Adaptive significance of facultative paedomorphosis in Triturus alpestris (Amphibia, Caudata): resource partitioning in an alpine lake

1. Facultative paedomorphosis is a polymorphism that has important evolutionary implications in promoting morphological differentiation and variation in habitat use. It occurs in several urodele species throughout the world. Several hypotheses based on life-history theory have been proposed to explain the wide range of habitats in which facultative paedomorphosis occurs, suggesting multifactorial causes.
2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro-habitat use and diet of two coexisting morphs in an alpine lake.
3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.
4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.
5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear.     

Bacterial 'cosmopolitanism' and importance of local environmental factors for community composition in remote high-altitude lakes

1. In October 2004, plankton samples were collected from six permanent lakes located between 4960 and 5440 m a.s.l. in the Mount Everest region (Nepal) to assess how spatial and local environmental factors affect natural bacterial community composition. Fingerprinting analysis of the bacterial 16S rRNA gene fragment was done by denaturing gradient gel electrophoresis (DGGE).
2. The number of DGGE bands (range: 12–23) was not correlated with lake area or remoteness, but there was a strong negative correlation with the ratio of catchment to lake area ( r  = −0.826, P  <   0.05), suggesting that hydraulic retention time affects the establishment of the bacterial community in these seepage lakes.
3. Most dominant sequences belonged to Betaproteobacteria except in two lakes where members of Bacteroidetes made the largest relative contribution. Up to 81% of the phylotypes had high similarity (>98 to 100%) in partial 16S rRNA gene sequence to those reported from other alpine lakes and glaciers around the world, suggesting the presence of 'cosmopolitan' bacteria.
4. An analysis based on dissimilarity matrices and the Mantel test revealed the existence of dissimilarities in bacterial community composition related to geographical distance over a small spatial scale (<6 km), but determined by local environmental constraints.
5. Our results suggest that several bacterial phylotypes are ubiquitous in the freshwater aquatic realm, but taxon sorting by local environmental constraints is important.     

Estimation of the in-situ settling velocity of particles in lakes using a time series sediment trap

SUMMARY 1. We outline a simple method for estimating the in-situ settling velocity of particles in wind disturbed lakes. The total sedimentation rate (primary and secondary sedimentation) was measured during storm events in two lakes using a time series sediment trap.
2. The sediment trap had 12 sample bottles which were programmed to open for periods of 3–4 h, giving total deployment times ranging from 36 to 48 h.
3. Wave mixed layer theory was used to infer if and when sediment resuspension occurred and the first order rate equation was used to estimate the settling velocity of resuspended particles.
4. The settling velocity during three resuspension events in Lough Neagh and one in Lough Macnean were 34.3, 29.5, 24.1 and 77.3 m day⁻¹, respectively. These are similar to values obtained using recent in-situ video imaging in marine environments, but much larger than previous lake sediment trap studies.     

The distribution and diversity of Chironomidae (Insecta: Diptera) in western Finnish Lapland, with special emphasis on shallow lakes

Aim Predictions of aquatic ecosystem change with global warming require basic data that accurately reflect the environmental conditions underlying species distributions. However, in remote arctic areas such baseline data are scarce. We assess the influence of environmental variables on chironomid distribution and taxon richness in shallow, isothermal lakes in a poorly studied arctic region. We pay particular attention to community variation along the treeline ecotonal zone where many environmental variables change abruptly in a relatively small area. Location Lake transect in Finnish Lapland spanning from boreal coniferous forest to arctic tundra. Methods Chironomid assemblages were determined from surface‐sediment samples of 50 shallow (< 10 m) natural lakes. Abundance and taxon richness data were related to 24 limnological variables using canonical ordination techniques (DCA, CCA, RDA). A Monte Carlo permutation procedure was used to assess the explanatory power of single variables. Between‐vegetation zone differences of richness were tested for statistical significance using one‐way anova . Results In total, 7771 chironomid head capsules were identified, consisting of 13 species, 10 species groups, four subgenera, 41 genera, four genus groups, five types and three with uncertain taxonomic affiliation. A hump‐shaped relationship between taxon richness and elevation was noted along the study transect with a peak in taxon richness occurring in mountain birch woodland lakes at middle elevations, decreasing then towards both warmer and colder ends of the elevation/temperature gradient. Of the individual parameters, sediment organic content, total organic carbon, pH, and lake‐specific air temperature accounted for the greatest amount of variation in the chironomid data. Main conclusions Maximum taxon richness occurred at mid‐elevations where aquatic algae also reached their maximum diversity. This area coincides with an ecotonal transitional zone, which seems more likely to account for the peak in species richness. Our study demonstrates that the factors most strongly affecting chironomids in Finnish Lapland (i.e. temperature, and ecosystem features) are those that with great probability will also change as a result of future climate change. This will likely have an effect on the distribution of chironomids in subarctic and arctic areas.     

Whitemere, a lake that defies some conventions about nutrients

1. Whitemere, a kettle-hole lake in north-west England (z_m,14 m, area 22.5 ha) has extremely high maximal concentrations (around 1 mg L⁻¹) of total phosphorus (TP) and soluble reactive phosphorus (SRP), and comparatively low maximal concentrations of dissolved inorganic nitrogen (<0.5 mg N L⁻¹). Bioassays indicate that its phytoplankton is nitrogen limited, and it has surface blue-green algal blooms in summer. Palaeoecological investigations have shown that high populations of cyanophytes occurred more than 6000 years ago, even before human settlement of the catchment.
2. The reasons for this combination of features are not immediately clear. This paper attempts to distinguish between two hypotheses: that the high phosphorus concentrations arise from input of phosphate-rich groundwater; and that the high phosphorus concentrations arise from concentration and recycling mechanisms within the lake.
3. The lake is entirely fed by ground water, direct rainfall and surface sheet flow. The concentrations of phosphorus in the ground water are much lower than in the lake water. The lake is stratified and has high phosphorus concentrations in the anaerobic hypolimnion in summer as a result of substantial release from the sediment. Vertical turbulence in the relatively weakly stratified water column may transfer substantial amounts to the epilimnion.There is also substantial phosphorus release from the sediments under the aerobic epilimnion.
4. There is little outflow of water and phosphorus. Most of the phosphorus is returned to the sediment under winter isothermal conditions, to be released again the following summer. The lake has probably maintained these mechanisms for millennia. Recent eutrophication is likely to have been driven by nitrogen inputs from greater intensification of agriculture in the catchment.     

Stable isotope analysis of archived roach (Rutilus rutilus) scales for retrospective study of shallow lake responses to nutrient reduction

1. There is increasing interest in the use of stable isotope analysis of archived materials to study the long-term impacts of lake perturbations, including nutrient manipulation or species invasion. We tested the utility of this approach in a shallow productive lake using the zooplanktivorous early life stages of roach ( Rutilus rutilus ), a fish species that is widespread throughout Eurasian lakes.
2. Barton Broad is a shallow lake with a well-documented history of earlier eutrophication followed by nutrient reduction, including sediment removal from 1997 to 2000. Using scale samples collected pre- and post-sediment removal, we demonstrated a strong, positive relationship between roach scale δ ¹³C and total phosphorus. We argue that this reflects a decrease in the phytoplankton production which had dominated dissolved inorganic carbon dynamics, and a relative increase in the contribution of respired carbon in the food web.
3. We also derived a scale : muscle isotope relationship for roach which allowed us to model changes in fish muscle against putative prey. Concomitant isotopic shifts in preserved zooplankton samples indicated that the phosphorus reduction measures had an ecosystem-wide impact and that changes in roach scale isotope values were not a result of fish switching diet.
4. Roach scale δ ¹⁵N increased after sediment removal. Since this was not due to a switch in fish diet, we suggest that it probably reflects the loss of nitrogen-fixing, heterocystous cyanobacteria from the plankton.     

Spatial Distribution of Helicobacter spp. in the Gastrointestinal Tract of Dogs

Background:  In dogs, the gastric Helicobacter spp. have been well studied, but there is little information regarding the other parts of the alimentary system. We sought to determine the spatial distribution of Helicobacter spp. in the gastrointestinal tract and the hepatobiliary system of dogs using culture-independent methods.
Materials and methods:  Samples of stomach, duodenum, ileum, cecum, colon, pancreas, liver, and bile from six dogs were evaluated for Helicobacter spp. by genus, gastric, and enterohepatic Helicobacter spp. Polymerase chain reaction, 16S rRNA gene sequence analysis, immunohistochemistry, and fluorescence in situ hybridization (FISH).
Results:  In the stomach, Helicobacter spp. DNA was detected in all six dogs, with H. bizzozeronii and H. felis identified by specific polymerase chain reaction. Helicobacter organisms were localized within the surface mucus, the lumen of gastric glands, and inside parietal cells. The small intestine harbored gastric and enterohepatic Helicobacter spp. DNA/antigen in low amounts. In the cecum and colon, Helicobacter spp. DNA, with highest similarity to H. bilis /flexispira taxon 8, H. cinaedi , and H. canis, was detected in all six dogs. Helicobacter organisms were localized at the mucosal surface and within the crypts. Gastric Helicobacter spp. DNA was detected occasionally in the large intestine, but no gastric Helicobacter spp. were present in clone libraries or detected by FISH.
Conclusions:  This study demonstrates that in addition to the stomach, the large intestine of dogs is also abundantly colonized by Helicobacter spp. Additional studies are necessary to investigate the association between enterohepatic Helicobacter spp. and presence of intestinal inflammatory or proliferative disorders in dogs.     

Mixotrophic ciliates in an Andean lake: dependence on light and prey of an Ophrydium naumanni population

1. Planktonic ciliates were examined during a spring–summer period (November 1998–April 1999) in the ultraoligotrophic Lake Moreno Oeste (41°5' S and 71°33' W, 758 m a.s.l), which belongs to the Nahuel Huapi System (Patagonia, Argentina). The lake is deep ( Z _max=90 m) and warm monomictic.
2. Sampling was performed at a mid-lake station, where vertical profiles of temperature and light were measured in situ , and samples for bacteria and ciliates enumeration were taken throughout the water column.
3. The peritrich Ophrydium naumanni , a freshwater pelagic ciliate with endosymbiotic Chlorella , was the dominant ciliate in the lake.
4.  Ophrydium naumanni and autotrophic picoplankton exhibit a clear coincidence in their vertical distribution ( P  < 0.05), preferring levels at or near the 1% of surface photosynthetically active radiation (PAR) irradiance. Both may have the same light requirements, or the coincidence may reflect a trophic relationship.
5. Dependence on light and prey by O. naumanni were studied using field experiments, in which we analysed ciliate grazing on bacteria, and in laboratory experiments, in which we compared particle uptake under dark and light conditions.
6.  Ophrydium naumanni was able to ingest particles [latex microspheres and fluorescently labelled bacteria (FLB)] in field and laboratory experiment, indicating that it has the potential to affect bacteria population of Lake Moreno Oeste.
7. Ciliate particle ingestion was observed to be dependent on light availability because under dark conditions, the ingestion was lowered ( P  < 0.05).     

Relationships between structure and function in streams contrasting in temperature

1. We studied 10 first-order Icelandic streams differing in geothermal influence in separate catchments. Summer temperature (August–September) ranged between 6 and 23 °C.
2. Macroinvertebrate evenness and species overlap decreased significantly with temperature whereas taxon richness showed no response. In total, 35 macroinvertebrate species were found with Chironomidae the dominant taxonomic group. Macroinvertebrate density increased significantly with temperature. Dominant species in the warm streams were Lymnaea peregra and Simulium vittatum . Algal biomass, macrophyte cover and richness were unrelated to temperature. Densities of trout ( Salmo trutta ), the only fish species present, reflected habitat conditions and to a lesser degree temperature.
3. Density of filter-feeders increased significantly with temperature whereas scraper density, the other dominant functional feeding group, was unrelated to temperature. Stable isotope analysis revealed a positive relationship between δ¹⁵N and temperature across several trophic levels. No pattern was found with regard to δ¹³C and temperature.
4. Leaf litter decomposition in both fine and coarse mesh leaf bags were significantly correlated to temperature. In coarse mesh leaf packs breakdown rates were almost doubled compared with fine mesh, ranging between 0.5 and 1.3 g DW 28 days⁻¹. Nutrient diffusion substrates showed that the streams were primarily nitrogen limited across the temperature gradient while a significant additional effect of phosphorous was found with increasing temperature.
5. Structural and functional attributes gave complementary information which all indicated a change with temperature similar to what is found in moderately polluted streams. Our results therefore suggest that lotic ecosystems could be degraded by global warming.     

Evidence for a lacustrine faunal refuge in the Larsemann Hills, East Antarctica, during the Last Glacial Maximum

Aim  There is no previous direct evidence for the occurrence of lacustrine refuges for invertebrate fauna in Antarctica spanning the Last Glacial Maximum (LGM). In the absence of verified LGM lacustrine refuges many species are believed to result from Holocene dispersal from sub-Antarctic islands and continents further north. If freshwater lake environments were present throughout the LGM, extant freshwater species may have been associated with Antarctica prior to this glacial period. This study looked at faunal microfossils in a sediment core from an Antarctic freshwater lake. This lake is unusual in that, unlike most Antarctic lakes, the sediment record extends to c . 130,000 yr bp , i.e. prior to the LGM.
Location  Lake Reid, Larsemann Hills, East Antarctica (76°23' E; 69°23' S).
Methods  Palaeofaunal communities in Lake Reid were identified through examination of faunal microfossils in a sediment core that extended to c . 130,000 yr bp .
Results  Ephippia and mandibles from the cladoceran Daphniopsis studeri and loricae of the rotifer Notholca sp. were found at all depths in the sediment, indicating that these two species have been present in the lake for up to 130,000 years. Copepod mandibles were also present in the older section of the core, yet were absent from the most recent sediments, indicating extinction of this species from Lake Reid during the LGM.
Main conclusion  The presence of D. studeri and Notholca sp. microfossils throughout the entire Lake Reid core is the first direct evidence of a glacial lacustrine refugium for invertebrate animals in Antarctica, and indicates the presence of a relict fauna on the Antarctic continent.     

Endophytic fungi decrease available resources for the aphid Rhopalosiphum padi and impair their ability to induce defences against predators

Abstract.  1. The production of winged morphs is a well known mechanism of induced defence in aphids to escape from natural enemies, and is also a reaction to poor resource quality.
2. Host plants of aphids often associate with endophytic fungi that have been shown to reduce the fitness of some species of aphids.
3. It was hypothesised that endophyte infection of host plants that represent a low quality plant resource should increase the aphid's induced response to a predator because both low plant quality and predator presence represent a stronger cue for wing production than predator presence alone.
4. In a laboratory experiment, bird cherry-oat aphids Rhopalosiphum padi L. were exposed to the factors predator threat and endophyte infection and the effects of these factors on the proportion of winged morphs produced by the aphid colonies was analysed.
5. The presence of endophytic fungi strongly decreased aphid colony sizes. When a predator threat was present, all colonies on endophyte-free grasses produced winged morphs whereas only a few colonies were able to produce winged morphs on endophyte-infected grasses. However, these few colonies produced larger proportions of winged morphs than colonies on endophyte-free grasses. Without a predator threat, no colonies on endophyte-infected grasses produced any winged morphs.
6. These results show that aphids in stressed conditions and with reduced fitness will only invest in inducible defences when predators are present but are unable to produce winged morphs in response to endophyte presence.     

Do moss samples,pollen traps and modern lake sediments all collect pollen in the same way? A comparison from the forest limit area of northernmost Europe

Moss polsters, pollen traps and lake surface sediment samples are commonly used as climate calibration data or as modern analogues for reconstructing vegetation from fossil profiles, but the differences in pollen content between these media have received little attention. This study aims to analyse how the three media differ in reflecting individual vegetation types and spatial differences in vegetation. 119 modern samples (64 moss polsters, 37 lake surface sediment samples and 18 pollen traps from which a collection was made annually) were taken from northern Fennoscandia and the Kola Peninsula as a broad transect crossing the northernmost forest limits of Betula pubescens ssp. czerepanovii (mountain birch), Pinus sylvestris (Scots pine) and Picea abies (Norway spruce). The pollen assemblages from these samples were compared with the surrounding vegetation visually and via PCA (principle components analysis) and cluster analysis. Both comparisons allow a correct distinction between pollen assemblages of arctic/alpine heath, mountain birch dominated areas, and boreal coniferous forests. The differences between the vegetation zones are stronger than the differences between the sampling media. Nevertheless, lake sediment samples from the mountain birch woodland zone tend to overestimate pine and underestimate birch. Pollen traps are biased towards lower tree pollen percentages and higher values of shrubs, herbs and Cyperaceae. This bias is especially strong in traps that have missing years in the data. Irrespective of the vegetation zone, pollen traps tend to have lower Pinus pollen percentages than in the adjacent moss polsters.     

Empirical modelling of lake water-temperature relationships: a comparison of approaches

1.  As a result of the role that temperature plays in many aquatic processes, good predictive models of annual maximum near-surface lake water temperature across large spatial scales are needed, particularly given concerns regarding climate change. Comparisons of suitable modelling approaches are required to determine their relative merit and suitability for providing good predictions of current conditions. We developed models predicting annual maximum near-surface lake water temperatures for lakes across Canada using four statistical approaches: multiple regression, regression tree, artificial neural networks and Bayesian multiple regression.
2.  Annual maximum near-surface (from 0 to 2 m) lake water-temperature data were obtained for more than 13 000 lakes and were matched to geographic, climatic, lake morphology, physical habitat and water chemistry data. We modelled 2348 lakes and three subsets thereof encompassing different spatial scales and predictor variables to identify the relative importance of these variables at predicting lake temperature.
3.  Although artificial neural networks were marginally better for three of the four data sets, multiple regression was considered to provide the best solution based on the combination of model performance and computational complexity. Climatic variables and date of sampling were the most important variables for predicting water temperature in our models.
4.  Lake morphology did not play a substantial role in predicting lake temperature across any of the spatial scales. Maximum near-surface temperatures for Canadian lakes appeared to be dominated by large-scale climatic and geographic patterns, rather than lake-specific variables, such as lake morphology and water chemistry.     

How does the vertical distribution of chlorophyll vary in littoral sediments of small lakes?

1. In this study, sediment chlorophyll profiles at twenty littoral stations in three oligo‐mesotrophic lakes were compared to test whether the vertical distribution of chlorophyll is related to site characteristics (light availability, temperature, physical disturbances) and whether these profiles differ between shallow and deep portions of the littoral zone.
2. The magnitude of chlorophyll peaks at the sediment surface did not vary with light intensity. Chlorophyll peaks in the shallow littoral zone had a weak tendency to decrease with increasing effective fetch. The magnitude of chlorophyll peaks at deeper sites was more closely related to water temperature than to substrate slope.
3. High chlorophyll concentrations were measured down to 1–3 cm in the sediments, both at shallow (< 2.5 m) and deep (4–10 m) stations. The depth to which high chlorophyll was found in sediments did not vary with effective fetch or sediment water content, two indices of wave disturbance in the shallow littoral zone, or with substrate slope, an index of sediment stability in the deep littoral zone. Sediment mixing is apparently not related to common indices of physical disturbances.
4. Between 8 and 100% of sediment surface chlorophyll was 'retained' 4–5 cm into the sediments. The proportion of chlorophyll 'retained' in littoral sediments increased with increasing depth, increasing lake productivity (total phosphorus concentration) and increasing lake pH.
5. Among‐core variability (standard error/mean) in chlorophyll concentration at the sediment surface ranged from less than 1% to 33% at different stations and was highest at shallow, exposed sites. These levels of variability are similar to those found in other periphytic communities.     

Classification, assessment and trophic reconstruction of Danish lakes using chironomids

1. Surface-sediment assemblages of subfossil chironomid head capsules from fifty-four primarily shallow and nutrient-rich Danish lakes were analysed using multivariate numerical techniques. The species data, comprising forty-one chironomid taxa, were compared to environmental monitoring data in order to establish a relationship between chironomid faunal composition and lake trophic state.
2. The subfossil assemblages were compared to the chironomid bathymetric distributions along transects from four lakes. Correspondence analysis and similarity coefficients showed that the subfossil assemblages, sampled in the lake centre, reflect the chironomid communities in the littoral at a depth of 2–7 m.
3. Two-way indicator species analysis (TWINSPAN) was used to classify the Danish lakes into five groups defined by trophic state, lake depth and pH. Eighteen chironomid taxa showed significant differences in abundance among the five groups. Canonical correspondence analysis (CCA) showed the chlorophyll a concentration ([Chl a ]) and Secchi depth to be the variables best correlated to the faunal data, and fourteen taxa were significantly correlated to [Chl a ].
4. The strong correlation between chironomid data and the ln-transformed ([Chl a ]) was used to create a weighted averaging (WA) model to infer lake trophic state. Several models were tested by cross validation (leave-one-out jack-knifing), and a simple WA model using inverse de-shrinking had a RMSEP_jack of 0.65 (ln units) and a r ²_jack of 0.67.
5. The results can be used in the assessment and reconstruction of lake trophic state for long-term monitoring and palaeoecological investigations of shallow, temperate lakes in the mesotrophic to hypertrophic nutrient range.     

Tissue nutrient concentrations in freshwater aquatic macrophytes: high inter-taxon differences and low phenotypic response to nutrient supply

1. The elemental composition and stoichiometry of aquatic plants has often been suggested to reflect the nutrient enrichment of aquatic habitats. However, the relationship is often weak. Moreover, uncertainties remain in the relevance of laboratory derived critical plant tissue nutrient concentrations to maximum yield or growth rates in the field.
2. Aquatic vascular plants and bryophytes, overlying water and sediment samples were collected to test whether freshwater aquatic macrophytes: (i) show tissue nutrient deficiencies when growing in oligotrophic freshwater habitats, and (ii) have strict homeostatic stoichiometry.
3. Plant nutrient concentrations were significantly related to total inorganic nitrogen (or nitrate), total dissolved phosphorus and sediment total phosphorus. However, these relationships were weak. Virtually all the variance in plant tissue nutrient concentrations, however, could be explained by species (taxon) identity.
4. Critical tissue nutrient concentrations for 95% maximum yield or 95% maximum growth rate in aquatic angiosperms, determined from laboratory bioassays, suggested that nutrients should not limit yield in wild aquatic macrophytes. However, there were a substantial number of samples where potential growth rate limitation was possible, particularly due to phosphorus.
5. Strict C : N : P stoichiometric ratios were found for both vascular plants and bryophytes, suggesting little scope for plants as indicators of nutrient enrichment, but provide robust stoichiometric data for studies on ecosystem metabolism and nutrient cycling.     

Hatching of cladoceran resting eggs: temperature and photoperiod

Summary 1. We identified temperature and photoperiod conditions under which the hatching of 45 cladoceran species could be elicited. Identification of appropriate hatching cues is of primary importance for the exploration of the ties between active and diapausing stages.
2. Incubation temperature affected the hatching success of resting eggs isolated from Danish, Belgian/Dutch and Spanish sediments. In general, most hatchlings and species were retrieved at 15 °C. Danish and Belgian/Dutch resting eggs hatched more successfully under a long day photoperiod than in continuous illumination.
3. Most species could be retrieved after incubation of resting eggs isolated from a limited amount of sediment (0.4 kg) under a single, well chosen combination of temperature and photoperiod. Processing additional sediment samples under seven more incubation regimes only allowed detection of 21% (Spain) to 34% (Denmark) more species.
4. The incubation period for resting eggs to hatch was strongly influenced by incubation temperature. Our results show that hatching experiments aimed at assessing cladoceran species richness and conducted at 15 °C should be continued for a period of at least 2 weeks, after which a random subset of hatchlings (e.g. n  = 100) can be selected from the total hatchling assemblage.     

Interaction effects of fish, nutrients, mixing and sediments on autotrophic picoplankton and algal composition

1. We examined the effects of nutrients, turbulent mixing, mosquitofish, Gambusia affinis Baird and Girard and sediments on algal composition, algal biomass and autotrophic picoplankton (APP) abundance in a 6-week experiment of factorial design in twenty-four 5-m³ outdoor mesocosms during late autumn 1995.
2. Turbulent mixing decreased surface temperature and increased turbidity, which also was increased by the addition of sediments. Total algal biomass was significantly enhanced by nutrients and mixing, and decreased by the sediment treatment. In the mixing × nutrient treatment, algal biomass increased more than expected from the individual effects, while the fish × mixing and mixing × sediment treatments increased algal biomass less than expected.
3.  Cryptomonas (cryptomonad) blooms were observed in the unmixed, high nutrient treatment; Synedra (diatom) blooms were observed in the high nutrient, high sediment treatment; Ulothrix (green algae) blooms were observed in the mixed, high nutrient, low sediment treatment.
4. Eukaryotic APP abundances were increased by sediment addition and by turbulent mixing, and increased synergistically by mixing × sediment and mixing × nutrient interactions. Prokaryotic APP abundances were decreased by nutrient enhancement and by a mixing × nutrient interaction. There were no main effects of fish on APP abundance, but fish were involved in some of the two–way interactions.
5. The large number of significant interaction effects indicates that APP and other phytoplankton are regulated by a complex set of interdependent factors which should be considered simultaneously in studies of phytoplankton population dynamics and community composition.     

Twentieth century human and climate impacts on a large mountain lake in southwest China

Subfossil chironomid and sediment geochemistry data from Lugu Lake, a large high-elevation lake in southwest China, were used to assess the influences of climate warming and direct human impacts on the lake through time. A 95-year-long sediment record was recovered from the lake. Principal components analysis (PCA) and redundancy analysis of fossil chironomid data were performed to determine the controlling factors on the chironomid community. The four prominent environmental controls were summer air temperature, organic matter C:N ratio (C_org:N), dry mass accumulation rate (DMAR), and total nitrogen. C_org:N proved to be the most important controlling factor through time. However, C_org:N and summer air temperature were highly co-linear, possibly due to temperature directly impacting lake productivity (and thus C:N ratios) through increased stratification and a longer growing season. PCA Axis 1 scores were a strong predictor of summer temperatures even after DMAR was factored out to account for direct human influences. The strong temperature–chironomid relationship over the last 50 years could be due to the lake becoming more responsive to climate warming after cultural eutrophication of the 1950s, as lakes with higher nutrient loads are shown to be more responsive to the effects of climate warming.     

Rapid detection of Brucella spp. by the loop-mediated isothermal amplification method

Aims:  To develop a rapid and sensitive method for detecting Brucella spp.
Methods and Results:  Two sets of six Brucella -specific primers for loop-mediated isothermal amplification (LAMP) were designed from the sequence of the Brucella abortus BCSP31 gene. The specificity and sensitivity were examined for six Brucella species (22 strains) and 18 non- Brucella species (28 strains). The LAMP assay was specific to Brucella spp. in 35 min at 63°C and sensitive (detected 10 fg of genomic DNA). The assay was also applied for the detection of Brucella DNA in contaminated milk and infected mouse organs.
Conclusions:  We developed a sensitive and specific LAMP assay for Brucella spp., with the test appearing to be useful for the detection of the pathogen from clinical and food samples.
Significance and Impact of the Study:  This is the first report of the development of LAMP for the detection of Brucella spp. As the LAMP assay can be performed at a constant temperature and its reactivity is directly observed with the naked eye without electrophoresis, our assay should be useful for the diagnosis of brucellosis as well as the detection of the bacteria in environmental or food samples.