Cylindrospermopsin production and release by the potentially invasive cyanobacterium Aphanizomenon ovalisporum under temperature and light gradients

The growth rates, production and release of the potent cytotoxin cylindrospermopsin (CYN) were studied in batch and semi-continuous cultures of Aphanizomenon ovalisporum (Cyanobacteria; Nostocaceae) strains UAM 289 and UAM 290 from Spain, over a gradient of temperatures (10–40 °C) and irradiances (15–340 μE m⁻² s⁻¹). This species grew in temperatures ranging from 15 °C to 35 °C as well as under all irradiances assayed. The growth rates ranged from 0.08 d⁻¹ to 0.35 d⁻¹, and the maximum growth was recorded above 30 °C and at 60 μE m⁻² s⁻¹. CYN was produced under all conditions where net growth occurred. Total CYN reached up to 6.4 μg mg⁻¹ dry weight, 2.4 μg mm⁻³ biovolume, 190.6 fg cell⁻¹ and 0.5 μg μg⁻¹ chlorophyll a. Although CYN concentrations varied only 1.9-fold within the 15–30 °C range, a drastic 25-fold decrease was observed at 35 °C. The irradiance induced up to 4-fold variations, with maximum total CYN measured at 60 μE m⁻² s⁻¹. An elevated extracellular CYN share ranging from 20% to 35% was observed during the exponential growth phase in most experiments, with extreme temperatures (15 and 35 °C) being related to the highest release (63% and 58%, respectively) and without remarkable influence of irradiance. Growth did not have a direct influence on either CYN production or release throughout the entire range of experimental conditions. Our study demonstrates a strong and stable production and release of CYN by A. ovalisporum along field-realistic gradients of temperature and light, thus becoming a predictive tool useful for the management of water bodies potentially affected by this ecologically plastic cyanobacterium.     

Temperature dependence of membrane-bound enzymes of the energy metabolism in Rhodospirillum rubrum and Rhodopseudomonas sphaeroides

Rhodospirillum rubrum grown either chemotrophically or phototrophically at 14°C and 30°C, was employed to study the effect of temperature on fatty acid composition as well as on several membrane bound functions involved in energy metabolism. Upon growth at both temperatures the fatty acid composition of membranes showed differences, which could be attributed to an incomplete formation of photosynthetically active membranes rather than specifically to the growth temperature. Activities of NADH dependent respiration and light induced proton extrusion by cells did not show discontinuities in Arrhenius plots down to temperatures of 15°C and 5°C, respectively. In contrast, coupling factor Mg²⁺- and Ca²⁺-ATPase as well as succinate cytochrome c oxidoreductase showed significant breaks at 20°C and 18°C, respectively. Similarly, in Rhodopseudomonas sphaeroides. NADH dependent respiration and light induced proton extrusion by cells was continuous over the entire range of temperatures applied. ATPase as well as succinate cytochrome c oxidoreductase, on the other hand, featured discontinuities in Arrhenius plots at 20°C and 19°C. The implication of the data on growth rates and membrane structure are discussed.Abbreviation Bchl baceteriochlorophyll     

Heterotrophic nitrification and aerobic denitrification by the bacterium Pseudomonas stutzeri YZN-001

A strain YZN-001 was isolated from swine manure effluent and was identified as Pseudomonas stutzeri. It can utilise not only nitrate and nitrite, but also ammonium. The strain had the capability to fully remove as much as 275.08 mg L⁻¹ NO₃⁻–N and 171.40 mg L⁻¹ NO₂⁻–N under aerobic conditions. Furthermore, At 30 °C, the utilization of ammonium is approximately 95% by 18 h with a similar level removed by 72 h and 2 weeks at 10 and 4 °C, respectively. Triplicate sets of tightly sealed serum bottles were used to test the heterotrophic nitrifying ability of P. stutzeri YZN-001. The results showing that 39% of removed NH₄⁺–N was completely oxidised to nitrogen gas by 18 h. Indicating that the strain has heterotrophic nitrification and aerobic denitrification abilities, with the notable ability to remove ammonium at low temperatures, demonstrating a potential using the strain for future application in waste water treatment.     

Influence of environmental factors on the growth in culture of a New Zealand strain of the fast-spreading algaHydrodictyon reticulatum (water-net)

Hydrodictyon reticulatum (L.) Lagerh. is a recent addition to the New Zealand flora and is expanding its distribution rapidly. Proliferations of the alga now constitute an economic nuisance in waters which have not previously suffered filamentous algal blooms. To better understand the current and likely future spread of the alga and to identify possible management options the alga's growth requirements have been investigated. A strain isolated from New Zealand tolerated temperatures between 5 and 40 °C and salinities from 0 to 5. Optimal growth was at 25 °C, 150 mol photon m^–2s^–1 and in freshwater. Nett photosynthesis was saturated at photon flux densities of 100 and 160 mol m^–2s^–1 at 12 and 20 °C, respectively. Growth rate was linearly related to internal N concentration and hyperbolically to internal P concentration. Minimum cellular nutrient contents, by weight, were 1% N and 0.2% P. Growth was saturated at contents of 5% N and 0.5% P under the conditions of culture (20 °C, 150 mol photon m^–2s^–1). The alga maintained optimal cellular N content at low ambient nitrate concentrations (100 mg m^–3) half optimum content at 18 mg m^–3. Affinity for filtrable reactive phosphorus was not unusually high compared to other filamentous algae. We suggest that this alga is occupying a niche in New Zealand which has been precluded from other filamentous nuisance algae by low N concentration and N:P ratio. The significance of these findings in setting environmental targets for management of this nuisance alga is discussed.Author for correspondence     

Rapid cold hardening increases cold and chilling tolerances more than acclimation in the adults of the sycamore lace bug, Corythucha ciliata (Say) (Hemiptera: Tingidae)

The sycamore lace bug, Corythucha ciliata is a new, invasive pest of Platanus trees in China. Although C. ciliata is often subjected to acute low temperatures in early winter and spring in northern and eastern China, the cold tolerance of C. ciliata has not been well studied. The objectives of this study were to determine whether adults of C. ciliata are capable of rapid cold hardening (RCH), and to compare the benefits of RCH vs. cold acclimation (ACC) in the laboratory. When the adult females incubated at 26 °C were transferred directly to the discriminating temperature (−12 °C) for 2 h, survival was only 22%. However, exposure to 0 °C for 4 h before transfer to −12 °C for 2 h induced RCH, i.e., increased survival to 68%. RCH could also be induced by gradual cooling of the insects at rates between 0.1 and 0.25 °C min⁻¹. The protection against cold shock obtained through RCH at 0 °C for 4 h was lost within 1 h if the adults were returned to 26 °C before exposure to −12 °C. Survival at both −12 and −5 °C was greater for RCH-treated than for ACC-treated adults (for ACC, adults were kept at 15 °C for 5 days), and the lethal temperature (2 h exposure) was lower for RCH-treated than for ACC-treated adults. The results suggest that RCH may help C. ciliata survive the acute low temperatures that often occur in early winter and early spring in northern and eastern China.     

Effect of temperature on vegetative growth among isolates of Metarhizium anisopliae and M. flavoviride

Effects of temperature on vegetative growth on a semi-synthetic medium of 22 isolates of Metarhizium anisopliae and 14 isolates of M. flavoviride were determined. The majority of isolates of both species grew between 11 and 32°C; several isolates grew at 8 and 37 °C. None of the isolates grew at 40 °C. Relative growth rate, calculated from the maximum growth rate for each isolate, was significantly affected by temperature and isolate, with significant isolate * temperature interactions. The maximum absolute growth rates among the isolates ranged from 2.5 mm to 5.9 mm/day. Optimal temperatures were generally between 25 and 32 °C with several isolates exhibiting optimal growth at temperatures as high as 32 °C. Overall, relative growth rates were greater in isolates of M. anisopliae than M. flavoviride at temperatures of 25 °C or lower; conversely mean relative growth rates were greater in M. flavoviride than M. anisopliae at temperatures higher than 25 °C. However, the two most cold tolerant isolates at 8 °C were M. flavoviride and the three most heat tolerant at 35 °C were M. anisopliae. Since temperature growth responses varied considerably between isolates, strain selection according to thermal tolerance may be warranted when choosing a strain for development as a microbial control agent.This revised version was published online in October 2005 with corrections to the Cover Date.     

Reproductive biology of Stictosiphonia hookeri (Rhodomelaceae,Rhodophyta) from Argentina,Chile, South Africa and Australia in laboratory culture

The red alga Stictosiphonia hookeri is epilithic in shaded habitats of the upper intertidal zone from 30 to 55° S. Thalli of this species from Argentina, Chile, South Africa and Australia, usually without reproductive structures when collected, all developed tetrasporangia in culture. Although good vegetative growth occurred in all nine isolates at 20–25 °C, 12:12 light: dark cycle, 10–30 µmol photons m^–2 s^–1, none reproduced in these conditions except one isolate from Australia. At 15 °C the four South African (34 °S) isolates developed tetrasporangial stichidia, and three completed a Polysiphonia-type life history. Gametophytes were unisexual or bisexual. At 15 °C one isolate from Chile (36 °S) formed tetrasporangia, but sporelings were not viable. At 10 °C isolates from Argentina and Chile (53 °S and 54 °S) formed tetrasporangia; however, only the Chile isolate completed a Polysiphonia-type life history with unisexual gametophytes. The temperature required to induce sporogenesis correlates with the range of water and air temperatures in the natural habitats of each isolate. In irradiances >50 µmol m^–2 s^–1 the thalli became yellow- brown within two weeks because of phycobiliprotein loss, but this did not impair growth or reproduction. The Argentina and Chile isolates were resistant to freezing in seawater for at least two days, showing no cell damage. The protein cuticle of the outer cell wall is repeatedly shed in culture. This may serve to minimize the attachment of epiphytes in the field.     

Factors affecting the distribution, abundance and diversity of fishes of small, soft-substrata tidal pools within Moreton Bay, Australia

Clearance rates of Limnoperna fortunei (Bivalvia) were investigated in laboratory experiments using monocultures of the alga Chlorella vulgaris. Experimental conditions included two mollusc sizes (15 and 23 mm), and three water temperatures (15, 20 and 25 °C) covering the normal seasonal range in the lower Paraná river and Río de la Plata estuary. Filtration rates obtained were, for the larger mussels: 9.9, 13.1 and 17.7 ml mg tissue dry weight^–1 h^–1 at 15, 20 and 25 °C, respectively; and for the smaller ones: 17.7, 20.8 and 29.5 ml mg^–1 h^–1. Differences between sizes and between temperatures (except 15 vs. 20 °C) were statistically significant. In absolute terms larger animals have higher clearance rates, but as a function of body mass smaller individuals feed more actively. Within the range of experimental values used, filtration rates were positively associated with water temperature. These clearance rates (125–350 ml individual^–1 h^–1) are among the highest reported for suspension feeding bivalves, including the invasive species Dreissena polymorpha, D. bugensis and Corbicula fluminea. High filtration rates, associated with the very high densities of this mollusc in the Paraná watershed (up to over 200,000 ind m^–2) suggest that its environmental impact may be swiftly changing ecological conditions in the areas colonized.     

Temperature and nutrient availability control growth rate and fatty acid composition of facultatively psychrophilic <Emphasis Type="Italic">Cobetia marina</Emphasis> strain L-2

A facultative psychrophilic bacterium, strain L-2, that grows at 0 and 5°C as minimum growth temperatures in complex and defined media, respectively, was isolated. On the basis of taxonomic studies, strain L-2 was identified as Cobetia marina. The adaptability of strain L-2 to cold temperature was higher than that of the type strain and of other reported strains of the same species. When the bacterium was grown at 5–15°C in a defined medium, it produced a high amount of trans-unsaturated fatty acids. By contrast, in a complex medium in the same temperature range it produced a low amount of trans-unsaturated fatty acids. In the complex medium at 5°C, the bacterium exhibited a three-fold higher growth rate than that obtained in the defined medium. Following a temperature shift from 11 to 5°C, strain L-2 grew better in complex than in defined medium. Furthermore, when the growth temperature was shifted from 0 to 5°C both the growth rate and the yield of strain L-2 growing in complex medium was markedly enhanced. These phenomena suggest that an upshift of the growth temperature had a positive effect on metabolism. The effects of adding complex medium components to the defined medium on bacterial growth rate and fatty acid composition at 5°C were also studied. The addition of yeast extract followed by peptone was effective in promoting rapid growth, while glutamate addition was less effective, resulting in a cis-unsaturated fatty acid ratio similar to that of cells grown in the complex medium. These results suggest that the rapid growth of strain L-2 at low temperatures requires a high content of various amino acids rather than the presence of a high ratio of cis-unsaturated fatty acids in the cell membrane.     

Towards an understanding of human impact upon the hydrology of Lake Naivasha,Kenya

The growth of a strain of Moina macrocopa (Straus 1820) isolated from an experimental stabilization pond in Marrakesh, was examined at seven concentrations of algae (6.25–6.25 × 10⁵ cells ml^–1 and at 5 different temperatures (15–30 °C)). Feeding conditions influenced the growth rate as well as the maximum size that reached 1.8 mm at 25 °C and at the highest algal concentration (6.25 × 10⁵ cell ml^–1). The life span and number of moltings reached a maximum (17.4 days and 13 moltings) at average nutrient concentrations (6.25 × 10⁵ cell ml^–1). Juvenile stages varied from 1 to 3 and adult ones from 6 to 8. In the temperature interval tested, growth rate increased with temperature while longevity decreased. Temperature had less effect on maximal size than nutrient availability. Population density (but not crowding) influenced longevity and survival but had no effect on growth.     

The effect of temperature,irradiance and animal size on incorporation rates of Simocephalus vetulus

Carbon incorporation rates of Simocephalus vetulus were measured to study the effects of the physical state of the animals, size of the animal, varying temperature and light conditions. Physical state of the animal showed little effect on incorporation rates after the first hour. Incorporation rates increased in proportion to the third power of animal size. Experimental animals collected at temperatures of 12, 20 or 25°C fed maximally at 10, 15 and 25°C respectively, when subjected to a feeding temperature range of 5 to 30°C. We have interpreted this as an indication that S. vetulus is able to acclimate and incorporate maximally at various temperatures after prolonged exposure to that temperature. When fed over an irradiation range of 0 to 4.68 × 10^–3 cal cm^–2 s^–1 incorporation rates were indirectly proportional to irradiance. This suggests a response to decreased irradiance in the weedy, littoral habitat of these animals.     

Thermus kawarayensis sp. nov., a new member of the genus Thermus, isolated from Japanese hot springs

A long-rod-shaped thermophilic microorganism, strain KW11, was isolated from a hot springs located in the Kawarayu, Gunma, Japan. Cloning and preliminary sequence analysis of 16S rDNA showed that this isolate belongs to the genus Thermus. The cells were 10–20 m long, about 0.8 m in diameter, and produced no pigment in contrast with most of the Thermus species previously reported. KW11 was an aerobic heterotroph and grew at temperatures ranging from 40–73°C, with optimal growth occurring at 68°C. The pH range for growth was from 5.8–8.9, with optimal growth around pH 7. KW11 was sensitive to ampicillin, penicillin G, kanamycin, and streptomycin. The G+C content of DNA was 69 mol%. The main fatty acids were 16:0 (52.9%), iso-15:0 (22.1%), and iso-17:0 (15.6%). The 16S rDNA sequence of KW11 showed 96.0, 95.8, and 95.4% similarity with the sequences of T. aquaticus, T. igniterrae, and T. thermophilus, respectively, and less than 95% with other Thermus species. The physiological differences and phylogenetic evidence indicated that strain KW11 represents T. kawarayensis, a novel species of the genus Thermus. The type strain is isolate KW11^T (JCM12314, DSM16200).     

Long-Term Temperature Acclimation of Photosynthesis in Steady-State Cultures of the Polar Diatom <Emphasis Type="Italic">Fragilariopsis cylindrus</Emphasis>

Cultures of the obligate psychrophilic diatom Fragilariopsis cylindrus (Grunow) were grown for 4 months under steady-state conditions at −1 °C and +7 °C (50 μmol photons m⁻² s⁻¹) prior to measurements in order to investigate long-term acclimation of photosynthesis to both temperatures. No differences in maximum intrinsic quantum yield of PS II (F_V/F_M) and relative electron transport rates could be detected at either temperature after 4 months of acclimation. Measurements of photosynthesis (relative electron transport rates) vs. irradiance (P vs. E curves) revealed similar values for relative light utilization efficiency (α = 0.57 at −1 °C, α = 0.60 at +7 °C) but higher values for irradiance levels at which photosynthesis saturates (E_K) at −1 °C and, therefore, higher maximum photosynthesis (P_MAX = 54 (relative units) at −1 °C, P_MAX = 49 at +7 °C). Nonphotochemical quenching (NPQ) measurements at 385 μmol photons m⁻² s⁻¹ indicated higher (37%) NPQ for diatoms grown at −1 °C compared to +7 °C, which was possibly related to a 2-fold increase in the concentration of the pigment diatoxanthin and a 9-fold up-regulation of a gene encoding a fucoxanthin chlorophyll a,c-binding protein. Expression of the D1 protein encoding gene psbA was ca. 1.5-fold up-regulated at −1 °C, whereas expression levels of other genes from Photosystem II (psbC, psbU, psbO), as well as rbcL, the gene encoding the Rubisco large subunit were similar at both temperatures. However, a 2-fold up-regulation of a plastid glyceraldehyde-P dehydrogenase at −1 °C indicated enhanced Calvin cycle activity. This study revealed for the first time that a polar diatom could efficiently acclimate photosynthesis over a wide range of polar temperatures given enough time. Acclimation of photosynthesis at −1 °C was probably regulated similarly to high light acclimation.     

The effects of crowding on growth of the European cuttlefish, Sepia officinalis Linnaeus, 1758 reared at two temperatures

The objective of this study was to examine the impact of crowding (stocking density) on food consumption and growth of juvenile Sepia officinalis reared at 17 and 25 °C. Two groups of 75 cuttlefish each were reared in closed seawater systems with water temperatures of 17 and 25 °C. Each group was subdivided into two treatments (three replicates per treatment): low-density (equivalent to 100 Sepia m⁻²) and high-density (equivalent to 400 Sepia m⁻²). Food consumption was measured daily and live wet body weight (g) was measured weekly over a 5-week study. The 25 °C treatment resulted in significantly higher growth rates and food consumption compared to the 17 °C treatment. Stocking density had no statistically significant effect on food consumption, gross growth efficiency (GGE), or weight at either temperature. However, the high-density treatments had slightly lower GGE values overall and growth in weight at 25 °C was slightly but consistently lower in the high-density treatment suggesting that stocking densities of 400 Sepia m⁻² may be approaching levels that impact feeding and growth.     

Effects on growth and sporulation of inactivation of a Bacillus subtilis gene (ctc) transcribed in vitro by minor vegetative cell RNA polymerases (E-sigma 37, E-sigma 32)

Summary The E-³⁷ gene ctc was inactivated by a site-specific insertion into the Bacillus subtilis chromosome. The resulting mutation inhibited sporulation by 95% at elevated temperatures (48° C). If the ctc ^- mutation is placed in a strain that carries a mutation in the closely linked but distinct spoVC gene, ctc now affects both growth and sporulation at elevated temperatures. Growth of the ctc ^- spoVC285 strain was transiently inhibited when exponentially growing cultures were shifted from 37° C to 48° C. A similar, but less pronounced growth lag, was also seen in a B. subtilis strain carrying only the spoVC-285 mutation. This finding suggests that both the ctc and spoVC products function in vegetatively growing B. subtilis.     

Temperature and light requirements for growth of two diatom species (Bacillariophyceae) isolated from an Arctic macroalga

In the present study, two abundant epiphytic diatom taxa were isolated from the assimilation hairs of the brown macroalga Chordaria flagelliformis collected in the Arctic Kongsfjorden (Spitsbergen, Norway), established as unialgal cultures and their growth rates determined under controlled photon fluence rate and temperature conditions. Using morphological (light and scanning electron microscopy) and SSU rRNA gene data both isolates (ROS D99 and ROS D125) were identified as members of a Fragilaria–Synedropsis clade. The molecular data of ROS D99 and ROS D125 were not identical to any other published sequence. While ROS D99 has been identified as Fragilaria barbararum mainly due to the SEM characteristics, ROS D125 could not be definitely identified although morphological data speak for Fragilaria striatula. Both diatom species showed similar growth rates at all temperatures and photon fluence rates tested. They grew well between 0 and 15°C with optimum temperatures of 12–14°C, but did not survive 20°C. Therefore, compared to Antarctic diatoms both taxa from Kongsfjorden can be characterised as eurythermal organisms. Increasing photon fluence rates between 2 and 15 μmol m⁻² s⁻¹ were accompanied with an almost twofold increase in growth rates, but photon fluence rates >15 μmol m⁻² s⁻¹ did not further enhance growth pointing to low light requirements. From these data optimum, minimum and maximum photon fluence rates and temperatures for growth can be assessed indicating that both diatoms are well acclimated to the fluctuating environmental conditions in the Arctic habitat.     

Effect of rearing temperature and larval density on larval survival, age at pupation and adult size of Anopheles gambiae

The effects of temperature and larval density on survival of larvae, growth rate, age at pupation, and adult size (measured as wing length and dry weight) of laboratory-reared Anopheles gambiae (Diptera: Culicidae) were studied. Larvae were reared at three temperatures (24, 27 and 30°C) and three densities (0.5, 1 and 2 larvae/cm²). The effects of density and temperature strongly interacted to determine the mosquitoes' life-history parameters. Survival was highest at the intermediate temperature of 27°C. The differences between the temperatures increased with increasing density. At 30°C survival decreased as density increased, but at 27°C increasing density led to higher survival. Age at pupation increased as temperature decreased from 30°C to 24°C and as density decreased from 2 to 0.5 larvae/cm². Adult size also increased as temperature decreased, but showed a negative correlation with density only at 27°C. In contrast, at 24°C and 30°C a decrease in density led to a decrease in adult size. Growth rate showed a similar pattern. At 27°C growth rate decreased as density increased, but at other temperatures the opposite trend was observed.     

Comparison of growth and lipid content in three <Emphasis Type="Italic">Botryococcus braunii</Emphasis> strains

The growth and lipid content of three Botryococcus braunii strains from China (CHN), United Kingdom (UK) and Japan (JAP) were compared at three temperatures (20, 25 and 30 ^∘C), three irradiances (60, 100 and 300 W m⁻²) and four salinities (0, 0.15, 0.25, and 0.5 M NaCl) for 30 days, respectively. In the temperature trial, the UK strain and JAP strain grew faster at 25 ^∘C than at other temperatures, while the CHN strain performed equally well at 20 and 25 ^∘C. The JAP strain grew slowest among the three strains at all temperatures, whereas the growth rate of the CHN and UK strains was similar at all temperatures except at 20 ^∘C. The UK strain contained the highest lipid content, but the CHN strain had the lowest lipid content at most temperatures. In the light trial, the highest growth rate was found in the UK strain and the lowest growth rate was observed in the JAP strain at most irradiances. The UK and JAP strains contained more lipids than the CHN strain at 60 and 100 W m⁻², but the lipid content was not significantly different among the three strains at 300 W m⁻². In the salinity trial, both the CHN and UK strains grew faster than the JAP strain at all salinities, but the growth rate between the CHN and UK strains was not different. However, the CHN strain had the lowest lipid content whereas the UK strain produced the highest lipids at most salinities. Our results indicate that the CHN strain and the UK strain grow faster than the JAP strain, but the UK and JAP strains produce more lipids than the CHN strain. The UK strain should be considered as a potential B. braunii strain for the exploitation of renewable energy.     

Temperature effect on growth rates of Eriophorum vaginatum roots

Summary Root growth rates of the sedge Eriophorum vaginatum L. were studied under controlled environmental conditions. The air temperature was maintained constant at 15°C while the root temperatures varied in 5°C intervals between 2° and 37° C (12° C excluded). Root growth rates of 1.2 mm d^-1 at 2°, 20.4 mm d^-1 at 32° C and 10.1 mm d^-1 at 37° C were recorded. A Q₁₀ of 3.2 was calculated for the temperature range from 7° to 27° C. Root growth rates at temperatures above 17° C declined after one week of growth. The degree of decline was proportional to the applied root temperature. Depletion of available nonstructural carbohydrate was the probable cause for this decline.     

Effect of Temperature and Illumination on Growth and Reproduction of the Green Alga Ulva fenestrata

The combined effect of temperature (5, 10, 15, and 20°C) and illumination (40 and 60 mE/(m² s)) on growth and reproduction of the green marine alga Ulva fenestrata P. et R. from the sublittoral zone of Amursky Bay, Sea of Japan, was studied in the laboratory environment in the months April–July, 2000. It was demonstrated that the temperature of 5°C and illumination of 40 mE/(m² s) are the most favorable for maintaining the vegetative mass of the algae. A water temperature of 10°C and illumination of 40 mE/(m² s) are the optimum conditions for vegetative growth of U. fenestrata thalli. A temperature decrease and increase by 5°C reduces the growth rate on average by 30%. Sporo- and gametogenesis in U. fenestrata are the most regular (every 10 days) and occupy the greatest disk area at a water temperature of 15°C and illumination of 40 mE/(m² s). Vegetative growth of thalli is sharply inhibited at the stage of cell preparation to gametogenesis a day before the beginning of gamete formation.