Some lower food web organisms in the nutrition of marine harpacticoid copepods: an experimental study

Some lower food web organisms from the marine littoral environment were studied as food for harpacticoid copepods. In laboratory experiments, it could be shown that, among the ciliates, the slow-movingUronema sp. was taken up while the fast-movingEuplotes sp. was not.Asterionella glacialis, a pennate diatom with spiny projections, was unsuitable as food. The centric diatomSkeletonema costatum was ingested by all harpacticoid species tested, includingTisbe holothuriae, Paramphiascella vararensis, Amphiascoides debilis andDactylopodia vulgaris. All are epibenthic and phytal species occurring in the shallow waters of Helgoland (North Sea). The amount of ciliate and algal carbon taken up was less than that provided by bacteria under laboratory conditions. However, some diatom food may be essential for the development ofD. vulgaris.     

Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light

Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing‐induced flashing light regimes. In this study, photosynthetic efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100 Hz at a light‐dark ratio of 0.1 and a flash intensity of 1000 µmol m⁻² s⁻¹. Light flashing at 100 Hz yielded the same photosynthetic efficiency and specific growth rate as cultivation under continuous illumination with the same time‐averaged light intensity (i.e., 100 µmol m⁻² s⁻¹). The efficiency and growth rate decreased with decreasing flash frequency. Even at 5 Hz flashing, the rate of linear electron transport during the flash was still 2.5 times higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of a light/dark cycle. Understanding photosynthetic growth in dynamic light regimes is crucial for model development to predict microalgal photobioreactor productivities. Biotechnol. Bioeng. 2011;108: 2905–2913. © 2011 Wiley Periodicals, Inc.     

A culture method for microalgal forms using two-tier vessel providing carbon-dioxide environment: studies on growth and carotenoid production

A culture method was developed for photoautotrophic culture of Haematococcus pluvialis, Chlorella vulgaris, Scenedesmus obliquus, Spirulina platensis, Nostoc and Stigonema in a two-tier flask consisting of nutrient media in the upper chamber and CO₂ generating buffer mixture (KHCO₃/K₂CO₃) in the lower chamber. The concentration of buffer mixture was varied to obtain desired levels of CO₂. CO₂ at 2.0% (v/v) level enhanced growth and chlorophyll content over control cultures (without CO₂ supplementation) in all microalgal species. Haematococcus pluvialis culture in BBM and KM1 media showed 6.71- and 2.07-fold increase in biomass yields with astaxanthin productivity at 7.26 and 7.48 mg l^–1 level respectively. CO₂ supplementation to C. vulgaris and S. obliquus cultures resulted in 5.97- and 7.30-folds increase in biomass with 2–3 fold increase in chlorophyll and carotenoid contents over their respective controls. Similarly 2–3 fold increase in chlorophyll and carotenoid contents were observed in Sp. platensis, Nostoc and Stigonema spp. This culture methodology will provide information on CO₂ requirement for growth of algae and metabolite production and also facilitates studies on the influence of light and temperature conditions.     

Enantioselective toxicological response of the green alga Scenedesmus obliquus to isocarbophos

Chiral compounds usually behave enantioselectively in phyto‐biochemical processes. Isocarbophos (ICP) is a chiral pesticide that is widely used. To evaluate the toxicological response of ICP and its enantiomers to Scenedesmus obliquus, algal growth, total chlorophyll, total soluble protein, and the superoxide anion radicals (O₂^?‐) were investigated. The microalgae were treated with ICP and its enantiomers at 0.01–10 mg/l for 96 h. The growth of S. obliquus was stimulated at low levels of ICP and its enantiomers (0.01–1 mg/l), but all were inhibited at high concentrations (10 mg/l). The total soluble protein content and total chlorophyll content of the tested green alga S. obliquus gradually increased, depending on the growth of algal cells in the medium. Meanwhile, the content of O₂^?‐ was decreased. Interestingly, the cell number and content of the chlorophylls and protein decreased with increasing levels of concentration, whereas O₂^?‐ increased. Our results indicated that enantioselectivity was observed in the dose–response of ICP and its enantiomers in S. obliquus. The high O₂^?‐ level might lead to the death of S. obliquus. The stimulation of growth suggests a regulatory mechanism that is related to the capability of the algae to adapt to the O₂^?‐. Chirality 24:481–485, 2012. © 2012 Wiley Periodicals, Inc.     

Carbon dioxide fixation by Chlorella kessleri, C. vulgaris, Scenedesmus obliquus and Spirulina sp. cultivated in flasks and vertical tubular photobioreactors

CO₂ at different concentrations were added to cultures of the eukaryotic microalgae, Chlorella kessleri, C. vulgaris and Scenedesmus obliquus, and the prokaryotic cyanobacterium, Spirulina sp., growing in flasks and in a photobioreactor. In each case, the best kinetics and carbon fixation rate were with a vertical tubular photobioreactor. Overall, Spirulina sp. had the highest rates. Spirulina sp., Sc. obliquus and C. vulgaris could grow with up to 18% CO₂.     

Effects of algal food quality on sexual reproduction of Daphnia magna

The objective of our study was to investigate sexual reproduction of Daphnia magna associated with mating behaviors and hatching rates, according to different algal food sources. Since a diatom is known to contain more abundant long‐chain poly unsaturated fatty acids (PUFAs), we hypothesized that the diatom‐consuming D. magna would exhibit more successful reproduction rates. Upon the hypothesis, we designed three experiments using two algal species, a green alga (Chlorella vulgaris) and a diatom (Stephanodiscus hantzschii). From the results, we found that the mating frequency and copulation duration increased in the treatment with S. hantzschii, resulting in a significant increase of hatching rates of resting eggs. In the other two repetitive mating strategies (e.g., one female vs. multiple males, and one male vs. multiple females), we found that the hatching rates of resting eggs were greater in the S. hantzschii treatment. In addition to the mating strategy, male body size significantly increased in the diatom treatment, hence average diameter of penis was also statistically different among the treatments (greater diameter in the S. hantzschii treatment). To examine the effect of algal food quality, we estimated quantity of fatty acids in the two algal species. Our result showed that S. hantzschii had a higher proportion of long‐chain PUFAs than C. vulgaris. Furthermore, a stable isotope analysis revealed that carbon and nitrogen originated from S. hantzschii were more assimilated to D. magna. In summary, our study manifested that diatom consumption of D. magna leads to more successful sexual reproduction. We then discussed how the diatom consumption of zooplankton influences food web dynamics in a freshwater ecosystem.     

SPONTANEOUS AND STIMULATED BIOLUMINESCENCE OF THE DINOFLAGELLATE CERATOCORYS HORRZDA (PERIDINIALES)1

This is the first report of spontaneous bioluminescence in the autotrophic dinoflagellate Ceratocorys horrida von Stein. Bioluminescence was measured, using an automated data acquisition system, in a strain of cultured cells isolated from the Sargasso Sea. Ceratocorys horrida is only the second dinoflagellate species to exhibit rhythmicity in the rate of spontaneous flashing, flash quantum flux (intensity), and level of spontaneous glowing. The rate of spontaneous flashing was maximal during hours 2–4 of the dark phase [i.e. circadian time (CT)16–18 for a 14:10 h LD cycle (LD14:10)], with approximately 2% of the population flashing-min^?1, a rate approximately one order of magnitude greater than that of the dinoflagellate Gonyaulax polyedra. Flash quantum flux was also maximal during this period. Spontaneous flashes were 134 ms in duration with a maximum flux (intensity) of 3.1×10⁹ quanta-s^?1. Light emission presumably originated from blue fluorescent microsources distributed in the cell periphery and not from the spines. Values of both spontaneous flash rate and maximum flux were independent of cell concentration. Isolated cells also produced spontaneous flashes. Spontaneous glowing was dim except for a peak of 6.4× 10⁴quanta-s^?1 cell^?1, which occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The total integrated emission of spontaneous flashing and glowing during the dark phase was 4×10⁹ quantacell^?1, equivalent to the total stimulable luminescence. The rhythms for C. horrida flash and glow behavior were similar to those of Gonyaulax polyedra, although flash rate and quantum flux were greater. Spontaneous bioluminescence in C. horrida may be a circadian rhythm because it persisted for at least three cycles in constant dark conditions. This is also the first detailed study of the stimulated bioluminescence of C. horrida, which also displayed a diurnal rhythm. Cultures exhibited >200 times more mechanically stimulated bioluminescence during the dark phase than during the light phase. Mechanical stimulation during the dark phase resulted in 6.7 flashes. cell^?1; flashes were brighter and longer in duration than spontaneous flashes. Cruise-collected cells exhibited variability in quantum flux with few differences in flash kinetics. The role of dinoflagellate spontaneous bioluminescence in the dynamics of near-surface oceanic communities is unknown, but it may be an important source of natural in situ bioluminescence.     

THE ROLE OF REACTIVE OXYGEN SPECIES IN COPPER TOXICITY TO TWO FRESHWATER GREEN ALGAE1

The role of reactive oxygen species (ROS) in copper (Cu) toxicity to two freshwater green algal species, Pseudokirchneriella subcapitata (Korshikov) Hindák and Chlorella vulgaris Beij., was assessed to gain a better mechanistic understanding of this toxicity. Cu‐induced formation of ROS was investigated in the two algal species and linked to short‐term effects on photosynthetic activity and to long‐term effects on cell growth. A light‐ and time‐dependent increase in ROS concentrations was observed upon exposure to environmentally relevant Cu concentrations of 50 and 250 nM and was comparable in both algal species. However, effects of 250 nM Cu on photosynthesis were different, leading to a 12% reduction in photosynthetic activity in P. subcapitata, but not in C. vulgaris. These results indicate that differences in species‐specific sensitivities measured as photosynthetic activity were not caused by differences in the cellular ROS content of the algae, but probably by different species‐specific ROS defense systems. To investigate the role of ROS in Cu‐mediated inhibition of photosynthesis, the ROS scavenger N‐tert‐butyl‐α‐phenylnitrone (BPN) was used, resulting in a reduction of Cu‐induced ROS production up to control level and a complete restoration of photosynthetic activity of Cu‐exposed P. subcapitata. This finding implied that ROS play a primary role in Cu toxicity to algae. Furthermore, we observed a time‐dependent ROS release process across the plasma membrane. More than 90% of total ROS were determined to be extracellular in P. subcapitata, indicating an efficient method of cellular protection against oxidative stress.     

Spectral filters for the control of Botrytis cinerea

Experiments performed in vitro examined the sporulation of Botrytis cinerea (grey mould) under different spectral distributions. Eighty‐three isolates, taken from plants of primula (Primula vulgaris) at different locations throughout the UK, were incubated in the dark, with visible light only and visible plus near‐ultraviolet (nUV) light. On average, compared to isolates not exposed to nUV, sporulation was increased 54‐fold following illumination with nUV light. No isolates showed complete insensitivity to near ultraviolet. New polyethylene materials with different optical properties were then tested on two typical isolates. A film which removed nUV up to 405 nm, compared to a film with nUV absorption up to 384 nm, resulted in the lowest production of conidia (by 5‐fold). The former film was used to clad horticultural polyethylene tunnels in which crops of P. vulgaris and strawberry were grown for two seasons and the incidence of B. cinerea assessed throughout the growth of the crops. The incidence of infection on the P. vulgaris and strawberries was reduced by c. 50% and c. 26% respectively with the nUV blocking film compared to a standard film. The results are discussed in terms of the potential of spectral filters as a novel means of grey mould control in greenhouse‐produced crops.     

Variation in flash speed of Japanese firefly,Luciola cruciata (Coleoptera: Lampyridae), identifies distinct southern “quick‐flash” population on Goto Islands,Japan

Luciola cruciata, a bioluminescent firefly endemic to Japan, communicates with species‐specific flashing patterns. Previous studies reported that flying males possess three distinct flashing frequencies: slow (4 s), intermediate (3 s) and fast (2 s). Our study focused on geographical variations in flashing patterns in the northwestern part of the Kyushu region of southern Japan (including its isolated islands) and their relationship to the mitochondrial COII region of firefly DNA. We found that “quick‐flash (1 s)” fireflies occur in the Goto Islands, at the western tip of Kyushu, and that, although they possess a unique haplotype, they do not differ much genetically from “fast‐flash” fireflies inhabiting mainland Kyushu. In contrast, although fireflies inhabiting the Tsushima and Iki Islands also possess a unique haplotype, their flashing patterns were the same (fast‐flash) as fireflies inhabiting mainland Kyushu. We determined that flash patterns of L. cruciata in Japan should be classified according to four flashing patterns: slow, intermediate, fast and quick.     

Macroalgal decomposition: Laboratory studies with particular regard to microorganisms and meiofauna

The microbial degradation of North Sea macroalgae was studied in laboratory microcosms, containing autoclaved seawater and a mixture of equal parts of air-driedDelesseria sanguinea, Ulva lactuca, andLaminaria saccharina (red, green and brown algae, respectively). To determine the influence of different organisms on the decomposition rate (expressed in terms of algal dry weight loss relative to the material present at time zero) and their development during decomposition processes, yeast, flagellates, ciliates, nematodes and a harpacticoid copepod species were introduced to the microcosms. Results show that microbial degradation compared to the controls was enhanced in the presence of non-axenic nematodes (Monhystera sp.) and protozoans, including bacterivorous ciliates (Euplotes sp. and aUronema-like sp.) and flagellates. No enhancement occurred with yeast (Debaryomyces hansenii) or with the harpacticoid copepodTisbe holothuriae. The most rapid algal dry weight loss (78.7% after 14 d at 18°C) occurred with the addition of raw seawater sampled near benthic algal vegetation and containing only the natural microorganisms present. These consisted mainly of bacteria with different morphological properties, whereby their numbers alone (viable counts) could not be correlated with algal dry weight loss. Although no single dominant species could be determined, lemon yellow pigmented colonies were frequently found. During decomposition in all microcosms the formation of algal particles 40–400 μm was observed, which were rapidly colonized by the other organisms present.     

The interactions between Chlorella vulgaris and algal symbiotic bacteria under photoautotrophic and photoheterotrophic conditions

A Chlorella vulgaris ATCC 13482 culture was semi-continuously cultivated for 18 months in a 4-L photobioreactor and formed associated consortia with other symbionts. Three symbiotic bacterial strains were isolated on heterotrophic medium agar plates. Based on 16S rDNA analysis, they were found to show closest similarity to Pseudomonas alcaligenes, Elizabethkingia miricola and Methylobacterium radiotolerans. C. vulgaris was co-cultured with each bacterial strain, and it was found that the symbiotic bacterium Pseudomonas sp. had a growth-promoting effect on C. vulgaris while the other two inhibited algal growth. The interactions between C. vulgaris and Pseudomonas sp. were further investigated under different cultivation conditions. The co-culture resulted in 1.4 times greater algal cell concentration than that of C. vulgaris alone under photoautotrophic condition. In contrast, the algal cell concentration was lower in the co-culture compared with single algal culture when glucose was supplied in the medium (photoheterotrophic). Under both cultivation conditions, the number of Pseudomonas sp. increased at the beginning of experiment, and then decreased. However, the bacterial number decreased to almost zero under photoheterotrophic conditions, while the growth of bacteria went into a stationary phase under photoautotrophic conditions. The chlorophyll content in C. vulgaris cell was higher in co-culture than in single algal culture. Algal cells in photoautotrophic condition showed higher photosynthetic efficiency compared to those in photoheterotrophic condition. Extracellular organic carbon dissolved in the medium continuously increased under photoautotrophic condition. The mutualistic and competing relationships between C. vulgaris and symbiotic bacteria observed in this study could aid our understanding of algae–bacteria interactions in nature as well as broadening its practical applications.     

Biotreatment of Industrial Wastewater by Selected Algal‐Bacterial Consortia

A new approach for remediation processes in highly polluted environments is presented. The efficiency of algal‐bacterial associations for the remediation of industrial wastewater of a pond in Samara, Russia, was investigated. After screening of algae and bacteria for the resistance to the wastewater the following strains were selected: the algal strains Chlorella sp. ES‐13, Chlorella sp. ES‐30, Scenedesmus obliquus ES‐55, several Stichococcus strains (ES‐19, ES‐85, ES‐86, ES‐87, ES‐88), and Phormidium sp. ES‐90 and the bacterial strains Rhodococcus sp. Ac‐1267, Kibdelosporangium aridum 754 as well as two unidentified bacterial strains (St‐1, St‐2) isolated from the collector pond. All the strains listed above were immobilized onto various solid carriers (capron fibers for algae; ceramics, capron and wood for bacteria) and used for biotreatment in a pilot installation. The results showed that the selected algae and bacteria formed stable consortia during the degradation of the waste, which was demonstrated for the first time for the green alga Stichococcus. Stichococcus and Phormidium cells attached to capron fibers with the help of slime and formed a matrix. This matrix fixed the bacteria and eukaryotic algae and prevented them from being washed off. A significant decrease in the content of the pollutants was observed: phenols were removed up to 85 %, anionic surface active substances (anionic SAS) up to 73 %, oil spills up to 96 %, copper up to 62 %, nickel up to 62 %, zinc up to 90 %, manganese up to 70 %, and iron up to 64 %. The reduction of the biological oxygen demand (BOD₂₅) and the chemical oxygen demand COD amounted to 97 % and 51 %, respectively.     

Allelopathic effects of the submerged macrophyte <Emphasis Type="Italic">Potamogeton malaianus</Emphasis> on <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis>

Allelopathic effects of the submerged macrophyte Potamogeton malaianus on Scenedesmus obliquus were assessed using a two-phase approach under controlled laboratory conditions. In the co-culture experiment (phase І), the growth of S. obliquus at two different initial cell densities was significantly inhibited by P. malaianus. Moreover, the growth inhibition was dependent on the biomass density of P. malaianus. Antioxidant enzymes (SOD, CAT and POD), MDA, APA, total soluble protein, protein electrophoretic pattern and morphology of S. obliquus were determined after the co-culture experiment was terminated. The activities of SOD, CAT, POD and APA at the low initial cell density were stimulated, the contents of MDA and total soluble protein were increased, and some special protein bands disappeared in P. malaianus treatments. The macrophyte had no effect on the activities of SOD and APA at the high initial cell density, but significantly influenced other physiological parameters of S. obliquus with the increase of biomass density. The morphology of S. obliquus showed no difference in the macrophyte treatments and the controls, and the cultures were dominated by 4-celled coenobia. The results indicated P. malaianus had significant allelopathic effects on the growth and physiological processes of S. obliquus. Moreover, the allelopathic effects depended on initial algal cell density, biomass density of the macrophyte, and their interaction. In the experiment of P. malaianus culture filtrates (phase II), filtrates from combined culture of plant and S. obliquus at the low initial cell density exhibited no apparent growth inhibitory effect on S. obliquus. The result showed that initial addition of growth-inhibiting plant filtrates had no allelopathic effect on S. obliquus. We concluded that the allelopathic effects on S. obliquus were found in the presence of P. malaianus, but not in P. malaianus filtrates. However, the absence of allelopathic effect on S. obliquus might be due to the very low concentrations of allelochemicals in the filtrates. Handling editor: S. M. Thomas     

Ability of selected accessions of Phaseolus vulgaris L. to restrict nodulation by particular rhizobia

Plant genotypes that limit nodulation by indigenous rhizobia while nodulating normally with inoculant-strain nodule occupancy in Phaseolus vulgaris. In this study, eight of nine Rhizobium tropici strains and six of 15 Rhizobium etli strains examined, showed limited ability to nodulate and fix nitrogen with the two wild P. vulgaris genotypes G21117 and G10002, but were effective in symbiosis with the cultivated bean genotypes Jamapa and Amarillo Gigante. Five of the R. etli strains restricted in nodulation by G21117 and G10002 produced an alkaline reaction in yeast mannitol medium. In a competition experiment in which restricted strains were tested in 1:1 mixtures with the highly effective R. etli strain CIAT632, the restricted strains produced a low percentage of the nodules formed on G2117, but produced over 40% of the nodules formed on Jamapa. The interaction of the four Rhizobium strains with the two bean genotypes, based on the percentage of nodules formed, was highly significant (P<0.001).     

PHYTOPLANKTON SELENIUM REQUIREMENTS: THE CASE FOR SPECIES ISOLATED FROM TEMPERATE AND POLAR REGIONS OF THE SOUTHERN HEMISPHERE1

A series of laboratory culture experiments was used to investigate the effect of selenium (Se, 0–10 nM) on the growth, cellular volume, photophysiology, and pigments of two temperate and four polar oceanic phytoplankton species [coccolithophore Emiliania huxleyi (Lohmann) W. W. Hay et H. P. Mohler, cyanobacterium Synechococcus sp., prymnesiophyte Phaeocystis sp., and three diatoms—Fragilariopsis cylindrus (Grunow) Kriegar, Chaetoceros sp., and Thalassiosira antarctica G. Karst.]. Only Synechoccocus sp. and Phaeocystis sp. did not show any requirement for Se. Under Se‐deficient conditions, the growth rate of E. huxleyi was decreased by 1.6‐fold, whereas cellular volume was increased by 1.9‐fold. Se limitation also decreased chl a (2.5‐fold), maximum relative electron transport rate (1.9‐fold), and saturating light intensity (2.8‐fold), suggesting that Se plays a role in photosynthesis or high‐light acclimation. Pigment analysis for Antarctic taxa provided an interesting counterpoint to the physiology of E. huxleyi. For all Se‐dependent Antarctic diatoms, Se limitation decreased growth rate and chl a content, whereas cellular volume was not affected. Pigment analysis revealed that other pigments were affected under Se deficiency. Photoprotective pigments increased by 1.4‐fold, while diadinoxanthin:diatoxanthin ratios decreased by 1.5‐ to 4.9‐fold under Se limitation, supporting a role for Se in photoprotection. Our results demonstrate an Se growth requirement for polar diatoms and indicate that Se could play a role in the biogeochemical cycles of other nutrients, such as silicic acid in the Southern Ocean. Se measurements made during the austral summer in the Southern Ocean and Se biological requirement were used to discuss possible Se limitation in phytoplankton from contrasting oceanographic regions.     

Comments on the taxonomic treatment of Micractinium reisseri (Chlorellaceae,Trebouxiophyceae), a common endosymbiont in Paramecium

Micractinium reisseri Hoshina, Iwataki et Imamura (Chlorellaceae, Trebouxiophyceae), an alga symbiotic with the ciliate Paramecium bursaria (Ehrenberg) Focker, was recently renamed M. conductrix (K. Brandt) Pröschold et Darienko. The name ‘conductrix’ was originally given to an algal endosymbiont of Hydra, a genus of Hydrozoa. Here, I outline key differences between symbionts of hydra and Paramecium, and therefore, argue against the validity of the taxonomic treatment of M. reisseri by Pröschold and colleagues.     

Comparison of biomass production and total lipid content of freshwater green microalgae cultivated under various culture conditions

The growth and total lipid content of four green microalgae (Chlorella sp., Chlorella vulgaris CCAP211/11B, Botryococcus braunii FC124 and Scenedesmus obliquus R8) were investigated under different culture conditions. Among the various carbon sources tested, glucose produced the largest biomass or microalgae grown heterotrophically. It was found that 1 % (w/v) glucose was actively utilized by Chlorella sp., C. vulgaris CCAP211/11B and B. braunii FC124, whereas S. obliquus R8 preferred 2 % (w/v) glucose. No significant difference in biomass production was noted between heterotrophic and mixotrophic (heterotrophic with light illumination/exposure) growth conditions, however, less production was observed for autotrophic cultivation. Total lipid content in cells increased by approximately two-fold under mixotrophic cultivation with respect to heterotrophic and autotrophic cultivation. In addition, light intensity had an impact on microalgal growth and total lipid content. The highest total lipid content was observed at 100 μmol m^?2s^?1 for Chlorella sp. (22.5 %) and S. obliquus R8 (23.7 %) and 80 μmol m^?2s^?1 for C. vulgaris CCAP211/11B (20.1 %) and B. braunii FC124 (34.9 %).     

Synergistic effects of different food species on life-history traits of Daphnia galeata

In this paper we describe the life history consequences of feeding Daphnia galeata with different food types in different concentrations. We fed the animals with four concentrations of two green algae Scenedesmus obliquus and Chlamydomonas globosa, given separately as well as in a 1:1 mixture. Growth, reproduction and condition of the animals and consequently the intrinsic rate of population increase, r, increased with the concentration of the food for all three experimental series. The life history parameters measured were lowest in the animals raised on C. globosa. Animals fed on S. obliquus showed higher values for r. We observed a distinct synergistic effect of the two algal species: growth, reproduction, condition and r were significantly higher for the animals raised on the mixed media as compared to the animals raised on the mono-algal media. We conclude that the two algal species represented complementary food resources.     

Biological hydrogen production by the algal biomass Chlorella vulgaris MSU 01 strain isolated from pond sediment

Chlorella vulgaris MSU 01 strain isolated from the sediment of the pond is able to produce molecular hydrogen in a clean way. To relate the dynamic coupling between the cultural conditions and biological responses, an original lab scale set up has been developed for hydrogen production. Different sources like mannitol, glucose, alanine, citric acid, aspartic acid, l-alanine, l-cysteine, sodium succinate and sodium pyruvate were used for algal media optimization. Corn stalk, from 1 to 5 g/L was tested for the effective algal growth and hydrogen production. The cell concentration of 1.6-19 g/L dry cell weight (DCW) was found at the 10th day. The kinetic parameters involved in the hydrogen production at 4 g/L corn stalk using the algal inoculum (50 mL) in the bioreactor volume (500 mL) was found to be with the hydrogen production potential (P_s) of 7.784 mL and production yield of (P_r) 5.534 mL respectively. The growth profile of the algal biomass at the above mentioned condition expressed the logistic model with R² 0.9988. The final pH of the broth was increased from 7.0 to 8.5-8.7. The anaerobic fermentation by C. vulgaris MSU 01 strain involved in the conversion process of complex carbon source has increased the H₂ evolution rate and higher butyrate concentration in the fermentate.