Dynamics of purple sulfur bacteria in a meromictic saline Lake Shunet (Khakassia,Siberia) in 2007–2013

According to the results of seasonal monitoring, in 2007–2013 purple sulfur bacteria morphologically similar to Thiocapsa sp. Shira_1 (AJ633676 in EMBL/GenBank) predominated in the anoxygenic phototrophic community of the water column of the meromictic Lake Shira (Khakassia, Siberia). No pronounced seasonal periodicity in the total cell number in the water column was revealed during the period of observation. In some years cell number during the period when the lake was covered with ice was reliably higher than in summer. The absence of seasonal periodicity was probably due to the low amplitude of seasonal variations in temperature and illumination in the redox zone, resulting from its relatively deep location (12–16 m). The year-to-year dynamics was characterized by a reliable decrease of the total cell number in 2009–2010 and maxima in 2007 and 2011–2012. Canonical correlation analysis revealed that water temperature in the redox zone was the best predictor of the PSB abundance in Lake Shira. Water temperature, in turn, depended on the depth of mixing of the water column. Intense mixing in 2009–2011 was probably responsible for decreased PSB abundance in the lake. On the other hand, the absence of deep winter mixing, resulting in stable conditions in the chemocline, favored the preservation of relatively high PSB biomass. Prediction of circulation depth, which depends mainly on the weather conditions and dynamics of the water level, is required for prediction of PSB abundance in Lake Shira. These results may be useful for paleolimnological reconstructions of the history of the lake based on the remnants of purple sulfur bacteria in bottom sediments.     

Some generalizations based on stratification and vertical mixing in meromictic Lake Shira,Russia, in the period 2002–2009

In a brackish, temperate, 24-m-deep Lake Shira, the profiles of salinity, temperature, oxygen and sulfide concentrations were measured on a seasonal basis from 2002 to 2009. The lake was shown to be meromictic with autumnal overturn restricted to mixolimnion. The depth of mixolimnion and position of oxic–anoxic interface varied annually. The spring mixing processes contribute to the formation of mixolimnion in autumn. The exceptionally windy spring of 2007 caused the deepening of mixolimnion in the winter of 2008. The winter position of oxic–anoxic interface was affected by the position of lower boundary of mixolimnion in all winters. The salinity in the winter mixolimnion increased compared with the autumn because of freezing out of salts from the upper water layers meters during ice formation and their dissolution in water below. The profiles of salinity and temperature were simulated by the mathematical 1-D model of temperature and salinity conditions taking into account ice formation. The simulated profiles generally coincided with the measured ones. The coincidence implies that simplified one-dimensional model can be applied to roughly describe salinity and density profiles and mixing behavior of Lake Shira.     

Seasonal Rotifer Dynamics in the Long-term (1969–2002) Record from Lake Kinneret (Israel)

Long-term (1969–2002) data record of biomass distribution of rotifers in Lake Kinneret is combined with previously published information on their metabolic activity and newly calculated population dynamics parameters to synthesize a model of their seasonal dynamics in Lake Kinneret. Nineteen rotifer species were recorded in routine samples collected in Lake Kinneret (Israel) in 7 offshore (deeper than 5 m), stations, at 12 discrete depths during 1969–2002. Organisms were sorted and counted (including external egg carrying females), biomass was measured and calculated for the entire lake stock (g_w.w m⁻²; mg l⁻¹). Rates of grazing, respiration and production were measured experimentally at three different temperature ranges. Results were extrapolated to the lake community for months with similar temperatures. Rotifera comprised 7% of total zooplankton biomass in Lake Kinneret whilst Cladocera and Copepoda 58 and 35% respectively. Rotifers were found to be more abundant during December–June and decline in summer months. Monthly (1969–2001) means indicated total grazing capacity of rotifers as 11%, respiration as 9% and production as 3.7% of the total zooplankton metabolic activity. Positive relations were indicated between rotifer and small bodied cladoceran numerical concentrations. Population growth models suggest that rotifers are not food limited in Lake Kinneret but that fish predation plays an important role in regulating abundance in spring-summer and fall.     

Phylogenetic analysis of the non-structural (NS) gene of influenza a viruses isolated in Kazakhstan in 2002–2009

Although the important role of the non-structural (NS1 and NEP) gene of influenza A in virulence of the virus is well established, our knowledge about the extent of variation in the NS gene pool of influenza A viruses in their natural reservoirs in Kazakhstan is incomplete. 17 influenza A viruses of different subtypes were studied in this paper. Seven types of haemagglutinin and five different neuraminidase subtypes in eight combinations were found among the isolated viruses. A comparison of nucleotide sequences of isolated viruses revealed a substantial number of silent mutations, which results in high degree of homology in amino acid sequences. By phylogenetic analysis it was shown that two distinct gene pools, corresponding to both NS allele A with 5 Clades and B, were present at the same time in Kazakhstan. The degree of variation within the alleles was very low. In our study allele A viruses had a maximum of 5% amino acid divergence in Clade while allele B viruses had only 4% amino acid divergence.     

Hydrochemical balance of Itkul–Shira lake system (Khakassia,Russian Federation)

The water and hydrochemical balance of Shira and Itkul lakes, located in the arid (steppe) zone in the Republic of Khakassia (Russian Federation), has been calculated. It is shown that Lake Itkul can be considered a drained lake, which significantly determines the basic differences of the hydrochemical balance in the two water bodies. The outflow of water from Itkul to Shira is, on average, 6791000 m3/year, and the average outflow of dissolved salts is 35697 t/year. Lake Shira can be considered a drainless water body with an evaporation mechanism of formation of the chemical composition of its waters, and Lake Itkul is considered a flowing water reservoir. The salt concentration in Itkul is not as high as that in Shira due to the lower influence of evaporation on the formation of the chemical composition of waters and time of their interaction. It has been assumed that this phenomenon is regular, rather than exceptional, for the arid zone of Northern and Central Asia.     

Seasonal changes in the waters of Lake Chilwa (Malawi) in a drying phase, 1966–68

Summary Lake Chilwa, Malawi (lat. 15°S; long. 36°E) has a potential area of open water of 700 km²; it is shallow and has no outlet. The lake level fluctuates in height with alternate wet and dry seasons, and the mean annual level rises and falls over a 6-year period. This study was conducted from the end of the wet season of 1966 to the end of the dry season of 1967, which was at the end of the 6-year cycle, and it preceded the complete drying of the lake in 1968 and its recovery in 1969, an event which last happened in 1922–23.Forthnightly samples of water were examined for electrical conductivity, sodium, potassium, calcium, magnesium, iron, chloride, alkalinity, sulphate, phosphate, silicate, nitrite, nitrate, albuminoid nitrogen, dissolved oxygen, pH and temperature.The lake water is characterized by chloride being half the concentration (in me/l) of sodium and equal to alkalinity. The conductivity initially 4210 µmho/cm, increased by a factor of 3 in 1966 and by 4 in 1967. Calcium and magnesium carbonate were precipitated in the hot dry months. The effect of a cyclone was to dilute the surface waters 20 times less than the previous month. The water was supersaturated with oxygen, except in the coolest months. The temperature varied between 21°C and 37°C and the pH between 8 and 11 units.The pattern of chemical factors depends on dilution and concentration due to climatic influences, on interactions of some ions with the biota, with each other and in some cases with the exposed mud. The significance of this pattern for the biology of the lake is discussed. The ionic composition is compared with that of other African lakes.This study, during an atypical period, is intended to assist plans to conserve the fishing industry, which in years of high lake level produces almost half the total catch of the country.

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Résumé Le Lac Chilwa, Malawi (lat. 15°S; long. 36°E) a une aire potentielle d'eau de 700 km²; le lac est peu profond et n'a pas de sortie. Le niveau du lac varie en hauteur selon les saisons humides et sèches qui se succédant, et le niveau moyen se lève et tombe pendant une période de six ans. L'étude du lac a eu lieu depuis la fin de la saison humide en 1966 jusqu'à la fin de la saison sèche en 1967. Cette étude se faisait à la fin d'une période de six ans et précédait le désèchement complet du lac en 1968 et son rétablissement en 1969, une situation qui a eu lieu pour la dernière fois en 1922–23.Tous les quinze jours on a examiné des échantillons d'eau quant à conductivité électrique, sodium, potassium, calcium, magnésium, fer, chloride, alcanité, sulfate, phosphate, silicium, nitrite, nitrate, substance albuminoide, oxygène dissolu, pH et température.L'eau du lac est caracterisée par chloride étant un demi-concentration (en me/l) de sodium et égale aux substances alcalines. La conductivité, au commencement 4210 umho/cm, a été augmentée par un facteur de 3 en 1966 et par 4 en 1967. Calcium et magnésium carbonate étaient précipites pendant les mois chauds et secs. L'effect d'un cyclône devait les eaux superficielles vingt fois moins que le mois précédent. L'eau était sursaturée d'oxygène, exceptépendant les mois plus froids. La température variait entre 21°C et 37°C et le pH entre 8 et 11 unités.La variation de facteurs chimiques dépend de la dilution et de la concentration dues aux influences climatologiques, des interactions de quelques ions avec les biota, mutuellement et en certain cas, avec la vase exposée. La signification de cette variation pour la biologie du lac est discutée. La composition ionique se compare avec celle d'autres lacs africains.Cette étude, pendant une période non-caractéristique, a pour but de soutenir des projets pour conserver l'industrie de poisson qui pendant les années ou le niveau du lac est haut produit à peu près la moitié de la prise totale du pays.

     

Ecology and Phenology of Freshwater Ostracods in Lake Gölköy (Bolu,Turkey)

Seventeen ostracod species were recorded from Lake Gölköy (Bolu, Turkey) between January 2000 and December 2001. Limnocythere inopinata is a new record for the Bolu region. Canonical Correspondence Analysis (CCA) explained 73% of the correlation between species and environmental variables, suggesting that the occurrence of many species is temporally variable, and is related to seasonal changes in physico-chemical conditions. The four most frequently occurring cosmopolitan ostracod species (Candona neglecta, Darwinula stevensoni, Physocypria kraepelini, and Cypridopsis vidua) accounted for more than 70% of the species recorded. Water temperature, dissolved oxygen (DO), and redox potential were the most affective variables on the species occurrence. Two species (C. vidua, I. bradyi) were positively correlated to redox potential, while such a correlation was negative for P. kraepelini. The most frequently occurring species C. neglecta was most closely related to the changes in redox potential, whereas C. vidua and D. stevensoni showed a positive correlation to water temperature. Negative strong correlation (p<0.01) was found between pH and I. bradyi, but correlation was positive and weak for C. vidua. Some species (e.g. L. inopinata) showed no clear relationship with any of those environmental variables. UPGMA clustering of species based on their occurrence in different ecological conditions revealed three main species assemblages. Analysis of species phenology using the ‘Ostracod Watch Model’ showed that temporal patterns of occurrence could be similar among species with similar ecological preferences. The current status of the lake is discussed based on the present study.     

Annual pollen spectrum variations in the air of Bratislava (Slovakia): years 2002–2009

Pollen grains in the atmosphere of Bratislava were quantitatively and qualitatively analysed during an 8-year period (2002–2009) using a Burkard volumetric pollen trap. The mean annual total pollen grain count recorded during this period was 36,608, belonging to 34 higher plant taxa (22 trees and/or shrubs and 12 herbaceous species). The maximum annual total pollen grain count (50,563) was recorded in 2003 and the minimum (14,172) in 2009. The taxa contributing the highest concentration of pollen grains were Betula, Urticaceae, Cupressaceae-Taxaceae, Populus, Pinus, Poaceae and Ambrosia. During the study period, there was a remarkable increase in the number of pollen grains from February to April, with the highest daily mean pollen counts recorded in April. Total pollen concentration began to decrease markedly in May, but there was a second increase between July and August, followed by a decrease in September. The timing and length of the pollen seasons varied. Betula and Poaceae showed a rather constant 2-year fluctuating rhythm. The relationships between airborne pollen concentration and meteorological variables were assessed. Based on these results, the first pollen calendar in Slovakia has been constructed for the area of Bratislava, which provides a great deal of useful and important information.     

Stability and change of phytoplankton communities in a highly dynamic environment—the case of large,shallow Lake Balaton (Hungary)

Time series data of key environmental variables (water temperature, global radiation, vertical light attenuation, internal P load) and biomass of four colour classes of photosynthetically active algae were collected during 2003 and 2004 with daily resolution. Using these data, seasonal patterns of phytoplankton were analyzed as a function of the dynamic environment. Abstraction of the environmental state as a point in multi-dimensional space was used to identify habitat templates of bloom-forming groups and derive an indicator of environmental stability/physical disturbance. These templates were synthesized into a simple threshold model that sufficiently simulated development and collapse of various blooms. Blooms were, however, rare events related to specific environments with strong, unidirectional forcing. Tentative quantification of disturbance and compositional stability/community change allowed discriminating disturbance-driven changes and autogenic succession with reasonable success. The two processes were found to be equally important in shaping the composition and biomass of phytoplankton.     

Specific carbonate–microbe interactions in the modern microbialites of Lake Alchichica (Mexico)

The role of microorganisms in microbialite formation remains unresolved: do they induce mineral precipitation (microbes first) or do they colonize and/or entrap abiotic mineral precipitates (minerals first)? Does this role vary from one species to another? And what is the impact of mineral precipitation on microbial ecology? To explore potential biogenic carbonate precipitation, we studied cyanobacteria–carbonate assemblages in modern hydromagnesite-dominated microbialites from the alkaline Lake Alchichica (Mexico), by coupling three-dimensional imaging of molecular fluorescence emitted by microorganisms, using confocal laser scanning microscopy, and Raman scattering/spectrometry from the associated minerals at a microscale level. Both hydromagnesite and aragonite precipitate within a complex biofilm composed of photosynthetic and other microorganisms. Morphology and pigment-content analysis of dominant photosynthetic microorganisms revealed up to six different cyanobacterial morphotypes belonging to Oscillatoriales, Chroococcales, Nostocales and Pleurocapsales, as well as several diatoms and other eukaryotic microalgae. Interestingly, one of these morphotypes, Pleurocapsa-like, appeared specifically associated with aragonite minerals, the oldest parts of actively growing Pleurocapsa-like colonies being always aragonite-encrusted. We hypothesize that actively growing cells of Pleurocapsales modify local environmental conditions favoring aragonite precipitation at the expense of hydromagnesite, which precipitates at seemingly random locations within the biofilm. Therefore, at least part of the mineral precipitation in Alchichica microbialites is most likely biogenic and the type of biominerals formed depends on the nature of the phylogenetic lineage involved. This observation may provide clues to identify lineage-specific biosignatures in fossil stromatolites from modern to Precambrian times.     

In vivo role of adenosine-5′-phosphosulfate reductase in the purple sulfur bacterium Allochromatium vinosum

Adenosine-5'-phosphosulfate (APS) reductase participates in the oxidation of sulfite to APS in Allochromatium vinosum. Oxidation of sulfite via the APS pathway yields ATP through substrate-level phosphorylation. An alternative enzyme for the oxidation of sulfite to sulfate, sulfite:acceptor oxidoreductase, has also been reported in Ach. vinosum. Oxidation of sulfite through this enzyme does not yield ATP. APS reductase is expressed constitutively in Ach. vinosum, suggesting that it performs an important role in this organism. However, studies carried out with batch cultures of an APS reductase mutant showed little or no differences in growth or in the rates of substrate oxidation when compared to the wild-type, therefore questioning the role of this enzyme. In an attempt to establish whether the ATP gain derived from APS-reductase-mediated oxidation of sulfite is relevant for energy-limited cultures, we compared growth of the wild-type SM50 and the APS-reductase-deficient mutant D3 when grown in continuous culture under different degrees of illumination. Little differences in the specific growth rates of the two strains were observed at light-limiting irradiances, suggesting that the ATP gained during sulfite oxidation through the APS reductase pathway does not constitute a significant energy input. However, at saturating irradiances, wild-type Ach. vinosum grew considerably faster than the mutant. Increasing the irradiance even further resulted in inhibition of the wild-type strain down to the level of the APS reductase mutant. The implications of these results are discussed.     

The influence of road salts on the salinity and the meromictic stability of Lake Svinsjøen,southeastern Norway

Primarily as a result of road salting, the water masses ofLake Svinsjøen, a small meromictic lake in southeasternNorway, have been subject to great changes in salinity duringthe period 1947–1995. The greatest change in saltconcentration has occurred in the upper part of themonimolimnion (depth 10–15 m) where mean conductivityincreased 104.2 per cent, from 143 to 292 S cm^–1. Inthe upper mixolimnion (depth 0-5 m), mean conductivity rosefrom 130 to 238 S cm^–1 during the same period. Theions responsible for the salinity changes were Na⁺ andCl^– from de-icing salts, and Ca²⁺ and Cl^– fromsalts used to keep down dust from roads. Further sources ofCa²⁺ are the road asphalt and increased weathering andleaching of the lime-rich rocks caused by acid precipitation,the main source of the additional inputs of SO tothe lake. The salinity changes caused major changes inmeromictic stability, S . In the period1947-1966, S increased by 24 g cm cm^–2,and the maximum level of meromictic stability, 125 gcm^–2, was found in 1966. As a result of higher rate ofsalt accumulation in the upper part of the monimolimnion andin the mixolimnion, S decreased by 30 g cmcm^–2 during the period 1966-1991, and a simultaneousrise in the chemocline took place. In the period 1991-1995 anadditional decrease of 26 g cm cm^–2 occurred. Continuedectogenic inputs of salts through processes typical of thetime period investigated will in future further weaken thelake's meromictic stability, and may cause the demise ofmeromixis in Lake Svinsjøen, a development which may haveimportant implications for primary productivity of thelake.     

Ecology,morphology and physiology of Chroothece richteriana (Rhodophyta,Stylonematophyceae) in the highly calcareous Río Chícamo,south-east Spain

The ecology of Chroothece was studied in the highly calcareous Río Chícamo, south-east Spain, in order to explain its success there, but rarity elsewhere. The river, which originates mainly from an underground aquifer, has water with high conductivity, sulphate and nitrate but low phosphate concentrations, the latter mainly organic. Chroothece occurs in mats and in lobed colonies reaching 4 cm in the broadest dimension. The colony surface consists of one layer of cells, each of which is attached to a stalk, which dichotomizes when the cell divides; stalks often extend to the colony base. The central region of many mat cells and almost all colony cells has a yellow to orange-brown colour, associated with the numerous lipid droplets densely covering the surface of the pyrenoid and arms of the star-shaped chloroplast. Field material and laboratory isolates indicate that stalk formation occurs under moderate P limitation and both stalks and cell sheath show high phosphatase activities. This also occurred in a culture collection strain maintained for 30 years in a very P-rich medium, but then transferred to a moderately P-limiting medium (c. 0.9 mg l^?1). We suggest that colony formation is initiated by aggregation of motile cells following P pulses in the water. Comparisons are made with Rivularia, a competitor in this nitrate-rich river, in spite of being a N₂-fixer. One difference is that Chroothece cells lie at the periphery of the colonies and are therefore exposed to maximum sunlight, whereas Rivularia trichomes grow inside colonies with photoprotection by scytonemin. However, the ability to withstand heavy grazing pressure may be an especially important factor favouring Rivularia here.     

Variability of the start of the growing season in Fennoscandia, 1982–2002

Fennoscandia is characterized by a large degree of climatic diversity. Vegetation phenology may respond differently to climate change according to the climatic gradients within the region. To map the annual and spatial variability of the start of the growing season (SOS) in Fennoscandia, the twice-monthly GIMMS-NDVI satellite dataset was used. The data set has an 8 × 8 km² spatial resolution and covers the period from 1982 to 2002. The mapping was done by applying pixel-specific threshold values to the NDVI data. These threshold values were determined form surface phenology data on birch (Betula sp.). Then, we produced NDVI based maps of SOS for each of the 21 years. Finally, the time differences between the SOS and the last day of snow cover, as well as dates of passing different temperatures, were analyzed for 21 meteorological stations. The analyses showed that 1985 was the most extreme year in terms of late SOS. In terms of early SOS, the year 1990 was by far the most extreme. Locally, the SOS has an average range of 1 month between the earliest and latest recorded SOS, with a trend towards a bigger range in the oceanic parts. The results indicate that a 1°C increase in spring temperatures in general corresponds to an advancement of 5–6 days in SOS. However, there is a clear trend according to the degree of oceanity, with a 1°C increase in the most oceanic parts corresponding roughly to 7–9 days earlier SOS, compared to less than 5 days earlier in the continental parts.     

Airborne bacteria in Kuwait (1986–1988)

Totally 341 outdoors air samples were taken by Casella Airborne Sampler at a height of 7 m in the Allergy Centre of Kuwait between 1986 and 1988. Bacillus was detected in 85.3% of the samples. Micrococcus (71.3%), Staphylococcus albus (65.4%). Gram-positive rods (53.4%) were more prevalent than gram-negative rods (23.7%). Higher counts were seen in 1986 (500 CFU m^?3) compared to 1987 (407 CFU m^?3) and 1988 (369 CFU m^?3). Relatively higher counts were seen in August and September and a smaller peak was found in February and March. The correlation between the various types was always positive and was frequently highly significant. High counts were seen with strong winds. Among the meteorological factors, wind speed was the only significant factor. High average of bacteria counts were found when winds were blowing from the land (574 CFU m^?3) compared with the sea (346.5 CFU m^?3). Higher average counts were observed in the days with sand storms (1769 CFU m^?3), with rising sand (534.8 CFU m^?3) and the other days with dust phenomena, compared with clear weather (317 CFU m^?3).     

Lake–peat bog transformation recorded in the sediments of the Stare Biele mire (Northeastern Poland)

The history of Stare Biele paleolake (northeast Poland) has been reconstructed using subfossil Cladocera remains and pollen and spores of aquatic and mire plants from a sediment core. Sediment accumulation began approximately 12,000 years ago during the Older Dryas chronozone. Throughout the entire Late Glacial period, the basin was a small, low-trophic state lake with a developed open-water zone. A well-recorded increase in the trophic state started at the beginning of Holocene. The lake reached its highest trophic level during the early and middle Atlantic chronozone. The first human activity in the lake catchment area occurred at this time, as recorded by fern spores and numerous charcoal grains. Repeated rises in lake water level are documented at the beginning and throughout the early part of the Younger Dryas. Two clear events of decreasing lake water levels are recorded, first during the middle part of the Younger Dryas and second in the Preboreal. Terrestrialization processes first intensified at the end of Atlantic period, which appears to correspond to a decrease in pH. Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water