EFFECTS OF TEMPERATURE AND ILLUMINANCE ON CELL DIVISION RATES OF THREE SPECIES OF TROPICAL OCEANIC PHYTOPLANKTON1

Three species of tropical oceanic phytoplankton were isolated from two locations in the eastern Pacific Ocean. Unialgal cultures were maintained in an enriched seawater medium. The effects of temperature, and, in separate experiments, illuminance, on the exponential cell division rates of those algae were investigated. For 2 isolates of Gymnoclinium sp. (probably G. simplex), maximum growth rates were 1.25 and 1.7 divisions/24 hr, the optimum temperature range was 23-29 C, the compensation illuminance was 35 ft-c, and the saturation illuminance was 750 ft-c and above. For a small species of Chaetoceros, the maximum growth rate was 6.0 divisions/24 hr, the optimum temperature range was 23-37 C, the compensation illuminance was 10 ft-c, and the saturation illuminance was 600 ft-c. For a small Nannochloris species, the maximum growth rate was 4.5 divisions/ 24 hr, the optimum temperature range was 27-37 C, and the saturation illuminance was 800 ft-c. Nannochloris grew heterotrophically by apparently utilizing organic matter supplied by soil extract.     

THE EFFECT OF DAYLENGTH AND LIGHT INTENSITY ON THE GROWTH RATE OF THE MARINE DIATOM DETONULA CONFERVACEA (CLEVE) GRAN1

The influence of 40 combinations of temperature (2, 7 C), light intensity (50, 200, 600, 1200, 1800 ft-c), and photoperiod (24, 15:9, 12:12, and 8:16 LD) at 30% salinity on the rate of cell division of the Narragansett Bay clone of Detonula confervacea (Det-1) was examined following appropriate preconditioning. At 2 C Detonula is a long day species (24 L) and prefers low light intensities (200–600 ft-c); poorest growth occurred at 12:12 and 8:16 LD, and the compensation intensity was about 10 ft-c. Increasing temperature to 7 C increased the mean growth rate, reduced the optimal daylength (15:9 LD), even though Detonula remained a long day species and increased the optimal light intensity (600–800 ft-c). The compensation intensity varied with daylength and ranged from about 10–50 ft-c. Photoperiods of 12:12 and 8:16 LD were least favorable for growth at both temperatures; light limitation and inhibition were observed at 50 and 1800 ft-c. respectively; inhibition was less pronounced at 7 C. There is some indication that the conditions of growth that the stock cultures were exposed to prior to preconditioning for use in the experiments may have sometimes influenced response. Detonula produced resting spores without nutrient depletion at 2 and 7 C at all light intensities when the photoperiod was lengthened. Auxospore formation was also observed. Although short daylengths (9:15 LD) limit Detonula's growth during the early stages of the winter bloom, it competes successfully against Skeletonema costatum initially. This results from its higher rates of growth and of photosynthesis at the prevailing temperature and light conditions and a lower compensation intensity than reported for Skeletonema. The main causes of Detonula's growth inception and termination in Narragansett Bay differ.     

RATES OF PHOTOSYNTHESIS AND RESPIRATION OF THE MOSS BRYUM SANDBERGII AS INFLUENCED BY LIGHT INTENSITY AND TEMPERATURE

Using differential respirometry and air enriched to 3% CO₂ (v/v), the rates of photosynthesis and dark respiration of the moss Bryum sandbergii were measured as influenced by temperature and light intensity. The optimal temperature for net (apparent) photosynthesis was between 24 to 30 C; however, the photosynthesis/respiration ratio was about 11 to 27 between 4 to 24 C and dropped to lower values at 34 C., which indicates a wide temperature tolerance for this moss in short-term experiments. The maximum temperature for photosynthesis was about 41 C and the minimum was below –5 C. At 20 C light saturation was approached at 6.2 mw cm^–2 (ca. 700 ft-c) but not completely reached at 12 mw cm^-2; the light compensation point was estimated to be 0.4 mw cm^-2 (ca. 40 ft-c). At 4 C light saturation and the compensation point were at lower levels and apparently solarization occurred at 12 mw cm^-2. Light intensity had little or no apparent effect on dark respiration. However, respiration increased with temperature over various ranges extending from –5 to 39 C with temperature quotients of about 2.5 to 1.2. The significance of these characteristics is discussed with respect to the ecological relationships of the species.     

EXPERIMENTAL OBSERVATIONS ON THE INFLUENCE OF TEMPERATURE,LIGHT, AND SALINITY ON CELL DIVISION OF THE MARINE DIATOM,DETONULA CONFERVACEA (CLEVE) GRAN2

The influence of 116 combinations of temperature (2, 7, 12, 16 C), salinity (5–35‰ at 5‰ intervals) and light (5 levels) on the mean daily cell division rate ( K ) of the Narragansett Bay clone of Detonula confervacea was examined following appropriate preconditioning. Growth did not occur at 16 C, but was excellent (K = 1.2–1.5) under certain combinations of light and salinity at 2, 7, and 12 C, being somewhat better at the 2 highest temperature levels. At 32%, and 1100–1200 ft-c, K increased approximately 2.5 fold from 0.6 to 1.5 between 2 and 12 C. A light-temperature relationship was found which had the general trend of an increased optimal light intensity with increasing temperature. Within the optimal salinity range of 15–30‰, the optimal light intensity was 200–600 ft-c at 2 C, 600–1200 ft-c at 7 C, and 1200–1800 ft-c at 12 C. The light-temperature relationship was most pronounced at 2 and 12 C. At 2 C, K decreased with increasing light intensity, but was independent of this factor at higher temperatures. The optimal salinity range of 15–30‰ was independent of temperature negligible growth occurred at 5‰. In situ and in vitro responses of Detonula confervacea to salinity were in general agreement but its pronounced cryophilic preference in nature (usually reaching maximum abundance below 1 C) contrasts with its excellent growth at 12 C in culture. The experiments suggest that termination of the bloom of Detonula confervacea in Narragansett Bay and elsewhere is not solely temperature-dependent. Temperature does not satisfactorily account for its apparent exclusion from waters contiguous to Narragansett Bay and from other more northerly portions of the northeastern coast of the U.S, or, together with light, for its equally surprising apparent unimportance in Norwegian coastal waters.     

THE GROWTH AND MORPHOLOGY OF THE SILICOFLAGELLATE DICTYOCHA FIBULA EHRENBERG IN CULTURE1,2

Dictyocha fibula was cultured in an enriched seawater medium from collections taken at Edmonds, Washington. The optimum temperature for growth is 10 C at salinity 24% and 160 ft-c illumination in Provasoli enriched seawater at the concentration of 7.5 ml/liter seawater. Average generation time is 49 hr. In addition to swimming cells with skeletons, swimming cells without skeletons and nonswimming coenocytes were observed in clonal cultures at 15 C.     

SALINITY EFFECTS ON GROWTH AND TOXIN CONTENT OF GONYAULAX EXCAVATA. A MARINE DINOFLAGELLATE CAUSING PARALYTIC SHELLFISH POISONING1

The optimum salinity for growth of Gonyaulax excavata (Braarud) Balech from Cape Ann, Massachusetts, is 30.5%o, and it grows well over a range of 20–40%o.It tolerates salinities of 11–43%o. Growth rates at 24 and 20%o are only ca. 10 and 20% less, respectively, than the maximum, 036 divisions/day. It is considered unlikely that salinity fluctuations in the coastal areas where this organism occurs significantly influence its growth rate. The paralytic toxin content in G. excavata increases with increasing salinity, up to 37%o. Therefore, the degree of toxicity of the organism in nature may be influenced by this environmental factor.     

EFFECT OF LIGHT AND TEMPERATURE INTERACTIONS ON GROWTH OF CRYPTOMONAS EROSA (CRYPTOPHYCEAE)1

Cryptomonas erosa Skuja, a planktonic alga, was grown in batch culture at different combinations of light intensity and temperature, under nutrient saturation. Growth was maximal (1.2 divisions · day^?1) at 23.5 C and 0.043 ly · min^?1, declining sharply with temperature (0.025 divisions-day^?1 at 1 C). With decreasing temperature, the cells showed both light saturation and inhibition at much reduced light intensities. At the same time the compensation light intensity for growth declined towards a minimum of slightly above 0.4 × 10^?4 ly · min^?1 (~1 ft-c) at 1 C or <0.1 ly · day^?1 (PAR). Cell division was more adversely affected by low temperature than carbon uptake, and the resulting excess production of photosynthate was both stored and excreted. Extreme storage of carbohydrates resulted in cell volumes and carbon content ca. 22 and 30 × greater, respectively, than the maxima observed for cells incubated in the dark, whereas, at growth inhibitory light levels, as much as 57% of the total assimilated carbon was excreted. A marked increase in cell pigment was observed at the lowest light levels (<10^?3 ly · min^?1), at high temperature. The growth response of C. erosa in culture provides insight into the abundance and distribution of cryptomonads and other small algal flagellates in nature.     

AUTECOLOGICAL STUDIES ON THE MARINE DIATOM RHIZOSOLENIA FRAGILISSIMA BERGON. I. THE INFLUENCE OF LIGHT,TEMPERATURE, AND SALINITY1

The influence of 113 combinations of temperature (9, 12, 18, 25, 30 C), salinity (5–35 ‰ at 5 ‰ intervals), and light (4 levels) on the mean daily cell division rate (K) of the Narragansett Bay clone of Rhizosolenia fragilissima was examined following appropriate preconditioning. Growth did not occur below 9 C, but was excellent (K =～1.2) under certain combinations of light and salinity at 12, 18, and 25 C. The optimal salinity of 20–25 ‰ was temperature independent. Growth was not measurable at 5 ‰, although survival occurred. At 20 ‰ and 1200 ft-c, K increased approximately 1.8-fold from 0.65 to ～1.2 between 9 and 18–25 C. The optimal light intensity was generally 600 ft-c, although several light-temperature-salinity trends were found. At 10 ‰ at all temperatures, the mean daily division rate decreased with increasing light above 600 ft-c, a response found at all salinities at 12 C, but not at other temperatures. Between 15 and 25 ‰, at 18 and 25 C, mean growth was independent of light intensity; at 30–35 ‰ a direct relationship with light may be present with maximum growth occurring at 1200–1800 ft-c. The in situ and in vitro responses of Rhiz. fragilissima to salinity and the optimum and upper temperature levels are in general agreement. However, growth failure below 9 C in vitro is at odds with reports that natural populations occur even at ?1.11 C. The questions of to what extent this discrepancy reflects the occurrence of thermal clones, different taxa, and/or experimental artifacts are briefly discussed. It is suggested that naturally occurring populations found below 9 C might be designated as Rhiz. fragilissima f. faeröensis, and that Rhiz. fragilissima f. bergonii be used for populations growing at higher temperatures, until this matter is resolved. Observations on auxospore formation are presented.     

THE HETEROTROPHIC CAPABILITIES OF CYCLOTELLA MENEGHINIANA1

Cyclotella meneghiniana grew heterotrophically in darkness when glucose in concentrations from 5 mg/liter to 10 g/liter was provided. The other compounds tested did not support growth. However, in continuous light (300 ft-c) growth wax not enhanced if glucose wax provided. Under diurnal conditions of light (300 ft-c) approximately 12–14 hr of darkness were required to observe the enhancement effects of glucose. Uptake studies with labeled glucose indicated that uptake is not dependent on glucose, but that it occurs only at low light intensities. Cells required 12–14 hr of darkness to develop the uptake system.     

PHOTOSYNTHESIS AND RESPIRATION OF ALPINE LICHENS

Photosynthetic and respiratory rates were studied in Cetraria islandica, C. nivalis, and Cladonia rangiferina in the alpine zone of Mt. Washington, New Hampshire. Measurements were made in the field using an infrared gas analyzer; light, temperature, and thallus water content were varied. In all species, considerable reduction in photosynthesis and respiration occurred with drying, more rapidly in photosynthesis than respiration. Optimal photosynthetic rates in all 3 species occurred at 15–20 C with light levels of 1,600 ft-c. Light compensation points ranged from 200 to 350 ft-c. Optimal respiratory rates were attained at 15 C in the 2 species of Cetraria and at 20 C in Cladonia. The data indicate that these wide-ranging, arctic-alpine and arctic-temperate lichens on Mt. Washington are quite well adapted to a moist, foggy environment with cool temperatures and low light levels, conditions which predominate in summer.     

ECOLOGICAL IMPLICATIONS OF CULTURE STUDIES ON NEREOCYSTIS LUETKEANA1

Meiospores, gametophytes grown in culture and then fragmented in a blendor, and young sporophytes of N. luetkeana, were grown at varying temperatures, light intensities, photoperiods, and densities. Vegetative growth occurred over a wider range of environmental conditions than did sexuality. Gametophytes matured at 5, 10, and 15 C but not at 20 C. Low light., 15 ft-c (161 lux), and short day photo-periods (8–16) inhibited or greatly retarded sexuality. Saturation intensities for sexuality occurred between 100 and 200 ft-c (1076 and 2152 lux). Maximal rates of sexuality occurred at or above light, intensities of 3200 ft-c hr/day on an alternating (16–8) light-dark cycle. Light was determined to be the single most important factor in sexuality and subsequent sporophyte growth. Increased density did not affect sexuality but significantly reduced sporophyte growth. Field light intensities beneath lower canopy kelps were below minimal light requirements for gametophyte maturation. These data support, the view that light sets the lower limits on vertical distribution and that, temperature is involved in the latitudinal range of N. luetkeana. These and other studies suggest that the anomalous shallow water depth distribution of N. luetkeana in the San Juan Islands is partly the result of competition for light and not light attenuation, per se.     

THE CONCHOCELIS PHASE OF THREE SPECIES OF PORPHYRA IN CULTURE

The Conchocelis phases of Porphyra perforata f. patens, P. cuneiformis and P. nereocystis were cultured from spores in a sterile artificial medium at 12 C and with 25 ft-c illumination for 10 hr daily. The cultures showed differences in duration of the vegetative phase, sporulation, liberation of spores, and the return to the leafy phase. Morphological differences were also noticed. Since the 3 species were grown under identical conditions, it is inferred that these characteristics are probably different for the 3 species studied.     

A SEAWATER MEDIUM FOR DINOFLAGELLATES AND THE NUTRITION OF CACHONINA NIEI1

Two media have been devised: an enriched seawater medium for culture of dinoflagellates and a defined medium for rapid growth of the dinoflagellate Cachonina niei. A wide range in salinity (10.23–42.38 g/liter NaCl) is tolerated by C. niei. Below 0.6 g/liter MgSO₄, 0.19 g/liter KCl, and 0.22 g/liter CaCl₂, the generation time greatly increases. Increase in MgSO₄ to 7.22 g/liter, KCl to 1.12 g/liter or CaCl₂ to 2.22 g/liter has little effect on generation time. The temperature optimum is 19–23 C. Saturating light intensity for growth is 1000 ft-c and for photosynthesis (determined manometrically) is slightly less than 2000 ft-c. Cachonina niei requires B₁₂ and thiamin. Neither silicate nor its competitive inhibitor germanate affects generation time or cell yield indicating silicon is not required. Of a variety of buffers tested, Tris is the best. Optimal growth occurs at pHs of 7.5–8.3. Glycerol is inhibitory and does not support dark growth.     

THE LIFE HISTORIES OF RHODOCHORTON PURPUREUM AND R. TENUE IN CULTURE

The life histories of the red algae Rhodochorton purpureum and R. tenue were studied in unialgal culture. Telrasporophytes produced sporangia in short day regimes (8–12 hr) with 50–200 ft-c cool white light at 10 or 15 C. Mature gametophytes were not observed in the Washington and Alaska clones of R. purpureum. Tetraspores from R. tenue and the California clones of R. purpureum give rise to unisexual gametophytes that are reproductive when smaller than the tetrasporophytes. The tetrasporophytes develop directly from the gonimoblast cells. Because of similarities in morphology and life histories, it is proposed that R. tenue be placed in synonomy with R. purpureum.     

NUTRITIONAL STUDIES ON THE CHLOROMONADOPHYCEAE: VACUOLARIA VIRESCENS AND GONYOSTOMUM SEMEN12

Unialgal, nonaxenic cultures of Vacuolaria virestcens Cienkowsky were grown in soil-water medium, in simple salt solutions with added peat and soil extract, and in synthetic medium. Doubling times in different media were determined: maximum growth rate (doubling time = 46.0 hr) was obtained in continuous light (210 ft-c) at 24 ± I C. Gonyostomum semen (Ehrenberg) Diesing was isolated from a natural population and grown in soil-water medium and a synthetic medium. Other techniques that have been used for culturing chloromonadophycean algae are reviewed.     

EXPLORING THE OPTIMUM CONDITIONS FOR MAXIMIZING THE MICROBIAL GROWTH OF Candida intermedia BY RESPONSE SURFACE METHODOLOGY

Exploring optimum and cost-efficient medium composition for microbial growth of Candida intermedia Y–1981 yeast culture growing on whey was studied by applying a multistep response surface methodology. In the first step, Plackett–Burman (PB) design was utilized to determine the most significant fermentation medium factors on microbial growth. The medium temperature, sodium chloride and lactose concentrations were determined as the most important factors. Subsequently, the optimum combinations of the selected factors were explored by steepest ascent (SA) and central composite design (CCD). The optimum values for lactose and sodium chloride concentrations and medium temperature were found to be 18.4 g/L, 0.161 g/L, and 32.4°C, respectively. Experiments carried out at the optimum conditions revealed a maximum specific growth rate of 0.090 1/hr; 42% of total lactose removal was achieved in 24 h of fermentation time. The obtained results were finally verified with batch reactor experiments carried out under the optimum conditions evaluated.     

THE TRANSITION FROM FILAMENTOUS TO TWO-DIMENSIONAL GROWTH IN FERN GAMETOPHYTES. II. KINETIC STUDIES ON PTERIDIUM AQUILINUM

Gametophytes of the fern Pteridium aquilinum were incubated 3 days in red light and then transferred to white light. The sequence of events occurring after the transfer was as follows: a swelling of the apical region within 1 hr; a reduction in cell elongation after 5 hr; a series of one-dimensional cell divisions between 10-25 hr; and the initiation of two-dimensional gametophytes after 25-50 hr. The percentage of two-dimensional gametophytes was proportional to the logarithm of the intensity of white light. The rate of elongation after 5 hr was inversely proportional to the logarithm of the intensity. The rates of cell divisions for one- and two-dimensional gametophytes were proportional to intensity up to 240 and 120 ft-c, respectively.     

Estimation of growth and exopolysaccharide production by two soil cyanobacteria,Scytonema tolypothrichoides and Tolypothrix bouteillei as determined by cultivation in irradiance and temperature crossed gradients

Two filamentous cyanobacteria of the genera Scytonema and Tolypothrix were reported to be effective for stabilizing soil in arid areas due to the production of significant amounts of extracellular polysaccharides (EPS). These EPS may also have applications in the biotechnology industry. Therefore, two cyanobacterial species, Scytonema tolypothrichoides and Tolypothrix bouteillei were examined using crossed gradients of temperature (8–40°C) and irradiance (3–21 W m^?2) to identify their temperature and irradiance optima for maximum biomass and EPS production. According to their reported temperature requirements, both strains were considered mesophilic. The optimum growth range of temperature in S. tolypothrichoides (27 to 34°C) was higher than T. bouteillei (22–32°C). The optimum irradiance range for growth of S. tolypothrichoides (9–13 W m^?2) was slightly lower than T. bouteillei (7–18 W m^?2). Maximum EPS production by S. tolypothrichoides occurred at similar temperatures (28–34°C) as T. bouteillei (27–34°C), both slightly higher than for maximum growth. The optimum irradiance range for EPS production was comparable to that for growth in S. tolypotrichoides (8–13 W m^?2), and slightly lower in T. bouteillei (7–17 W m^?2). The Redundancy Analysis confirmed that temperature was the most important controlling factor and protocols for field applications or for mass cultivation can now be developed.     

EFFECTS OF TEMPERATURE AND IRRADIANCE ON THE GROWTH OF TWO FRESHWATER PHOTOSYNTHET1C CRYPTOPHYTES1

Effects of light and temperature on growth of two freshwater photosynthetic cryptophytes of different cell size were studied in batch cultures. For the smaller Cryptomonas 979/67, Steele's model and equation of Platt et al. described the relationship between growth rate and photon flux density (PFD), whereas a hyperbolic tangent function gave a better fit for the larger Cryptomonas 979/62. Maximum growth rates given by the three models were consistent with each other, but the hyperbolic tangent function gave slightly lower estimates. Maximum growth rates in relation to temperature were well described for both species by the model of Logan et al. The optimum temperature for growth for Cryptomonas 979/67 was ca. 24.5° C and 19.0° C for Cryptomonas 979/62. The lethal temperatures were 30.4° C and 23.1° C for 979/67 and 979/62, respectively. The estimated maximum growth rates were 1.38 div.·day^?1 for Cryptomonas 979/67 and 0.87 div.·day ^?1 for Cryptomonas 979/62. There were interspecific differences in photoadaptation strategies, as Cryptomonas 979/67 required relatively high PFDs to show net growth, whereas Cryptomonas 979/62 grew at lower irradiances. Cryptomonas 979/67 showed photoinhibition soon after the saturation point, but Cryptomonas 979/62 tolerated a much wider range of irradiance. From their growth responses to light, Cryptomonas 979/ 67 appears to be a stenotopic and Cryptomonas 979/ 62 a eurytopic strain.     

ADAPTATION OF CERATIUM FURCA AND GONYAULAX POLYEDRA (DINOPHYCEACE) TO DIFFERENT TEMPERATURES AND IRRADIANCES: GROWTH RATES AND CELL VOLUMES1

Growth rates and cell volumes of Ceratium furca Ehrenberg and Gonyaulax polyedra Stein were determined during the log phase of growth in cultures which had been extensively adapted to one of three temperatures and five irradiances. At each temperature, curves for the growth rate vs. irradiance for both species had light-limited and light-saturated regions. Three properties of these curves characterized the response of each species to temperature: the light-saturated growth rate, the irradiance at which growth became light-saturated and the compensation irradiance for growth. For both species, the first two properties generally decreased with declining growth temperature, while the compensation irradiance declined for Ceratium but had a V-shaped response pattern for Gonyaulax. The light-saturated growth rates were generally higher for Ceratium than for Gonyaulax, while the irradiance at which growth became saturated and the compensation irradiance were lower for Ceratium. The changes in cell volume associated with the irradiance and temperature of growth were very different for Ceratium and Gonyaulax. The cell size of Gonyaulax increased as irradiance and temperature decreased, while cell volumes of Ceratium did not change with temperature but were smallest at the highest and lowest growth irradiances. In general, the growth rate patterns were similar for Ceratium and Gonyaulax, while those for cell size were different. The maximum growth rate, the irradiance at which growth became saturated, the compensation irradiance, and the cell volume all showed that Ceratium grew at the same rate or faster than Gonyaulax over the entire range of irradiances and temperatures examined.