Actinosporean stages of Myxozoan parasites of oligochaetes from Nera River basin, Central Italy

The aim of this study was to check the occurrence of actinosporean stages of Myxozoan parasites of oligochaetes in the Nera River basin (Central Italy). The investigation was conducted near twelve trout farms (rainbow and brown trout) along the Nera River and in the littoral of the Piediluco Lake. Four actinosporean types, belonging to the collective groups aurantiactinomyxon, triactinomyxon, raabeia and echinactinomyxon, were detected in some of the biotopes investigated (Piediluco Lake and Sordo River). Differential diagnosis, carried out on a sub-sample of spores, showed a complete fitting with forms previously described in literature, with the exception of the triactinomyxon type.     

Comparative analysis of the phytoplankton of fifteen lowland fluvial systems of the River Plate Basin (Argentina)

The phytoplankton of fifteen lowland courses of the River Plate Basin is compared and characterized by means of multivariate analyses.The cluster analysis performed with the more abundant species of each fluvial system reveals three main groups. Rivers with a high discharge and a large floodplain are grouped on the basis of the dominance of several Aulacoseira species. An eutrophic flora typified by Cyclotella meneghiniana, Synedra ulna and several green algae occurs in the smaller rivers with high conductivity, low transparency and important discharge variations. A third group comprises the Uruguay River and its tributaries, characterized by the presence of several pennatae diatoms and flagellates: Amphipleura pellucida, Surirella tenera, Terpsinoe musica, Navicula cuspidata, Eudorina elegans, Pandorina morum and Peridinium gatunense.The Principal Component Analysis based on a data matrix of physical, chemical and hydrological parameters revealed similar results. The ordination according to the first two components reflects the geographic location of these systems in the River Plate Basin, responding to a decreasing gradient of conductivity, pH and solids and an increasing minimum temperature. The rivers were ordinated by means of a Correspondence Analysis based on the main algal groups.     

The effects of dissolved heavy metals on attached diatoms in the Uintah Basin of Utah,U.S.A.

The relationships of diatom species to dissolved heavy metals in the streams of the Uintah Basin of Utah were studied through four seasons of 1977–1978. Niche center gradient analysis, cluster analysis and correlation analysis were performed.Achnanthes minutissima, Cyclotella meneghiniana, Cymbella minuta, Gomphonema parvulum, Navicula secreta var.apiculata, Nitzschia frustulum, Nitzschia frustulum var.perminuta, Nitzschia frustulum var.perpusilla, Nitzschia palea, andSynedra ulna appear to be indicator species of high or low heavy metal concentrations. Several other species also showed meaningful relationships to high or low heavy metal concentrations.Dept. of Physics and Astronomy, Brigham Young UniversityDept. of Physics and Astronomy, Brigham Young University     

Composition and abundance of phytoplankton in tributaries of the lower Colorado river,Grand Canyon region

Phytoplankton distribution and abundance in eleven tributaries of the Colorado River within the Grand Canyon were investigated from April, 1975 to June, 1976. During this period a total of 56 genera and 156 species of phytoplankton was identified. Phytoplankton species of the individual tributaries were quite distinct, with only four diatom species, Diatoma vulgare, Navicula tripunctata, Nitzschia linearis and Synedra ulna, common to all the tributaries. Bright Angel Creek, Shinumo Creek and Elves Chasm were the tributaries with the most diverse algal flora, whereas Vaseys Paradise, Tapeats Creek, Deer Creek and Havasu Creek showed the lowest species richness. Elves Chasm and Diamond Creek had the highest phytoplankton numbers. Phytoplankton abundance and species richness appeared to be influenced by high turbidity, current velocity, fluctuating water levels and age of the water. Some of the dominant algal species, Biddulphia laevis, Cocconeis pediculus, Cymbella ventricosa, Epithemia sorex, Gomphonema parvulum and Synedra ulna, showed significant correlations with specific physico-chemical characteristics of the tributaries.Grand Canyon National Park Colorado River Research Series Contribution No. 66. This research was supported by the National Park Service, U. S. Department of the Interior.     

Seasonal Physical,Chemical and Algal Changes in Five Rivers Flowing Through the Oil Sands Region of Alberta,Canada

Seasonal studies concentrating upon physical and chemical parameters and the epilithic algal community were conducted at specific sites in five tributary rivers flowing through the oil sands region of northeastern Alberta, Canada into the Athabasca River. Numerically cyanophycean algae (Lyngbya aerugineo-caerulea, Phormidium sp., Calothrix braunii, Nostoc spp. and Anabaena affinis) dominated followed by diatoms (Achnanthes lanceolata, Cocconeis pediculus, Cocconeis placentula, Epithemia sorex, Epithemia turgida, Gomphonema acuminatum, Gomphonema longiceps v. subclavata, Gomphonema olivaceum, Nitzschia fonticola, Nitzschia palea, Synedra rumpens, and Synedra ulna). One exception was the Hangingstone River where chlorophycean algae (Stigeoclonium pachydermum and Cladophora glomerata) were next in importance to the cyanophytes. Seasonal fluctuations in algal species and numbers were influenced by a myriad of interacting parameters. Physically disruptive forces (current velocity and discharge) appeared more important than dissolved nutrients. They were also responsible for affecting the chemical composition of the water itself.     

Growth ofPhormidium sp. in aerobic secondary piggery waste-water

The potential of a cyanobacteriumPhormidium sp., for the tertiary treatment of piggery waste-water chemical oxygen demand , 3000 mg·1^–1, using an aerobically stabilized secondary effluent, was studied. Batch cultures were carried out in 2-1 glass reactors and in a 30-1 glass-fibre carousel reactor. The nutrient removal efficiency as well as biomass production were compared in synthetic mineral medium and in different concentrations of aerobically stabilized piggery effluent. The best performance ofPhormidium sp. ocurred in diluted stabilized secondary effluent (1:1). Removal efficiencies were 100% for P-PO₄ ^–3, 50% for N-NH₄ ^–1 and 35% for N-NO₃ ^– in small-volume cultures; and 31% for P-PO₄ ^–3, 100% for N-NH₄ ^– and 70% for N-NO₃ ^– in an open carousel reactor. Biomass production on the aerobically stabilized effluent was six times higher in the 2-1 reactors and 1.7 times higher in the carousel reactor when compared to the synthetic medium.     

Short-term response of monospecific and natural algal biofilms to copper exposure

The effect of copper additions (Cu ranging from 0 to 30?µM) on the photosynthesis of three different microalgal biofilms was studied to identify the factors that cause sensitivity differences between benthic and pelagic algae. The response of biofilms which colonized artificial substrata in the River Meuse was compared with those of two laboratory-grown monospecific biofilms, one consisting of the diatom Synedra ulna, and the other composed of a filament-forming cyanobacterium, Oscillatoria sp. The photosynthetic yield Φ_II (quantum efficiency of photosystem II) was studied with PAM (Pulse Amplitude Modulated) fluorimetry. S. ulna biofilms appeared to be the most sensitive to Cu, followed by the cyanobacteria, while natural biofilms, dominated by supposedly very sensitive diatom species such as Melosira varians and Diatoma vulgare, were the most resistant to Cu. In the highly productive biofilms, pH is suggested to play a role in lowering toxicity by helping the precipitation of cupric ions. Cu accumulation by the biofilms during the exposure period followed a linear relationship with Cu concentration, saturation not being observed; natural biofilms had an accumulation factor of 1–2.5?×?10³ relative to the concentrations in the water, while the diatoms growing unattached to the substratum had a higher concentration factor, up to 4.9?×?10³. It was concluded that the physical structure of the biofilm (package of cells and thickness), and not the species composition, was the main factor regulating the sensitivity of the biofilm to Cu toxicity during short-term exposures.     

The recent diatom history of Loch Leven, Kinross

Diatoms in the top metre of lake sediment have been studied for indications or recent changes in the environment of Loch Leven. The diatoms indicate a eutrophic, alkaline lake with Melosira italica ssp. subarctica, Tabellaria Flocculosa and Stephanodiscus astraea the dominant taxa at the base of the 1-m section. There is then an appeance of Melosira ambigua and Stephanodiscus hantzschii suggesting a richer environment. Post A.D. 1816 changes in taxa suggest possible correlation with the lowering of lake level in 1830 and the dominance of Diatoma elongatum, Cyclotella pseudostelligera, Stephanodiscus astraea var. minutula, S. tenuis, S. hantzschii, and Synedra rumpens and var. soctica in zone 4 agrees with present-day plankton records.     

Resource Ratios and Phytoplankton Species Composition in a Strongly Stratified Lake

The epilimnetic phytoplankton and its relations to nutrient content in Lake Verevi through the whole vegetation period in 2000 were studied. Lake Verevi (surface 12.6 ha, mean depth 3.6 m, maximum depth 11 m) is a hypertrophic hard-water lake, where the so-called spring meromixis occurs due to an extremely warm spring. Most dissolved nutrients in the epilimnion were low already in spring, and their concentrations were quite stable during the study period. The concentration of total silicon was very low in spring but increased rapidly in summer. Total phosphorus followed the pattern for stratified eutrophic lakes, and total nitrogen was quite high. The stoichiometric N:P ratio fluctuated between 25 and 81. The dynamics of phytoplankton biomass with a spring peak from April to May and a late summer peak from July to August is typical of Estonian eutrophic lakes. Green algae and chrysophytes occurred in the phytoplankton throughout the vegetation period. The spring peak was dominated by diatoms (Synedra ulna and Synedra acus var. angustissima) and the summer peak was caused by Aphanizomenon klebahnii and Ceratium hirundinella. The study showed that in physically stratified systems, the total concentration of limiting resources and plain physical factors (light and temperature) may be more important in the determination of phytoplankton dominants than different resource ratios. A combination of light and temperature optimum, along with nutrient utilization and transport capacity, effectively segregates phytoplankton species and can be used for the explanation of seasonal succession pattern.     

Phytoplankton periodicity of the Waitaki Lakes,New Zealand

The Waitaki River system in the South Island of New Zealand includes three large glacially-formed headwater lakes, Tekapo, Pukaki and Ohau, which drain into the manmade Lake Benmore. Phytoplankton periodicity was followed from December 1975 to January 1980 as part of a study investigating possible changes in these lakes as a consequence of hydroelectric development. The phytoplankton was highly dominated by diatoms, e.g., Diatoma elongatum, Cyclotella stelligera, Asterionella formosa, and Synedra acus, but in lakes Ohau and Benmore populations of green algae occasionally developed. In all four lakes seasonal phytoplankton periodicity was observed with maximum biomass in spring and summer. In Lake Tekapo, the first lake in the chain, maximum biomass did not exceed 300 mg m^–3, but in the very turbid Lake Pukaki the maximum summer biomass ranged between 300 and 800 mg m^–3. In Lake Ohau, the least turbid lake, maximum biomass was around 1 000 mg m^–3. In the newly created Lake Benmore periodicity was less evident and summer maxima reached over 1 500 mg m^–3. The phytoplankton periodicity in these lakes is greatly influenced by seasonal patterns of turbidity from inflowing glacial silt.     

EPIPELIC AND EPILITHIC DIATOM ASSEMBLAGES IN MONTEZUMA WELL NATIONAL MONUMENT,ARIZONA1

Epipelic and epilithic diatom assemblages in Montezuma Well National Monument, Arizona, were identified and analyzed by H' (species diversity), species number, J' (evenness), relative abundance, SIMI (similarity index), and DI (dissimilarity index) values. The epipelic assemblage was found to be a tri-dominant association of Cyclotella pseudostelligera f. parva Czar. & Blinn, Cocconeis placentula var. lineata (Ehr.) V.H. and Achnanthes linearis (W. Sm.) Grun. The epilithic assemblage was a tri-dominant association of Rhoicosphenia curvata (Kütz.) Grun. ex Rabh., Cy. Pseudostelligera f. parva and Synedra ulna (Nitz.) Ehr. Both associations persisted throughout the year. Of the 83 taxa observed, 51 were common to both assemblages, 24 were restricted to the epipelon, and 8 were restricted to the epilithon. On a yearly basis, the epipelic assemblage exhibited less diversity (H') than the epilithon, even though the latter exhibited fewer taxa. The use of mean diversity values was also determined to be unacceptable. Cy. Pseudostelligera f. parva and S. ulna appeared more abundant under high light intensity and duration, Fragilaria construens var. venter (Ehr.) Grun. favored low light intensity and duration, whereas A. linearis, R. curvata and Co. placentula var. lineata were tolerant of a variety of intensities and durations. On a yearly basis, both assemblages exhibited slight similarity (SIMI, DI). The use of SIMI values for comparing assemblages with few highly abundant taxa was determined to be unacceptable and under these conditions, the use of DI was recommended.     

The composition and abundance of phytoplankton in Lake Bukoni,western Uganda

Lake Bukoni is one of the crater lakes in western Uganda. Investigations into this lake is limited compared to other African lakes. Data on phytoplankton ecology in the lake are lacking. Phytoplankton consists of a community of photosynthetic, microscopic plants adapted to suspension in water. They constitute ‘hidden flora’ which make an important contribution to the primary productivity of a water mass. Some phytoplankton taxa, among them species belonging to Cyanophyta, are known to influence ecological transformations and to cause health hazards in water bodies that are used by humans. From July 2004 to December 2005, phytoplankton was collected from two sites (inshore and offshore) in Lake Bukoni. An inverted microscope, Sedgwick counting chamber and multiple tally denominator were used to quantify the phytoplankton. Phytoplankton was dominated by nonheterocystous cyanoprokaryotes especially Lyllgbya limnetica followed by the diatoms Synedra ulna and Fragillaria mutabilis. The inshore site had more phytoplankton species. Differences in phytoplankton diversity and density were mainly attributed to mixing and presence of macrophytes. The occurrence of large numbers of cyanoprokaryotes poses a potential health hazard to the local people who utilize the water from Lake Bukoni. The dominance of cyanoprokaryotes might result in ecological transformations like loss of biodiversity.     

Characteristics of nutrient dynamics in Lake Sagate,Japan, a shallow sand dune lake

We examined differences in digestibility and viability following gut passage through water penny larvae (Psephenus herricki) of Synedra ulna and Achnanthidium lanceoloatum, two common diatom taxa that differ in growth habit and autecological characteristics. Prior to the experiment, diatoms were cultured in Chu-10 media in petri plates to establish a monospecific biofilm to offer grazers. After collection, insects were left to clear their guts over night, allowed to graze for 3 hours on diatom biofilms, and then placed in vials over 1-mm mesh to defecate. Samples from source material and from insect feces were mounted in syrup media and the ratio of chloroplast-containing to empty diatom frustules was microscopically assessed. In addition, subsamples from source material and feces were sprayed onto agar plates prepared with Chu-10 and individual cells were mapped and tracked for 5 days to quantify reproduction. Cells of both S. ulna and A. lanceolatum taken from source material formed colonies on agar. Achnanthidium lanceolatum cells from insect feces also formed colonies, but with lower densities than those from source material. In contrast, none of the S. ulna cells tracked from fecal cultures formed colonies, and the percentage of S. ulna cells that were dead was significantly greater in feces relative to source material. Dead cell percentages of A. lanceolatum were also higher in feces relative to source material, but to a lesser degree than observed for S. ulna. These findings have potential implications for linking patterns of energy transfer in stream ecosystems and the structure and dynamics of benthic microalgal communities.     

Longitudinal Changes in the Bacterial Community Composition of the Danube River: a Whole-River Approach

The Danube River is the second longest river in Europe, and its bacterial community composition has never been studied before over its entire length. In this study, bacterial community composition was determined by denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified portions of the bacterial 16S rRNA gene from a total of 98 stations on the Danube River (73 stations) and its major tributaries (25 stations), covering a distance of 2,581 km. Shifts in the bacterial community composition were related to changes in environmental conditions found by comparison with physicochemical parameters (e.g., temperature and concentration of nutrients) and the concentration of chlorophyll a (Chl a). In total, 43 distinct DGGE bands were detected. Sequencing of selected bands revealed that the phylotypes were associated with typical freshwater bacteria. Apparent bacterial richness in the Danube varied between 18 and 32 bands and correlated positively with the concentration of P-PO₄ (r = 0.56) and negatively with Chl a (r = −0.52). An artificial neural network-based model explained 90% of the variation of apparent bacterial richness using the concentrations of N-NO₂ and P-PO₄ and the distance to the Black Sea as input parameters. Between the cities of Budapest and Belgrade, apparent bacterial richness was significantly lower than that of other regions of the river, and Chl a showed a pronounced peak. Generally, the bacterial community composition developed gradually; however, an abrupt and clear shift was detected in the section of the phytoplankton bloom. Large impoundments did not have a discernible effect on the bacterial community of the water column. In conclusion, the riverine bacterial community was largely influenced by intrinsic factors.     

Local effects of a sedentary grazer on stream algae

1. Larvae of the sedentary aquatic caterpillar Petrophila confusalis (Walker) construct silken retreats around which they feed; outside these clearly demarcated grazed areas, stream algae are exposed to a variety of mobile grazers. Comparisons of the algal community inside and just outside grazed zones were made for third- and fifth-instar Petrophila in the South Fork of the Eel River, California. 2. Densities of both the filamentous macroalga Cladophora and diatom assemblages were significantly reduced within the grazed areas during both larval instars. Grazing of diatoms was taxonomically non-selective. 3. In spring, the grazed zones were relatively large (mean = 22.7 cm²) and visibly increased epilithic spatial patchiness. 4. Per cent composition of diatom assemblages inside and outside the grazed areas differed during the third instar but not during the fifth instar. During the third instar, the grazed zone contained more Synedra ulna (a common immigrant) and less Gomphonema olivaceum (a late-successional species).     

Denitrification of a landfill leachate with high nitrate concentration in an anoxic rotating biological contactor

The denitrification performance of a lab-scale anoxic rotating biological contactor (RBC) using landfill leachate with high nitrate concentration was evaluated. Under a carbon to nitrogen ratio (C/N) of 2, the reactor achieved N-NO₃ ⁻ removal efficiencies above 95% for concentrations up to 100 mg N-NO₃ ⁻ l⁻¹. The highest observed denitrification rate was 55 mg N-NO₃ ⁻ l⁻¹ h⁻¹ (15 g N-NO₃ ⁻ m⁻² d⁻¹) at a nitrate concentration of 560 mg N-NO₃ ⁻ l⁻¹. Although the reactor has revealed a very good performance in terms of denitrification, effluent chemical oxygen demand (COD) concentrations were still high for direct discharge. The results obtained in a subsequent experiment at constant nitrate concentration (220 mg N-NO₃ ⁻ l⁻¹) and lower C/N ratios (1.2 and 1.5) evidenced that the organic matter present in the leachate was non-biodegradable. A phosphorus concentration of 10 mg P-PO₄ ³⁻ l⁻¹ promoted autotrophic denitrification, revealing the importance of phosphorus concentration on biological denitrification processes.     

The distribution of temperature,oxygen and nutrients in Lake Bukoni,Uganda

Temperature, oxygen and nutrients were determined in the permanently stratified Lake Bukoni from July 2004 to December 2005. Meromixis has resulted from the nature of the surrounding hilly topography and the almost vertical crater walls that exclude the effects of light winds. These circumstances and the tropical temperature regime ensure permanent stratification in the offshore part of the lake. From about 20 m to the bottom, the water was out of circulation and devoid of oxygen. Water samples from such depths had a strong smell of hydrogen sulphide gas. The inshore site, with greater turbulence and littoral area, had a uniformly oxygenated water column compared with the offshore site. According to information from members of the community around the lake, ‘fish kills’ have taken place but on irregular occasions. The nutrients (N, P and Si) were well distributed in the inshore site. In the offshore site, the concentrations were generally lower in the uppermost 20 m but more than double near the mud surface. Soluble reactive phosphorous was the least abundant nutrient while soluble reactive silicon was the most abundant nutrient. The high Si : P ratios have led to the dominance of species like Synedra ulna Ehr.     

Can bacteria outcompete phytoplankton for phosphorus? a chemostat test

Although the bacterioplankton of lakes are usually considered primarily in terms of mineralization processes, recent studies suggest that they may also strongly compete for phosphorus with the phytoplankton. In the present study, we have tested in chemostat culture, and found support for the hypotheses that (1) a freshwater bacterium (Pseudomonas paucimobilis), whose carbon source is excretion from a phosphorus-limited alga (Synedra ulna var.danica), can outcompete that alga for phosphorus (P) under widely varied P supply rates; (2) exogenously-supplied organic carbon positively influences bacterial biomass and negatively influences algal biomass; (3) the ratio of bacterial to algal phosphorus uptake in short-term³²P orthophosphate uptake experiments is an accurate predictor of their relative long-term phosphorus assimilation (i.e., growth) in mixed culture.     

The use of artificial spawning substrates as media to support the reproduction of Eurasian perch in Lake Piediluco

Lake Piediluco is a naturally regulated lake used for hydroelectric purposes. Management of the lake and the eutrophic conditions of its waters have had a negative impact on fish populations, particularly that of Eurasian perch (Perca fluviatilis L.). In order to increase the natural reproduction of this species, an experimental program was undertaken from 1997 to 2003 to facilitate reproduction by providing artificial spawning substrates. In Lake Piediluco perch spawn from March to May. Egg ribbons ranged in length from 30 to 180 cm and contained from 12,740 to 205,466 eggs. The fraction of degenerated eggs ranged from 0.20% to 63.30% (average 10.20%). The results demonstrate the effectiveness of artificial substrates as suitable substrates for the reproduction of perch. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries