Some effects of giant Andean stem-rosettes on ground microclimate,and their ecological significance

The effect of giant Andean stem-rosettes (Coespeletia lutescens) on air and soil temperatures was studied in the Páramo de Piedras Blancas (Venezuela) at 4265 and 4385 m altitude during the dry season, which is the coldest season in this tropical mountain area. Maximum air temperatures beneath a plant canopy were only slightly higher than in the open. Minimum temperatures below the stem-rosettes were 4.7° to 7.0°C higher than in the open. This substantially reduced the intensity of nightly freezing. Soil temperature minima at 20 cm depth were 2.4° to 4.2°C higher below plants, but maxima were somewhat lower than in bare soil. These microclimatic alterations are ecologically significant for stemprosette seedlings, which should have a higher probability of survival due to the reduced frequency of frost and needle ice formation below large plants. Warmer soils at night should also result in greater water uptake by seedlings during the early morning hours, thus reducing dry-season mortality.     

Life cycle and growth ofPotamogeton crispus L. in a shallow pond,ojaga-ike

The life cycle and growth ofPotamogeton crispus L. were studied in a shallow pond, Ojaga-ike. With respect to the shoot elongation and seed and turion formations, the life cycle of this plant in the pond could be divided into following five stages: germination, inactive growth, active growth, reproductive and dormant stages. It was suggested that the plant showed these successive stages depending mainly upon water temperature. The turions germinated on the bottom in autumn when the water temperature fell below ca. 20 C. The plant showed hardly any growth during winter (December—early March) when the temperature was below 10 C. In the spring when the bottom water temperature rose to above 10 C (mid-March), the plant started to grow again and the shoot elongated rapidly at the rate of 4.2 cm day⁻¹ until the shoot apex reached the pond surface in late April. Both the increment of node number and the internodal elongation were associated with this rapid shoot growth. On 10 May (last sampling date), the mean values of shoot length, internodal length and the number of nodes estimated for 10 predominant plants were 238.2±5.6 cm, 7.1±0.8 cm and 34.9±4.0 cm, respectively. The turion formation and flowering occurred during the period from mid-April to mid-May when the surface water temperature ranged 19 and 22 C. The dry weight of a plant reached the maximum mean value of 1180 mg on 10 May. At its peak biomass, an individual plant produced 1–10 turions (5.5 on average) of which the mean individual turion dry weight was 53.2 mg. The turion dry weight accounted for ca. 42% of the total plant biomass m⁻² at that time.     

A survey of the spawning of perch (Perca fluviatilis), pike (Esox lucius), and roach (Rutilus rutilus), using artificial spawning substrates in lakes

The development of spawning in perch, pike and roach in Lake Geneva has been studied by means of artificial spawning substrates, laid at different depths, from 1984 to 1993. In Lake Geneva, perch spawned in May. A rise of surface water temperature up to 14 °C stimulated spawning activity while bad weather (surface temperature at 10 °C) induced a spread of the spawning period over more than one month. The spawning period was delayed in years when the mean width of perch egg-ribbons was the largest; this corresponded to the biggest females. At the beginning of the spawning period (early in May), perch preferentially chose a depth of 4 m to spawn. In contrast, at the end of the spawning period, maximum spawning intensity was observed at a depth of 12 m. This phenomenon was more pronounced when water temperature rose above 14 °C in the top 4 m while it remained below 12 °C at a depth of 12 m. Pike spawned at the end of April and at the beginning of May in Lake Geneva. They preferred spruce branches among the different spawning substrates that we tested in Lake Vouglans. When the water temperature increased at the surface of Lake Geneva, pike preferred to lay their eggs on substrates set at 3 m depth where the temperature was cooler than in the surface layer (10.5 °C vs 14 °C). Roach spawned during the last two weeks of May or during the first two weeks of June in Lake Geneva, depending on water temperature. Spawning had generally been spread over a week, but a sudden decrease of water temperature could slow spawning intensity. Roach were able to lay their eggs on natural or synthetic substrates, located 0.5 m below the surface near the shore as well as, at a distance of several hundred metres from the shore. The survival of eggs was always above 90% for perch and roach and generally above 70% for pike.     

Germination and water dispersal of seeds from a threatened plant species Penthorum chinense

To conserve a threatened plant species (Penthorum chinense Pursh) in Japan, seed germination responses to pretreatment (imbibition and/or chilled), temperature and light, and seed dispersal by water were examined. The seeds collected from abandoned paddy fields in a warm temperate region, central Japan, germinated in light (14 h photoperiod; light 22°C, dark 21°C) after a moist-chilled treatment. After this pretreatment, the seeds germinated well at 10–25°C (optimum temperature 15°C), but did not germinate in darkness even at the optimum temperature. Most of the seeds floated on distilled water, but 20–60% of the seeds that were collected from several populations sank in distilled water, indicating dimorphism in seed dispersal by water. The floating and sunken seeds did not show significant differences in weight and germination rate within a population. The addition of a surface-active agent in distilled water submerged the seeds, indicating that the buoyancy of the seeds is attributable to an oil coating on the seed surface that enhances the interfacial tension on the seeds. Three times the number of seeds sank in river water collected from a rural area than in distilled water. A greater number of seeds also sank in water that had increasing concentrations of linear alkylbenzenesulfonate, which is a major component of synthetic detergents. This suggests that the water dispersal of this species is suppressed by surface-active agents, including detergents, in river water.     

Air and soil temperature differences in controlled environments,as a consequence of high radiant flux densities and of day/night temperature changes

Summary Soil/air temperature differences were measured in 15 cm diameter plastic pots and in 30-cm diameter fibre pots under high radiant flux densities in a controlled environment cabinet. When there was no surface insulation or shading on the sides of the plastic pots, soil temperatures at –1 cm equilibrated at 7.5°C above air temperature. Reflective surface covering and shading on the sides of the pot reduced this difference to 2.4°C. In the fibre pots with reflective surface covering and side shading, soil equilibrium temperature was 1°C below air temperature, but equilibration time was 8 to 9 hours following day/night temperature changes.     

Behavioural thermoregulation of the Andean toad (Bufo spinulosus) at high altitudes

Summary The body temperature of free-ranging Andean toadsBufo spinulosus was measured either directly or radiotelemetrically during two 15-day periods at 3200 m elevation in the Mantaro Valley, Central Perú. All toads attempted to maintain their diurnal sum of body temperature within a narrow range. Consequently thermoregulatory behaviour differed according to cloud cover and precipitation. If the sky was clear, toads emerged from their hiding place and exposed themselves to solar radiation during 3–5 h in the morning. Core temperature increased up to 15° C above the air temperature in shade and reached maximum values of about 32° C. At air temperatures (in sun) exceeding 29° C, toads maintained body temperatures below 32° C by evaporative cooling. Following heliothermic heating during the moring toads retreated to the shade, thereby decreasing body temperature below air temperature. Under overcast sky toads remained exposed during the whole day displaying body temperatures at or slightly above ambient levels. Quantitative models to predict the core temperature of toads under the different weather conditions demonstrated that the substrate temperature was the main energy source accounting for 64.6–77.9% of total variance whereas air temperature was of minor importance (1.5–4.4%). The unexplained variance was probably due to evaporative cooling. The volume of urine stored into the urinary bladder of toads varied diurnally; during basking in the morning hours most bladders contained large volumes of urine, whereas during the afternoon the bladders were mostly empty. The bladder contents probably serve as water reserves during basking when evaporative water loss was high. Toads preferred sites that provided shady hiding places as well as sun-exposed bare soil within a radius of 5 m. However, they frequently changed their centers of activity and moved to other sites in 20–70 m distance after periods of 2–5 days. The helio-and thigmothermic behaviour of the Andean toad permits the maintenance of high core temperature during morning which probably increases the digestion rate and accelerate growth. Evaporative cooling and preference of shady sites were employed to regulate body temperature below the morning levels in response to the constraints of water balance. Periodic changes between thigmothermic behaviour and locomotory activity during the night maintains body temperature above air temperature and prolongs the period of food uptake.Dedicated to Prof. Dr. H. Schneider on the occasion of his sixtieth birthday     

Autecological investigations on marine diatoms 6:Rhizosolenia robusta Norman,Rhizosolenia imbricata Brightwell andRhizosolenia shrubsolei Cleve

The warm oligo-eurytherm diatomsRhizosolenia robusta Norman andRhizosolenia imbricata Brightwell were cultured to determine the temperature range for the best competitive position by growth. Comparison of their generation times with those of other diatoms indicate thatR. robusta reaches this position around 20 °C andR. imbricata above 25 °C. The temperature ranges for growth were 12 °C up to 28 °C forR. robusta and 12 °C to above 30 °C forR. imbricata. The use of both species as indicator species for warm water currents is discussed on account of their lower temperature limit. The cold oligo-eurytherm diatomRhizosolenia shrubsolei had a temperature range for growth of below –1.0 °C to 25 °C. Our experimental results demonstrate thatR. imbricata andR. shrubsolei can be considered separate species.     

Winter biology of the blacknose dace,Rhinichthys atratulus,in a southern Ontario stream

Synopsis The winter habitat of stream-dwelling blacknose dace Rhinichthys atratulus is identified and described from underwater observations in a southern Ontario stream. In late November as water temperatures declined below 5.0°C, dace moved into crevices beneath rubble with a mean maximum diameter of 15.9 cm. Focal point water depth was significantly greater in winter and mid-depth water velocity was significantly faster than measured in the summer. Dace were not observed in open water again until late March when water temperatures increased to 4.0°C. Winter diet analyses which showed minimal feeding were consistent with the seasonal changes in condition factor and percentage body water suggesting a general depletion of body reserves over winter. This physiological change was more pronounced in juveniles.     

Analysis of the spatial variability of maize root density

Water absorption by and seedling emergence of barley (Hordeum vulgare) seeds was studied in a two layer drying out system. Seeds were placed 3 cm below surface in sandy loam (Typic Ustochrept) soil having 4 or 7g.100g^–1 water underlain by wet (10g.100g^–1) layer 2, 4 or 6cm below seed. The study was carried out at 18°, 23°, 28° and 33°C with and without a thin liquid-flow barrier placed on top of the wet layer.Water absorption by seed and coefficient of rate of emergence showed parabalic relation with temperature and strong soil-water × temperature interactions. Liquid-flow barrier considerably reduced the seed water absorption, percent emergence and coefficient of rate of emergence showing thereby that liquid flow was the principal mode of upward water transport from the wet soil to the seed. Influence of both the wet soil and the liquid-flow barrier was detectable up to about 8 cm; shorter the distance greater the effect. It is concluded that in a drying out seed-zone, in addition to wetness of the soil surrounding the seed the wetness of the soil several cm below the seed is also crucial for seedling emergence. Also indicated that the optimum temperatures in drying out seed-zones are different from those in the absence of evaporation.     

The effect of changing the composition of phosphatidylglycerol from thylakoid polar lipids of oleander and cucumber on the temperature of the transition related to chilling injury

The composition and phase behavior of some lipid classes and mixtures of thylakoid polar lipids were measured to investigate their role as determinants of the temperature of the transition associated with chilling injury. For Nerium oleander L., a plant which acclimates to growth temperature, a mixture of the phosphatidylglycerol (PG) and sulfoquinovosyldiacylglycerol (SQDG) showed transition temperatures of 22° and 10° C for plants grown at 45° and 20° C, respectively. This difference was similar to the 9 Celsius degrees differential in the transition of the polar lipids and indicated that the PG and-or the PG-SQDG mixture could be the major determinants of the transition temperature. Reconstitution of the PG-SQDG mixture from 20°-grown oleander with the galactolipids from 45°-grown plants, however, reduced the transition temperature by only 4 Celsius degrees. This indicates that some, low-melting-point lipids, which are structurally capable of forming a co-gel with the high-melting-point lipids, also play a role in determining the temperature of the transition and that the composition of these low-melting-point lipids also changes with growth temperature. More specific information on the role of PG was obtained using polar lipids from Cucumis sativus L., a chilling-sensitive plant. For this material the transition in the polar lipids was reduced from 9° to 5° and 4° C when the transition of the PG was reduced from 32° to 25° and 22° C. This was accomplished by reducing the proportion of disaturated molecular species in PG from 78 to 56 and 44 mol% by the addition of a fraction of the PG enriched in unsaturated molecular species. The data indicate that the transition temperature of the polar lipids of cucumber would be reduced to below 0° C, typical of a chillinginsensitive plant, when the transition temperature of PG was reduced to 15° C and this would occur at 21 mol% of disaturated molecular species. It is concluded that the transition in the thylakoid polar lipids, associated with chilling injury, involves both high- and low-meltingpoint lipids but can be reduced when the transition temperature of the high-melting-point component is reduced.Abbreviations DGDG digalactosyldiacylglycerol - MGDG monogalactosyldiacylglycerol - PG phosphatidylglycerol - SQDG sulfoquinovosyldiacylglycerol     

Influence of krummholz mat microclimate on needle physiology and survival

Summary Microclimate and photosynthesis of krummholz mat growth forms of Picea engelmanii (Parry) and Abies lasiocarpa [Hook.] Nutt. were investigated to determine structural features which may aid survival in alpine environments. The structure of krummholz mats was described in terms of the vertical distribution of leaf area index and leaf area density, which exceeded 50 m^-1 (based on total leaf surface area) near the canopy surface and approached zero below 30 cm from the surface in both species. Photosynthetic photon flux density (PPFD, 0.4–0.7 m wavelengths) and wind decreased by an average of 6 and 50-fold, respectively, between 1 m above and 10 cm below mat surfaces in both species. Needle temperatures on a P. engelmannii krummholz mat during July averaged about 2°C above air temperature during the day, with a maximum overtemperature of greater than 20°C above T _air during one sunlit period. At night, needle temperatures averaged 3–4°C below T _air.Net photosynthesis in year-old P. engelmannii shoots reached a maximum at 15–20°C during July and August. Surface shoots were light saturated at near 1200 moles m^-2s^-1 PPFD, and had higher photosynthetic rates than subsurface, predominantly shaded shoots above 800 moles m^-2s^-1. Shade shoots had higher photosynthetic rates when PPFD was below 600 moles m^-2s^-1, and at 250 moles m^-2s^-1 shade shoots maintained about 50% of the net photosynthetic rate of sun shoots at light saturation. Shade shoots appeared capable of benefitting photosynthetically from elevated temperatures within krummholz mats despite relatively low light levels. Especially rapid photosynthesis may occur when canopy needles are illuminated by sunflecks and needle temperatures rise by 10° C or more.Snow cover appears crucial for the survival of needles during winter. Snow accumulated within krummholz needle canopies before the sub-canopy zone of unfoliated branches became filled. The concentrated needle growth in the krummholz canopy captured snow in early autumn without support from ground-level snowpack. Early snow cover in both species prevented cuticle abrasion and resulted in high winter needle water contents and viabilities for subsurface compared to surface needles which became abraded, severely dehydrated, and had high mortality between December and February, especially on windward sides of shoots.Extremely high concentrations of needles within krummholz mat canopies created an aerodynamic structure which elevated needle temperatures to more optimal photosynthetic levels in summer and resulted in more efficient snow accumulation in winter. These factors appear crucial for winter needle survival. Thus, krummholz mats appear to be an important adaptation in growth form which provides survival benefits in both summer and winter.     

The range of micrometeorological diversity in the biological environment

The range of temperature and humidity conditions that can exist simultaneously at or near the ground surface on a bright summer day in a temperate climate are shown in a diagram. Cool and warm conditions are defined as having respectively a lower and a higher temperature than the air at a height of 1.50 m above the surface of the ground. Similarly, humid and dry conditions are defined by a lower and a higher saturation deficit (S.D.), respectively. Cool, humid conditions are found in the open shade where only diffuse solar radiation is received. In high reed vegetations on wet soil, temperatures can lie 8°C below that of the free atmosphere and humidity is close to the saturation point. Warm and humid conditions are found in thin vegetations on damp soil with a temperature excess of up to 10°C and a strongly reduced S.D. In dry grassland, air temperatures 1 cm above the ground are up to 20°C higher and S.D. up to 40 mm Hg higher than at a height of 1.50 m. On suitably oriented slopes covered with dark organic material, surface temperatures can reach 50°C above the air temperature.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, Israel.     

Foraging at the thermal limit: burrowing spiders (Seothyra,Eresidae) in the Namib desert dunes

Summary In the Namib Desert dunes, the web of Seothyra sp. (Eresidae) comprises sticky silk lining the edges of a horizontal mat on the sand surface. The spider sits in a silk-lined burrow attached to the mat. Arthropods become entangled in the sticky silk of the mat and are attacked and pulled into the burrow by the spider. We investigated the influence of sand surface temperature on the activity of spiders during the summer. We determined the range of thermal conditions encountered by spiders, their temperature tolerance and the influence of temperature on foraging activity and prey handling behavior. The environmental temperatures available to Seothyra vary from 17–33° C at the coolest time of day to 33–73° C at the hottest. When prevented from retreating into burrows, spiders showed signs of thermal stress at about 49° C, whereas unrestrained spiders continued to forage at web temperatures above 65° C by moving between the hot surface mat and the cooler burrow. Spiders responded quicker to prey stimuli during the hot hours of the day and completed prey capture sequences in significantly less time at surface temperatures above 49° C than below. Furthermore, captured arthropods succumbed more quickly at high surface temperatures. Our study supports the hypothesis that web design and thermoregulatory behaviors enable Seothyra to hunt under extreme thermal conditions.     

Morphology ofrsw1, a cellulose-deficient mutant ofArabidopsis thaliana

Summary Therswl mutant ofArabidopsis thaliana is mutated in a gene encoding a cellulose synthase catalytic subunit. Mutant seedlings produce almost as much cellulose as the wild type at 21 °C but only about half as much as the wild type at 31 °C. We used this conditional phenotype to investigate how reduced cellulose production affects growth and morphogenesis in various parts of the plant. Roots swell in all tissues at 31 °C, and temperature changes can repeatedly switch them between swollen and slender growth patterns. Dark-grown hypocotyls also swell, whereas cotyledons and rosette leaf blades are smaller, their surfaces are more irregular and their petioles shorter. Leaf trichomes swell and branch abnormally. Plants readily initiate inflorescences at 31 °C which have shorter but not fatter bolts and stomata which bulge above the uneven surface of internodes. Bolts carry the normal number of flowers, but their stigmas protrude beyond the shortened sepals and petals. Anthers dehisce normally, but self-fertilisation is reduced because the stigma is well above the anthers. Anther filaments are short and show a crumpled surface. Viable pollen develops, but female reproductive competence and postpollination development are severely impaired. We conclude that theRSW1 gene is important for cellulose synthesis in many parts of the plant and that reduced cellulose synthesis suppresses organ expansion rather than organ initiation, causes radial swelling only in the root and hypocotyl, but makes the surfaces of many organs uneven. We discuss some possible reasons to explain why different organs vary in their responses. The morphological changes suggest that RSW1 contributes cellulose to primary walls but do not yet exclude a role during secondary-wall deposition.Dedicated to Professor Brian E. S. Gunning on the occasion of his 65th birthday     

Spring behavioral patterns of the apple blossom weevil

Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.     

Behavioral thermoregulation of largemouth bass,Micropterus salmoides,and bluegill,Lepomis macrochirus,in a nuclear reactor cooling reservoir

Synopsis Behavioral responses which allow largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus, to survive under unusually high temperature conditions were examined. Distribution of fish was ascertained by angling. Body temperatures of 4 fish were obtained using radio transmitters. Temperatures of other fish were measured after fish were captured by angling. Both species were restricted in range by lethal water temperatures and therefore inhabited a greater portion of a thermally altered reservoir in winter than in summer. Under unheated conditions (during reactor shutdown), bass occupied shallow areas with an abundance of submerged logs and stumps, a deep area with springs, and a cove where the effluent canal entered the reservoir. Commencement of reactor operation resulted in an increase in water temperature to more than 50°C in summer. Bass and bluegill retreated to three refuges and remained there until the reactor shut down and the reservoir cooled. In the refuges, bass experienced a wide variety of temperatures, but adults generally avoided temperatures above 31°C. Large adult bass (>40 cm) occupied particular positions in a refuge cove, medium size bass (15–40 cm) swam in the open water, and small bass (相似文献   

Water relations and photosynthesis of a barrel cactus,Ferocactus acanthodes,in the Colorado desert

Summary The structural characteristics, water relations, and photosynthesis of Ferocactus acanthodes (Lemaire) Britton and Rose, a barrel cactus exhibiting Crassulacean acid metabolism (CAM), were examined in its native habitat in the western Colorado desert. Water storage in its succulent stem permitted nighttime stomatal opening ot continue for about 40 days after the soil water potential became less than that of the stem, a period whe the plant would be unable to extract water from the soil. After 7 months of drought and consequent unreplenished water loss from a plant, diurnal stomatal activity was not observed and the stem osmotic pressure was 6.4 bars, more than double the value measured during wet periods with nighttime stomatal opening. F. acanthodes had a shallow root system (mean depth of 8 cm) which responded within 24 h to rainfall.When the nocturnal stem surface temperature was raised from 8.0° C to 35.0° C, the stomatal resistance increased 4-fold, indicating that cool nighttime temperatures are advantageous for gas exchange by F. acanthodes. Moreover, the optimal temperature for CO₂ uptake in the dark was only 12.6° C. CO₂ uptake at night became maximal for 3.0 mEinsteins cm^-2 of photosynthetically active radiation incident during the preceding day, and the minimum number of incident quanta absorbed per CO₂ fixed was 68. The transpiration ratio (mass of water transpired/mass of CO₂ fixed) had the relatively low value of 70 for an entire year, consistent with values obtained for other CAM plants. The total amount of water annually diverted to the floral structures was about 6% of the stem wet weight. The annual growth increment estimated from the net CO₂ assimilation corresponded to about 10% of the stem mass for barrel cacti 34 cm tall, in agreement with measured dimension changes, and indicated that such plants were about 26 years old.     

The role of temperature in the regulation of the circadian rhythm of CO2 fixation in Bryophyllum fedtschenkoi

Detached leaves of Bryophyllum fedtschenkoi Hamet et Perrier kept in normal air show a single period of net CO₂ fixation on transfer to constant darkness at temperatures in the range 0–25 °C. The duration of this initial fixation period is largely independent of temperature in the range 5–20 °C, but lengthens very markedly at temperatures below 4 °C, and is reduced at temperatures above 25 °C. The onset of net fixation of CO₂ on transfer of leaves to constant darkness is immediate at low temperatures, but is delayed as the temperature is increased. The ambient temperature also determines whether or not a circadian rhythm of CO₂ exchange occurs. The rhythm begins to appear at about 20 °C, is most evident at 30 °C and becomes less distinct at 35 °C. The occurrence of a distinct circadian rhythm in CO₂ output at 30° C in the absence of a detectable rhythm in PEPCase kinase activity shows that the kinase rhythm is not a mandatory requirement for the rhythm of PEPCase activity. However, when it occurs, the kinase rhythm undoubtedly amplifies the PEPCase rhythm.Abbreviation PEPCase phosphoenolpyruvate carboxylase We thank the Agricultural and Food Research Council for financial support for this work.     

Emergence of chironomidae from Findley Lake in the coniferous forest of the cascade mountains after early and late thaws

Chironomidae were collected in floating emergence traps on 27.5 m deep Findley Lake in the coniferous forest of the Cascade Mountains, USA, from 1972 to 1975. There was considerable yearly variation in the date of thaw, the total number of Chironomidae that emerged and the relative abundance of each species. In 1972, 1973 and 1975 when there were early thaws, Tanytarsus and Procladius were the most common Chironomidae. Many of the common species started to emerge before the lake had completely thawed. In 1973 when most of the lake thawed June 7 and the surface water reached a maximum temperature of 19.25 °C in July, the Tanytarsus chinyensis group, Stictochironomus and Chironomus started to emerge from deep water when there was still ice along shore. Procladius nr gretis and Orthocladius started to emerge two days after the last ice had melted. In 1974 when most of the lake did not thaw until July 30–31, the surface water reached a maximum temperature of only 12.5 °C in August. Only a fifth as many Chironomidae emerged as in 1973. Most of these were Procladius and Orthocladius which had their maximum emergence when most of the lake was still frozen. The emergence of each species was reduced except Orthocladius. Procladius contributed the greatest biomass that emerged each year, but the second greatest biomass was contributed by different genera each year.