Microclimate and evapotranspiration in two wet grassland communities

Vertical profiles of soil temperature and of the dry and wet bulb temperature of the air, relative humidity and wind velocity were measured within and above stands ofJunco-Molinietum Preising 1951 (facies ofDeschampsia caespitosa) andCaricetum gracilis Almquist 1929 on selected sunny days during the growing season. Evapotranspiration was computed by means of the heat-budget equation. The principal difference between the two communities has been found in the soil temperature. The stand of theCaricetum gracilis occupies a habitat with a cooler soil and with a higher ground water level than the stand of theJunco-Molinietum coeruleae, facies ofDeschampsia caespitosa. The evapotranspiration per unit ground area was higher by some 20% in theCaricetum gracilis. The evapotranspiration per unit above-ground biomass was much the same in both communities.     

Factors governing the spatial and temporal distribution of Chironomid larvae in the Maarsseveen lakes with special emphasis on the role of oxygen conditions

Distribution patterns of the larvae of Chironomidae are compared in three water systems in The Netherlands, which vary in trophic state and oxygen regimes. The life cycles and flying periods of some dominant chironomid species in two of the investigated lakes, Lakes Maarsseveen I and II, are determined by comparing data on the seasonal variations in larval densities with existing literature on Chironomidae in the Maarsseveen lakes. In the oligo-mesotrophic Lake Maarsseveen I (LM I), hypoxic or anoxic conditions in the hypolimnion are observed only at the end of the stratification period. A clear zonation of the chironomid fauna is present in this lake. The littoral zone is dominated byCladotanytarsus gr.mancus andStictochironomus sticticus, the littoriprofundal zone byTanytarsus bathophilus, and the profundal zone byChironomus anthracinus. In comparison with the other species in LM I,T. bathophilus larvae show the most variable distribution patterns over time. Larvae are found in all depths from July to September, but disappear from the hypolimnion as soon as oxygen conditions deteriorate. In the eutrophic Lake Maarsseveen II (LM II), oxygen depletion of the hypolimnion starts immediately after the onset of the thermal stratification in June, and continues until autumnal turnover in November. In this lake, the chironomid community consists primarily ofS. sticticus andCl. gr.mancus, and is confined to the narrow littoral zone. No chironomid larvae are found in the deeper parts of the lake. The eutrophic Lake Gijster in the Brabantse Biesbosch is a deep, man-made reservoir, that is artificially destratified during the summer. In this lakeTanytarsus bathophilus is found in the profundal sediments, whereas almost noChironomus is found in this zone. It is concluded that oxygen conditions existing in the deeper regions of the investigated lakes in large part determine the occurrence and distribution of chironomid species. The distribution ofT. bathophilus is limited by unfavorable oxygen conditions and not by the trophic state of the lake. These findings are part of a thesis (HEINIS, 1993).     

Evolutionary trends in Mio-Pliocene Leporinae, based onTrischizolagus (Mammalia, Lagomorpha)

New material ofTrischizolagus dumitrescuae from Moldova and Ukraine is described. The variation of p3 inTrischizolagus shows the gradual shift of morphotype frequencies from the ‘Hypolagus’ pattern in Turolian through the mixture of three patterns (including ‘Nekrolagus’ morphotype) in Early Ruscinian to the dominant ‘Alilepus’ pattern in the Late Ruscinian samples. These transformations took place parallel to that of the North AmericanNekrolagus. Probably North AmericanSylvilagus, Brachylagus, andRomerolagus had an North American origin fromNekrolagus, whereas Eurasiatic and AfricanOryctolagus, Caprolagus, Nesolagus, andPoelagus could have originated in the Old World fromTrischizolagus.     

The subdivisions of Magnistipula Engl. (Chrysobalanaceae)

A conspectus of the subgenera and sections ofMagnistipula is provided. Of the two subgenera occurring on the African mainland, subgenusMagnistipula is divided into the sectionsMagnistipula,Animalculum andPeregrinator, whereas subgen.Pellegriniella is monotypic. A Malagasy subgenus,Tolmiella, is new; its two species,M. cerebriformis andM. tamenaka, are transferred fromHirtella.     

Stem aerenchyma as a character separating hymenachne and sacciolepis (Gramineae,Panicoideae)

Hymenachne andSacciolepis, two closely related tropical genera, have been distinguished by the saccate second glume in the latter, a trait lacking in the former. It is difficult to assign certain species to genus on this basis alone. A survey of both genera showed that aerenchyma fills the stem pith region ofHymenachne species but is absent or nearly so fromSacciolepis species. The leaf epidermis ofHymenachne bears prickle cells, which have not been reported fromSacciolepis. Additional anatomical details are given forH. amplexicaulis.     

About the finding of Pallasiola quadrispinosa (G.O. Sars, 1867) (Gammaridae: Amphipoda) in Lake Vishtynetskoye (Kaliningrad region)

Lake Vishtynetskoye is the only water body in Kaliningrad region where the glacial freshwater relict Pallasiola quadrispinosa (G.O. Sars, 1867) inhabits. Amphipods were recorded in the littoral zone of the lake in autumn and winter 2008. In the biotope with silty shell limestone, amphipods were recorded only in winter (20 ind./m²). The abundance of P. quadrispinosa was 200 ind/m² in autumn and 60 ind/m² in the biotope of sand with overgrowths of water horsetail in winter. At present amphipod, P. quadrispinosa is registered in 12 lakes of Vishtynetsky (Suwalki) Upland.     

Structure and dynamics of zooplankton communities in the littoral zone of some North Carolina lakes

Species composition and seasonal, dynamics of zooplankton in the littoral zone were studied in three piedmont North Carolina lakes for one year. Nygaard's compound index indicated oligotrophic conditions in Belews Lake and eutrophic conditions in Salem Lake and Lake 150. A total of 32 species of zooplankton were found in the samples. Significantly fewer species of truely littoral zooplankton were present in the oligotrophic lake regardless of season (P < 0.05). Eutrophication appears to favor increased diversity in zooplankton of the littoral zone. Habitat heterogeneity, provided by a well developed littoral zone containing aquatic macrophytes, may be the major factor contributing to the maintenance of more taxa of zooplankton in eutrophic systems.Distinct taxa of Cladocera and Copepoda are present in the littoral zone, exhibiting seasonal dynamics that are largely different from the limnetic fauna. Such dynamics may result from predation by characteristically limnetic species of cyclopoid copepods which seek prey in the littoral zone. The numerical and seasonal abundance of predators and prey are inversely related and the true littoral taxa, represented in the present study by the genera Alona, Chydorus, Pleuroxus, Sida, Simocephalus, and Eucyclops, contained no predaceous species. The seasonal dynamics of these genera are very similar even in widely separated geographical regions, indicating that the factor(s) responsible operate independently of climatic and chemical variables. Intrazooplankton predation appears to be a more plausable explanation than segregation along depth which, although consistent with data from studies of limnetic waters, cannot be related to populations of zooplankton in shallow littoral areas.     

Communities of charophytes in water bodies and water courses in the north of the endorheic basin of the Ob-Irtysh interfluve (Western Siberia)

As a result of investigations in 60 lakes in the north of the endorheic basin of the Ob-Irtysh interfluve (Western Siberia) in 2001–2009, nine syntaxa (types of plant communities) of the association rank were distinguished using the Braun-Blanquet approach: Charetum fragilis, C. contrariae, C. intermediate, C. tomentosae, C. asperae, Nitellopsidetum obtusae, Charetum canescentis, C. altaicae, and C. vulgaris. The relatively low coenotic diversity is due to the predominance of brackish and saline lakes in the surveyed area. Charetum fragilis is the most common in the forest-steppe zone; Charetum tomentosae and Charetum canescentis are frequent in the steppe zone. The ranges of salinity for charophytes species and communities have been estimated. Charophytes in the studied area grew successfully and formed communities in eutrophic and even hypertrophic waters.     

The vertical distribution and abundance of <Emphasis Type="Italic">Gammarus lacustris</Emphasis> in the pelagic zone of the meromictic lakes Shira and Shunet (Khakassia,Russia)

The vertical distribution and abundance of Gammarus lacustris in the pelagic zone of two fishless meromictic lakes, L. Shira and L. Shunet, in Southern Siberia (Russia), was studied with the underwater video recording system and using vertical hauls. In both lakes, during summer stratification, Gammarus was distributed non-homogenously, with a stable peak in the metalimnion. The average depth of Gammarus population in the pelagic zone was significantly correlated with the depth of the thermocline. Gammarus abundances obtained using vertical plankton hauls with net were quite comparable with those obtained from video records. The peak abundance of Gammarus in the pelagic zone of the lakes observed with underwater video amounted up to 400 individuals m⁻², while the peak animal densities in the metalimnion reached 50 ind. m⁻³. The data are compared with previously published abundances of Gammarus in the littoral of Lake Shira. Both littoral and pelagic can be equally important habitats for amphipods in meromictic lakes. The absence of fish in the pelagic zone, high oxygen concentration, low water temperature, increased seston concentration, elevated water density in the metalimnion and the anoxic hypolimnion can be the most probable combination of factors that are responsible for the peak of Gammarus in the metalimnion of these lakes.     

TheAspergillus nidulans geneschsA andchsD encode chitin synthases which have redundant functions in conidia formation

We previously isolated three chitin synthase genes (chsA, chsB, andchsC) fromAspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, namedchsD, fromA. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 ofSaccharomyces cerevisiae and Chs3 ofCandida albicans. Disruption ofchsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae. However, double disruption ofchsA andchsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption ofchsC andchsD caused no defect. Thus it appears thatchsA andchsD serve redundant functions in conidia formation.     

Taxonomic revision of the Kimmeridgian (Upper Jurassic) genusMesosimoceras (Ammonoidea) and institution of the new genusPresimoceras (Ammonitina,Idoceratinae)

Presimoceras is a new genus of Idoceratinae. The biostratigraphical range ofPresimoceras is limited to theStrombecki, Divisum and lower part of theAcanthicum Zone within the Kimmeridgian (in the Southern European sense). The genusMesosimoceras (Idoceratinae) was instituted by Spath (1925), withSimoceras cavouri Gemmellaro as type species; this genus is here emended with the institution ofPresimoceras n. gen. The species groupcavouri-risgoviense is preserved in the emended genusMesosimoceras, while the groupherbichiludovicii-teres is accommodated inPresimoceras on account of the radical and numerous differences and the stratigraphical gap betweenMesosimoceras andPresimoceras. As type species of the new genusAmmonites nodulatus Quenstedt is designated. The new genus is here subdivided into three groups of species:herbichi, ludovicii andteres. Phylogenetically,Presimoceras is derived fromPassendorferia, Mesosimoceras fromNebrodites.     

Benthos of Lake Mikri Prespa (North Greece)

An extensive sampling of Lake Mikri Prespa was carried out in summer 1990, aimed at evaluating benthic abundance, recording the species involved and detecting their response to some environmental variables. Three oligochaete species are endemic to the region,Potamothrix prespaensis, Psammoryctides ochridanus variabilis andPsammoryctides ochridanus typica. The bathymetric curve of the benthos resembles that of eutrophic lakes. A great abundance ofChironomus plumosus andChaoborus flavicans occurred. Four community patterns were revealed by TWINSPAN analysis, division level two, explicitly discriminated by the influence of substrate type, depth, C/N ratio and pH. Species richness and diversity was minimal in the profundal and maximal in the shallows, whilst the equitability index was high in all site groups. Depth and bottom type were the most important variables in defining species distribution. More precisely,Chironomus plumosus, Chaoborus flavicans andPotamothix hammoniensis were ubiquitous, preferring mostly deep waters.Tanytarsus sp.,Einfeldia dissidens, Cladopelma lateralis, Tanypus punctipennis andPotamothrix prespaensis favoured shallower and less productive waters with a bottom rich in decaying plant fragments, and thePsammoryctides species showed a littoral origin and regular occurrence on gravel beds. A few species displayed a particular distribution with changes of depth, C/N ratio and pH.     

Chironomid fauna of the lakes from the Pechora river basin (east of European part of Russian Arctic): Ecology and reconstruction of recent ecological changes in the region

We investigated chironomid fauna of surface sediments and a short sediment core (Bol’shoy Kharbey Lake) from Pechora river basin, Northern Russia. Twenty three investigated lakes have thermokarst, glacial or floodplain origin and are characterised by low mineralization, mostly hydrocarbon-calcium type of water and low concentration of nutrients. Most of the lakes have circumneutral pH around ≤7 and only two lakes are slightly more acidic with pH ≤ 6. Ninety six chironomid taxa were identified in the surface sediments. Distribution of chironomids in the studied region is driven by continentality, mean T_July and рН. Chironomid communities from the core of the B. Kharbei Lake demonstrate the highest similarity with the fauna of the deeper lakes of the glacial origin. The glacial lakes have the highest indices of continentality and the lowest winter temperatures within the investigated data set. The chironomid fauna of the glacial lakes is composed of the profundal, oligotrophic and cold-stenotherm taxa. The fauna of the floodplain and thermokarst lakes is more closely related to T_July and is composed of littoral and phytophilic taxa of meso–or eutrophic waters and moderate temperature conditions. The fauna of the acidic thermokarst lakes considerably differs from the other lakes. Chironomid communities here are represented by tolerant to acidification taxa, and by the typically littoral and shallow water acid-tolerant taxa that apparently also can tolerate acidification. Studied sediment record covers ca last 200 years. The reconstructed T_July during the entire period remain slightly below the modern temperatures. From 1970 reconstructed T_July shows steady increase to the modern level. The reconstructed water depths (WDs) of the lake are higher than today till 1980. The highest WDs are reconstructed for ca 1970. After that the WDs gradually decrease to the modern level. Changes of the WDs are most probably related to changes in the precipitation rate.     

Long-term change of the littoral Cladocera in the Tatra Mountain lakes through a major acidification event

In our study, we focused on littoral Cladocera living and feeding in shallow shore parts of 46 mountain lakes in the Tatra Mountains (Slovakia and Poland). The studied lakes underwent a major acidification event in the 1980s and are now in the process of recovery. Lakes were divided into three categories based on their sensitivity to acidification: 5 extremely sensitive (ES), 11 acid sensitive (AS), and 30 non-sensitive (NS) lakes. In our study, we included historical data from the literature, and data from sediment core and littoral samples, which together represent the evolution of the littoral communities from a pre-industrial period up to the present. In total, 11 littoral species were found belonging to three cladoceran families. Most of the species were members of the family Chydoridae: Alona affinis, A. quadrangularis, A. rectangula, A. guttata, Acroperus harpae, Alonella excisa, A. nana, Chydorus sphaericus, and Eurycercus lamellatus. One species belonged to each family Daphniidae (Ceriodaphnia quadrangula) and Polyphemidae (Polyphemus pediculus). The most numerous littoral taxa were Alona affinis, Acroperus harpae, and Chydorus sphaericus. All species reacted to decreased pH levels during peak acidification in the 1980s by disappearing from most of the lakes of all categories; the only persisting species was Chydorus sphaericus. Most species returned to the lakes when pH started to increase in the 1990s, although their return was noticeably slower in AS lakes. Alona quadrangularis decreased its distribution range over the studied period; Polyphemus pediculus was mostly detected in the 1910s only. The number of species was highest in all lake categories when dwarf pine was present in the lake catchment. On the whole, the littoral community was richest in NS lakes.     

Legionella in aquatic habitats in the Mount Saint Helens blast zone

Illnesses of undiagnosed etiology among researchers exposed to lakes and streams in the Mt. St. Helens blast zone after the 18 May 1980 eruption prompted us to determine the occurrence and potential virulence ofLegionella (Legionnaries' disease bacteria) in aquatic habitats near Mt. St. Helens during the summers of 1981 and 1982. Concentrations ofL. pneumophila, L. micdadei, L. gormanii, L. dumoffii, andL. bozemanii, determined by microscopic counts using direct immunofluorescent staining, ranged from <10⁴ to 10⁵ cells/l in lakes and rivers outside the Mt. St. Helens blast zone while the numbers ofLegionella in aquatic habitats inside the blast zone were from 10⁵ to 10⁷ cells/l.Legionella numbers were consistently highest in North Coldwater and Spirit lakes, which received water from hydrothermal seeps.Legionella pneumophila serogroups 4 and 6 were isolated from North Coldwater Lake in 1981 and from South Coldwater Creek in 1982, indicating that potentially virulent strains ofLegionella persist in aquatic habitats in the blast zone of Mt. St. Helens.Technical paper no. 6923, Oregon Agricultural Experiment Station.     

New species and combinations in Odontonema (Acanthaceae)

Six new species ofOdontonema are described:Odontonema album, O. amicorum, O. breedlovei, O. laxum, O. mortonii andO. speciosum. In addition two new combinations are proposed forOdontonema,O. glaberrimum andO. nitidum var.album, and nine species are transferred fromOdontonema to other acanthaceous genera, namelyAnisacanthus ramosissimus, Buceragenia foliaceo-bracteata, Pseuderanthemum cuspidatum, P. hookerianum, P. interruptum, P. paniculatum, P. stenostachyum, Stenostephanus longistaminus andStreblacanthus dubiosus.     

A new species of Psathyrella (Agaricales,Coprinaceae) from Mexico with discussions on the known species

Psathyrella hypertropicalis, a new species, is described from a high mountain (Cofre de Perote) in the State of Veracruz, Mexico above the subtropical zone. This species is intermediate betweenP. velutina of the temperate regions andP. sepulchralis from the subtropical regions of Mexico. A list of the 26 species ofPsathyrella of Mexico is presented, of which 21 are from the tropics and subtropics, three from the temperate regions (P. velutina, P. spadicea, andP. hypertropicalis), and two with a broad distribution (P. candolleana andP. disseminata). Eleven are only known from Mexico.     

Habitats and Littoral Zone Fish Community Structure of Two Natural Lakes in Southeast Brazil

The fish community and habitat structure in the littoral zone of lakes Pedra and Hortência, middle Rio Doce Valley, Brazil, were investigated in three sampling periods from August 1992 to May 1993. A total of 9106 fishes were collected, including 11 species in Lake Hortência and 12 species in Lake Pedra. Diversity was higher in Lake Hortência, although total fish abundance was the same for both lakes, with no significant temporal differences. The length distribution of the majority of fish species was similar between lakes. Geophagus brasiliensis was the dominant species (number/biomass) in all habitats of the two lakes in all three sampling periods. A striking difference in total fish abundance in relation to habitat types, which we attribute to physical variables, especially the abundance of macrophytes was observed. Negative impacts attributable to the local Eucalyptus sp. plantations were not detected in the fish community structure of Lake Hortência, which is probably due to the maintenance of the riparian vegetation contributing to similar physical environmental conditions in the littoral zone and high similarity in fish community structure between the two lakes. However, further studies on fish community structure and potential Eucalyptus impacts are suggested as necessary to improve conservation measures of the lakes and their fish faunas.     

Spatio-temporal niche partitioning of closely related picocyanobacteria clades and phycocyanin pigment types in Lake Constance (Germany)

We found that the clade-specific abundance dynamics of Synechococcus type picocyanobacteria in the pelagic and littoral zone macro-habitats of Lake Constance (Germany) challenge the hypothesis of a regular annual succession of picocyanobacteria genotypes in temperate zone lakes. Methods used in this study were quantitative Taq nuclease assays (TNA), denaturing gradient gel electrophoresis (DGGE), a 19-month time series analysis (with two isothermal and two stratified periods) and genotyping of a new littoral phycocyanin (PC)-rich Synechococcus strain collection. The recorded differences between the two macro-habitats and between seasons or years, and the observed effect of water column mixis in winter on the inversion of clade-specific dominance ratios in Lake Constance might explain the known inter-annual differences in abundance and dynamics of the autotrophic picoplankton (APP) in lakes. The APP in Lake Constance shows a high genetic diversity with a low overall abundance, similar to the APP in the Baltic Sea, but different from Lake Biwa in Japan or lakes in the UK. Our results indicate that APP bloom events in both macro-habitats of Lake Constance are driven by phycoerythrin-rich Synechococcus genotypes of the Subalpine Cluster I. DGGE revealed the presence of a diverse periphyton (biofilm) community of the PC-rich Synechococcus pigment type in the littoral zone in early spring, when no such community was detectable in the pelagic habitat. A more sensitive and quantitative approach with TNA, however, revealed an intermittent presence of one PC-rich genotype in the plankton. We discuss the seasonal development of the pelagic and littoral PC-rich community, and while we cannot rule out a strain isolation bias, we found that isolated PC-rich strains from the pelagic habitat have different genotypes when compared to new littoral strains. We also observed littoral substrates colonized by specific PC-rich Synechococcus genotypes.