Navicula Seminulum Research Articles

Evaluación breve de la presencia de diatomeas y su relación con algunos parámetros físico-químicos en el río Pirro, Heredia, Costa Rica

La evaluación de la calidad de agua en ecosistemas fluviales en áreas urbanas en el trópico, basada en la utilización de diatomeas, es escasa. Este estudio exploratorio pretendió establecer la composición y riqueza de especies de diatomeas en relación con los parámetros físicos químicos como elemento base para un monitoreo de la microcuenca urbana del río Pirro, Heredia, Costa Rica. Los materiales se colectaron en la parte alta, media y baja del río durante la época seca, lluviosa y de transición. Se analizó el pH, el oxígeno disuelto, la conductividad, la temperatura y la composición de diatomeas raspando una superficie de 20 cm x 20 cm de rocas. Se observaron 18 especies de diatomeas con poca abundancia, con presencia de Navicula seminulum, N. minima y N. cryptotenella que son indicadoras de condiciones moderadas de contaminación y del género Nitzschia que presenta especies tolerantes a contaminantes. La mayor diversidad de especies de diatomeas ocurrió en la época lluviosa y se observaron diferencias significativas entre las épocas del muestreo y la riqueza de especies. Se concluye, con base en la presencia de especies, que el río Pirro presenta condiciones sanitarias malas y que el cauce bajo es el sitio más afectado por la contaminación. Pero es necesario aumentar la información en esta temática.

The effects of different monospecific benthic diatoms on larval settlement, metamorphosis, survival, and growth of Haliotis asinina Linnaeus in the South China Sea

Settlement, metamorphosis, survival, and growth of Haliotis asinina larvae exposed to settlement surfaces coated with biofilms of four local diatom species (Navicula seminulum,Navicula parva,Nitzschia alexandria, Amphora coffeaeformis) were assessed. After 24 h and 72 h, N. alexandria induced the highest settlement rate (p 0.05) for any diatom treatment, but after 72 h, all diatoms induced a significantly higher metamorphosis rate than the control (p 0.05) in diatom film treatments, relative to control. By day 20, post-larvae survived best on slats with N. alexandria (79.86 %). Survival among treatments was the lowest on slats with N. seminulum (54.91 %), and no live larvae were found in the control. Post-larvae on slats with A. coffeaeformis showed the highest daily growth rate of shell length (DGsl) (87.44 μm d−1). Post-larvae on slats with N alexandria showed the lowest DGsl (55.66 μm d−1). Commercial nursery slats seeded with N. alexandria will result in high and consistent settlement, metamorphosis, and survival, while slats with A. coffeaeformis will ensure sufficient food for rapid growth of the H. asinina post-larvae.

Settlement, growth and survival of abalone, Haliotis discus hannai, in response to eight monospecific benthic diatoms

The settlement, early growth and survival of the larval abalone Haliotis discus hannai in response to eight monospecific benthic diatoms were examined in the laboratory. Postlarvae showed active settling and feeding behaviour in all diatom species and in naturally occurring diatoms. Larval settlement rates differed significantly between experimental substrata after 24 h and 48 h. Nitzschia sp. (96.67 %), Hantzschia amphioxys var. leptocephala (95.00 %) and Navicula seminulum (90.00 %) strongly induced larval settlement of H. discus hannai. Postlarvae could feed on benthic diatoms (< 36 μm in shell length) with both weak and strong adhesion on the 4th day after settlement. Greatest growth (shell length) occurred on Nitzschia sp. (786.84 μm ± 2.50 SE and 773.09 μm ± 2.09 SE). Survival of postlarvae was also greatest on Nitzschia sp. (95.33 % ± 1.45 SE). These results indicate the effectiveness of Nitzschia sp., H. amphioxys var. leptocephala, N. seminulum, Rhaphoneis surirella and Navicula corymbosa as single species over natural diatoms in larval settlement and postlarvae growth of H. discus hannai. Thus, Nitzschia sp. has the best potential diet for larval settlement and postlarvae growth of H. discus hannai. H. amphioxys var. leptocephala and N. seminulum can be used as cues to induce larvae settlement, and R. surirella and N. corymbosa can be used as food for growing postlarval.

Combined Exposure to Hydrogen Peroxide and LightSelective Effects on Cyanobacteria, Green Algae, and Diatoms

The selective toxicity of H2O2 was investigated to develop a potential tool for limiting cyanobacterial blooms and to better understand the occurrence of cyanobacteria and other phytoplankton species in relation to reactive oxygen species in surface waters. The cyanobacterium Microcystis aeruginosa, the green alga Pseudokirchneriella subcapitata, and the diatom Navicula seminulum were tested under pulse exposure to H202 in the dark and at various irradiances. H2O2 was decomposed at rates depending on algal species and was proportional to irradiance. The cyanobacterium was affected by H202 at 10 times lower concentrations than green alga and diatom, and a strong light-dependent toxicity enhanced the difference. The inhibition was measured as photosynthetic yield (Fv/Fm) in pulse amplitude modulated fluorometry, and was confirmed by changes in minimal fluorescence (F0) and photosynthetic oxygen evolution. Single doses of 0.27 mg L(-1) of H202 caused 50% inhibition to M. aeruginosa at high irradiance. Such concentration overlaps with the highest levels of 0.34 mg L(-1) observed in natural waters, suggesting that H202 may act as a limiting factor for cyanobacterial growth.

The potential value of different species of benthic diatoms as food for newly metamorphosed sea urchin Strongylocentrotus intermedius

Eight benthic diatom species were isolated from coastal seawater of Dalian, Liaoning, China and their potential as food for aquaculture was evaluated based on their cell characteristics and effect on settlement, growth and survival of newly metamorphosed S. intermedius. All species were within the size range ingested by juvenile sea urchins, i.e. 6.74–35.89 μm. Cellular growth rates ranged from 0.44 divisions day − 1 ( Rhaphoneis surirella) to 0.73 divisions day − 1 ( Navicula seminulum). Eight monocultures of benthic diatoms, mixed diatoms (an equal mixture of the eight species), natural occurring diatoms, and a control (no diatoms) were used as substrata and food to evaluate larval settlement and juvenile growth of S. intermedius. Larval settlement rates differed significantly between experimental substrata after 24 h ( p < 0.05) and 48 h ( p < 0.01). A significantly higher number of larvae settled on R. surirella (53.34% ± 2.22 SE) and Nitzschia sp. (58.32% ± 5.00 SE) compared to N. corymbosa (15.00% ± 0.56 SE), A. coffeaeformis (8.34% ± 2.78 SE) and the control (5.00% ± 1.67 SE) ( p < 0.05) plates. Juveniles could detach benthic diatoms with both weak and strong adhesion on the sixth day after settlement when the mouth opened and the teeth could be seen. Greatest growth (test diameter) occurred on N. corymbosa (631.64 μm ± 1.14 SE). Survival of juvenile was also greatest on N. corymbosa (95.83% ± 1.05 SE). These results indicate the effectiveness of Nitzschia sp., R. surirella, A. proteus var. oculata and N. corymbosa as single species over mixed diatoms and natural diatoms in larval settlement and juvenile growth of S. intermedius. Thus, Nitzschia sp. has the best potential diet for larval settlement and juvenile growth of S. intermedius. R. surirella can be used as cue to induce larvae settlement, and A. proteus var. oculata and N. corymbosa can be used as food for growing juveniles. Nitzschia sp., R. surirella, A. proteus var. oculata and N. corymbosa can be used as good food by sea urchin hatcheries or nurseries, which have traditionally operated with natural diatom films in China, to improve growth and survival of post-larvae, and increase the consistency of production.

Atomic force microscopy study of living diatoms in ambient conditions.

We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species -Eunotia sudetica, Navicula seminulum and a yet unidentified species - are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge.

Translocation of microbenthic algal assemblages used for In situ analysis of metal pollution in rivers

Effects of metal pollution from a zinc factory on microbenthic algal communities were assessed in three neighboring streams on the Dutch-Belgian border. Diatom species composition was experimentally related to water quality by transferring racks with colonized glass discs from a polluted stream to a reference stream and vice versa. The succession of species and the changes in biomass and metal accumulation were measured during experiments in spring, autumn, and winter. Metal concentrations and dry weight in translocated biofilms tended to conform with those in local biofilms within an incubation time of 14 to 18 days. Bray-Curtis similarity values from the different communities indicated that diatom communities responded more completely to the metal-polluted conditions than to the reference water quality. Cymbella minuta, Diatoma vulgare var. ehrenbergii, Navicula sp., and Melosira varians had a lower percentage in assemblages placed in the metal-polluted streams. In contrast, Pinnularia sp. and Neidium ampliatum decreased in assemblages from the polluted streams that were transferred to the reference stream. Achnanthes minutissima and Navicula seminulum (N. atomus) proliferated on any translocation, possibly reflecting an opportunistic strategy and a high tolerance for Zn and Cd. The behavior of the species in relation to metal pollution generally accorded with observations in the literature. However, it seems that metal tolerance is not the only selective factor, and other ecological variables may also influence the composition of microphytobenthic communities.http://link.springer-ny. com/link/service/journals/00244/bibs/37n1p19.html

THE EPILITHIC DIATOM FLORA OF A PRISTINE AND A POLLUTED RIVER IN COSTA RICA, CENTRAL AMERICA

Results from a study on the epilithic diatom communities of a polluted river (Rio Grande de Tarcoles basin) and an unpolluted river (Rio Savegre) in the Central and Southern part of Costa Rica are presented. In this context the taxonomy of diatoms, the most abundant group of algae found in both rivers, is discussed. Altogether 125 diatom taxa were identified in the epilithic communities of these two rivers. The most abundant species in the R. Grande de Tarcoles basin were: Navicula goeppertiana, Gomphonema parvulum, G. sp. aff. pumilum, Nitzschia palea, N. amphibia, N. inconspicua, N. clausii, N. frustulum, Navicula seminulum and N. schroeterii var. escambia. The most abundant species in the R. Savegre were: Achnanthes minutissima, Cymbella sinuata, Rhoicosphenia abbreviata, Cocconeis placentula, Gomphonema rhombicum, Nitzschia fonticola, Fragilaria pinnata and Achnanthes subhudsonis. In addition, Navicula cryptotenella, N. capitatoradiata, Fragilaria ulna and Achnanthes sp. aff. ricula were distributed u...

BENTHIC DIATOM DISTRIBUTION IN A PENNSYLVANIA STREAM: ROLE OF pH AND NUTRIENTS1

ABSTRACTBuffalo Creek is in a forested watershed in eastern Pennsylvania and is relatively acid in upstream reaches (pH∼6), becoming alkaline downstream (pH∼8). Temperature, nitrogen (NO3‐N) and phosphorus (O‐PO4) increase significantly downstream whereas N/P declines. Nutrient‐diffusing substrata were deployed in triplicate at an upstream and downstream site. Six treatments included two concentrations of nitrate, two concentrations of phosphate, nitrogen + phosphate, and a control. Substrata were collected after 18 days, scraped and analyzed for accrual of chlorophyll a and algal community structure. Chlorophyll a and algal biovolume were greatest downstream across all nutrient treatments. At the community level, accrual appeared to be limited by phosphorus at upstream sites. Downstream accrual also may have been phosphorus‐limited, but the results were equivocal. Benthic algae on all treatments at both sites were ∼96% diatoms. Minimal overlap in species composition was observed between upstream and downstream sites. Of the 75 species of diatoms encountered in the study, 58 species did not occur at the upstream site and 10 species did not occur at the downstream site. The upstream site was depauperate in species and dominated by Eunotia exigua (Bréb. ex Kütz.) Rabh., which showed a positive response to phosphorus and accounted for over 50% of the biomass across treatments. The downstream site showed a four‐fold increase in species richness. Communities at this site contained some species that appeared to be phosphorus‐limited, e.g. Melosira varians Ag., and others that seemed to be nitrogen‐limited, e.g. Diatoma vulgare Bory and Navicula seminulum Grun. We conclude that extreme conditions upstream (low pH, high N/P) result in a species‐poor community dominated by acidophilous phosphorus‐limited diatoms. Increases in downstream nutrients and pH result in a relatively rich and diverse community.

BENTHIC DIATOM DISTRIBUTION IN A PENNSYLVANIA STREAM: ROLE OF pH AND NUTRIENTS

Buffalo Creek is in a forested watershed in eastern Pennsylvania and is relatively acid in upstream reaches (pH∼6), becoming alkaline downstream (pH∼8). Temperature, nitrogen (NO3-N) and phosphorus (O-PO4) increase significantly downstream whereas N/P declines. Nutrient-diffusing substrata were deployed in triplicate at an upstream and downstream site. Six treatments included two concentrations of nitrate, two concentrations of phosphate, nitrogen + phosphate, and a control. Substrata were collected after 18 days, scraped and analyzed for accrual of chlorophyll a and algal community structure. Chlorophyll a and algal biovolume were greatest downstream across all nutrient treatments. At the community level, accrual appeared to be limited by phosphorus at upstream sites. Downstream accrual also may have been phosphorus-limited, but the results were equivocal. Benthic algae on all treatments at both sites were ∼96% diatoms. Minimal overlap in species composition was observed between upstream and downstream sites. Of the 75 species of diatoms encountered in the study, 58 species did not occur at the upstream site and 10 species did not occur at the downstream site. The upstream site was depauperate in species and dominated by Eunotia exigua (Bréb. ex Kütz.) Rabh., which showed a positive response to phosphorus and accounted for over 50% of the biomass across treatments. The downstream site showed a four-fold increase in species richness. Communities at this site contained some species that appeared to be phosphorus-limited, e.g. Melosira varians Ag., and others that seemed to be nitrogen-limited, e.g. Diatoma vulgare Bory and Navicula seminulum Grun. We conclude that extreme conditions upstream (low pH, high N/P) result in a species-poor community dominated by acidophilous phosphorus-limited diatoms. Increases in downstream nutrients and pH result in a relatively rich and diverse community.

Interrelation between epilithic algae and algae contained in the digestive tracts of Asellus hilgendorfii

(1) The main dominant species of attached microalgae are Homoeothrix janthina and Cloniophora plumosa in both August and December.(2) The contents of a digestive tract consist mainly of the detritus including small amount of micro-algae and inorganic materials.(3) The main dominant species in the contents of a digestive tract are Navicula seminulum among the all Asellus hilgendorfii examined at every stations in August. Another common species is Gomphonema subangur which appeares more than 10%.(4) The contents of a digestive tract in December are occupied mostly with the detritus which might derive from the decomposition of the leaves.(5) The similarity index Cλ of the micro-algal composition in the digestive tract between A. hilgendorfii at the same station are strongly affected by the appearance of filamentous algae, H. janthina and C. plumosa(6) To measure the algal electivity by A. hilgendorfii based on the method of Ivelv (1961), there is a tendency for both H. janthina and C. plumosa to be avoided, while N. seminulum are selected in August.

Periphyton, chlorophyll a, and diatoms of the Middle Fork of the Salmon River, Idaho

Periphyton samples were collected at 15 sites in the Middle Fork of the Salmon River drainage basin, Idaho, USA to test certain principles of the River Continuum Concept (RCC) and to characterize the diatom communities. The standing crop of chlorophyll a increased from 2nd to 4th order streams, peaked in the 5th order stream, and declined in higher orders. These data support the RCC predictions except that peak values were reached somewhat earlier, in terms of stream order, because of the lack of shading in these streams. Also, downstream decreases were not completely attributable to increasing turbidity and decreasing benthic productivity, and may be partially related to discharge. The number of scraping invertebrates was positively correlated with the standing crop og periphyton (AFDM, not chlorophyll a); this, too, supports the predictions of the RCC. One hundred forty‐five species of diatoms were identified and the system is characterized by an Achnanthes minutissima – Fragilaria pinnata ‐ Navicula seminulum–Cocconeis placentula community.

CONTINUOUS FLOW CULTURE OF BENTHIC DIATOMS AND ITS APPLICATION TO BIOASSAY1,2

ABSTRACTThe benthic diatom, Navicula seminulum var. hustedtii Patr, was isolated from the field and studied in laboratory cultures. Experiments were conducted to determine the suitability of Millipore membranes and solidified agar substrate for diatom colonization under continuous flow conditions. Diatom colonization showed large variation and low reproducibility on Millipore membranes of different materials and pore sizes. Solidified agar substrate supported stable and reproducible colonization and is nutritionally neutral, translucent, homogeneous and easy to sample. The diatom colonization process on agar substrate involved four growth phases: i) pioneer; ii) exponential; iii) steady state; and, iv) vanishing. The culture system was also used in bioassay, testing the toxic effect of copper on the growth of benthic diatoms. The proposed method provides a useful means for studying autecology of benthic diatoms as well as for bioassay work.

Alcune Forme Teratologiche Comparse in Colture diNavicula MinimaGrun. eNavicula SeminulumGrun

Abstract Some teratological forms present in cultures of «Navicula minima» Grun. and «Navicula seminulum» Grun. — The teratological frustules of the Navicula minima and of the Navicula seminulum which appeared in the old cultures on the agarized soil have examined at the electron microscope. The alterations are particularly concerned with the contour of the valve, the position, the size and the number of the central and polar nodules, the axial area often fragmented like the raphe and the striae are oriented variously on the plane of the valve. The causes of such alterations can be found in the nutritional conditions and the unfavorable environments. The examined teratological forms, however bizzar and numerous have in common the characteristic of presenting their structure in relation to the distribution of the 2ones of major thickness of the walls; which are the first to appear in the initial formation of the new thecae; for this reason it is in this moment that the definitive, normal or teratological s...

Studio Comparativo della Struttura e del Ciclo Biologico di Due Diatomee di Acqua Dolce:Navicula MinimaGrun. ENavicula SeminulumGrun: II. Struttura e Ciclo Biologico: diNavicula SeminulumGrun. ColtivataIn Vitro

Abstract Comparative study of the structure and of the biological cycle of two fresh water diatoms: « Navicula minima » Grun. and « Navicula seminulum » Grun. II. Structure and biological cycle of « Navicula seminulum » Grun. cultivated « in vitro ». — The Navicula seminulum Grun. was isolated in a clonal culture adopting the cultural soil agarized by Tanada. The investigations were conducted in a particular way in two clones, even though very similar to each other, and, for a better definition of the « type » studied, the integral description of the diatom under examination made by various authors was reported. It was revealed that the existent divergences on this matter often are notable also in connection with the institution of numerous varieties within the species, of which the variety intermedia Hustedt, the variety radiosa Hustedt, the var. Bergii A. Cleve-Euler, the var. brevis A. Cleve-Euler, the var. fragilarioides Grun., and others, whose validity is not yet demonstrated on the basis of deepened studies. The biological cycle of the N. seminulum Grun. occurs according to the observed procedures for the N. minima Grun., even though the maximum length is about 18–20 μ and the minimum around 4 μ. The cells enter into sexual reproduction when they reach dimensions of about 8,5 μ, on the condition that the nutritious conditions are of the best. The gamy occurs between two partners, one of which pours its entire protoplast into the other through a short canal for copulation, behaving, therefore, as a masculine component. The auxozygotes restore the maximum dimensions of the cells and the cycle repeats itself once more, spending on the average about 4 to 5 months. During the vegetative multiplication the proportions between the length of the axis at its apex and that across the apex length alterred, passing from a maximum value of about 4 to a minimum value of about 1,30; this phenomenon was represented graphically by means of lines of regression. The form of the valve, for some reason, undergoes a gradual modification, passing from a linear-elliptical form, with evident swelling in the middle part and characteristically rounded extremity, to a form simply elliptical and, at times, not quite round. As regards the structure of the frustule, the N. seminulum presents an axial area, narrow and linear, an ample central area enlarged transversally, and striae very evident in numebr of 18–20 in 10 μ. The wall of the frustule, examined by the electric microscope, appears to be of the laminar type with striae constituted of coupled rows of holes disposed in an alternate manner. This structural element is certainly of considerable diagnostic importance, and will have to keep itself present when one wishes to relate to N. seminulum Grun. several varieties, mentioned a little above, whose systematic position is actually uncertain.

Studio Comparativo della Struttura e del Ciclo Biologico di Due Diatomee di Acqua Dolce:Navicula MinimaGrun. ENavicula SeminulumGrun.: III. Esame Dei Caratteri diNavicula MinimaGrun. E diNavicula SeminulumGrun

Abstract Comparative study of the structure and of the biological cycle of two fresh water diatoms: « Navicula minima » Grun. and « Navicula seminulum » Grun. III. Examination of the characteristics of « N. minima » Grun. and « N. seminulum » Grun. — After studing separately the Navicula minima Grun. and the Navicula seminulum Grun. the various characteristics of the two have been compared and contrasted for purpose of classification. The form and dimentions of the frustules, the density and the structure of the streaks, the structure of the walls, the life circle, aspects of their growths, and some anomalies, most especially, as regards the streaks were examined. It was found the among such numerous characteristics, only one, that is, the presence of the streaks formed by double rows of pores in N. seminulum rather than of a simple file as in N. minima makes one thinks that, in spite of strong similarities existing between these two Naviculae, they are to be regarded as belonging to e different systemati...

Studio Comparativo della Struttura e del Ciclo Biologico di Due Diatomee di Acqua Dolce:Navicula MinimaGrun. ENavicula SeminulumGrun: I. Struttura e Ciclo Biologico diNavicula MinimaGrun. ColtivataIn Vitro

Abstract Comparative study of the structure and of the biological cycle of two fresh water diatoms: « Navicula minima » Grun. and « Navicula seminulum » Grun. I. Structure and biological cycle of « Navicula minima » Grun. cultivated « in vitro ». — The Navicula minima Grun. was isolated in a clonal culture using cultural soil agarized by Tanada. To accomplish the biometrical and structural study of the frustules, the cleaning was performed with concentrated sulphuric acid and sodium nitrate. The observations of the chromatophores, the nucleus, and the ribosomes were executed with a fluorescent microscope using Acridine orange. Before to expose the experimental part some descriptions made by various researchers were reported, emphasizing the existence of considerable differences among those in the same species. The structure of the frustule is that which is typical of all the Naviculae in the species under examination a narrow axial area is present and a central area rather enlarged transversally. The wall...