the initial DEA. The number of denitrifying bacteria was 10 times lower than inin situ sediment. In the top two centimetres, the DEA rose by 75% of its initial value, after 82 days. Polychaetes were only added after a return to near pre-disturbance levels to ensure that our data on the effects of their addition would not be disturbed by changes in the sediment. Introduction of Polychaetes increased the denitrifying population and DEA in the first layer (0–2 cm) of the sediment after 15 days. After 45 days, the surface of the polychaete burrows in sediment was 1.3 to 1.5 times higher than after 15 days, resulting in an increase in solute exchange between seawater and the top layer of sediment. An inhibitory effect of oxygen on denitrification was detected in the uppermost layer only.     

Environmental and temporal patterns in bioturbation in the Cambrian–Ordovician of Western Newfoundland

The early Paleozoic emergence of bioturbating (sediment-dwelling and -mixing) animals has long been assumed to have led to substantial changes in marine biogeochemistry, seafloor ecology, and the preservation potential of both sedimentary and fossil archives. However, the timing of the rise of bioturbation and environmental patterns in its expansion have long been subjects of debate—resolution of which has been hampered, in part, by a paucity of high-resolution bioturbation data or of systematic investigations of facies trends in lower Paleozoic bioturbation. To address these issues, we conducted an integrated sedimentological and ichnological characterization of the Cambrian–Ordovician Port au Port succession and Cow Head Group of western Newfoundland, encompassing over 350 meters of stratigraphy logged at the centimeter to decimeter scale. We find that, across a wide range of marine facies, bioturbation does not on average exceed moderate intensities—corroborating observations from other lower Paleozoic successions indicating that the early Paleozoic development of bioturbation was a protracted process. Moreover, bioturbation intensities in the Port au Port succession and Cow Head Group are commonly characterized by considerable variability at even fine scales of stratigraphic resolution and changes in bioturbation intensity correlate strongly with variability in sedimentary facies. We observe that facies recording nearshore depositional environments and carbonate-rich lithologies are each characterized by the highest intensities of both burrowing and sediment mixing. These data highlight the need for a high-resolution and facies-specific approach to reconstructing the evolutionary history of bioturbation and suggest that average levels of bioturbation, although relatively low throughout this interval, increased notably earlier in nearshore marine settings.     

植被格局对土壤入渗和水沙过程影响的模拟试验研究

合理的植被格局能够提高土壤入渗性能和抗冲性,有效阻蚀减沙,平衡土壤保持与土壤水分保蓄二者关系,进而促进生态环境的改善。基于径流小区人工模拟降雨,研究了多种植被格局生物量密度（0、50%、100%）和分布方式（坡上分布、坡下分布、均匀分布）的土壤入渗、产流、产沙特征以及土壤储水量变化。结果表明：使用Philip模型、Kostiakov模型、Horton模型模拟坡面入渗过程,Horton模型的拟合结果最优。不同植被格局产流率的变化趋势基本一致,大体可分为两个阶段：初期阶段迅速增长,中后期阶段增长变缓并逐渐趋于稳定状态。产沙率的变化趋势随植被格局的不同而略有差异。相较于产流过程,产沙过程变化剧烈、规律性差。总体而言,降低生物量密度能够增加降雨期间的径流量（从19.21 mm到25.44-38.09 mm再到51.79 mm）和侵蚀量（从118.97 g/m²到237.57-597.90 g/m²再到1400.29 g/m²）,土壤水分得到更好的保蓄。从植被分布方式的角度来看,均匀分布的植被格局有利于更好地控制土壤侵蚀和径流,却促进了土壤水分的消耗。坡下分布的植被格局,例如植被过滤带的形式,能够最好地同时控制水土流失和土壤耗水。权衡考虑水土流失防治与土壤水分消耗,建议采用适宜密度（本研究为110 g/m²）且集中分布在出口附近的植被格局。     

沉积物再悬浮对浮游藻类影响的模拟实验研究

作为浅水湖泊的重要特性之一,由风浪等动力作用引起的沉积物再悬浮对浮游藻类的初级生产力、群落结构具有重要意义。本研究通过生长季节(5-6月)在太湖梅梁湾湖岸的中宇宙模拟实验,比较在同样的外源负荷下浮游藻类对不同的沉积物再悬浮程度的影响特征,以及其主要的影响因子。实验在约250L的大桶中进行,通过位于沉积物-水界面的水泵的动力作用,模拟了三个不同程度沉积物再悬浮:无再悬浮即对照、弱悬浮和强悬浮程度。实验结果显示:(1)对照、弱悬浮和强悬浮之间悬浮物浓度呈显著性梯度变化,平均值分别为5、30、40 mg·L^-1,水下20cm光密度分别为表面光密度的80%、35%和25%。TN和TP在悬浮处理组显著高于对照组,但是弱悬浮和强悬浮之间差异不显著。生物可利用的各种溶解性营养盐形式对再悬浮的响应特征不明显。(2)浮游藻类生物量和群落结构对再悬浮的响应显著。对照组的Chla在整个实验阶段都很低,强悬浮组和弱悬浮组的平均Chla分别5倍和2倍于对照组。实验初始浮游藻类群落种类多样性低,优势种群主要为隐藻(隐藻属Cryptomonas spp.和蓝隐藻Chroomonas acuta)。再悬浮处理显著促进了隐藻的生长,但弱悬浮和强悬浮之间差异不显著。对照组优势种群演替为微小型种类蓝隐藻和绿藻门的纤维藻属(Ankistrodesmus sp.)。(3)以相对丰度为统计数据,浮游动物群落结构对再悬浮的响应显著,弱悬浮和强悬浮之间差异不显著。对照组的枝角类大型种类溞属(Daphnia spp.)丰度显著高于再悬浮处理组,枝角类小型种类象鼻溞属(Bosmina spp.)和网纹溞属(Ceriodaphnia spp.)、轮虫丰度则呈相反趋势。可见,再悬浮促进了沉积物营养盐的释放和水下光照的衰减,还影响了浮游动物的群落结构,使其向摄食藻类能力较差的种类演替,从而在上行(bottom-up)和下行(top-down)两个方面影响了浮游藻类的现存量和群落结构。     

Development of a biotic index using stream macroinvertebrates to assess stress from deposited fine sediment

相似文献   

From Demographic Strategies to Mathematical Models: Trends in Population Dynamics Studies of Aquatic Oligochaeta

The existence of a negative relationship between fine sediment infiltration during the incubation period and salmonid embryo survival has often been discussed in the literature. However, few studies have specifically addressed this relationship in the field. We conducted a field experiment to examine the relationship between survival of Atlantic salmon (Salmo salar) embryos contained in incubation baskets and the patterns of fine sediment infiltration into the baskets during the incubation period. The results indicate that survival to pre-eyed (STPE), eyed (STE) and hatched (STH) stages of development were all negatively correlated with the percentage of fine sediment entering the baskets. STPE and STE were most strongly affected by silts and clays (<0.063 mm) although this size class represented only a small fraction of the grain size distribution inside the incubation baskets (0.03–0.41%). STH was most strongly correlated with the infiltration of medium sand (0.25–0.50 mm) material. On average, 66% of the implanted embryos survived to the pre-eyed stage of development compared to 63% for the eyed and 48% for the hatched stages of development.     

Biological guidelines for freshwater sediment based on BEnthic Assessment of SedimenT (the BEAST) using a multivariate approach for predicting biological state

Abstract This paper describes the first results for an alternative approach to the development of sediment quality criteria in the nearshore areas of the Laurentian Great Lakes. The approach is derived from methods developed in the United Kingdom for establishing predictive relationships between macroinvertebrate fauna and the physico-chemistry of riverine environments. The technique involves a multivariate statistical approach using (i) data on the structure of benthic invertebrate communities, (ii) functional responses (survival, growth and reproduction) in four sediment toxicity tests (bioassays) with benthic invertebrates; and (iii) selected environmental variables at 96 reference (‘clean’) sites in the nearshore areas of all five Great Lakes (Lakes Superior, Huron, Erie, Ontario and Michigan). Two pattern recognition techniques (using the computer software package PATN) are employed in the analysis: cluster analysis and ordination. The ordination vector scores from the original axes of the pattern analysis are correlated (using CORR in SAS) with environmental variables which are anticipated to be least affected by anthropogenic activities (e. g. alkalinity, depth, silt, sodium etc.). Multiple discriminant analysis (MDA) is used to relate the site groupings from the pattern analysis to the environmental variables and to generate a model that can be used to predict community assemblages and functional responses at new sites with unknown but potential contamination. The predicted community assemblages and functional responses are then compared with the actual benthic communities and responses at a site, and the need for remedial action is determined. The predictive capability of the discriminant model was confirmed by performing several validation runs on subsets of the data. An example of the use of the model for sediment in Collingwood Bay (an area of concern designated by the IJC in Georgian Bay, Lake Huron) is presented and the technique is shown to be more precise in determining the need for remediation than the currently used provincial sediment quality criteria based on Screening Level Concentration (SLC) and laboratory toxicity tests. The ultimate goal of the study is the development of a method to determine the need for, and the success of, remedial action and to predict what benthic communities should look like at a site if it were clean and what responses of organisms in sediment toxicity tests constitute an acceptable end-point.     

Modelling the influence of bioturbation on the vertical distribution of sedimentary phosphorus in L. Esrom

A multilayer sediment-water exchange model was used to evaluate the importance of bioturbation in the profundal sediments of L. Esrom. The temporal variation of the vertical distribution of sedimentary phosphorus fractions was modelled with an objective function of 1.50. Deviations between measured and simulated values occurred in the spring, where the measured pool of sedimentary phosphorus sharply declined in the surface sediments. The application of a model for the activity ofChironomus anthracinus based on biomass, oxygen consumption and temperature improved the model in the spring period. The downwards transport of easy-degradable surface sediments reduced the average release of sedimentary phosphorus from 12 mg P · m⁻² · day⁻¹ to 11 mg P · M⁻² · day⁻¹. The introduction of a similar model for the other important burrowing species in L. Esrom,Potamothrix hammoniensis, lowered the objective function to 1.37 and increased the average release to 12.5 mg P · m⁻² · day⁻¹. The minor role of bioturbation in sediment processes is discussed.     

Effects of the burrowing mayfly,Hexagenia, on nitrogen and sulfur fractions in lake sediment microcosms

Effects of the burrowing mayfly, Hexagenia, on nitrogen and sulfur fractions of sediment, and overlying water were determined. Laboratory microcosms were used to reproduce the benthic environment. The activities of Hexagenia increased sediment Eh (1.98 ± 0.486 (22) mV · day ⁻¹), and decreased pH in sediment (−0.007 ± 0.001 (22) day ⁻¹) and overlying water(-0.024 ± 0.004 (10) day⁻¹). In the control, Eh decreased and pH did not change. The presence of Hexagenia also markedly increased ammonia in sediment (5.46 ± 0.14 (22) ppm N · day⁻¹) and overlying water (0.792 ± 0.154 (10) ppm N · day⁻¹), while the control did not change. In addition, the sulfate fraction of sediment (0.177 ± 0.006 (17)% dry mass) and water (50.0 ± 4.9 (5) mg · I⁻¹) in microcosms with Hexagenia was greater than that of the control (0.151 ± 0.005 (16)% dry mass; 14.7 ± 1.71 (3) mg · 1⁻¹) at the termination of the experiment. Hexagenia may also stimulate the mineralization of carbon-bonded sulfur. The general role of Hexagenia in altering sediment chemistry is discussed.     

Restoration of an Ecosystem Function to Revegetation Communities: The Role of Invertebrate Macropores in Enhancing Soil Water Infiltration

Guidelines for revegetation in agricultural landscapes may not address restoration of ecosystem functions because management is focused on the replanting stage, although certain functions are delivered by organisms that colonize revegetation months or years later. We investigated the ecosystem function of water infiltration to tree root zones and channels, delivered by invertebrates that form soil macropores. We measured macropore density and infiltration rates at revegetation sites established on retired grazing land, in relation to site age, tree species composition, and geographical location, compared with adjacent matched pastures. Revegetated sites had significantly more macropores than pastures, and revegetation sites aged 11–20 years had more macropores than sites aged 3–5 and 6–10 years. Tree species had a marginal effect, with more macropores in sites with Acacia spp. and Eucalyptus spp. than those with Eucalyptus spp. only. Besides ants, the main groups of soil burrowers were mygalomorph and lycosid spiders and also ground‐nesting native bees. Infiltration rates in revegetation sites aged 11–20 years were double those of pastures and of 3–5 and 6–10 year sites. This is the first study to quantify the rate of recovery of an invertebrate‐driven soil hydrological ecosystem function following revegetation.     

Silica and diatom growth in Lough Neagh: the importance of internal recycling

1. Lough Neagh is a large eutrophic lake with a high dissolved silica (SiO2) concentration arising from the basaltic rock in parts of the catchment and the normal winter maximum concentration is over 8 mg L−1. Based on frequent observations between 1974 and 1997, the annual cycles of SiO2 input, uptake and release are explored.
2. Large spring blooms of the planktonic diatoms Aulacoseira subarctica Haworth and Stephanodiscus astraea occur every year and are terminated by SiO2 depletion. Although there are periods when one diatom species has dominated the other, over the period as a whole, the two diatoms appear to be in a stable coexistence.
3. A model of the effect of river inputs on lake concentration shows that without SiO2 release from the sediment, the maximum spring dissolved SiO2 concentration (and hence diatom crop) would be only about one-third of that actually observed.
4. It is concluded that within-lake processes play a large role and are potentially more variable than catchment processes in determining the available SiO2 in Lough Neagh.
5. The role of benthic animals, especially Chironomus anthracinus, in the sediment SiO2 release process is discussed. Field data suggest the SiO2 release rate is highly sensitive to temperature, but this could be partly caused by an interaction between temperature and animal activity.     

Heavy metals (Cu,Zn, Pb,Cd) in sediment,zooplankton and epibenthic invertebrates from the area of the continental slope of the Banc d'Arguin (Mauritania)

The concentrations of copper, zinc, lead and cadmium in the surface sediment (upper 5 mm) were generally higher in the silt fraction than in the bulk sediment. No significant geographical trend in the metal concentrations of the surface sediments was found, nor a correlation between concentrations in bulk sediment as well as in the silt fraction and the % silt could be established. In general, the metal concentrations in both bulk sediment and silt are lower, when compared to marine environments in other climatological regions.In zooplankton, the metal concentrations were relatively high: expressed in µg g^–1 on a dry weight (D.W.) basis, they ranged from 15–90 for copper, 70–580 for zinc, 12–55 for lead and 4–10 for cadmium.In epibenthic invertebrate species, both in crustaceans and bivalve molluscs, the concentrations of copper, zinc, and lead were in the same order of magnitude as compared to corresponding species from other geographical latitudes. Cadmium concentrations were relatively low, ranging from 0.13–0.42 µg g^–1 D.W. in the bivalve molluscs Pitaria tumens and from 0.04–0.27 µg g^–1 D.W. in the shrimp Processa elegantula. Also in the crab species Ilia spinosa, Inachus sp. and Pagurus sp., the cadmium concentrations were low, varying between 0.1 and 0.2 µg g^–1 D.W.No significant relation between the metal concentration in whole-body samples and sediment (either bulk or silt) was present. Also no gradient was apparent in concentrations in organisms sampled at different depths (5 to 200 m) along two off-shore transects perpendicular to the Banc d'Arguin. Data indicated lower metal concentration in epibenthic organisms from sampling stations along a northern transect (southwest of Cap Blanc) than in organisms from the southern transect, off Cap Timiris.Evidence was obtained for a considerable atmospheric input of heavy metals, in particular zinc and lead, in a certain area along the continental slope of the Banc d'Arguin.     

Application of arsenic field test kit to stream sediment: effect of fine particles and chemical extraction

Abstract

The field test kit for the on-site analysis of arsenic has been previously evaluated for aqueous solutions such as surface water and groundwater. In this study, the field test kit was optimized for arsenic determination in a sandy sediment The field test kit was found to be applicable to on site screening of arsenic contamination at levels around 6 mgkg^?1, the soil regulatory standard for arsenic concentration in Korean soils. However, the method requires a simple chemical pre-extraction. This arsenic extraction has been optimized and the effects of soil–solution ratio, extraction time and fine particles are discussed in detail. The fine particles in the sediment sample strongly bind to arsenic resulting in variability of its extraction, both in extractability and extraction time. Under the optimized conditions, the arsenic content using the field test kit had a high regression coefficient with respect to that found by chemical analysis of the sediment sample.     

Influence of Chironomus plumosus larvae on ammonium flux and denitrification (measured by the acetylene blockage- and the isotope pairing-technique) in eutrophic lake sediment

Bythotrephes invaded Harp Lake, Ontario, Canada, in the early 1990s. Here we describe seasonal changes in the size, abundance and life history of the invader. The weight of Bythotrephes could be accurately estimated (r² =0.90) from the length of its body and the state of development of its brood, but substantial (22%) corrections for shrinkage in sugarformalin were required. The seasonality of the size and abundance of Bythotrephes was apparently regulated by the interaction of fish predation, temperature-mediated growth, the availability of the invader's prey, and switches in its reproductive biology. The vernal increase in the growth of the Bythotrephes population lagged behind increases in water temperature and abundances of preferred prey, most probably because of predation by lake herring (Coregonus artedi). Bythotrephes abundance increased rapidly in early July; however, the population maximum was brief. After the abundance of their preferred prey crashed in mid-July, Bythotrephes body size declined, and adult females switched from parthenogenic to resting egg production. Population size declined in consequence. In the summer, female Bythotrephes committed most of their energy to growth between instar I and II, but to egg production for instars II and III. The biology of the Harp Lake population differed from that observed in other recently invaded lakes in several ways – the lag in population growth in the spring, the small change in body size between instars II and III, the decline in body size in August, and the co-incident switch by mature females to resting egg production. These inter-lake differences in biology indicate we have more to learn about Bythotrephes before we can predict its influence on the inland lakes of North America.     

Feeding and bioturbation effects of the sand dollar Peronella lesueuri (L. Agassiz, 1841) (Echinodermata) on microphytobenthos and sediment fluxes

Respiration and excretion rates of a key bioturbating species, the sand dollar Peronella lesueuri, were measured in mesocosms at three different temperatures. Benthic oxygen and nutrient fluxes were additionally measured at winter and summer temperatures to assess the impact of P. lesueuri on ecosystem processes. Oxygen consumption by sand dollars increased significantly with wet weight at all three temperatures 16, 19, and 23 °C. Ammonia release also increased with body weight. The weight vs. oxygen uptake relationship was similar at 19 and 23 °C but oxygen uptake was significantly reduced at the lower exposure temperature. The bioturbation caused by sand dollar P. lesueuri reduced the photosynthetic rate of the microphytobenthos (MPBs) but had a much smaller and less obvious effect on nutrient fluxes across the sediment–water interface.