Wave-induced sediment resuspension in the Öre estuary,northern Sweden

Material transported by the Öre River in northern Sweden is all deposited within the estuary which means that resuspension is necessary for the transport of particles out of the estuary. Wave-induced sediment resuspension in the estuary was studied by monitoring the distribution of suspended particles during a resuspension-redeposition cycle. The particle concentration in the water mass was measured with a light scattering probe, calibrated by comparison with the amount of particles collected on a filter.After a long period with calm weather and a low river input less than 100 tonne of suspended particulate matter was present in the estuary. However, during a period with stormy conditions significant resuspension of sediment particles occurred within the estuary. Two days after the storm approximately 1125 tonne of suspended particulate matter was found in the estuary. Most (61%) of the suspended matter was found in the deepest third of the water column, although up to 17% was present in the top third of the water column. The total load of particulate matter in the water column remained constant until day four after the storm, but a significant redistribution of the particulate matter occurred both in the vertical and horizontal directions. Nine days after the storm, a significant amount of particles (c. 350 tonnes) was still in suspension.     

Sedimentation of river-transported particles in the Öre estuary,northern Sweden

Sedimentation of river transported particles in the Öre Estuary was studied during spring flow (April–May, 1989). River input was calculated as the product of discharge and particle concentration in the river water. The concentration of suspended matter in the estuary water was determined with a light-scattering probe at 25 depth profiles throughout the estuary. The sedimentation was measured using sediment traps on 5 stations along a line from the river mouth to the mouth of the estuary. Sampling was carried out on four dates with different water discharge.The extension of the particle plume varied during the observation period mainly due to variation in river discharge. The maximum extension of the river plume occurred during the peak of the spring flow and covered approximately 70% of the estuary area. The sedimentation rates were generally high and the average retention time for a particle in the water column was less than 1 day which verifies that the river transported fine-grained particles are primary deposited within the estuary. The major part of the river input of suspended matter was deposited near the river mouth. There was a surplus of the total sedimentation compared to the river input which was due to wave-induced resuspension, especially in the eastern part of the estuary.     

东辽河流域河湖光学吸收特性的季节变化

吸收特性是水体重要的光学特性,也是建立水色反演分析模型的基本参数.本文利用2011年6、9、10月在二龙湖和2012年10月在东辽河的实测数据,通过测定水体营养水平和颗粒物、有色可溶性有机物(CDOM)等光学活性物质的吸收系数,分析了东辽河河湖的光学物质吸收特性和季节变化.结果表明: 二龙湖水体9月处于富营养状态,6月营养水平较低,10月则处于中营养水平;东辽河随采样点位置的差异呈现不同程度的富营养化.水体各组分的吸收系数均随营养水平的增加而逐渐增大.6、10月二龙湖水体总悬浮颗粒物吸收光谱与非色素颗粒物吸收光谱相似,在总吸收中占主导作用的是CDOM;9月总悬浮颗粒物吸收光谱则与浮游植物吸收光谱类似,浮游植物的吸收对总吸收的贡献率最大.6、9月二龙湖浮游植物吸收系数[a_ph(440)]与总磷(TP)呈正相关,6月二龙湖a_ph(440)与溶解有机碳(DOC)呈正相关,非藻类颗粒物吸收系数[a_d(440)]仅与叶绿素a浓度(Chl a)具有相关性.二龙湖(9月)与东辽河a_ph(675)均与Chl a、卡尔森指数(TLI)相关性较好.东辽河流域的河湖水体光学特性存在比较明显的差异:东辽河水体的浮游植物吸收光谱曲线展现出了两种不同类型,浮游植物、非藻类颗粒物、CDOM的贡献率随采样点的不同而相差较大;营养水平较高的9月二龙湖与东辽河水体浮游植物主导了水体光谱吸收,而在二龙湖营养水平较低的月份中(6、10月),颗粒物与CDOM共同主导水体光谱吸收;6月二龙湖与10月东辽河水体CDOM的组成为大分子颗粒物,而9与10月其组成更趋向于小分子颗粒物.     

Environmental chemistry of rivers and lakes, Part VII. Fractionation by calculation of suspended particulate matter in Lake Biwa into three types of particles of different origins

During the period from July 1992 to March 1995, suspended particulate matter in Lake Biwa was collected at 1-month intervals, and the contents of Al, Si, and P were determined. Based on the analytical data, the particulate matter was fractionated by calculation into three types of particles of different origins: particles of terrigenous origin, particles of diatom origin, and particles due to microorganisms except for diatoms. The relative abundance of the respective particles was featured in water depth-time (month) diagrams, with contours in terms of weight per liter of lake water. As a result, the characteristic distributions of the particles were revealed, and their inherent roles in natural purification were distinguished from each other. Of the three types of particles, the particles of diatom origin were anticipated to be the principal scavengers not only of nutritious elements of silicon and phosphorus, but also of various metal ions dissolved in the lake. Received: October 5, 2000 / Accepted: June 6, 2001     

Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River

Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside.     

The Influence of Bauxite Tailings on the Cladoceran Populations of Lake Batata,Amazonia, Brazil

Lake Batata receive tailings from bauxite mining for ten years (1979-1989). This material, with 7-9% of solid particles, changed some ecological conditions of part of the lake. In order to study the influence of this material on the cladoceran populations, seasonal and intensive studies were made of abundance and brood size of the animals and of some environmental parameters such as transparency, suspended material, POC (<30pm), total bacteria and chlorophyll a. Reduced transparency and high suspended matter attested to the greater quantity of tailings in the water column, in the area impacted by tailings. Greater oscillations of density and brood size at stations in the impacted area appear to indicate less stable conditions in this part of the lake.     

Impact of hydrology on free-living and particle-associated microorganisms in a river floodplain system (Danube, Austria)

1. A floodplain segment of the Danube River downstream of Vienna was studied during the hydrologically most dynamic phase (spring–summer) to evaluate the significance of connection between the main channel and the floodplain segment for particle abundance and quality as well as for bacterial and viral parameters, both free‐living and attached to particles. 2. Hydrological connectivity between the main channel and its floodplain segment (expressed as water age) influenced particle abundance and quality. Polysaccharide‐containing particles [Alcian positive‐stained particles (ASP)] and protein‐containing particles [Coomassie positive‐stained particles (CSP)] each contributed a substantial fraction to total suspended solids and were both positively related to water age. ASP were about twice as abundant as CSP. 3. Water age influenced bacterial and viral abundance and the bacterioplankton productivity in the surrounding water. Free‐living bacterial abundance and their bacterial secondary production (BSP) increased continuously with water age, best described by a linear regression. Water age also significantly impacted BSP and per cell BSP of bacteria attached to particles. The abundance of attached bacteria and viruses was not influenced by water age. 4. Bacteria and viruses on particles were influenced by particle quality. Their abundance on particles was closely related to particle size. Particle‐attached bacteria accounted on average for 30.34% (± 3.09) of the total bacterial abundance. A variable and occasionally significant proportion of viruses, between 0.43% and 35.06%, were associated with particulate material. 5. Bacteria attached to particles were significantly more productive than their free‐living counterparts. Their per‐cell activity was on average 8.6 times higher than that of the free‐living fraction. 6. Hydrological connectivity between the Danube River and its floodplain is crucial not only for the exchange of water, sediment and nutrients, but also for microbiota, thus influencing microbial life, distribution and activity.     

Aggression Level in Different Water Velocities Depends on Population Origin in Grayling, Thymallus thymallus

Phenotypic plasticity is recognized as an important mechanism of adaptation. However, because of its potential costs and limits, it has been hypothesized to be reduced and ultimately become lost when there is no selection for its maintenance. Heterogeneous environments in particular are expected to favour and thus maintain plastic phenotypes. Lakes and rivers differ in their flow regimes. In addition to higher average water velocity, rivers are characterized by distinct spatial and temporal variation in water flow, whereas lakes can be regarded as quite uniform in this respect. We studied whether behaviour, which is generally considered to be highly plastic, shows differences in the degree of plasticity between lake and river populations of the European grayling, Thymallus thymallus, fry in response to different water velocities. Given that aggressive behaviour in fish has been shown to relate to ambient flow regime, we compared aggressiveness of hatchery‐reared grayling originating from hatchery stocks of two lake and two river populations in still and flowing water. River fish showed higher aggressiveness in flowing water compared with still water, whereas aggressiveness of lake fish did not appear to vary according to water velocity. The higher plasticity of aggressiveness evoked in river fish by different water velocities may thus represent an adaptation to more variable flow and presumably related feeding conditions in their natural environment.     

Comparison of bacterial production in sediments, epiphyton and the pelagic zone of a lowland river

1. The microbial metabolism of organic matter in rivers has received little study compared with that of small streams. Therefore, we investigated the rate and location of bacterial production in a sixth‐order lowland river (Spree, Germany). To estimate the contribution of various habitats (sediments, epiphyton, and the pelagic zone) to total bacterial production, we quantified the contribution of these habitats to areal production by bacteria. 2. Large areas of the river bottom were characterized by loose and shifting sands of relatively homogenous particle size distribution. Aquatic macrophytes grew on 40% of the river bottom. Leaf areas of 2.8 m² m^?2 river bottom were found in a 6.6 km river stretch. 3. The epiphyton supported a bacterial production of 5–58 ng C cm^?2 h^?1. Bacterial production in the pelagic zone was 0.9–3.9 μg C L^?1 h^?1, and abundance was 4.0–7.8 × 10⁹ cells L^?1. Bacterial production in the uppermost 2 cm of sediments ranged from 1 to 8 μg C cm^?3 h^?1, and abundance from 0.84 to 6.7 × 10⁹ cells cm^?3. Bacteria were larger and more active in sediments than in the pelagic zone. 4. In spite of relatively low macrophyte abundance, areal production by bacteria in the pelagic zone was only slightly higher than in the epiphyton. Bacterial biomass in the uppermost 2 cm of sediments exceeded pelagic biomass by factors of 6–22, and sedimentary bacterial production was 17–35 times higher than in the overlying water column. 5. On a square meter basis, total bacterial production in the Spree was clearly higher than primary productivity. Thus, the lowland river Spree is a heterotrophic system with benthic processes dominating. Therefore, sedimentary and epiphytic bacterial productivity form important components of ecosystem carbon metabolism in rivers and shallow lakes. 6. The sediments are focal sites of microbial degradation of organic carbon in a sand‐bottomed lowland river. The presence of a lowland river section within a river continuum probably greatly changes the geochemical fluxes within the river network. This implies that current concepts of longitudinal biogeochemical relationships within river systems have to be revised.     

Electron-opaque microscopic fibrils in lakes: Their demonstration,their biological derivation and their potential significance in the redistribution of cations

Summary In lakes, the non-living particulate and the colloidal organic component are usually much greater in mass than the living component. Electron microscopy reveals that electron-opaque, non-rigid fibrils of approximately 3 to 10 nm diameter are found abundantly on the surfaces of common lake algae and microbes, free in the water column and free on the surface of the lake bottom. Filtration experiments and some microscopical evidence indicate that these fibrils are readily lost by cells without concomitant cell damage. Individual fibrils may form complex meshlike aggregates which can break apart and reassociate. Meshlike aggregates also appear to adhere to cells and large suspended particles. The behaviour and contact relations of the fibrils and their aggregates suggest a role in contact cation exchange. This suggested role is bolstered by a composition of 20 to 30 percent uronic acid residues for washed samples from lake water. Water from axenic algal cultures and from lakes can be processed by a combination of filtration and centrifugation techniques to yield quantities of purified fibril preparations permitting chemical analyses. Initial analyses show some of their physical characteristics to be appropriate to the principal component of an hypothetical, organic, carrier system for the redistribution of bound but biologically available cations in lakes.     

Juvenile lake sturgeon monitoring and determinants of year‐class strength in the Rupert River,mid‐northern Québec,Canada

In 2007, Hydro‐Québec began the construction of the Rupert Diversion in conjunction with the Eastmain‐1A and Sarcelle powerhouses. The partial diversion of the Rupert River became operational in 2009. Mitigation measures to preserve lake sturgeon (Acipenser fulvescens) habitat downstream of the diversion include an instream flow, weir and spurs to maintain water levels, and fish passage channels and spawning grounds. An environmental follow‐up was done in the reduced‐flow section of the Rupert. The baseline status was established from 2007 to 2009 and follow‐up studies were conducted from 2010 through 2012, and in 2014 and 2016. Besides presenting results from Hydro‐Québec's environmental monitoring, analyses were performed to search for determinants of year‐class strength. The results of the lake sturgeon monitoring activities indicate that the abundance of juveniles ≤8‐year‐old in the reduced flow section of the river remained similar or increased. Although larval production increased in post diversion conditions, cohort strength tended to decrease as did juvenile growth. Year‐class strength was positively correlated with spring and summer flow. Also, a significant, strong negative correlation was found between estimated larval abundance and water temperature during larval drift.     

Sediment resuspension effects on alkaline phosphatase activity

Sediment cores, including the associated lake water, were collected from a shallow hypereutrophic lake located in central Florida. Alkaline phosphatase activity (APA) was measured as an indicator of potential organic P mineralization. In both the sediment and water columns, APA was mainly associated with particulate matter; < 10% of APA was within the soluble phase. This suggests that for enzymatic hydrolysis to occur the hydrolyzable organic compounds must be in close proximity to the particle-bound enzyme complex. Both total P (TP) and APA decreased with depth in the sediment, whereas soluble reactive P increased in the 20–40 cm fraction. Resuspension of surficial sediments resulted in an immediate increase in APA, total suspended solids, TP, total Kjeldahl N, and total organic C within the overlying water column. However, these concentrations decreased rapidly following cessation of turbulence and settling of the sediments, emphasizing the close association of these parameters with the sediment.     

Origin and succession of phytoplankton in a river-lake system (Spree,Germany)

The River Spree (Germany) flows through an impoundment and several shallow lakes in its middle and lower course. In this river-lake system, the seasonal and longitudinal dynamics of dominant phytoplankton populations were studied in relation to retention time of water, mixing conditions and nutrient supply from 1988–92. Some phytoplankton species populated the same river section for weeks or months each year at their season. Such stable populations have to origin from river zones functioning like mixed reactors. In the Spree system, centric diatoms originated from an impoundment and filamentous cyanobacteria from a flushed lake with longer retention time of water. Downstream, biomass and composition of phytoplankton altered nearly simultaneously along the system.The fate of planktonic organisms washed from mixed reactors into the flow depended on the conditions at the zones of origin. During spring, populations dominating phytoplankton communities of the well-mixed lakes grew further under river conditions. However the biomass of summer species, adapted to intermittent stratification, was halved along the river course. These seasonal differences were probably caused by lower maximum growth rates of summer species and enhanced losses (photorespiration, sedimentation or grazing of benthic filter feeders, but not of zooplankton) of algal populations under river conditions in summer.Phytoplankton assimilation, settlement of diatoms, or denitrification caused declining (probably growth limiting) concentrations of dissolved inorganic phosphorus (spring), silicon (early summer) or nitrogen (summer) along the river course, respectively. The minimum content of DRP was often followed by a clear-water phase. Reduced DSi supply selected against diatoms and additional DIN shortage favoured N₂-fixing cyanobacteria in the last lake of the system.R-strategists (sensu Reynolds) were selected in both the flushed, shallow lakes and the lowland river. In general, the biomass of cyanobacteria increased within the lakes and declined along the river course. Some diatom populations grew in the river, but were grazed or settled down in the lakes. Beside this general picture, different populations from the same phylogenetic group did not necessarily perform in similar ways.     

The use of invertebrate functional groups to characterize ecosystem attributes in selected streams and rivers in south Brazil

An analysis conducted at nine stream/river sites in the Atlantic Forest region in the State of Paraná, Brazil used macroinvertebrate functional feeding group (FFG) assessments to evaluate ecological condition of the sites. The FFG approach categorizes qualitative macroinvertebrate collections according to their morphological-behavioral adaptations for food acquisition (e.g. scrapers that harvest non-filamentous, attached algae from stable surfaces in flowing water). FFG ratios were employed as surrogates for stream/river ecosystem attributes: balance between autotrophy and heterotrophy; linkage between riparian inputs of coarse particulate organic matter and in-stream food webs; relative dominance of fine particulate organic matter in transport (suspended load) compared to that deposited in the sediments; and geomorphic stability of the channel. The analyses indicated that all nine sites were heterotrophic, six of the nine carried expected levels of suspended organic load and showed below expected linkage with riparian inputs, and in only two were stable substrates limiting. The implications of the findings and recommendations for further analysis and modifications of the protocol are discussed.     

Suspended matter in the Scheldt estuary

The Scheldt estuary is characterised by a specific energy pattern resulting from the interaction of wave energy, tidal energy and river energy. It divides the estuary into three parts and governs suspended matter transport and distribution pattern. Observation of suspended matter transport shows the existence of three estuarine turbidity maxima (ETM), a marine-dominated ETM in the lower estuary at the river mouth, a river-dominated ETM in the upper estuary with suspended matter concentration reaching up to 300 mg/l, and the most important tide-dominated ETM in the middle estuary with suspended matter concentrations from several hundred milligrams per litre up to a few grams per litre. Resuspension is the dominant phenomenon in this last ETM due to the tidal related bottom scour, which is initiated when a critical erosion velocity of 0.56 m/s is exceeded. An assessment of residual current along the axis of the estuary shows distinctive pattern between the surface water flow and the near bottom water flow. Also the local morphology of the river, natural or man-made, has a prominent effect on the orientation and strength of the residual currents flowing along either side of the river or river bend. Evaluation of suspended matter concentration in relation to the current flow shows no systematic correlation either because of phenomena as scour lag and settling lag mainly in the middle estuary, or because of the current independency character of uniform-suspension mainly in the upper and lower estuary. Quantification of suspended matter load exhibits a net downstream transport from the upper estuary, a near-equilibrium sustainable status in the middle estuary and a net upstream transport of suspended matter from the lower estuary. The characteristic of suspended matter is induced by and is a function of e.g. tidal phase, spring-neap tide, longitudinal and vertical distribution mechanisms, seasons, short and long terms of anthropogenic influence and/or estuarine maintenance. Suspended matter is dominated by complex and cohesive organo-mineral aggregates. It consists of a variable amount of an inorganic fraction (average of 89%) and an organic fraction and occurs largely as flocs, the size of which is remarkably larger in the upper estuary and smallest within the ETM in the middle estuary. Independent time series measurements (1990–2000) of suspended matter property show an increasing sand fraction, a decreasing organic matter content, a rise in ¹³C as well as a decrease in water transparency. These independent measurements exhibit coherent consequences of estuarine maintenance operations. Maintenance dredging of the shipping channel and harbours and dumping operation in the Scheldt strengthen marine influence further landward, resulting in a sustained tidal range increment and upstream flow and transport of suspended matter.     

梯级水电站开发对香溪河悬浮颗粒物粒径及浓度的影响

通过对香溪河悬浮颗粒物粒度及浓度的实验分析,研究梯级水电站开发对河流悬浮颗粒物的影响,结果表明:(1)香溪河干流悬浮颗粒物粒径由上游到中游逐渐减小,并且在无水电站干扰时颗粒物粒径减小幅度较大;(2)从进水口至出水口河段,水电站悬浮颗粒物粒径总体变化不显著;(3)水电站从进水口河段至出水口河段,总悬浮颗粒物浓度(CTPM)在某些位置有所增加,有机颗粒物浓度(CPOM)无明显变化.悬浮颗粒物粒度及浓度的变化与水流流速及流量有着相当大关系.     

Sedimentation of phosphorus in limnetic and estuarine environments in the River Öre system,northern Sweden

Sedimentation of phosphorus was studied during the spring flood in April and May 1991 in Lake Örträsket and the Öre Estuary, northern Sweden. Lake Örträsket has an area of 7.3 km² and a mean depth of 22 m and is located 100 km from the coast halfways along the course of the River Öre. The river ends in a semi-closed low salinity estuary with an area of ca. 50 km² and a mean depth of 16 m. Sedimentation of phosphorus, iron and organic carbon were measured with sediment traps in Lake Örträsket and in the Öre Estuary. Characterization of particulate phosphorus in river water, sediment trap material and sediments were performed by the sequential extraction procedure proposed by Hieltjes & Lijklema (1980). Apart from being an efficient trap for suspended particles including particulate phosphorus, Lake Örträsket was shown to serve as a source for particulate material during spring 1991. The Öre Estuary, on the other hand, constitutes an efficient trap for the total supply of river-borne phosphorus during the spring flood period. Phosphorus was shown to be closely related to iron in particulate material in both the lake and the estuary. Adsorption of phosphorus on settling inorganic particles seems to be an important process, which is particularly pronounced in the estuary.     

Meiobenthic response to river-borne benthic particulate matter – a microcosm experiment

1. Benthic communities inhabiting river–lake interfaces are confronted with temporal variation in the import of river‐borne material to the associated littoral zone. The primary objective of this study was to evaluate the exposure to river‐borne benthic particulate matter as a force shaping the meiofauna of the river–lake interface. 2. In a 2 × 2 factorial design, combinations of strongly and weakly river‐influenced communities (near or far from the river mouth) with and without river‐borne benthic particulate matter enrichment were studied in laboratory microcosms to assess the response of the heterotrophic meiobenthos to river‐borne matter. 3. Nematodes dominated both habitat types and were the only meiofaunal taxon that responded to the enrichment. 4. A strong interactive effect between experimental enrichment and location of site was observed. Whereas nematodes from the littoral habitat close to the river mouth responded to the enrichment only marginally, nematodes from the remote site were strongly affected in the presence of river‐borne particulate matter. 5. In the non‐enriched samples of the remote site, the number of nematodes increased greatly over time. Among nematode feeding types, deposit feeders dominated over chewers at the beginning of the experiment but both types were equally abundant at the end. In the presence of river‐borne matter the increase of chewers ceased and a shift in feeding type composition did not occur. 6. It was shown that for river–lake interface meiofaunal assemblages in relative proximity, the same taxon might respond differently if exposed to an external pressure, e.g. river‐borne components. These components may have a stronger influence on taxa with longer life cycles.     

Transport and distribution of trace elements and other selected inorganic constituents by suspended particulates in the Salton Sea Basin, California, 2001

In order to examine the transport of contaminants associated with river-derived suspended particles in the Salton Sea, California, large volume water samples were collected in transects established along the three major rivers emptying into the Salton Sea in fall 2001. Rivers in this area carry significant aqueous and particulate contaminant loads derived from irrigation water associated with the extensive agricultural activity, as well as wastewater from small and large municipalities. A variety of inorganic constituents, including trace metals, nutrients, and organic carbon were analyzed on suspended material isolated from water samples collected at upriver, near-shore, and off-shore sites established on the Alamo, New, and Whitewater rivers. Concentration patterns showed expected trends, with river-borne metals becoming diluted by organic-rich algal particles of lacustrine origin in off-shore stations. More soluble metals, such as cadmium, copper, and zinc showed a more even distribution between sites in the rivers and off-shore in the lake basin. General distributional trends of trace elements between particulate and aqueous forms were discerned by combining metal concentration data for particulates from this study with historical aqueous metals data. Highly insoluble trace metals, such as iron and aluminum, occurred almost entirely in the particulate phase, while major cations and approximately 95% of selenium were transported in the soluble phase. Evidence for greater reducing conditions in the New compared to the Alamo River was provided by the greater proportion of reduced (soluble) manganese in the New River. Evidence of bioconcentration of selenium and arsenic within the lake by algae was provided by calculating “enrichment” concentration ratios from metal concentrations on the algal-derived particulate samples and the off-shore sites. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005 Roy A. Schroeder—Retired.