Bacterial community shift along a subsurface geothermal water stream in a Japanese gold mine

Change of bacterial community occurring along a hot water stream in the Hishikari gold mine, Japan, was investigated by applying a combination of various culture-independent techniques. The stream, which is derived from a subsurface anaerobic aquifer containing plentiful CO₂, CH₄, H₂, and NH₄⁺, emerges in a mine tunnel 320 m below the surface providing nutrients for a lush microbial community that extends to a distance of approximately 7 m in the absence of sunlight-irradiation. Over this distance, the temperature decreases from 69°C to 55°C, and the oxidation-reduction potential increases from –130 mV to +59 mV. In the hot upper reaches of the stream, the dominant phylotypes were: 1) a deeply branching lineage of thermophilic methane-oxidizing -Proteobacteria, and 2) a thermophilic hydrogen- and sulfur-oxidizing Sulfurihydrogenibium sp. In contrast, the prevailing phylotypes in the middle and lower parts of the stream were closely related to ammonia-oxidizing Nitrosomonas and nitrite-oxidizing Nitrospira spp.. Changes in the microbial metabolic potential estimated by competitive PCR analysis of genes encoding the enzymes, particulate methane monooxygenase (pmoA), ammonia monooxygenase (amoA), and putative nitrite oxidoreductase (norB), also substantiated the community shift indicated by 16S rRNA gene analysis. The diversity of putative norB lineages was assessed for the first time in the hot water environment. Estimation of dominant phylotypes by whole-cell fluorescent in situ hybridization and changes in inorganic nitrogen compounds such as decreasing ammonium and increasing nitrite and nitrate in the mat-interstitial water along the stream were consistent with the observed transition of the bacterial community structure in the stream.     

Aquatic hyphomycetes of a sulphur spring

Aquatic hyphomycetes of a sulphur spring in the Western Ghat region of Karnataka were investigated by the following methods: leaf litter observations, water filtration, analysis of natural and induced foam. The samples were collected and studied from three sites, the spring proper (site I), the connecting region of the spring and the rivulet (site II) and the spot where the spring joins the rivulet (site III). The number of species of hyphomycetes encountered at the three sites were 1, 14 and 20, respectively. The sulphide content of the spring ranged between 0.1–3.1 mg l^–1 and the temperature between 26.5–36.5 °C. In another experiment submerged coffee leaves from a fresh water stream were collected and incubated in spring water, stream water and well water at different temperatures (16–40 °C). A maximum of 18 species of hyphomycetes sporulated at 22 °C followed by 17 species at 28 °C, irrespective of the source of water in which the leaves were incubated. Based on these studies, we conclude that the presence of only one species in the spring proper (site I) was not due to the higher sulphide content, but to the high temperature.     

Longitudinal distribution of macroinvertebrate assemblages in a glacially influenced stream system in the Italian Alps

1. The longitudinal distribution of macroinvertebrates was investigated in June, August and September 1996 and 1997 in the Conca glacial stream and its tributary (Italian Alps; 46°N, 10°E). The principal aim was to test the 22 model that predicts the succession of faunal groups downstream of the glacial snout in relation to water temperature and channel stability. The effect of a non‐glacial tributary on the taxonomic richness and density patterns occurring in the glacial stream was also considered. 2. Channel stability showed an atypical longitudinal trend in the Conca glacial stream, being high in the upper part with Pfankuch Index values between 30 and 33. Water temperature exceeded 6 °C at all stations, with average values below 2 °C occurring only within 700 m from the glacial snout. 3. Taxonomic richness and diversity increased downstream. Taxonomic richness in the glacial stream (at about 1.5 km from the glacier) was comparable with the tributary and the reach after the confluence. Abundance also increased downstream in the glacial stream, but not as greatly as the number of taxa. 4. At higher taxonomic levels, the community structure in the tributary stations appeared to be similar to the two stations in the glacial stream just upstream of the confluence. The effect of the tributary was evident mainly at the genus or species level of the Chironomidae community. Some taxa found in the non‐glacial stream (e.g. Cricotopus fuscus, Eukiefferiella coerulescens, Metriocnemus sp., Paratrichocladius rufiventris, P. skirwitensis, Rheocricotopus effusus and Smittia sp.) were found also in the Conca stream but only after the confluence. 5. The upper glacial reach (within 700 m from the glacier snout) was dominated by the chironomid Diamesa spp. Less than 400 m from the glacier other Diamesinae (Pseudokiefferiella parva) and a few Orthocladiinae, especially Orthocladius (Euorthocladius) rivicola gr., colonized the stream. Some Diamesinae maintained relatively dense populations at mean water temperature around 5 °C, while some Orthocladiinae colonized reaches with mean water temperature <3 °C. 6. Contrary to the 22 model, Dipteran families such as Empididae and Limoniidae were more abundant in the upper stations than Simuliidae; non‐insects such as Nematoda and Oligochaeta were also numerous at some sites. Leuctridae, Taeniopterygidae and Nemouridae were the first Plecoptera to appear upstream, while Chloroperlidae were restricted to the lower reaches. Among Ephemeroptera, Heptageniidae were more abundant than Baetidae in the glacial sites. 7. In this glacial system channel stability and maximum temperature did not show the expected longitudinal trend and thus a typical kryal community was confined within 700 m from the glacier snout where summer mean water temperature was below 4 °C.     

The effects of geothermal water inflow on longitudinal changes in benthic macroinvertebrate community composition of a temperate stream

Studies of macroinvertebrate communities in thermal streams are highly geographically localized and mostly faunistical, making the efforts to understand in situ water thermal regime effects on those biocoenoses barely achievable. We examined the effects of geothermal water inflow on benthic macroinvertebrate community composition in a temperate stream. Environmental data analysis has shown that water temperature is a major factor determining the faunistical composition, especially downstream of the geothermal water inflow situated some 20 m upstream of locality V3. The increase in mean annual water temperature from 11.5±4.1 °C at locality V2 to 22.0±5.0 °C at locality V3 induced an enormous shift in community composition from a diverse one, composed mainly of Gammaridae, Simuliidae, Chironomidae, Trichoptera and Ephemeroptera, and to a lesser extent of Plecoptera, Coleoptera, other Diptera, Hirudinea, Odonata, Mollusca and Oligochaeta, to a uniform one strongly dominated by Chironomidae, Mollusca and Oligochaeta, comprising 98.9±0.5% of collected individuals. While the disappearance of Plecoptera and Ephemeroptera and the increase in representation of Mollusca and Oligochaeta at locality V3 might be solely explained by water temperature increase, in the case of Chironomidae the increase in water discharge and relatively high annual water temperature variation at locality V3 had additional positive effects. However, the latter factor induced disappearance of Gammaridae at locality V3. In addition to the increase in water temperature, increase of water velocity significantly determined the longitudinal dynamics of Coleoptera.     

Bacterial Community Structure Along Moisture Gradients in the Parafluvial Sediments of Two Ephemeral Desert Streams

Microorganisms inhabiting stream sediments mediate biogeochemical processes of importance to both aquatic and terrestrial ecosystems. In deserts, the lateral margins of ephemeral stream channels (parafluvial sediments) are dried and rewetted, creating periodically wet conditions that typically enhance microbial activity. However, the influence of water content on microbial community composition and diversity in desert stream sediments is unclear. We sampled stream margins along gradients of wet to dry sediments, measuring geochemistry and bacterial 16S rRNA gene composition, at streams in both a cold (McMurdo Dry Valleys, Antarctica) and hot (Chihuahuan Desert, New Mexico, USA) desert. Across the gradients, sediment water content spanned a wide range (1.6–37.9% w/w), and conductivity was highly variable (12.3–1,380 μS cm⁻²). Bacterial diversity (at 97% sequence similarity) was high and variable, but did not differ significantly between the hot and cold desert and was not correlated with sediment water content. Instead, conductivity was most strongly related to diversity. Water content was strongly related to bacterial 16S rRNA gene community composition, though samples were distributed in wet and dry clusters rather than as assemblages shifting along a gradient. Phylogenetic analyses showed that many taxa from wet sediments at the hot and cold desert site were related to, respectively, halotolerant Gammaproteobacteria, and one family within the Sphingobacteriales (Bacteroidetes), while dry sediments at both sites contained a high proportion of taxa related to the Acidobacteria. These results suggest that bacterial diversity and composition in desert stream sediments is more strongly affected by hydrology and conductivity than temperature.     

Studies on the aquatic hyphomycetes of a sulfur spring in the Western Ghats, India

Studies on the occurrence of aquatic hyphomycetes were carried out in Panekal sulfur spring in the Western Ghats, India by incubation of leaf litter and analysis of natural foam and of induced foam. Sampling was done once every three months over a period of two years from September 1989 to June 1991. The temperature, pH, dissolved oxygen, and sulfide content of water were also measured. No fungi were observed within the spring, whereas 16 species belonging to 13 genera were isolated from two outflow sites of the stream. The percent frequency of Triscelophorus monosporus was high (24.0%). The temperature of water in the spring ranged between 30.0 and 38.5°C and the sulfide content between 3.2 and 4.3 mg 1^–1. Studies showed that sulfide water (4.0 mg 1^–1). from the spring inhibited the growth of the colonies of Dactylella aquatica, Phalangispora constricta, Tetracladium setigerum, Vermispora cauveriana, and Wiesneriomyces laurinus. When the leaves colonized by aquatic hyphomycetes were incubated at different temperatures in sulfur-spring water and stream water separately, sporulation was not observed in any of the fungi at and above 35°C except Phalangispora constricta, which could sporulate at 35°C. At lower temperatures (15–30°C) relatively fewer species were found to sporulate in sulfur-spring water than in stream water. Correspondence to: K.M. Kaveriappa     

The steppes and deserts of the Xizang Plateau (Tibet)

The Xizang Plateau (Tibet) covers a vast area over 4 000 m with a severe environment. Steppes and deserts are widely distributed on the plateau to the west of 91.5°E. Poaceae, Asteraceae, Fabaceae and Cyperaceae are the most important families in the composition of steppe communities. The steppe can be divided into high-cold steppe and montane steppe. The former one is characterized by the Stipa purpurea community, which occupies a vast area with a cold, dry climate: annual mean temperature 0 to –6°C, annual rainfall is 150–300 mm; The latter one is distributed in some limited regions, where the climate is less severe: annual mean temperature 0–7°C, annual rainfall is 150–400 mm. The representative communities here are the Stipa glareosa and S. bungeana communities. Chenopodiaceae and Asteraceae play a principal role in both high-cold and montane deserts. The high-cold desert is unique. Its major representative is the Ceratoides compacta community, which is found at about 5 000 m, in an extremely cold and very dry climate. The Ceratoides latens and Ajania fruticulosa communities are the common ones of the montane desert which mainly appears below 4 600 m in elevation, where the annual temperature is about 0°C and the rainfall is less than 100 mm. The distribution of the steppe and the desert communities shows a clear regional differentiation, and an equally clear vertical distribution pattern.     

Bacterial Community Composition in Central European Running Waters Examined by Temperature Gradient Gel Electrophoresis and Sequence Analysis of 16S rRNA Genes

The bacterial community composition in small streams and a river in central Germany was examined by temperature gradient gel electrophoresis (TGGE) with PCR products of 16S rRNA gene fragments and sequence analysis. Complex TGGE band patterns suggested high levels of diversity of bacterial species in all habitats of these environments. Cluster analyses demonstrated distinct differences among the communities in stream and spring water, sandy sediments, biofilms on stones, degrading leaves, and soil. The differences between stream water and sediment were more significant than those between sites within the same habitat along the stretch from the stream source to the mouth. TGGE data from an entire stream course suggest that, in the upper reach of the stream, a special suspended bacterial community is already established and changes only slightly downstream. The bacterial communities in water and sediment in an acidic headwater with a pH below 5 were highly similar to each other but deviated distinctly from the communities at the other sites. As ascertained by nucleotide sequence analysis, stream water communities were dominated by Betaproteobacteria (one-third of the total bacteria), whereas sediment communities were composed mainly of Betaproteobacteria and members of the Fibrobacteres/Acidobacteria group (each accounting for about 25% of bacteria). Sequences obtained from bacteria from water samples indicated the presence of typical cosmopolitan freshwater organisms. TGGE bands shared between stream and soil samples, as well as sequences found in bacteria from stream samples that were related to those of soil bacteria, demonstrated the occurrence of some species in both stream and soil habitats. Changes in bacterial community composition were correlated with geographic distance along a stream, but in comparisons of different streams and rivers, community composition was correlated only with environmental conditions.     

Low Temperature Tolerance of Pacu, Piaractus mesopotamicus

Pacu, Piaractus mesopotamicus (=Colossoma mitrei), is a South American warm water fish species found in the temperature range of 15–35°C. The culture of a warm water species in temperate regions demands knowledge on its temperature requirements. Pacu introduction into the Israeli fish culture system is being considered. Temperature range in the region is 8–33°C, thus the minimum winter water temperatures might be a limiting factor. To determine what is the minimum temperature pacu would tolerate, and hence which overwintering operations in warm-temperate regions are required for this warm water species, low temperature tolerance tests in the laboratory and observations in the field were carried out. Laboratory experiments reducing temperature by 1–3°C per day were carried out with fish of 150–200g, about the size pacu reach after one culture season. The field observations compared survival of two-year-old pacu of 1.3kg mean weight overwintered in outdoors and in greenhouse ponds. For one-year-old fish 7.5°C was found to be the lower temperature tolerance limit. Two-year-old fish withstand short exposures to this temperature rather well and their lower tolerance limit might be lower. This indicates that in warm-temperate regions pacu should survive in outdoors ponds. In this case some loss of weight should be expected, and suspension of feeding when temperature drops below 16–18°C is recommended to avoid wasting feed that the fish will not consume anyway. To be in the safe side, inflow of the warmest available water into the ponds is recommended if maximum water temperature drops to 10°C or below. Overwintering in greenhouses or other heated facilities would be recommended if an exceptionally cold winter is expected and for regions with lower winter minimum temperatures.     

Effects of hyperthermia and hypothermia on spontaneous contractions of the adult rabbit testicular capsule

Spontaneous contractions of the isolated testicular capsule of the adult rabbit have been found to be markedly sensitive to heat and cold stress. Testicular capsular contractions may provide a propulsive pumping action for transporting nonmotile sperm out of the testis and into the epididymis where they can then attain motility. An optimal temperature for the amplitude of spontaneous contractions of the rabbit testicular capsule occurred at 32 – 34°C. An increase in thein vitro organ bath temperature from 37 to 40°C caused a marked decrease in the amplitude of spontaneous contractions. A complete and irreversible cessation of spontaneous contractions occurred at 48°C for at least 30 min after cooling to 37°C. A decrease in temperature from 37 to 26°C resulted in a marked decrease in frequency and amplitude progressing to a complete but reversible cessation of spontaneous contractions at 16°C. Marked changes in the frequency and amplitude of spontaneous contractions of the isolated testicular capsule began to be observed when the tissue was exposed to organ bath temperatures of 3°C above and below the normal intra-testicular temperature. These data suggest that exposure of men to fever or excessively hot baths as well as swimming in excessively cold water or extreme cold weather exposure may have inhibitory effects on testicular capsular spontaneous contractions which may interfere with sperm transport.     

Macroinvertebrate community structure in relation to environmental variables in a Swiss glacial stream

1. Benthic macroinvertebrate distribution was examined in relation to channel characteristics (including stability), substratum, hydraulic variables, primary production (chlorophyll a ) and coarse particular organic matter (CPOM) in an alpine glacial stream, the Mutt (Upper Rhône valley, Switzerland). Co-inertia analysis and canonical correspondence analysis were used to identify the major environmental gradients influencing community variations.
2. The Mutt (length: 3.6 km, altitudinal range: 1800–3099 m a.s.l.) exhibited typical characteristics of a kryal stream. Average summer temperature remained below 2 °C immediately downstream from the snout but was on average 5 °C higher 1700 m downstream. Seasonal variations in water sources were evidenced by the high late-summer (September) contribution of groundwater with increased conductivity.
3. Sixty-six taxa were recorded from the five reaches sampled at three periods (snowmelt, ice melt and low water in late summer) in 1996 and 1997, of which 29 were Chironomidae. Three taxa of Diamesinae were the first colonizers of the stream below the glacier, but 16 taxa, including Ephemeroptera, Plecoptera and Trichoptera, were already recorded 200 m downstream. Water depth, channel slope and Pfankuch's Index of channel stability were strongly correlated with the longitudinal faunal gradient. Maximum temperature, current velocity and water conductivity were also correlated, but to a lesser extent.
4. The rapid incorporation of non-chironomid taxa into the stream community represented a departure from Milner & Petts's (1994) conceptual model of invertebrate succession downstream of glacial margins. The results confirmed that glacial stream communities are primarily driven by physical determinants.     

Intracellular multiplication ofLegionella pneumophila in amoebae isolated from hospital hot water tanks

We studied the ability ofLegionella to multiply in potable water samples obtained from investigations of nosocomial legionellosis. AutochthonousLegionella multiplied in three of 14 hospital water samples after incubation at 35°C and 42°C. All three samples were from hot water tanks. Multiplication did not occur when a selected sample was filtered through a 0.45-m membrane and reinoculated with indigenousLegionella. We isolated bothLegionella pneumophila and one or more species of free-living amoebae, primarity members of theHartmannellidae, from each of these hot water tank samples. Amoebae from a total of six hot water tank samples were used for cocultivation studies withL. pneumophila. All amoebae supported multiplication ofLegionella in coculture at 35°C. Four of six isolates of amoebae supported multiplication oflegionella at 42°C, while none supported multiplication at 45°C. Gimenez staining and electron microscopy showed thatLegionella multiplied intracellularly in amoebae. Control of these amoebae in potable water may prevent colonization and multiplication ofLegionella in domestic hot water systems.     

Physical and biological changes to a lengthening stream gradient following a decade of rapid glacial recession

In mountains, environmental gradients are steep in both terrestrial and aquatic systems, and climate change is causing upward shifts of physical and biological features of these gradients. Glacial streams are an interesting system to evaluate such shifts both because streams have a linear nature (for simplicity of analysis), and because the stream habitat will at least temporarily lengthen as it follows receding glaciers upward. The Tschierva Glacier, Swiss Alps, receded 482 m upstream from 1997 to 2008. We tested the null hypothesis that the physical and biological stream gradient below this glacier maintained the same structure between these time periods, but simply shifted upward following the glacial source. We compared longitudinal patterns of water temperature and zoobenthic community structure in 1997 and 2007–2008 during three seasons (spring, summer, fall) along the uppermost ca. 5 stream km. Upward shifts were evident, including colonization of the newly exposed stream reaches by cold‐adapted taxa, and the appearance in 2007/2008 of four lower‐altitude species that were previously absent. Overall, however, results rejected the null hypothesis, instead revealing significant changes in gradient structures. These included a more steeply increasing temperature profile downstream of the glacier and increased amplitude of seasonal community turnover in 2007/2008 vs. 1997. Long‐term (1955–2007) flow records revealed increasing short‐term and seasonal hydrologic variability, which might have influenced the increased intra‐annual community variability. The steepening of the temperature gradient was likely caused by a warming lake‐outlet tributary upon which glacial influence was diminished between 1997 and 2007/2008. These results suggest that upward‐shifting gradients in glacial streams can involve complex interactions with other landscape elements and that local‐scale climate response can progress even more rapidly than the rate of glacial recession.     

Thermal,chemical, and optical properties of Crater Lake,Oregon

Crater Lake covers the floor of the Mount Mazama caldera that formed 7700 years ago. The lake has a surface area of 53 km² and a maximum depth of 594 m. There is no outlet stream and surface inflow is limited to small streams and springs. Owing to its great volume and heat, the lake is not covered by snow and ice in winter unlike other lakes in the Cascade Range. The lake is isothermal in winter except for a slight increase in temperature in the deep lake from hyperadiabatic processes and inflow of hydrothermal fluids. During winter and spring the water column mixes to a depth of about 200–250 m from wind energy and convection. Circulation of the deep lake occurs periodically in winter and spring when cold, near-surface waters sink to the lake bottom; a process that results in the upwelling of nutrients, especially nitrate-N, into the upper strata of the lake. Thermal stratification occurs in late summer and fall. The maximum thickness of the epilimnion is about 20 m and the metalimnion extends to a depth of about 100 m. Thus, most of the lake volume is a cold hypolimnion. The year-round near-bottom temperature is about 3.5°C. Overall, hydrothermal fluids define and temporally maintain the basic water quality characteristics of the lake (e.g., pH, alkalinity and conductivity). Total phosphorus and orthophosphate-P concentrations are fairly uniform throughout the water column, where as total Kjeldahl-N and ammonia-N are highest in concentration in the upper lake. Concentrations of nitrate-N increase with depth below 200 m. No long-term changes in water quality have been detected. Secchi disk (20-cm) clarity varied seasonally and annually, but was typically highest in June and lowest in August. During the current study, August Secchi disk clarity readings averaged about 30 m. The maximum individual clarity reading was 41.5 m in June 1997. The lowest reading was 18.1 m in July 1995. From 1896 (white-dinner plate) to 2003, the average August Secchi disk reading was about 30 m. No long-term changes in the Secchi disk clarity were observed. Average turbidity of the water column (2–550 m) between June and September from 1991 to 2000 as measured by a transmissometer ranged between 88.8% and 90.7%. The depth of 1% of the incident solar radiation during thermal stratification varied annually between 80 m and 100 m. Both of these measurements provided additional evidence about the exceptional clarity of Crater Lake.     

THE ALGAE OF WAIMANGU CAULDRON (NEW ZEALAND): DISTRIBUTION IN RELATION TO pH1

The pH of the main body of thermal water and of the outlet of Waimangu Cauldron (Frying Pan Lake) is 3.8, whereas hot springs flowing into this lake are alkaline, pH 8.2–8.7. Where these waters meet there are pH gradients, and it is possible to find a series of habitats differing in pH but having approximately the same temperature (54–56 C). Where the pH is above 4.8 the blue-green alga Mastigocladus laminosus is present, and where the pH is below this value the eucaryotic alga Cyanidium caldarium is the sole photosynthetic microorganism at temperatures less than 55 C. Rocks resting on the bottom of Waimangu Cauldron surrounded by water of pH 3.8 have Mastigocladus laminosus growing on them, but measurements of pH directly in these algal mats showed that the microenvironment of the alga was actually above pH 4.8. A simple experiment showed that it is probably the rock, per se, that initiates a tiny island of alkalinity in the acid lake, permitting M. laminosus to become established. The outlet of Waimangu Cauldron is a hot acid stream which becomes progressively alkaline as it descends through Waimangu Valley, due to inflow of alkaline water from springs and a cold stream. Blue-green algae were found in this stream when the pH was greater than 5.0 and C. caldarium when the pH was less than 4.0. In one region where the pH was between 4.0 and 5.0, both blue-green algae and C. caldarium were seen, although in moribund state. These data, provide further information on the lowest pH values at which blue-green algae are able to grow.     

The influence of coal ash and thermal discharges upon the distribution and bioaccumulation of aquatic invertebrates

The distribution, density and uptake of twenty elements by aquatic invertebrates inhabiting a drainage system, that received excessive coal ash effluent (275 JTU of turbidity) at one end and thermal loading (44.5°C) at the other end, was studied for 15 months. The ash settling basin filled during the first eight months of sampling which resulted in the release of ash effluent directly into the receiving system. Density of invertebrates was lowest in the 300 m stream between the ash basin and swamp and highest 1200 m beyond the stream-swamp confluence where ash influence was minimal. Invertebrate density was lowest in the stations where turbidity from ash effluent was greatest. The most tolerant invertebrates to coal ash stress were odonates (Libellula sp. and Enallagma sp.), crayfish (Procambarus sp.), amphipods (Gammarus sp.) and gastropods (Physa. sp.), and midges (Chironomidae) when the basin was filling. During the period of ash overflow, all groups were either reduced in numbers or absent. In the thermally stressed station, Libellula sp. was the predominant invertebrate sampled when water temperature ranged from 25.5–45.5°C (257-1=28.7°C) all aquatic invertebrates were limited in numbers and density when temperature exceeded the lower and upper ranges of 10.0–38.0°C.This research was supported by AEC Contract AT (38-1-824)This research was supported by AEC Contract AT (38-1-824)     

Reef coral survival and mortality at low temperatures in the Arabian Gulf: new species-specific lower temperature limits

A series of cold fronts passing over the western Arabian Gulf from December 1988 to March 1989 produced the longest period of sustained low water temperatures ever recorded in a coral reef area. Sea water temperatures recorded on two reefs during this period provide new estimates of lower thermal limits for reef coral survival. Severe mortality of the corals Acropora pharaonis and Platygyra daedalea occurred at the northern site where minimum temperatures fell below 11.5°C on four consecutive days and mean daily temperatures were 13°C or less for more than 30 days. However, Porites compressa, the principal reef-former in this area, and various faviid corals initially showed only sub-lethal effects and appeared normal after six months. Corals were not damaged at the southern site, where minimum water temperature fell below 12.5°C for two consecutive days, but mean temperatures were 14°C or less for only 5 non-consecutive days.     

The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes

Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha.     

Hot spring frogs (Buergeria japonica) prefer cooler water to hot water

“Hot spring frog” is an informal name used for the Japanese stream tree frog (Buergeria japonica), which is widely distributed in Taiwan and the Ryukyu Archipelago in Japan. Some populations of the species are known to inhabit hot springs. However, water temperature can be extremely high around the sources of hot springs. Thus, it is questionable whether B. japonica selectively inhabits such dangerous environments. To address this question, we conducted a series of observations of water temperature preferences of a hot spring population of B. japonica in Kuchinoshima Island in Japan: (a) a field observation of tadpole density in water pools of different temperatures, (b) a field observation of water temperatures where adult males appear for breeding, and (c) an indoor observation of water temperatures selected by adult females for oviposition. As a result, tadpoles showed a higher density in cooler water. Adult males avoided water pools hotter than 37°C, and adult females selected cooler pools for oviposition. Camera records also showed that adult individuals tend to appear around cooler pools. Thus, we did not find any support for the hypothesis that hot spring frogs prefer hot water. Conversely, they apparently tended to prefer cooler water if it was available. Water temperatures around the sources of the hot spring exceed thermal tolerances of the species and could be a strong selective pressure on the population. Thus, the ability to sense and avoid lethal temperatures may be a key ecological and physiological characteristic for the species that inhabit hot springs.     

Inducing sporulation in Alternaria solani I. Effect of water treatment

The sporulation was induced when fully grown cultures were given dip or spray treatment with distilled water (cold or hot) and thereafter, kept partially covered at different temperatures. Cultures dipped in cold water (4° C) for 4 minutes or sprayed with cold water (4° C) or hot water (58° C) and thereafter incubated at room temperature (13–26° C) in diffused sunlight, produced maximum number of spores within 60 hours. Incubating water treated cultures in diffused sunlight or complete darkness and age and scraping of the cultures had a considerable effect upon intensity of sporulation. The cultures yield a number of subsequent crops of spores when scraped and given dip treatment with cold or hot water, after obtaining each crop of spores.