The effect of medium on selected life-history traits in three clones of Lecane inermis (Rotifera) from activated sludge

We tested the effect of various culture media on life-history traits in three clones of the rotifer Lecane inermis, a potential bulking control agent. Four types of media were tested: a filtrate of activated sludge, mineral water, and each of these media enriched with molasses. The number of live and dead individuals and the number of amictic eggs were counted during the 14-day experiment, and the egg ratio (ER) and mortality rate were calculated. We found that the rotifers were well adapted to the changes in chemical composition of the medium and that the addition of molasses resulted in a significant increase in rotifer abundance. The highest ER was noted after two days, reaching a maximum of 4 eggs per female in treatments with filtrate and molasses-enriched filtrate. The life-history traits varied depending on the clone and the medium, but all of the clones were able to survive and proliferate, even after 14 days of starvation.     

Control of bulking in a full scale plant by addition of talc (PE 8418)

A very severe bulking problem (Type 021 N) in the water treatment plant of Bodegraven in The Netherlands was solved by the addition of a specially shaped talqueous powder, PE 8418. After addition of this mineral product, the SVI dropped almost instantaneously from 850 ml/g to 250 ml/g and over the next 2 weeks decreased further to 100 to 125 ml/g. A ratio PE 8418/biomass of 0.6:1 was sufficient to keep the SVI at this level. The settling velocity of the sludge increased from <1.0m/h to 1.5 m/h. These settling properties allowed normal plant operation. During the first 2 weeks of the experiment, scum on the final clarifier and the aeration tank caused some problems. It is assumed that the complete incorporation of PE 8418 particles into the flocs takes some time, if a large quantity of this product is added at once. Meanwhile, free particles may contribute to stabilization of gas bubbles, viz. flotation of activated sludge.     

黔中地区潜在蒸散发的时空变化及对土地利用变化的响应

土地利用变化对潜在蒸散发的影响是水文等相关领域研究的热点问题.基于黔中地区1995-2015年气象数据,应用Penman-Monteith公式估算潜在蒸散发(ET0),同时利用1995-2015年5期土地利用数据,分析近20年该地区ET0的时空变化特征以及不同土地利用类型对ET0的影响.结果表明:1995-2015年黔...     

Ammonia, a selective agent for methane production by syntrophic acetate oxidation at mesophilic temperature.

In biogas processes, methane production from acetate proceeds by either aceticlastic methanogenesis or through syntrophic acetate oxidation (SAO). In the present study, the pathway for methane production from acetate was analysed; i) during a gradual increase of the ammonia concentration (final concentration 7 g NH(4)(+) -N/L) in a semi-continuous lab-scale anaerobic digester (4.3 L), operating at mesophilic temperature (37 degrees C) or ii) in diluted enrichment cultures (100 ml) experiencing a gradual increase in ammonia, sodium, potassium and propionic acid. The pathway for methane formation was determined by calculating the (14)CO(2)/(14)CH(4) ratio after incubating samples with (14)C-2-acetate. In the anaerobic digester, as well as in the enrichment cultures, the (14)CO(2)/(14)CH4 ratio clearly increased with increasing ammonium-nitrogen concentration, i.e. as the ammonia concentration increased, a shift from the aceticlastic mechanism to the syntrophic pathway occurred. The shift was very distinct and occurred as the NH(4)(+) -N concentration rose above 3 g/l. No shift in pathway was seen during increasing concentrations of sodium, potassium or propionic acid. The shift to SAO in the biogas digester resulted in a twofold decrease in the specific gas and methane yield.     

Seasonal and spatial variation in algal growth potential and growth-limiting nutrients in a shallow endorheic lake: Lake Pátzcuaro (Mexico)

The present research focused on the functional role of the phytoplankton of an economically important endorheic tropical lake from the perspective of algal growth bioassays. The algal growth potential of the lake water was compared for littoral and pelagic sites during the wet and dry seasons. Algal growth potentials at open waters reached minimum and maximum values following the seasonal alternation of dilution (by rain) and concentration (by evaporation) respectively. Conversely, at southern littoral stations high algal growth responses related to the availability of nutrients from point contamination sites. There was no such effect at nearby offshore sites or elsewhere in the lake which suggests filtration and competitive interactions for these nutrients between phytoplankton and littoral macrophytes. Nitrogen and phosphorus both acted consistently as limiting nutrients at open waters by colimitation. Nitrogen to phosphorus ratios seemed to approach equilibrium where limitation easily shifted to one element or the other temporally and spatially.     

1956-2015年高邮市气温和降水量变化特征研究

综合小波分析等多种统计方法,从趋势、突变、周期多方面解析高邮市1956-2015年气温、降水量时间序列近60年的变化特征。结果表明:近60年高邮市整体呈增温趋势,线性递增率约为0.30℃/10a,年平均气温自20世纪80年代中期开始波动上升,而年降水量波动平稳,略有上升,线性递增率约为2.2 mm/10a;滑动T检验结合MannKendall检验得出气温在1998年左右出现增暖突变,未检测到降水量变异点;Morlet小波变换说明年平均气温在55a时间尺度下周期性最为显著,年降水量周期变化存在56、43、20~30、9a这4类较明显的时间尺度,其中56a周期震荡最强烈,20~30a周期性最弱;气温主周期与降水量第一主周期(56a)相关。     

An analysis of 0+ barbel (Barbus barbus) response to discharge fluctuations in a flume

We studied the response in velocity use and time in refuge of 0+ juvenile barbel (Barbus barbus) to an increase in discharge in a flume. Each of five treated and five control fish were observed individually in separate eight‐hour experiments. Observations (trials) were arranged into a hierarchically structured, semi‐randomized sampling schedule consisting of four time levels: phase (4 h) ? period (2 h) ? sub‐period (30 min) ? trial (120 s). Increased discharge caused treated barbel to use higher velocities than control individuals, with individual differences in behaviour present at the various temporal tiers. Individual responses were modelled as either random‐walk or short‐memory processes, and those by treated fish were generally abrupt and permanent, with only one individual showing a gradual and permanent use of the higher velocities. Time in refuge was not affected by increased discharge, except for one fish that sought shelter after intervention. There was a significant relationship for most treated individuals between selection of lower velocities and time in refuge, and most barbel (both treated and control) showed significant deviations of used from mean flume velocities. The potential of the proposed approach to assess memory‐based individual fish responses to discharge and its consequences for (PHABSIM‐oriented) behavioural studies is discussed, and the mosaic of barbel behaviours observed is compared with available laboratory and field studies. Copyright © 2005 John Wiley & Sons, Ltd.     

The behavioural response of migratory sea lamprey (Petromyzon marinus) to potential damage-released larval and migratory chemical alarm cues

We investigated the presence of damage-released alarm cues and the reactions they may cause in landlocked migratory sea lamprey (Petromyzon marinus) using semi-natural laboratory conditions during the day. In two separate experiments, migratory sea lampreys were exposed to stimuli prepared from the skinless carcasses and skin tissue of larval sea lamprey and from the skin tissue and muscle tissue of migratory sea lamprey. Migratory female sea lamprey swam significantly longer after being exposed to the stimulus prepared from the skinless carcass of larval sea lamprey. No significant changes were seen in the behaviour of the migratory female lamprey in response to larval skin extract or in the behaviour of male sea lamprey to any experimental extract in the larval extract experiment. In the second experiment that utilised migratory lamprey stimuli, neither male and nor female migratory sea lamprey showed a significant difference in their behavioural response among different treatments and controls. Our findings indicate that adult female sea lamprey respond strongly to damage-released alarm cues from larval sea lamprey; hence, the latter holds promise for sea lamprey behavioural manipulations for control purposes during the day. Further research is needed to examine responses to damage-released alarm cues at night, when migratory sea lampreys are more active.     

Seasonal variation in trophic structure and restoration effects in a deep perialpine lake (Lake Lugano,Switzerland and Italy)

Using monitoring data from the South Basin of Lake Lugano (Switzerland and Italy), we examined seasonal responses of phytoplankton and herbivorous zooplankton biomass to nearly three decades (1989–2017) of phosphorus (P) management to ask: [1] what is the trophic structure of the lake, [2] whether trophic structure and the effects of nutrient management varied seasonally, and [3] what are the implications of the existent trophic structure for the restoration of the lake. Trophic structure varied seasonally, including a structure consistent with strong consumer control (exploitation food chain) in spring and fall, and an unexpected structure in summer, characterized by a negative correlation between phytoplankton biomass and phosphorus. This structure was explained by accumulation of inedible phytoplankton (mainly cyanobacteria) at low P concentrations. Owing to a lack of apparent resource (P) control, P-management had no detectable effects on phytoplankton biomass. The trophic structures identified in the lake provides explanations for this lack of response to P-management and for the differences between the responses of the South Basin of Lake Lugano and other perialpine lakes. Based on the results, lake restoration practice would benefit from a greater understanding and an increased ability to predict trophic structure within and across lakes.     

Seasonal variation in the phytoplankton of a saline lowland river (Buenos Aires,Argentina) throughout an intensive sampling period

The aim of this survey was to analyse seasonal variations in phytoplankton composition and abundance with respect to temperature and conductivity values at two sampling sites in the Salado River's lower basin: El Destino and Guerrero. Samples were taken twice a week from 9 March 2004 to 20 July 2004. A total of 145 and 143 species were identified for these two sites, respectively. Infrequent species were discarded to avoid statistical misinterpretations. Autocorrelation analyses (Ljung‐Box Q‐statistic) were performed in order to establish seasonal patterns for species abundance. Similar significant (p < 0.05) autocorrelation patterns were observed for phytoplankton species composition, temperature and conductivity, thus, illustrating correlations with seasonal behaviour. On the basis of these data, species were grouped as (1) late‐summer: with 34 species well represented in warm waters (>22°C) (e.g. Planctonema lauterbornii and Chroococcus spp.); (2) winter: with 10 species that reached their highest densities in cold waters (<12°C) (e.g. Binuclearia eriensis and Microcystis firma); (3) transitional: of only four species with abundance peaks during intermediate conditions (15.5°C average) such as Closteriopsis acicularis and Nodularia spumigena and (4) independent: with 22 species of random behaviour whose autocorrelations remain within confidence limits. These four classifications pertain to species with similar presence at both sampling sites; the rest of the species evinced slightly different patterns. An apparent season‐associated succession of species was detected with those adapted to the warm, stagnant water of the late summer being replaced by others acclimated to the cold water of the winter. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrological control of filamentous green algae in a large fluvial lake (Lake Saint-Pierre,St. Lawrence River,Canada)

Filamentous green algae (FGA) often proliferate in nutrient-rich rivers under low flow conditions. We assessed the hydrological and meteorological variables controlling the occurrence and composition of FGA in Lac Saint-Pierre (LSP), the largest of the St. Lawrence River fluvial lakes. We hypothesized that, under nutrient-rich conditions, hydrology and climate would be the main drivers of FGA occurrence and composition. We tested this hypothesis during the 2005 growing season, by fortnightly sampling at 7 stations within Anse-du-Fort, a 9 km² LSP embayment chronically exposed to the inflow of two tributaries draining farmland. Cladophora was the prevalent genus (89% occurrence), but Oedogonium, Hydrodictyon, and Spirogyra were at times dominant. Hydrological (depth, water level change) and meteorological variables (hours of sunshine, wind velocity) were the best predictors of FGA occurrence (r² = 0.55), but no water quality variable was significant in any model. The generality of our findings was then assessed using lake-wide FGA occurrence from surveys conducted over 6 years (2000–2001 and 2005–2008) of widely different hydrological and climatic conditions. Years of low water levels (2001 and 2007) coincided with early occurrence, highest prevalence and longest seasonal FGA persistence. Validation of model predictions using remote sensing images yielded a 74% success rate in forecasting FGA. We identified a water level limit for FGA occurrence (< 4.07 m above sea level). This limit provides a simple operational guideline for managers, improving our ability to predict FGA proliferation under increasingly low discharge and warming climatic conditions forecasted for the St. Lawrence River.     

Diel variation of limnological parameters in a reservoir in northeastern Brazil (Boa Esperança, Maranhão/Piauí): Rainy period

The diel variation of limnological parameters, measured in Boa Esperança Reservoir, Brazil during the rainy period, exhibited small temperature gradients characterized by an increase in temperature by midday, followed by a partial homogenization of the water column in the night and the early morning. The result was an increase in the epilimnion to a depth of 17 m. The pH and dissolved oxygen concentrations showed higher values at the surface, with the occurrence of anomalies (concentrations higher than at the surface) of the latter variable in the epilimnion, probably as a result of the activity of primary producers and/or losses of oxygen to the atmosphere. The chemical forms of iron in the reservoir exhibited increasing concentrations with depth, as a result of an increase in the concentration of seston and/or accentuated reduction of the levels of oxygen in the bottom layers. The reduction of Fe³⁺ to Fe²⁺ in the bottom water layers in the reservoir, in addition to the primary production process in the epilimnion, could explain the increased phosphorus in the bottom water layer. The concentrations of nitrogen compounds did not exhibit relevant changes or a defined evolution profile, except for nitrate, which showed an outstanding increase in the bottom water layers, suggesting it could be an important nitrogen source for primary producers. Although not unequivocal, these data suggest that ecosystem instability in Boa Esperança Reservoir is the product of short diel thermal variations, and the reduced input of allochthonous materials and nutrients from local catchment. These conditions guarantee the oligotrophic status of Boa Esperança Reservoir for the present time.     

Biofilm control in water by advanced oxidation process (AOP) pre-treatment: effect of natural organic matter (NOM)

The main goal of this study was to examine the influence of natural organic matter (NOM) on the efficiency of H?O?/UV advanced oxidation process (AOP) as a preventive treatment for biofilm control. Pseudomonas aeruginosa PAO1 biofilm-forming bacteria were suspended in water and exposed to various AOP conditions with different NOM concentrations, and compared to natural waters. H?O?/UV prevented biofilm formation: (a) up to 24 h post treatment - when residual H?O? was neutralized; (b) completely (days) - when residual H?O? was maintained. At high NOM concentrations (i.e. 25 mg/L NOM or 12.5 mg/L DOC) an additive biofilm control effect was observed for the combined H?O?/UV system compared to UV irradiation alone, after short biofilm incubation times (<24 h). This effect was H?O? concentration dependent and can be explained by the high organic content of these water samples, whereby an increase in NOM could enhance (?)OH production and promote the formation of additional reactive oxygen species. In addition, maintaining an appropriate ratio of bacterial surviving conc.: residual H?O? conc. post-treatment could prevent bacterial regrowth and biofilm formation.     

Use of a fishery model (FAST) to explain declines in the stocked barramundi (Lates calcarifer) (Bloch) fishery in Lake Tinaroo, Australia

Electrofishing, a fishery‐independent technique, was used to determine the size structure of a stocked impoundment barramundi (Lates calcarifer) fishery in Australia, in order to determine their size and age structure. Along with known recruitment values (stockings), this information was used to back‐calculate the mortality on each successive age class of fish. Using the fisher model, Fishery Analysis Simulation Tool (FAST), it was found that the fishery biomass reached a peak in the 1990s, and has since fallen rapidly because of the lack of successful recruitment until 2003. The fishery sampled in 2002 was dominated by older age fish classes (10⁺ to 14⁺ years old), which is opposite to that naturally found in wild fisheries. Although no juvenile L. calcarifer was found in the gut contents, cannibalism is suggested as an overriding cause for recent recruitment failure. Possible future management options for stocking apex piscivorous fish species into closed water systems also are suggested.     

Intragenomic variation of rDNA internal transcribed spacers in the endemic Baikal sponge Lubomirskia baikalensis (Pallas, 1776) (Spongillida,Lubomirskiidae): Implications for Porifera barcoding

Baikal endemic sponges are a species group for which species identification is difficult and the taxonomy is insufficiently developed. The rDNA ITS (internal transcribed spacers) are practical molecular markers for sponges. However, intragenomic polymorphism of the ITS spacers has recently been detected in many organisms including marine and freshwater sponges. We for the first time demonstrate intragenomic polymorphism of the ITS region in the sponge family Lubomirskiidae. We identified 27 new ITS1 and ITS2 haplotypes. The level of intragenomic polymorphism of the ITS1 and ITS2 regions in Lubomirskia baikalensis was 0.1–2.0%, which overlaps with the intraspecific polymorphism of L. baikalensis and to the interspecific polymorphism within Lubomirskiidae. Thus, the detected level of intragenomic polymorphism of Lubomirskiidae suggests species identification of Baikal sponges using ITS sequences would be difficult. The reasons for the lack of concerted evolution of the ITS spacers in Lubomirskiidae may be hybridization or insufficient divergence time. Our work contributes to the development of sponge barcoding markers.     

Interannual variation in spawning success of striped bass (Morone saxatilis) in the Saint John River,New Brunswick

Barriers such as dams have been cited as a serious threat to striped bass survival, especially when they affect or impede migration and access to spawning grounds. On the Saint John River, New Brunswick, the installation of the large Mactaquac Dam in the immediate vicinity of a historic striped bass spawning location was suspected to have caused the arrest of striped bass reproduction and the collapse of the native striped bass population. In 2014, juvenile striped bass of confirmed Saint John River origin were documented in the river for the first time since 1979. In the current study, we examined juveniles from 6 years of sampling to determine corresponding years of successful recruitment. We also tracked adult striped bass matching the ancestry of native Saint John River juveniles to determine the timing and location of spawning. Over 5 years, we observed an annual upstream migration by adult striped bass to historic spawning areas near Fredericton, identified a dominant year class of Saint John River origin juveniles reproduced in 2013, and linked the apparent successful production of year classes to definable discharge conditions, that is, extended periods of sustained flow >36 hr downstream from the Mactaquac Dam. The results of this study suggest important first management actions towards recovering and sustaining the re‐discovered striped bass population in the Saint John River, New Brunswick.     

Modelling a turbidity current in Soyang reservoir (Korea) and its control using a selective withdrawal facility

Persistent turbidity in reservoirs and their downstream after flood events is one of most important environmental issues in Korea. Recently, modification of withdrawal facility and installation of a new selective withdrawal structure (SWS) have been implemented for the mitigation of downstream impact and sediment loading into water treatment facilities. This study was to explore the characteristics of flood density flow induced into Soyang Reservoir and the transport processes of suspended sediments (SS) through application of coupled two-dimensional hydrodynamic and particle dynamic models (TM-1, TM-2 and TM-3). The TM-3 including a turbidity attenuation rate as a lumped parameter showed best performance in reproducing the magnitude and distribution of SS in the reservoir. The validated model was applied to evaluate the effectiveness of SWS, which was designed for the reservoir, with 6 different historical flood events. The magnitude of vertical mixing of the turbidity plume and its persistence within the reservoir were closely correlated to the ratio of the volume of turbidity flow to the total reservoir storage (the theta value). The operation of SWS showed a positive effect as long as theta is between 0.3 and 0.6 but negative when theta = 0.83 for the study reservoir, thus it should be optimized based on the theta value for a better management of the reservoir.     

Assessing channel geometry in response to land use disturbance in a low-relief,glacially conditioned setting

Bankfull stage, the highest flow elevation contained by a river channel before overbank flooding occurs, is the presumed threshold for channel morphological change. At bankfull, the channel boundary experiences the highest shear stress, producing somewhat predictable hydraulic relationships and a cross-sectional form. However, land use and glacial conditioning can profoundly impact a channel's geomorphic responses. Two common methods characterize bankfull flow: one based on flow frequency and other based on channel form. This study considers a simplified approach to identify upstream land use relative to estimates of bankfull flow versus a channel's geometric form. The approach compares archived geomorphic surveys of 140 river reaches in southern Ontario, Canada, to 2-year flood quantiles modelled from historical flood data of 207 gauge stations. Flood frequency analysis determines that annual maximum series (AMS) datasets, fitted to optimized probabilistic distributions, underestimate discharge for low-magnitude, high-frequency flood events compared to partial duration series (PDS) datasets. For smaller drainage areas (<100 km²) associated with an extensive agricultural activity and/or urbanization, the estimates of bankfull discharge (Q_bf) generated by cross-sectional channel geometry are greater than the gauge-derived Q₂ values. Channels impacted by high levels of upstream land use disturbance show statistically significant lower width-to-depth ratios (p < 0.001) and a trend towards a finer D₅₀ bed material, suggesting enhanced surface runoff delivering more mobile finer sediments and channel confinement or incision. This research quantifies the formative bankfull stage to better understand the link between land use and a channel's ‘natural’ hydrogeomorphic response in a low-relief, glacially conditioned setting.     

Mobility of contaminants in relation to dredging operations in a mesotidal estuary (Tagus Estuary,Portugal)

During the construction of a New Bridge over the Tagus estuary 2.5 million tons of sediments were dredged, part of this quantity being contaminated material. The extension and intensity of the water turbidity associated with dredging operating varied with the tidal conditions but the resuspended material collected near the bucket dredger did not present a concnetration increment in metals and PCB, when compared to the estuarine suspended sediments. The calculated distribution coefficients suggest that some contaminants in solids near the dredger were not in equilibrium with the water. A 24-hour laboratory experiment demonstrated the complexity and quickness of anoxic sediments oxidation. In such a short period of time metals in the solids change their fractionation. A second laboratory simulation showed that mussels accumulate metals and PCB congeners when placed in turbid aerated water.