The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Bruce Jefferson - One of the best experts on this subject based on the ideXlab platform.
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The influence of ultrasound frequency and power, on the algal species Microcystis aeruginosa, Aphanizomenon flos-aquae, Scenedesmus subspicatus and Melosira sp.
Environmental technology, 2020Co-Authors: Diane Purcell, Simon A Parsons, Bruce JeffersonAbstract:We report on the effectiveness of sonication on controlling the growth of four problematic algal species which are morphologically different and from three algal divisions. Two cyanobacterial species Microcystis aeruginosa (unicellular) and Aphanizomenon flos-aquae (filamentous), one green alga Scenedesmus subspicatus (colonial) and lastly a diatom species Melosira sp. (filamentous) were subjected to ultrasound of selected low to high frequencies ranging from 20 to 1144 kHz. Microcystis aeruginosa and Scenedesmus subspicatus highest cell removal rates were 16 +/- 2% and 20 +/- 3% when treated with the same ultrasound frequency of 862 kHz but differing energy levels of 133 and 67 kWh m(-3), respectively. Aphanizomenon flos-aquae best removal rate was 99 +/- 1% after 862 kHz and 133 kWh m(-3) of energy, with Melosira sp. achieving its highest cell removal at 83% subsequent to ultrasound of 20 kHz and 19 kWh m(-3). Microcystis aeruginosa and Scenedesmus subspicatus are considered non-susceptible species to ultrasound treatment from a water treatment perspective due to their low cell removal rates; however, photosynthetic activity reduction of 65% for Microcystis aeruginosa does indicate the possible utilization of ultrasound to control bloom growth, rather than bloom elimination. Conversely, Aphanizomenon flos-aquae and Melosira sp. are deemed species highly susceptible to ultrasound. Morphological differences in shape (filamentous/non-filamentous) and cell wall structure (silica/peptidoglycan), and presence of gas vacuoles are probable reasons for these differing levels of susceptibility to ultrasound.
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the influence of ultrasound frequency and power on the algal species microcystis aeruginosa aphanizomenon flos aquae scenedesmus subspicatus and Melosira sp
Environmental Technology, 2013Co-Authors: Diane Purcell, Simon A Parsons, Bruce JeffersonAbstract:We report on the effectiveness of sonication on controlling the growth of four problematic algal species which are morphologically different and from three algal divisions. Two cyanobacterial species Microcystis aeruginosa (unicellular) and Aphanizomenon flos-aquae (filamentous), one green alga Scenedesmus subspicatus (colonial) and lastly a diatom species Melosira sp. (filamentous) were subjected to ultrasound of selected low to high frequencies ranging from 20 to 1144 kHz. Microcystis aeruginosa and Scenedesmus subspicatus highest cell removal rates were 16±2% and 20±3% when treated with the same ultrasound frequency of 862 kHz but differing energy levels of 133 and 67 kWh m−3, respectively. Aphanizomenon flos-aquae best removal rate was 99±1% after 862 kHz and 133 kWh m−3 of energy, with Melosira sp. achieving its highest cell removal at 83% subsequent to ultrasound of 20 kHz and 19 kWh m−3. Microcystis aeruginosa and Scenedesmus subspicatus are considered non-susceptible species to ultrasound treatmen...
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characterisation of algogenic organic matter extracted from cyanobacteria green algae and diatoms
Water Research, 2008Co-Authors: Rita K Henderson, Simon A Parsons, Andy Baker, Bruce JeffersonAbstract:Abstract Algogenic organic matter (AOM) can interfere with drinking water treatment processes and comprehensive characterisation of AOM will be informative with respect to treatability. This paper characterises the AOM originating from four algae species ( Chlorella vulgaris , Microcystis aeruginosa , Asterionella formosa and Melosira sp.) using techniques including dissolved organic carbon (DOC), specific UV absorbance (SUVA), zeta potential, charge density, hydrophobicity, protein and carbohydrate content, molecular weight and fluorescence. All AOM was predominantly hydrophilic with a low SUVA. AOM had negative zeta potential values in the range pH 2–10. The stationary phase charge density of AOM from C. vulgaris was greatest at 3.2 meq g −1 while that of M. aeruginosa and Melosira sp. was negligible. Lower charge density was related to higher hydrophobicity, while it was related in turn to increasing proteins >500 kDa:carbohydrate ratio. This demonstrates that AOM is of a very different character to natural organic matter (NOM).
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successful removal of algae through the control of zeta potential
Separation Science and Technology, 2008Co-Authors: Rita K Henderson, Simon A Parsons, Bruce JeffersonAbstract:Abstract Algae can interfere with treatment processes at a water treatment works. Coagulation control is critical to reduce the impact of algae on downstream processes. This paper investigates the coagulation and flotation of four species of algae – Asterionella formosa, Melosira sp., Microcystis aeruginosa, and Chlorella vulgaris. The zeta potential at optimum removal was measured and it was observed that when the zeta potential was reduced to between −8 mV and +2 mV, removal of algae and associated organic material was optimized, irrespective of the coagulant dose or pH. Process control using zeta potential is therefore a viable tool for algae removal.
David G. Mann - One of the best experts on this subject based on the ideXlab platform.
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Sperm ultrastructure in the diatoms Melosira and Thalassiosira and the significance of the 9 + 0 configuration
Protoplasma, 2013Co-Authors: Masahiko Idei, Keigo Osada, Tamotsu Nagumo, Takeshi Nakayama, Shinya Sato, David G. MannAbstract:The most complete account to date of the ultrastructure of flagellate cells in diatoms is given for the sperm of Thalassiosira lacustris and Melosira moniliformis var. octogona , based on serial sections. The sperm are uniflagellate, with no trace of a second basal body, and possess a 9 + 0 axoneme. The significance of the 9 + 0 configuration is discussed: lack of the central pair microtubules and radial spokes does not compromise the mastigoneme-bearing flagellum’s capacity to perform planar beats and thrust reversal and may perhaps be related to sensory/secretory function of the sperm flagellum during plasmogamy. The basal bodies of diatoms are confirmed to contain doublets rather than triplets, which may correlate with the absence of some centriolar proteins found in most cells producing active flagella. Whereas Melosira possesses a normal cartwheel structure in the long basal body, no such structure is present in Thalassiosira , which instead possesses ‘intercalary fibres’ linking the basal body doublets. No transitional helices or transitional plates are present in either species studied. Cones of microtubules are associated with the basal body and partially enclose the nucleus in M. moniliformis and T. lacustris . They do not appear to be true microtubular roots and may arise through transformation of the meiosis II spindle. A close association between cone microtubules and tubules containing mastigonemes may indicate a function in intracellular mastigoneme transport. No correlation can yet be detected between methods of spermatogenesis and phylogeny in diatoms, contrary to previous suggestions.
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Sperm ultrastructure in the diatoms Melosira and Thalassiosira and the significance of the 9 + 0 configuration.
Protoplasma, 2012Co-Authors: Masahiko Idei, Keigo Osada, Tamotsu Nagumo, Takeshi Nakayama, Shinya Sato, David G. MannAbstract:The most complete account to date of the ultrastructure of flagellate cells in diatoms is given for the sperm of Thalassiosira lacustris and Melosira moniliformis var. octogona, based on serial sections. The sperm are uniflagellate, with no trace of a second basal body, and possess a 9 + 0 axoneme. The significance of the 9 + 0 configuration is discussed: lack of the central pair microtubules and radial spokes does not compromise the mastigoneme-bearing flagellum’s capacity to perform planar beats and thrust reversal and may perhaps be related to sensory/secretory function of the sperm flagellum during plasmogamy. The basal bodies of diatoms are confirmed to contain doublets rather than triplets, which may correlate with the absence of some centriolar proteins found in most cells producing active flagella. Whereas Melosira possesses a normal cartwheel structure in the long basal body, no such structure is present in Thalassiosira, which instead possesses ‘intercalary fibres’ linking the basal body doublets. No transitional helices or transitional plates are present in either species studied. Cones of microtubules are associated with the basal body and partially enclose the nucleus in M. moniliformis and T. lacustris. They do not appear to be true microtubular roots and may arise through transformation of the meiosis II spindle. A close association between cone microtubules and tubules containing mastigonemes may indicate a function in intracellular mastigoneme transport. No correlation can yet be detected between methods of spermatogenesis and phylogeny in diatoms, contrary to previous suggestions.
Masahiko Idei - One of the best experts on this subject based on the ideXlab platform.
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Sperm ultrastructure in the diatoms Melosira and Thalassiosira and the significance of the 9 + 0 configuration
Protoplasma, 2013Co-Authors: Masahiko Idei, Keigo Osada, Tamotsu Nagumo, Takeshi Nakayama, Shinya Sato, David G. MannAbstract:The most complete account to date of the ultrastructure of flagellate cells in diatoms is given for the sperm of Thalassiosira lacustris and Melosira moniliformis var. octogona , based on serial sections. The sperm are uniflagellate, with no trace of a second basal body, and possess a 9 + 0 axoneme. The significance of the 9 + 0 configuration is discussed: lack of the central pair microtubules and radial spokes does not compromise the mastigoneme-bearing flagellum’s capacity to perform planar beats and thrust reversal and may perhaps be related to sensory/secretory function of the sperm flagellum during plasmogamy. The basal bodies of diatoms are confirmed to contain doublets rather than triplets, which may correlate with the absence of some centriolar proteins found in most cells producing active flagella. Whereas Melosira possesses a normal cartwheel structure in the long basal body, no such structure is present in Thalassiosira , which instead possesses ‘intercalary fibres’ linking the basal body doublets. No transitional helices or transitional plates are present in either species studied. Cones of microtubules are associated with the basal body and partially enclose the nucleus in M. moniliformis and T. lacustris . They do not appear to be true microtubular roots and may arise through transformation of the meiosis II spindle. A close association between cone microtubules and tubules containing mastigonemes may indicate a function in intracellular mastigoneme transport. No correlation can yet be detected between methods of spermatogenesis and phylogeny in diatoms, contrary to previous suggestions.
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Sperm ultrastructure in the diatoms Melosira and Thalassiosira and the significance of the 9 + 0 configuration.
Protoplasma, 2012Co-Authors: Masahiko Idei, Keigo Osada, Tamotsu Nagumo, Takeshi Nakayama, Shinya Sato, David G. MannAbstract:The most complete account to date of the ultrastructure of flagellate cells in diatoms is given for the sperm of Thalassiosira lacustris and Melosira moniliformis var. octogona, based on serial sections. The sperm are uniflagellate, with no trace of a second basal body, and possess a 9 + 0 axoneme. The significance of the 9 + 0 configuration is discussed: lack of the central pair microtubules and radial spokes does not compromise the mastigoneme-bearing flagellum’s capacity to perform planar beats and thrust reversal and may perhaps be related to sensory/secretory function of the sperm flagellum during plasmogamy. The basal bodies of diatoms are confirmed to contain doublets rather than triplets, which may correlate with the absence of some centriolar proteins found in most cells producing active flagella. Whereas Melosira possesses a normal cartwheel structure in the long basal body, no such structure is present in Thalassiosira, which instead possesses ‘intercalary fibres’ linking the basal body doublets. No transitional helices or transitional plates are present in either species studied. Cones of microtubules are associated with the basal body and partially enclose the nucleus in M. moniliformis and T. lacustris. They do not appear to be true microtubular roots and may arise through transformation of the meiosis II spindle. A close association between cone microtubules and tubules containing mastigonemes may indicate a function in intracellular mastigoneme transport. No correlation can yet be detected between methods of spermatogenesis and phylogeny in diatoms, contrary to previous suggestions.
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Successive observations on the fertilization of a centric diatomMelosira moniliformis var.octagona
The botanical magazine = Shokubutsu-gaku-zasshi, 1992Co-Authors: Masahiko Idei, Mitsuo ChiharaAbstract:The details of fertilization in the centric diatom, Melosira moniliformis var. octagona , were examined by light microscopy with a video system. The sperm penetrated into the egg cell through a temporary opening of the oogonium. The flagellum of the sperm was brought into the egg cell and it remained active for a few minutes. Three observations on the behavior of the sperm and egg cell during fertilization are shown.
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successive observations on the fertilization of a centric diatom Melosira moniliformis var octagona
Journal of Plant Research, 1992Co-Authors: Masahiko Idei, Mitsuo ChiharaAbstract:The details of fertilization in the centric diatom,Melosira moniliformis var.octagona, were examined by light microscopy with a video system. The sperm penetrated into the egg cell through a temporary opening of the oogonium. The flagellum of the sperm was brought into the egg cell and it remained active for a few minutes. Three observations on the behavior of the sperm and egg cell during fertilization are shown.
Simon A Parsons - One of the best experts on this subject based on the ideXlab platform.
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The influence of ultrasound frequency and power, on the algal species Microcystis aeruginosa, Aphanizomenon flos-aquae, Scenedesmus subspicatus and Melosira sp.
Environmental technology, 2020Co-Authors: Diane Purcell, Simon A Parsons, Bruce JeffersonAbstract:We report on the effectiveness of sonication on controlling the growth of four problematic algal species which are morphologically different and from three algal divisions. Two cyanobacterial species Microcystis aeruginosa (unicellular) and Aphanizomenon flos-aquae (filamentous), one green alga Scenedesmus subspicatus (colonial) and lastly a diatom species Melosira sp. (filamentous) were subjected to ultrasound of selected low to high frequencies ranging from 20 to 1144 kHz. Microcystis aeruginosa and Scenedesmus subspicatus highest cell removal rates were 16 +/- 2% and 20 +/- 3% when treated with the same ultrasound frequency of 862 kHz but differing energy levels of 133 and 67 kWh m(-3), respectively. Aphanizomenon flos-aquae best removal rate was 99 +/- 1% after 862 kHz and 133 kWh m(-3) of energy, with Melosira sp. achieving its highest cell removal at 83% subsequent to ultrasound of 20 kHz and 19 kWh m(-3). Microcystis aeruginosa and Scenedesmus subspicatus are considered non-susceptible species to ultrasound treatment from a water treatment perspective due to their low cell removal rates; however, photosynthetic activity reduction of 65% for Microcystis aeruginosa does indicate the possible utilization of ultrasound to control bloom growth, rather than bloom elimination. Conversely, Aphanizomenon flos-aquae and Melosira sp. are deemed species highly susceptible to ultrasound. Morphological differences in shape (filamentous/non-filamentous) and cell wall structure (silica/peptidoglycan), and presence of gas vacuoles are probable reasons for these differing levels of susceptibility to ultrasound.
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the influence of ultrasound frequency and power on the algal species microcystis aeruginosa aphanizomenon flos aquae scenedesmus subspicatus and Melosira sp
Environmental Technology, 2013Co-Authors: Diane Purcell, Simon A Parsons, Bruce JeffersonAbstract:We report on the effectiveness of sonication on controlling the growth of four problematic algal species which are morphologically different and from three algal divisions. Two cyanobacterial species Microcystis aeruginosa (unicellular) and Aphanizomenon flos-aquae (filamentous), one green alga Scenedesmus subspicatus (colonial) and lastly a diatom species Melosira sp. (filamentous) were subjected to ultrasound of selected low to high frequencies ranging from 20 to 1144 kHz. Microcystis aeruginosa and Scenedesmus subspicatus highest cell removal rates were 16±2% and 20±3% when treated with the same ultrasound frequency of 862 kHz but differing energy levels of 133 and 67 kWh m−3, respectively. Aphanizomenon flos-aquae best removal rate was 99±1% after 862 kHz and 133 kWh m−3 of energy, with Melosira sp. achieving its highest cell removal at 83% subsequent to ultrasound of 20 kHz and 19 kWh m−3. Microcystis aeruginosa and Scenedesmus subspicatus are considered non-susceptible species to ultrasound treatmen...
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characterisation of algogenic organic matter extracted from cyanobacteria green algae and diatoms
Water Research, 2008Co-Authors: Rita K Henderson, Simon A Parsons, Andy Baker, Bruce JeffersonAbstract:Abstract Algogenic organic matter (AOM) can interfere with drinking water treatment processes and comprehensive characterisation of AOM will be informative with respect to treatability. This paper characterises the AOM originating from four algae species ( Chlorella vulgaris , Microcystis aeruginosa , Asterionella formosa and Melosira sp.) using techniques including dissolved organic carbon (DOC), specific UV absorbance (SUVA), zeta potential, charge density, hydrophobicity, protein and carbohydrate content, molecular weight and fluorescence. All AOM was predominantly hydrophilic with a low SUVA. AOM had negative zeta potential values in the range pH 2–10. The stationary phase charge density of AOM from C. vulgaris was greatest at 3.2 meq g −1 while that of M. aeruginosa and Melosira sp. was negligible. Lower charge density was related to higher hydrophobicity, while it was related in turn to increasing proteins >500 kDa:carbohydrate ratio. This demonstrates that AOM is of a very different character to natural organic matter (NOM).
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successful removal of algae through the control of zeta potential
Separation Science and Technology, 2008Co-Authors: Rita K Henderson, Simon A Parsons, Bruce JeffersonAbstract:Abstract Algae can interfere with treatment processes at a water treatment works. Coagulation control is critical to reduce the impact of algae on downstream processes. This paper investigates the coagulation and flotation of four species of algae – Asterionella formosa, Melosira sp., Microcystis aeruginosa, and Chlorella vulgaris. The zeta potential at optimum removal was measured and it was observed that when the zeta potential was reduced to between −8 mV and +2 mV, removal of algae and associated organic material was optimized, irrespective of the coagulant dose or pH. Process control using zeta potential is therefore a viable tool for algae removal.
Eugene A Silow - One of the best experts on this subject based on the ideXlab platform.
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the Melosira years of lake baikal winter environmental conditions at ice onset predict under ice algal blooms in spring
Limnology and Oceanography, 2015Co-Authors: Stephen L Katz, Lyubov R Izmesteva, Stephanie E Hampton, Ted Ozersky, Kirill Shchapov, Marianne V Moore, Svetlana V Shimaraeva, Eugene A SilowAbstract:Winter primary production in seasonally ice-covered lakes historically has not been well studied, but it is increasingly recognized as an important component of lake metabolism. Lake Baikal in Siberia is not only the World's oldest, deepest, and most biologically diverse lake, but also where large under-ice blooms of the diatom Aulacoseira baicalensis (formerly Melosira) occur in some years. The phenomenon of “Melosira years” is noteworthy both for the intensity of the diatom blooms, in which total under-ice production can be a majority of total annual production, and for the enigmatic regularity of their occurrence every 3–4 yr. The degree to which these episodic blooms might be controlled by external forcing and endogenous lake processes has been debated for decades. We used a 50-yr time series of phytoplankton observations to statistically model the occurrence of Aulacoseira blooms as a function of meteorological and climatological predictor variables. The results support the hypothesis that a confluence of meteorological conditions in the preceding fall season, which favor clear ice formation with minimal snow cover, also favor Aulacoseira blooms in the following spring. Further, we observe that this confluence of factors is related to relatively strong states of the Siberian High which, while not strictly periodic, do explain a significant fraction of the interannual bloom pattern. Finally, our analyses show that the timing of the peak abundance of A. baicalensis shifted 1.6 months later across the 50-yr time series, corresponding with the delay in ice-on timing that has been associated with climate change.
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The “Melosira years” of Lake Baikal: Winter environmental conditions at ice onset predict under‐ice algal blooms in spring
Limnology and Oceanography, 2015Co-Authors: Stephen L Katz, Stephanie E Hampton, Ted Ozersky, Kirill Shchapov, Marianne V Moore, Svetlana V Shimaraeva, Lyubov R. Izmest'eva, Eugene A SilowAbstract:Winter primary production in seasonally ice-covered lakes historically has not been well studied, but it is increasingly recognized as an important component of lake metabolism. Lake Baikal in Siberia is not only the World's oldest, deepest, and most biologically diverse lake, but also where large under-ice blooms of the diatom Aulacoseira baicalensis (formerly Melosira) occur in some years. The phenomenon of “Melosira years” is noteworthy both for the intensity of the diatom blooms, in which total under-ice production can be a majority of total annual production, and for the enigmatic regularity of their occurrence every 3–4 yr. The degree to which these episodic blooms might be controlled by external forcing and endogenous lake processes has been debated for decades. We used a 50-yr time series of phytoplankton observations to statistically model the occurrence of Aulacoseira blooms as a function of meteorological and climatological predictor variables. The results support the hypothesis that a confluence of meteorological conditions in the preceding fall season, which favor clear ice formation with minimal snow cover, also favor Aulacoseira blooms in the following spring. Further, we observe that this confluence of factors is related to relatively strong states of the Siberian High which, while not strictly periodic, do explain a significant fraction of the interannual bloom pattern. Finally, our analyses show that the timing of the peak abundance of A. baicalensis shifted 1.6 months later across the 50-yr time series, corresponding with the delay in ice-on timing that has been associated with climate change.