Bi-algal Cultures Research Articles

Allelopathic interactions between the bacillariophyte Skeletonema costatum and the raphidophyte Heterosigma akashiwo

We investigated growth interactions between Skeletonema costatum (Greville) Cleve and Heterosigma akashiwo (Hada) Hada ex Hara et Chihara using bi-algal cultures under axenic conditions. When inoculated at high cell densities, growth of both species was coincidentally sup- pressed. In other combinations of inoculation density, the species first reaching stationary phase sub- stantially reduced maximum cell densities of the other species. When cultured together under condi- tions without cell contact, growth of S. costatum and H. akashiwo were both suppressed. Furthermore, despite re-enrichment with nutrients, filtrates from dense cultures of S. costatum and H. akashiwo reciprocally reduced their maximum cell densities. In additional experiments, growth of Chaetoceros muelleri was also suppressed with filtrates from the above cultures, but growth of Pro- rocentrum minimum was not. Therefore, growth interactions between these species strongly suggest the involvement of allelopathic substances secreted by both species. Finally, growth and interaction of S. costatum and H. akashiwo in bi-algal cultures were simulated using a mathematical model. This model indicated that S. costatum and H. akashiwo steadily approach a stable equilibrium point of about 3.4 × 10 5 cells ml -1 and 4.8 × 10 5 cells ml -1 , respectively, when the 2 species coexist.

Interactions between Prorocentrum donghaiense Lu and Scrippsiella trochoidea (Stein) Loeblich III under laboratory culture

Interactions between Prorocentrum donghaiense Lu and Scrippsiella trochoidea (Stein) Loeblich III, two species of causative bloom dinoflagellates in China, were investigated using bi-algal cultures under controlled laboratory conditions. The growth of P. donghaiense and S. trochoidea were significantly suppressed when the initial cell densities were set at 1.9 × 10 4 cells mL −1 or 1.9 × 10 5 cells mL −1 for P. donghaiense and 1.0 × 10 4 cells mL −1 for S. trochoidea when the initial size/density ratio was 1:1 or 10:1, respectively, but no out-competement was observed in either bi-algal culture by the end. The simultaneous assay on the culture filtrate showed that P. donghaiense filtrate prepared at a lower initial density (1.9 × 10 4 cells mL −1) stimulated the co-cultured S. trochoidea at a density of 1.0 × 10 4 cells mL −1, but filtrate at a higher density (1.9 × 10 5 cells mL −1) depressed its growth. Differently, the filtrate of S. trochoidea at a density of 1.0 × 10 4 cells mL −1 significantly suppressed the growth of P. donghaiense at a density of 1.9 × 10 4 cells mL −1, but had little stimulatory effect on P. donghaiense at a density of 1.9 × 10 5 cells mL −1compared to the control ( P > 0.05). It is likely that these two species of microalgae interact with each other mainly by releasing allelochemical substance(s) into the culture medium, and a direct cell-to-cell contact was not necessary for their mutual interaction. We then quantify their interactions in the bi-algal culture by using a mathematical model. The estimated parameters from the model showed that the inhibition exerted by S. trochoidea on P. donghaiense was about 43 and 24 times stronger than the inhibitory effect that P. donghaiense exerted on S. trochoidea when the initial size/density were 1:1 and 10:1, respectively. S. trochoidea seemed to have a survival strategy that was superior to P. donghaiense in the bi-algal culture under controlled laboratory conditions. We also observed a closely positive relationship between the initial cell density and its effect on the co-cultured microalga by measuring the fluorenscence: filtrate prepared from higher initial cell density had stronger interference on the co-cultured microalga. Moreover, pre-treated under different temperature conditions (30 °C, 60 °C and 100 °C) would significantly changed the effect of culture filtrate on the co-cultured microalga. Result inferred that P. donghaiense or S. trochoidea would release allelochemicals into the bi-algal culture medium and the allelochemicals might be a mixture with temperature-sensitive components in it.

Growth inhibition and formation of morphologically abnormal cells of Akashiwo sanguinea (Hirasaka) G. Hansen et Moestrup by cell contact with Cochlodinium polykrikoides Margalef

We investigated the growth interaction between Cochlodinium polykrikoides and Akashiwo sanguinea using bi-algal cultures. When cultured together, morphologically abnormal cells of A. sanguinea appeared and the growth of A. sanguinea notably decreased. When C. polykrikoides and A. sanguinea were cultured separately in inner and outer wells separated by a membrane with a pore size of 3 μm, neither species showed suppressed growth and no morphologically abnormal cells of A. sanguinea were observed. Furthermore, filtrates from C. polykrikoides cultures did not affect the cell morphology or the growth of A. sanguinea. When the abnormal cells of A. sanguinea were transferred from bi-algal cultures into fresh medium and cultured as a mono-algal culture, cells recovered their normal morphology and multiplied. Therefore, the growth inhibition and formation of morphologically abnormal cells of A. sanguinea would be induced by constant cell contact with C. polykrikoides.

Growth inhibition of Gyrodinium instriatum (Dinophyceae) by Skeletonema costatum (Bacillariophyceae)

Interactions between the red tide-forming dinoflagellate Gyrodinium instriatum Freudenthl et Lee and the diatom Skeletonema costatum (Greville) Cleve were investigated in bialgal cultures. The growth rates and maximum cell densities of G. instriatum decreased dramatically in cultures containing S. costatum. In addition, morphologically abnormal cells of G. instriatum were observed in these cultures, and many cells lost their motility. Conversely, the growth of S. costatum was generally not influenced by the presence of G. instriatum, although small etiolated cells of S. costatum were occasionally observed when the initial cell density of G. instriatum was high. The growth of G. instriatum and S. costatum in the bialgal cultures was simulated using a mathematical model. This interactive model indicated that G. instriatum and S. costatum steadily approach a stable equilibrium point of about 5 × 103 cells ml−1 and 12 × 105 cells ml−1 respectively, when the two species coexist.

Interactions between the bloom-forming dinoflagellates Prorocentrum donghaiense and Alexandrium tamarense in laboratory cultures

Interactions between Prorocentrum donghaiense and Alexandrium tamarens, two bloom-forming dinoflagellates, were investigated using bi-algal cultures. All P. donghaiense died, but A. tamarense was hardly affected by the end of the experiment when the initial cell density was set at 1.0 × 10 4 cells mL − 1 for P. donghaiense and 0.28 × 10 4 cells mL − 1 for A. tamarense. However, significant growth suppression occurred in either species when the initial cell density of P. donghaiense increased to 1.0 × 10 5 cells mL − 1 in the bi-algal culture, but no out-competement was observed. The simultaneous assay on the culture filtrates showed that P. donghaiense filtrate prepared at a lower initial density (1.0 × 10 4 cells mL − 1 ) stimulated growth of the co-cultured A. tamarense (0.28 × 10 4 cells mL − 1 ), but filtrate at a higher initial density (1.0 × 10 5 cells mL − 1 ) depressed its growth. The filtrate of A. tamarense at a density of 0.28 × 10 4 cells mL − 1 killed all P. donghaiense at a lower density (1.0 × 10 4 cells mL − 1 ), but only exhibited an inhibitory effect on it at a higher density (1.0 × 10 5 cells mL − 1 ). It is likely that these two species of microalgae interfere with each other mainly by releasing allelochemical substance(s) into the culture medium, and a direct cell-to-cell contact was not necessary for their mutual interaction . The allelopathic test further proved that A. tamarense could affect the growth of co-cultured P. donghaiense by producing allelochemical(s); moreover, A. tamarense culture filtrate at the stationary growth phase (SP) had a strongly inhibitory effect on P. donghaiense compared to that at the exponential phase (EP). Results also demonstrated a dose-dependent relationship between the microalgal initial cell density and the degree of the allelopathic effect. The growth of P. donghaiense and A. tamarense in the bi-algal cultures was simulated using a mathematical model to quantify the interaction. The estimated parameters from the model showed that the inhibition exerted by A. tamarense on P. donghaiense was about 17 and 8 times stronger than the inhibition P. donghaiense exerted on A. tamarense, when the initial cell density was set at 1.0 × 10 4 and 1.0 × 10 5 cells mL − 1 for P. donghaiense, respectively, and 0.28 × 10 4 cells mL − 1 for A. tamarense in the bi-algal cultures. A. tamarense seems to have a survival strategy that is superior to that of P. donghaiense in bi-algal cultures under controlled laboratory conditions.

Interactions between the red tide dinoflagellates Heterocapsa circularisquama and Gymnodinium mikimotoi in laboratory culture

Abstract Interactions between Heterocapsa circularisquama and Gymnodinium mikimotoi, causative red tide dinoflagellates, were investigated using bialgal cultures. G. mikimotoi was killed by H. circularisquama when the initial cell density of each species was set at 200 cells ml−1. However, cells of H. circularisquama transformed to temporary cysts when the initial cell density of G. mikimotoi was increased to 2000 cells ml−1. Thus the interaction between H. circularisquama and G. mikimotoi was found to be dependent upon the initial cell densities of the two species. Culture filtrate of H. circularisquama induced no inhibitory effect on the growth of G. mikimotoi. Similarly when separated by a membrane filter, G. mikimotoi grew well when cultured with H. circularisquama. G. mikimotoi appear to be killed by cell contact with H. circularisquama. In growth experiments using a culture filtrate of G. mikimotoi and cultures separated by a membrane filter, G. mikimotoi was shown to secrete a substance that inhibited the growth of H. circularisquama. However, the inhibitory effect of the medium was found at higher cell densities of G. mikimotoi than in the bialgal cultures at which the growth of H. circularisquama was suppressed and formed temporary cysts. It is likely that the inhibitory effect of G. mikimotoi on H. circularisquama in the bialgal cultures occurred mainly by direct cell contact. The growth of H. circularisquama and G. mikimotoi in the bialgal cultures was simulated using a mathematical model to quantify the interaction. The degree that G. mikimotoi was inhibited by H. circularisquama was found to be three times larger than the inhibitory effect of G. mikimotoi on H. circularisquama.

Interactions between the prasinophycean tidal pool flagellates Pyramimonas parkeae and Tetraselmis apiculata in batch culture

Field observations have shown apparent competition between Pyramimonas parkeae Norris et Pearson and Tetraselmis apiculata (Butcher) Butcher in tidal pools. To test this, growth studies on both algae in unialgal and bialgal batch culture were undertaken. Growth in bialgal culture revealed distinct interactions between the two species. In bialgal cultures both P. parkeae and T. apiculata had increased growth rates compared with unialgal cultures. In addition, interactions between the two species in bialgal culture caused either a decrease (P. parkeae), or an increase (T. apiculata), in the yield and day-21 count compared with the same growth parameters measured in unialgal culture. Possible mechanisms of interaction between P. parkeae and T. apiculata are discussed.

A modified logistic growth equation: Effects of cadmium chloride on the diatom, Thalassiosira weissflogii and the dinoflagellate, Amphidinium carteri in unialgal and bialgal batch cultures

A simple modification to the logistic equation is proposed: it extends the description of microbial population growth in batch cultures from the exponential, through the stationary, into the decline phase. The modified equation described the effects of cadmium chloride on a diatom and a dinoflagellate in unialgal and bialgal cultures by specifying changes in four parameters: the specific rate of growth, an asymptotic maximum population density, the specific rate of decline, and a parameter related to the time at which the population density is reduced to one half of its value at stationary phase.

MORPHOGENESIS OF MONOSTROMA OXYSPERMUM (KÜTZ.) DOTY (CHLOROPHYCEAE) IN AXENIC CULTURE, ESPECIALLY IN BIALGAL CULTURE1

ABSTRACTThe typical morphology of Monostroma oxyspermum (Kütz.) Doty is lost in axenic culture. In synthetic media of the ASP type, it grows as a colony‐like mass composed of round cells with numerous rhizoids. Such a mass is a fragile structure which falls apart upon shaking, or slight touch, into small cell‐groups and single cells or cells with a long rhizoid. Only temporary saccate or monostromatic fronds appear and reach 1–2 mm in length when grown in enriched seawater media, but disintegrate and become a colony‐like mass. The typical morphology is easily restored by adding at specific intervals filtrates of bacterial cultures and supernatant medium from axenic brown and red algal cultures to the basal medium (ASP7), or by reinfecting the Monostroma with an appropriate bacterial flora. Furthermore, the typical morphology in also maintained by bialgal cultures between Monostroma and other axenic strains of various species of seaweeds except the species belonging to the Chlorophyceae. Monostroma thus appears to utilize some substances released by most species of brown and red algae for its typical growth. Active substances released by bacteria, brown and red algae have not yet been identified and purified. However, it is demonstrated that in axenic cultures many species of seaweeds produce active extracellular substances which play an important role in growth and Morphogenesis of other species of seaweeds.

Population dynamic studies on phytoplankton cultures

Prorocentrum micans Ehrenberg and Gymnodinium splendens Lebour were cultivated in a halfsynthetic medium at 18°C. The generation time was 43.6≦46.8≦50.5 h for P. micans and 49.0≦53.7≦59.3 h for G. splendens. Variation of nutrient concentrations did not influence the generation time, but caused changes in the production rate of new cells. In the stationary phase, P. micans populations grew by 735±50 cells/ml in filtered sea water without addition of nutrients and by 5437±1214 cells/ml with the addition of 500 μg-at NO3-N/l and 30 μg-at PO4-P/l. In bi-algal cultures, P. micans shows changes in generation time and in cell production, whereas with G. splendens changes occur only in cell production. The degree of change depends on the ratio of the two algae as defined at the start of the experiments (see Table 3). P. micans did not grow in the filtered medium previously used to cultivate G. splendens, whereas G. splendens did grow in the filtrate of P. micans cultures. Presumably G. splendens excretes an inhibiting factor affecting the growth of P. micans, whereas the effect on G. splendens production exerted by P. micans seems to be due to nutrient competition. The relevance of the results obtained from in vitro experiments on the interpretation of in situ population dynamics is discussed.