Distribution of Macrophytes in Relation to Environmental Factors in the Ter River,N. E. Spain

Most of the tested water quality factors increase downstream coinciding with changes in the aquatic vegetation, from typical species of fast-flowing oligotrophic waters to those of slower-flowing eutrophic waters. Several statistic analyses were carried out to relate physical and chemical parameters with plant distribution. Five vegetation types are found in a longitudinal distribution along the river system. They are dominated by bryophytes in the initial parts before the reservoirs and by higher plants in the final parts after the reservoirs.     

Evaluating climatic and non-climatic influences on ion chemistry in natural and man-made lakes of Nebraska,USA

Conductivity and major ion chemistry data were analyzed for a suite of Nebraska (USA) natural lakes, reservoirs, sand pits, and barrow pits to evaluate the magnitude of climatic versus non-climatic influence on ionic concentration and composition. In both natural lakes and sand and barrow pits, conductivity is positively related to longitude and reflects decreasing effective moisture from east to west. Reservoirs showed no relationship between lake conductivity and location, probably because the reservoirs are very strongly influenced by groundwater and surface water inflow and have shorter residence times relative to the other lake types. At smaller spatial scales, conductivity among natural lakes is variable. Lakes that are at low elevation within a groundwater flow system were fresh, because of substantial input of fresh groundwater. In contrast, lakes at high elevation exhibited a wide range of conductivity, probably because of differences in the degree of connection to groundwater and surface to volume ratio impacts on evaporation rates. Differences also were evident among natural lakes in terms of their response to seasonal changes in precipitation. Sub-saline and saline lakes showed more seasonal variation in conductivity than freshwater lakes, and lakes in the more arid part of the state showed larger responses to precipitation change than those in areas to the east that receive higher precipitation.     

Patterns in the Distribution of Cladocerans (Crustacea: Branchiopoda) in Lakes Across a North–south Transect in Alaska, USA

The remains of cladocerans were examined from the surface sediments of 51 freshwater sites along a north–south transect spanning Alaska. We identified 27 cladoceran taxa from the sediments, consisting primarily of littoral chydorid species. Variations in cladoceran assemblages were related to measured physical and chemical variables using multivariate techniques. Redundancy analysis (RDA) indicated that lake depth, total phosphorus (TP), and altitude all had a significant influence in determining the composition of cladoceran assemblages. Cladoceran communities in tundra and forest-tundra lakes, which were relatively shallow and nutrient-poor, had relatively low abundances of pelagic Cladocera, and were primarily composed of several littoral chydorid species. Among pelagic cladoceran species, there was a distinct shift in dominance from the Bosminidae in lakes in the southern boreal forest region to Daphniidae in lakes in the northern boreal forest. Daphnia dominated lakes had significantly higher total phosphorus, specific conductivity, and calcium concentrations than lakes dominated by Eubosmina. Overall, the relative importance of physical and chemical factors in structuring cladocerans is similar to other previously studied regions, and suggests the Cladocera may be useful as ecological and paleoenvironmental indicators in this region.     

Structure of fish assemblages in seven tropical reservoirs in southeastern Brazil during the rainy season; what matters: physico‐chemical or hydrological connectivity influences?

Closely connected reservoirs were hypothesized to have more similar fish compositions than do spatially isolated reservoirs, and that environmental variables play an important role in shaping assemblage structure on a local scale. Fish assemblages and environmental variables were sampled in seven reservoirs constructed to generate hydroelectricity, with most inflowing water coming directly or via transposition of the Paraiba do Sul River, in Southeastern Brazil. Using gill nets and environmental measurement variables, fish collections were carried out between January and February 2008 (wet season), when increases in temperature and rainfall increase hydrological connectivity, facilitating fish movements throughout the river‐reservoir system. Mean fish density, biomass and the number of species did not differ significantly among the seven reservoirs. On the other hand, the assemblage structure differed among almost all pairs of reservoirs. Of the reservoirs connected in series, only two (Santana and Vigário) showed a similar assemblage structure, suggesting that hydrological connectivity plays a minor role. Physico‐chemical variables changed among reservoirs and seemed to play an important role in determining the assemblage structure, with higher conductivity (average = 108 μS cm^?1) and TDS – total dissolved solid (0.07 g L^?1), and low pH (5.8) in the Pereira Passos Reservoir associated with a high number of the Siluriformes Loricariichthys castaneus, and with the opposite conditions in Tocos (conductivity = 27 μS cm^?1; TDS = 0.02 g L^?1; pH = 7) that were associated with a high number of the carnivorous Characiformes Oligosarcus hepsetus and Hoplias malabaricus. A direct relationship was found between abundance of the catfishes Pimelodus fur and Glanidium albescens and high turbidity (90.4 NTU) and low temperature (25.3°C) and transparency (0.1 m) in the Ilha dos Pombos Reservoir. Moreover, a close relationship was found between high abundance of the cichlid Cichla kelberi and the high temperature and transparency of Lajes (28.3°C; 2.2 m) and Santa Branca (27.1°C; 2.6 m) reservoirs. These findings support the hypothesis that physico‐chemical variables structure fish assemblages in reservoirs, but that hydrological connectivity seems to play a minor role in shaping assemblage structure. However, other unmeasured variables (e.g. physical habitat characteristics and biotic interactions) and other seasons need to be evaluated in further studies.     

Multi-scale approach using phytoplankton as a first step towards the definition of the ecological status of reservoirs

The growing need to analyse the present state of ecosystems and predict their rate of change has triggered a demand to explore species environment relationships for assessing alterations under anthropogenic influence. The Water Framework Directive (WFD) requires the definition of different types of water bodies which are of relevance when assessing their ecological status. The main aim of this study was to define of the types of Portuguese reservoirs located in the North and Centre of Portugal and to assess their ecological status using phytoplankton as water quality indicators. In this study, sampling was carried out in 34 reservoirs during four seasons (spring, summer, autumn and winter), through a period of 8 years (1996–2004).Two groups of reservoirs could be distinguished, from the multivariate statistical analysis based on environmental variables and on phytoplankton assemblages: G1, lowland reservoirs located in the main rivers (Douro and Tagus), with a very low residence time, characterized by higher water mineral content (hardness and conductivity), higher concentrations of nutrients (namely, nitrates), dominated by Bacillariophyta and Chlorophyta and characterized by the presence of tolerant of poor environmental conditions species, mainly associated with meso and eutrophic states of water bodies; G2, deeper high altitude reservoirs, largely located in tributaries, with high residence time, presenting a specific species composition under reference conditions, with higher species richness. The transition from deeper and colder reservoirs (reference sites) to shallow and warmer reservoirs (impaired sites), was evident in G2, contrarily to G1, and was mostly positively correlated to organic pollution and mineral gradients. The results presented here are fundamental for the development of a routine for monitoring ecological status according to the WFD.     

Nutrients,Conductivity and Plankton in a Landscape Approach to a Pampean Saline Lowland River (Salado River,Argentina)

Nutrients, conductivity and other physical and chemical parameters were measured seasonally in the main channel and in tributaries of the Salado River basin during the period March 1997–June 1999. The sampling began in a low water period and later included flood events. High water events were associated with high proportions of allochthonous compounds (polyphenols, suspended solids and organic matter). Nutrients and conductivity were related to hydrological conditions and different land uses in the catchment. A relationship was found between the land-use and nutrient concentrations due to the inflow of diffuse sources from agricultural lands. High nutrient concentrations and conductivity recorded in the headwaters were, respectively, related to the intensive agriculture in this area and the inflow of saline groundwater, drained by canals from endorheic basin to the main channel. Their effects on the middle and lower reaches were related to the discharge and inputs of other sub-catchments. Nutrients, sulphates, alkalinity and conductivity declined downstream towards the river mouth. The consequences for the plankton community of these spatio-temporal changes in the chemical characteristics are discussed. The heterogeneity of the Salado River is related to seasonality, land use and the geomorphological features of the basin.     

Hydrologic and climatic regimes limit phytoplankton biomass in reservoirs of the Upper Paraná River Basin,Brazil

In reservoirs of the Upper Paraná River Basin, Brazil Paraguay, phytoplankton biomass is generally low relative to reservoirs in other parts of the world. To investigate what might be limiting phytoplankton biomass in the Upper Paraná reservoirs, we used an empirical approach wherein climatic conditions in the basin as well as chemical, hydrological and morphometrical characteristics of 13 reservoirs, were compared against those prevailing in 58 reservoirs of the south-central United States. In both regions, phytoplankton biomass was correlated with chemical, hydrological and morphometrical characteristics of the reservoirs. There were no differences in phosphorus concentrations between the two regions, nitrogen levels were higher in the Upper Paraná, ionic concentrations were higher in the south-central United States and there were major differences in all physical characteristics considered. In reservoirs of the south-central United States, hydraulic retention time increased and discharges decreased during the post-spawning period allowing increases in phytoplankton biomass; in the Upper Paraná River Basin, discharges peaked during the post-spawning period, delaying the peak of phytoplankton blooms until after completion of the post-spawning period. Our comparison between the two sets of reservoirs suggests that hydrologic regimes dictate differences in phytoplankton biomass and that hydrology of the Upper Paraná River Basin, exacerbated by climatic patterns, deter phytoplankton production despite suitable levels of essential nutrients.     

Ecology and fishery management of reservoirs in India

India has 19 370 small reservoirs with a total water surface area of 3 153 366 ha. At least 100 of them have been subjected to scientific studies. Habitat variables responsible for a reservoir's productivity can be summed up into climatic, morphometric and hydro-edaphic factors. The peninsular reservoirs are characterized by a narrow range of fluctuations in water and air temperature across seasons, a phenomenon which prevents the formation of thermal stratification. Many reservoirs in the upper peninsula show thermal stratification during summer. Wind-induced turbulence facilitates the return of nutrients to the trophogenic zone. Most reservoirs on the mountain slopes of Western Ghats, Himalayas and the other highlands are deeper, with steeper basin walls, compared to irrigation impoundments. Mean depth does not show any direct correlation with productivity, either at primary or fish level. A high shoreline development index gives a better indication of productivity. Plankton, benthos and periphyton pulses of Indian reservoirs coincide with the months of least level fluctuations. Oligotrophic tendencies shown by some reservoirs are mainly due to poor nutrient status and other chemical deficiencies. In most cases, poor water quality is accountable to poor catchment soil. Low levels of phosphate and nitrate are not indicative of low productivity due to quick recycling of these nutrients. Specific conductivity reflects the production propensities of reservoirs satisfactorily. Almost all productive reservoirs have a klinograde oxygen curve and a vertical stratification of chemical variables such as pH, carbon dioxide, total alkalinity and specific conductivity. High seasonal rainfall and discharge of water during monsoon result in high flushing rates, which do not favour colonization by macrophytic communities. Similarly, inadequate availability of suitable substrata retards the growth of periphyton. Plankton constitutes the major link in the trophic structure. A rich plankton community with well-marked succession is the hallmark of Indian reservoirs with blue-green algae as the major component. The main factors that retard the growth of benthos are a rocky bottom, frequent water level fluctuation and rapid deposition of silt and other suspended particles. Large reservoirs, on average, harbour 60 species of fishes, of which at least 40 contribute to the commercial fisheries. Fast-growing Indian major carps are the prominent commercial fishes. Dam construction has adversely affected populations of many other species such as Tenualosa ilisha, Torspp. and Cirrhinus spp. Formulae for estimating fish yield potential and stocking density are described. While culture-based fisheries have been successfully practiced in many small reservoirs, the management norm followed in medium and large reservoirs is primarily on capture fishery. In large and medium reservoirs, stocking was successful only when stocked fishes bred. Indian experience on species enhancement and introductions is described. Environmental enhancement of small reservoirs has been attempted in some reservoirs of Tamil Nadu. Modeling, using standard population parameters, such as the density-dependent growth, size dependent mortalityand weight–length relationshipis discussed. Two exotic fishes viz., Oreochromis mossambicus and Cyprinus carpio have been introduced into Indian reservoir with discouraging results. Hypophthalmichthys molitrix, after an accidental introduction, has performed well in Gobindsagar, a reservoir with a distinct cold water regime. Reservoir fisheries in India are well poised for development, provided scientific management norms are adopted.     

Structure of the L2 lipopolysaccharide core oligosaccharides of Neisseria meningitidis.

Three different oligosaccharides were identified following mild acid hydrolysis of the lipopolysaccharide obtained from Neisseria meningitidis serotype 2 and their structures elucidated by combined chemical and physical techniques. The use of 500 MHz 1H nmr in both one- and two-dimensional modes as well as nuclear Overhauser effect experiments were employed. To assist in the structural assignments the oligosaccharides were also degraded by chemical and enzymatic procedures to smaller fragments. The oligosaccharides were all triantennary nonasaccharides in which the longest antenna terminates in lacto-N-neotetraose. Two of the nonasaccharides (major components), not separable by column chromatography, were distinguishable only by their different patterns of phosphorylethanolamine substitution and the third minor component by the absence of this substituent.     

Comparative limnology of nine lakes of Jammu and Kashmir Himalayas

Two lakes in the lower Siwalik Himalayas, five in the Kashmir valley and two situated in the high mountains of the Kashmir Himalayas were investigated for their physico-chemical and biological features. The lakes, differing significantly in their morphology and in thermal behaviour, rank from the subtropical monomictic to the dimictic type. The lakes at high altitudes (> 3000 m) have very low electric conductivity which increases with the decrease in altitude. The most dominant ions in water are calcium and bicarbonate. The macrophytic vegetation of the lakes does not show any definite relationship either with altitude or with physico-chemical milieu. In the lakes with low fertility the phytoplankton is dominated by diatoms and Chlorophyceae but in eutrophic lakes Cyanophyceae predominate. The zooplankton population of the lakes is mainly comprised of rotifera. On the basis of general limnological features and the rates of phytoplankton production most of the lakes may be categorized either as eutrophic or in the process of rapid evolution. Only one lake is oligotrophic.     

Environmental factors associated with toxic cyanobacterial blooms across 20 drinking water reservoirs in a semi-arid region of Brazil

Cyanobacteria are known to produce a wide variety of bioactive, toxic secondary metabolites generally described as hepatotoxins, neurotoxins, cytotoxins, or dermatoxins. In Brazil, the regular monitoring of cyanobacterial toxins has intensified after the death of 65 patients in a hemodialysis clinic in Caruaru in the state of Pernambuco due to microcystin exposure. The primary objective of this study was to use multivariate statistics that incorporated environmental parameters (both biotic and abiotic) to forecast blooms of cyanobacteria and their toxic secondary metabolites in 20 drinking water reservoirs managed by the Water Treatment Company of Ceará (CAGECE) in the semi-arid region of Ceará, Brazil. Across four years (January 2013 to January 2017), 114 different phytoplankton taxa were identified, including 24 cyanobacterial taxa. In general, Ceará reservoirs were dominated by cyanobacteria due to eutrophication but also because of the dry and warm climate found throughout the region. Interestingly, specific cyanobacterial taxa were influenced by different biotic and abiotic factors. For example, nitrogen-to-phosphorus (N:P) and evaporation were positively related to saxitoxin-producing taxa, especially Raphidiopsis raciborskii, while temperature, electrical conductivity, total phosphorus, and transparency (measured as Secchi depth) were positively associated with microcystin-producing taxa, such as Microcystis aeruginosa. Climate forecasts predict higher evaporation and temperatures in the semi-arid Ceará region, which will likely magnify droughts and water scarcity as well as promote toxic cyanobacterial blooms in reservoirs in the future. Therefore, understanding the factors associated with algal blooms dominated by specific taxa is paramount for water resource management.     

The pathway of pepsin-catalysed transpeptidation. Evidence for the reactive species being the anion of the acceptor molecule

Several minor pepsinogens, present in extracts of bovine fundic mucosa obtained from the fourth stomach or abomasum, were separated from the main pepsinogen by chromatography on hydroxyapatite at pH7.3. The major pepsinogen and two of these minor pepsinogens were studied in detail. All three zymogens have N-terminal Ser-Val-, C-terminal -Val-Ala and not more than 1mol of glucose/mol of protein; no significant differences in amino acid composition were found. The pepsinogens differ in their organic phosphate content, which accounts for their chromatographic separation. By activation at 0 degrees C and pH2, a corresponding series of pepsins is formed. These enzymes were separated by hydroxyapatite chromatography at pH5.7. All the pepsins have N-terminal valine, C-terminal alanine and are free from carbohydrate. Again the only difference detected among them is in their organic phosphate content. The pepsins of high phosphate content are converted by an acid phosphatase in vitro into pepsins of low phosphate content.     

Covalent structure of the minor monomeric beta-lactoglobulin II component from donkey milk

The complete primary structure of the minor beta-lactoglobulin II component from donkey milk is presented. It has been established by amino-acid sequencing and mass-spectrometry analysis of intact protein and peptides obtained after enzymatic and chemical cleavages. The molecular mass and the pI of the protein are calculated to be 18,261 Da and 4.5 respectively. Despite the close structural similarity of the donkey and horse major beta-lactoglobulin I components, their minor beta-lactoglobulin II components show substantial differences in sequence. Most observed exchanges are clustered at residues 78-106 where only 6 amino-acid residues are conserved. The primary structure of donkey beta-lactoglobulin II reveals some unusual features of minor beta-lactoglobulins II and gives new light to the evolution of beta-lactoglobulins and other lipocalins involved in retinol binding or reproductive functions.     

CHEMICAL AND PHYSICAL CHARACTERISTICS OF SHALLOW GROUND WATERS IN NORTHERN MICHIGAN BOGS,SWAMPS, AND FENS

Fifteen chemical and physical characteristics were examined in samples of shallow ground water taken in midsummer at 15-30 cm below the surface in six bogs, 15 swamps, and six fens. The wetland types were identified on the basis of their vegetation. Three groups of covarying water characteristics were identified by factor analysis. Factor I included Ca, Mg, Si, pH, alkalinity, conductivity and to a much lesser extent Na, and reflects the degree of telluric water influence in the wetland. Factor 2 included reactive-P, total-P, NH₃-N, and to a lesser extent K, and consists of elements that primarily enter interstitial water via organic matter decomposition. Factor 3 included Na, Cl, and to a much lesser extent K. The wetlands formed two distinct groups with respect to water chemistry: weakly minerotrophic (pH 3.8-4.3) including all bogs and moderately to strongly minerotrophic (pH 5.5-7.4) including all swamps and fens. The bogs had very low values for Factor 1 characteristics and moderate values for the remaining characteristics. The swamps and fens had moderate to high values for Factor 1 characteristics and showed considerable overlap in this respect. The fens had consistently low values for Factor 2 characteristics but overlapped with some swamps which also had low Factor 2 scores. Failure to completely separate the vegetationally very distinct swamps and fens from each other on the basis of their physical and chemical water characteristics indicates that another factor, probably water level regime, is of major importance in determining their vegetation type.     

Plankton populations of Lake Leake and Tooms Lake—Oligotrophic Tasmanian Lakes

The characteristic feature of Lake Leake and Tooms Lake is their great similarity in physical and chemical limnology. This similarity extends to the plankton populations in general terms, both lakes being dominated by Cyclotella stelligera Cleve et Grun. and having few other species. Floristic differences are minimal. Despite this floristic similarity distinct differences exist in plankton periodicity, principally in that of Cyclotella stelligera. The extreme oligotrophy of the lakes, already suspected from their low nutrient levels, is confirmed by the extremely meagre standing crops.     

Soil Organic Matter and Management of Plant-Parasitic Nematodes

Organic matter and its replenishment has become a major component of soil health management programs. Many of the soil''s physical, chemical, and biological properties are a function of organic matter content and quality. Adding organic matter to soil influences diverse and important biological activities. The diversity and number of free-living and plant-parasitic nematodes are altered by rotational crops, cover crops, green manures, and other sources of organic matter. Soil management programs should include the use of the proper organic materials to improve soil chemical, physical, and biological parameters and to suppress plant-parasitic nematodes and soilborne pathogens. It is critical to monitor the effects of organic matter additions on activities of major and minor plant-parasitic nematodes in the production system. This paper presents a general review of information in the literature on the effects of crop rotation, cover crops, and green manures on nematodes and their damage to economic crops.     

Responses of the planktonic diatom Asterionella formosa Hassall to abiotic environmental factors in a reservoir complex (south-eastern France)

The River Durance and its main tributary, the Verdon, are both highly regulated rivers flowing in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different geographical, morphometric, climatic, hydrodynamic and chemical characteristics. The planktonic diatom Asterionella formosa Hassall, which has undesirable cyclic effects from the water management point of view, was studied in this complex of reservoirs located in the Mediterranean region. The results indicate that only the monomictic calcareous reservoirs show a bimodal pattern of Asterionella formosa abundance. The population dynamics of this algal species was found to depend on both the morphometric features and the hydraulic mode of management (retention time) used at each reservoir, as well as on the physical (temperature, suspended matter) and chemical (nitrogen, silica, calcium) characteristics of the water.     

Effect of main-stem dams on zooplankton communities of the Missouri River (USA)

The persistence of plankton in flowing water presents an enigma, i.e., how can populations be sustained while constantly losing individuals downriver? We examined the distribution and abundance of zooplankton from 146 sites on the Missouri River (USA) and found large shifts in the dominance of major taxa between management zones of this regulated river. Crustacean zooplankton were dominant in the inter-reservoir zone of the river, and their taxonomic composition was similar to regional lakes and reservoirs. The exponential decline of cladocerans and copepods with distance from main-stem dams suggests that conditions within the river are adverse to population growth and that reservoirs are the main source of these crustaceans in the river. Rotifers dominated in the channelized zone of the river. High algal biomass and rapid population growth rates likely allow persistence of rotifers in segments of the river that do not receive direct reservoir inputs. Rotifers were less abundant in the inter-reservoir zone, suggesting that their numbers are limited by internal processes, such as food or predators. Since zooplankton are known to be an important food for larval fishes in rivers, this shift of major taxa in regulated rivers has implications for river food webs.     

Effects of sewage disposal into the White Nile on the plankton community

Twenty water samples and 30 plankton samples were taken from the sewage disposal site (El Lamab, south of Khartoum), from 250 m upstream and 250 m downstream during January–March, 1987 and Februar–April, 1988. The water samples were examined for physical and chemical characteristics. Plankton samples were examined for species composition and relative abundance of phytoplankton and zooplankton.At the disposal site, the sewage effluent increased conductivity, nutrients and suspended solids, elevated BOD, and depleted oxygen. The pattern of abundance in the phytoplankton was almost reversed, due to the disappearance of many diatoms, replaced by blue-green algae, and the appearance of Euglenophyceae, found only at the disposal site. Copepods dominated over cladocerans, which are usually dominant under natural conditions. Rotifers, normally less abundant, also flourished at the disposal site. However, these effects were localized: physical, chemical and biological conditions returned to normal 250 m downstream.Dept. of Zoology, Hydrobiological Research Unit, University of Khartoum     

A comparative analysis of the relationship between phytoplankton standing crops and environmental parameters in four eutrophic prairie reservoirs

An analysis was performed with multivariate statistical methods of the relationship between chlorophyll a concentrations and eighteen physico-chemical parameters measured over a six year period in four eutrophic Nebraska reservoirs. In the reservoirs with relatively clear water early in the growing season, physical factors (Secchi depth, turbidity, temperature) and non-nutrient chemical factors (alkalinity, hardness, C. O. D.) were significantly related to chlorophyll a concentrations, but macronutrients (nitrogen and phosphorus) were not. In the reservoir with persistent abiogenic turbidity, chemical factors including nitrogen and phosphorus were significant but physical factors were not. Six models based upon intercorrelations between measured parameters and chlorophyll a are evaluated for their usefulness in accounting for chlorophyll a variance. The best model accounts for 67–70 percent of the total variation in chlorophyll a in the four reservoirs.