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Tatsuya Oda - One of the best experts on this subject based on the ideXlab platform.
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possible factors responsible for the fish killing mechanisms of the red tide phytoplankton chattonella Marina and cochlodinium polykrikoides
Coastal Environmental and Ecosystem Issues of the East China Sea, 2010Co-Authors: Daekyung Kim, Tatsuya OdaAbstract:Generation of reactive oxygen species (ROS) such as superoxide (O2 –) and hydroxyl radical (·OH) by Chattonella Marina could be confirmed by ESR spin trapping method. Several lines of evidence suggested that cell surface structure of C. Marina, glycocalyx, has NADPH-dependent O2 – generation system. Immunohistochemical analysis of gill lamellae from yellowtail exposed to C. Marina using antiserum against crude glycocalyx demonstrated that there were the antigns recognaised by the antiserum on the surface of gill lamellae. The results suggest that continuous accumulation of discharged glycocalyx on the gill surface occurs during C. Marina exposure, which may be responsible for the ROSmediated severe gill tissue damage leading to fish death. As compare to C. Marina, the levels of O2 – and H2O2 detected in Cochlodinium polykrikoides were trace levels. Furthermore, no significant increase in O2 – generation by C. polykrikoides was observed in the presence of lectins or fish mucus prepared from skin and gill of yellowtail, whereas C. Marina generated increased level of O2 – responding to these stimuli. The cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on HeLa cells, but the extract of C. Marina had almost no effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the culture of C. polykrikoides, and the medium gradually became viscous, but no such change was observed in the medium of C. Marina. These results suggest that ichthyotoxic mechanisms of C. Marina and C. polykrikoides are different. ROS may play a significant role in the fish-killing activity of C. Marina, whereas in the case of C. polykrikoides, certain toxic substances or polysaccharides are mainly responsible for the toxicity rather than ROS.
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mode of action of an antialgal agent produced by a marine gammaproteobacterium against chattonella Marina
Aquatic Microbial Ecology, 2006Co-Authors: Takuji Nakashima, Daekyung Kim, Satoshi Takeshita, Kenichi Yamaguchi, Yousuke Miyazaki, Tatsuya OdaAbstract:A marine gammaproteobacterium, strain MS-02-063, was able to kill Chattonella Marina, a noxious red tide phytoplankton. However, the algicidal activity of bacterial cells washed with the planktonic medium was significantly reduced. These results suggest that strain MS-02-063 produces an extracellular substance, the pigment, PG-L-1, that showed a potent algicidal effect on C. Marina. The LD 50 value of PG-L-1 was calculated to be approximately 8.5 μg ml -1 . At the approximate LD 50 concentration of 10 μg ml -1 , a morphological change, which seemed to be due to the inhibition of cell division, was observed in C. Marina. Almost all cells of C. Marina were destroyed readily at 100 μg ml -1 of PG-L-1, and the cytostatic activity of PG-L-1 against this phytoplankton was observed at a concentration of 1 μg ml -1 during the 5 d of incubation. A sublethal concentration of PG-L-1 of 10 μg ml -1 significantly inhibited the reactive oxygen species (ROS) production by C. Marina. ROS production has been previously reported to be essential for normal growth of C. Marina (Oda et al. 1995; Biosci Biotechnol Biochem 59:2044-2048). Therefore, the inhibitory effect of PG-L-1 on ROS production may lead to growth inhibition of C. Marina, at least in part. The pigment, PG-L-1, may be a useful compound not only as an applicable agent for the mitigation of harmful algal blooms, but also as an experimental tool to analyse the ROS production system in a red tide phytoplankton such as C. Marina.
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nitric oxide synthase like enzyme mediated nitric oxide generation by harmful red tide phytoplankton chattonella Marina
Journal of Plankton Research, 2006Co-Authors: Daekyung Kim, Kenichi Yamaguchi, Tatsuya OdaAbstract:The unicellular marine phytoplankton Chattonella Marina is known to exhibit potent fish-killing activity. Previous studies have demonstrated that C. Marina produces reactive oxygen species (ROS), and ROS-mediated ichthyotoxic mechanism has been postulated. However, the exact toxic mechanism is still controversial. In this study, we obtained evidence that C. Marina produces nitric oxide (NO) under normal growth conditions. We utilized chemiluminescence (CL) reaction between NO and luminol-H 2 O 2 to detect NO in C. Marina cell suspensions. In this assay, significant CL was observed in C. Marina in a cell-number-dependent manner, and this was diminished by the addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a specific NO scavenger. The NO generation by C. Marina was also confirmed by a spectrophotometric assay based on the measurement of the diazo-reaction-positive substances (NO x ) and by fluorometric assay using highly specific fluorescent indicator of NO. The NO level in C. Marina was significantly decreased by N G -nitro-L-arginine methyl ester (L-NAME), a specific NO synthase (NOS) inhibitor. The addition of L-arginine resulted in the increased NO level, whereas NaNO 2 had no effect. These results suggest that a NOS-like enzyme is mainly responsible for NO generation in C. Marina.
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cardiac output during exposure to chattonella Marina and environmental hypoxia in yellowtail seriola quinqueradiata
Marine Biology, 2003Co-Authors: K S Lee, Atsushi Ishimatsu, H Sakaguchi, Tatsuya OdaAbstract:The experiments were undertaken to measure, for the first time, cardiac output in yellowtail (Seriola quinqueradiata) during exposure to a harmful red tide flagellate (Chattonella Marina). The responses were compared with those during exposure to environmental hypoxia to evaluate the significance of the drop of arterial oxygen partial pressure (PaO2) in the fish-kill mechan- isms by C. Marina. PaO2 immediately decreased, whereas heart rate (HR) was maintained until shortly before death during exposure to C. Marina. Suffocation developing during the exposure resulted from a decrease in blood oxygen content, but not from lowered blood flow to the tissue. Although exposure to both C. Marina and hypoxia immediately decreased PaO2, arterial oxygen content (CaO2) and pH (pHa) were significantly lower, whereas HR and cardiac output ( _ Q remained significantly higher, for the C. Marina-exposed fish than for hypoxia-exposed fish. Although the drop in PaO2 appears to play a pivotal role in the mechanisms of fish death by C. Marina, other physiological response(s) should also be considered.
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mechanism of superoxide anion generation in the toxic red tide phytoplankton chattonella Marina possible involvement of nad p h oxidase
Biochimica et Biophysica Acta, 2000Co-Authors: Daekyung Kim, Atsushi Ishimatsu, Tatsuya Oda, Atsushi Nakamura, Tarou Okamoto, Nobukazu Komatsu, Takaji Iida, Tsuyoshi MuramatsuAbstract:Red tide phytoplankton Chattonella Marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. Marina, the mechanism of ROS generation in C. Marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. Marina cells showed NAD(P)H-dependent O2− generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. Marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. Marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. Marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. Marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O2− production in C. Marina.
Daekyung Kim - One of the best experts on this subject based on the ideXlab platform.
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possible factors responsible for the fish killing mechanisms of the red tide phytoplankton chattonella Marina and cochlodinium polykrikoides
Coastal Environmental and Ecosystem Issues of the East China Sea, 2010Co-Authors: Daekyung Kim, Tatsuya OdaAbstract:Generation of reactive oxygen species (ROS) such as superoxide (O2 –) and hydroxyl radical (·OH) by Chattonella Marina could be confirmed by ESR spin trapping method. Several lines of evidence suggested that cell surface structure of C. Marina, glycocalyx, has NADPH-dependent O2 – generation system. Immunohistochemical analysis of gill lamellae from yellowtail exposed to C. Marina using antiserum against crude glycocalyx demonstrated that there were the antigns recognaised by the antiserum on the surface of gill lamellae. The results suggest that continuous accumulation of discharged glycocalyx on the gill surface occurs during C. Marina exposure, which may be responsible for the ROSmediated severe gill tissue damage leading to fish death. As compare to C. Marina, the levels of O2 – and H2O2 detected in Cochlodinium polykrikoides were trace levels. Furthermore, no significant increase in O2 – generation by C. polykrikoides was observed in the presence of lectins or fish mucus prepared from skin and gill of yellowtail, whereas C. Marina generated increased level of O2 – responding to these stimuli. The cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on HeLa cells, but the extract of C. Marina had almost no effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the culture of C. polykrikoides, and the medium gradually became viscous, but no such change was observed in the medium of C. Marina. These results suggest that ichthyotoxic mechanisms of C. Marina and C. polykrikoides are different. ROS may play a significant role in the fish-killing activity of C. Marina, whereas in the case of C. polykrikoides, certain toxic substances or polysaccharides are mainly responsible for the toxicity rather than ROS.
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mode of action of an antialgal agent produced by a marine gammaproteobacterium against chattonella Marina
Aquatic Microbial Ecology, 2006Co-Authors: Takuji Nakashima, Daekyung Kim, Satoshi Takeshita, Kenichi Yamaguchi, Yousuke Miyazaki, Tatsuya OdaAbstract:A marine gammaproteobacterium, strain MS-02-063, was able to kill Chattonella Marina, a noxious red tide phytoplankton. However, the algicidal activity of bacterial cells washed with the planktonic medium was significantly reduced. These results suggest that strain MS-02-063 produces an extracellular substance, the pigment, PG-L-1, that showed a potent algicidal effect on C. Marina. The LD 50 value of PG-L-1 was calculated to be approximately 8.5 μg ml -1 . At the approximate LD 50 concentration of 10 μg ml -1 , a morphological change, which seemed to be due to the inhibition of cell division, was observed in C. Marina. Almost all cells of C. Marina were destroyed readily at 100 μg ml -1 of PG-L-1, and the cytostatic activity of PG-L-1 against this phytoplankton was observed at a concentration of 1 μg ml -1 during the 5 d of incubation. A sublethal concentration of PG-L-1 of 10 μg ml -1 significantly inhibited the reactive oxygen species (ROS) production by C. Marina. ROS production has been previously reported to be essential for normal growth of C. Marina (Oda et al. 1995; Biosci Biotechnol Biochem 59:2044-2048). Therefore, the inhibitory effect of PG-L-1 on ROS production may lead to growth inhibition of C. Marina, at least in part. The pigment, PG-L-1, may be a useful compound not only as an applicable agent for the mitigation of harmful algal blooms, but also as an experimental tool to analyse the ROS production system in a red tide phytoplankton such as C. Marina.
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nitric oxide synthase like enzyme mediated nitric oxide generation by harmful red tide phytoplankton chattonella Marina
Journal of Plankton Research, 2006Co-Authors: Daekyung Kim, Kenichi Yamaguchi, Tatsuya OdaAbstract:The unicellular marine phytoplankton Chattonella Marina is known to exhibit potent fish-killing activity. Previous studies have demonstrated that C. Marina produces reactive oxygen species (ROS), and ROS-mediated ichthyotoxic mechanism has been postulated. However, the exact toxic mechanism is still controversial. In this study, we obtained evidence that C. Marina produces nitric oxide (NO) under normal growth conditions. We utilized chemiluminescence (CL) reaction between NO and luminol-H 2 O 2 to detect NO in C. Marina cell suspensions. In this assay, significant CL was observed in C. Marina in a cell-number-dependent manner, and this was diminished by the addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a specific NO scavenger. The NO generation by C. Marina was also confirmed by a spectrophotometric assay based on the measurement of the diazo-reaction-positive substances (NO x ) and by fluorometric assay using highly specific fluorescent indicator of NO. The NO level in C. Marina was significantly decreased by N G -nitro-L-arginine methyl ester (L-NAME), a specific NO synthase (NOS) inhibitor. The addition of L-arginine resulted in the increased NO level, whereas NaNO 2 had no effect. These results suggest that a NOS-like enzyme is mainly responsible for NO generation in C. Marina.
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mechanism of superoxide anion generation in the toxic red tide phytoplankton chattonella Marina possible involvement of nad p h oxidase
Biochimica et Biophysica Acta, 2000Co-Authors: Daekyung Kim, Atsushi Ishimatsu, Tatsuya Oda, Atsushi Nakamura, Tarou Okamoto, Nobukazu Komatsu, Takaji Iida, Tsuyoshi MuramatsuAbstract:Red tide phytoplankton Chattonella Marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. Marina, the mechanism of ROS generation in C. Marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. Marina cells showed NAD(P)H-dependent O2− generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. Marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. Marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. Marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. Marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O2− production in C. Marina.
Tsuyoshi Muramatsu - One of the best experts on this subject based on the ideXlab platform.
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mechanism of superoxide anion generation in the toxic red tide phytoplankton chattonella Marina possible involvement of nad p h oxidase
Biochimica et Biophysica Acta, 2000Co-Authors: Daekyung Kim, Atsushi Ishimatsu, Tatsuya Oda, Atsushi Nakamura, Tarou Okamoto, Nobukazu Komatsu, Takaji Iida, Tsuyoshi MuramatsuAbstract:Red tide phytoplankton Chattonella Marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. Marina, the mechanism of ROS generation in C. Marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. Marina cells showed NAD(P)H-dependent O2− generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. Marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. Marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. Marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. Marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O2− production in C. Marina.
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oxygen radical mediated toxic effects of the red tide flagellate chattonella Marina on vibrio alginolyticus
Marine Biology, 1992Co-Authors: Tatsuya Oda, Atsushi Ishimatsu, M Shimada, Satoshi Takeshita, Tsuyoshi MuramatsuAbstract:Toxic mechanisms of the red tide flagellate, Chattonella Marina, collected in 1985 from Kagoshima Bay, Japan, were studied at the subcellular level. C. Marina was found to reduce ferricytochrome c at a rate related to the concentration of plankton cells. Ca. 50% of the cytochrome c reduction was inhibited by the addition of 100 U superoxide dismutase ml-1. These results suggest that a part of the cytochrome c reduction was caused by a superoxide anion which was extracellulary released from C. Marina. Moreover, a small amount of hydrogen peroxide was detected in the C. Marina suspension using the fluorescence spectrophotometric assay method. The identity of the hydrogen peroxide was confirmed by its reaction with 500 U catalase ml-1. It is thus proposed that C. Marina produces harmful active oxygen radicals and therefore exhibits a toxic effect on surrounding living organisms. In agreement with these results, C. Marina strongly inhibited the proliferation of marine bacteria, Vibrio alginolyticus, in a plankton/bacteria co-culture system. The growth inhibition of bacteria caused by C. Marina was related to the density and the metabolic potential of C. Marina. Ruptured plankton showed no toxic effect on the bacteria. Furthermore, the toxic effect of C. Marina on V. alginolyticus was completely suppressed by the addition of catalase and superoxide dismutase. In addition to these radical-scavenging enzymes, a chemical scavenger, sodium benzoate, also had a protective effect. These results suggest that oxygen radicals are important in the toxic action of C. Marina.
Erik Kristensen - One of the best experts on this subject based on the ideXlab platform.
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Rhizosphere O2 dynamics in young Zostera Marina and Ruppia maritima
Marine Ecology Progress Series, 2015Co-Authors: Zeljko Jovanovic, Erik Kristensen, M. Pedersen, Morten Larsen, Ronnie N. GludAbstract:Zostera Marina and Ruppia maritima often share the same habitat, but R. maritima appears more resistant to environmental stress. We investigated the impact of light intensity and water column O2 concentrations on radial oxygen loss (ROL), in young specimens of Z. Marina and R. maritima. Planar optode imaging revealed that ROL of Z. Marina was localized to the root tip, while R. maritima showed ROL along extensive root sections. The total root biomass of the 2 spe- cies was similar, but, while R. maritima had only 1 root, of which 33% of its length showed ROL, Z. Marina had 2 to 5 individual roots, where only 2 to 3 exhibited O2 leakage, but then only at root tips. ROL resulted in an oxic volume of 4.26 ± 0.51 mm 3 plant �1 for Z. Marina and 5.39 ± 0.47 mm 3 plant �1 for R. maritima (n = 3). ROL per plant at light saturation was 2.32 ± 0.30 and 2.89 ± 0.38 nmol h �1 for Z. Marina and R. maritima, respectively. These values declined by 71 and 60% in darkness. However, both species were able to maintain ROL as long as ambient O2 levels remained >50% air saturation. The calculated ROL integrated over a 24 h cycle was 48.8 ± 10.6 nmol O2 plant �1 d �1 (n = 3) for R. maritima and 30% less for Z. Marina. The ability of R. mar- itima to maintain higher ROL than Z. Marina could be an important feature defining its potential for colonizing and maintaining growth in eutrophic sediments.
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burial of seeds and seedlings by the lugworm arenicola Marina hampers eelgrass zostera Marina recovery
Journal of Experimental Marine Biology and Ecology, 2011Co-Authors: Thomas Bruun Valdemarsen, Erik Kristensen, Kim Wendelboe, Jonas T Egelund, Mogens FlindtAbstract:Abstract Eelgrass ( Zostera Marina ) used to dominate the vegetation in Odense Fjord, Denmark, and covered > 17 km 2 of the shallow fjord in 1983. Decades of excessive nutrient loading has lead to decreased eelgrass distribution, and only ~ 2 km 2 is covered at present. The state of low eelgrass coverage has not changed despite significant improvements of water quality in the past > 10 years, and lugworms, Arenicola Marina , have colonized the former eelgrass areas (1–8 ind. m −2 ). It was hypothesized that the lack of eelgrass recovery was due to A. Marina , which was investigated by a combined field and laboratory approach. At a study site where eelgrass used to dominate, a seasonal study of lugworm population dynamics and sediment reworking activity was performed. Additionally, density dependent burial of eelgrass seeds and seedlings due to sediment reworking by A. Marina was investigated in mesocosm experiments. Our results indicate that A. Marina may negatively impact eelgrass recovery, since sediment reworking lead to rapid burial of eelgrass seeds and seedlings; within 1–2 months, 95% of seeds and 75% of seedlings were buried below critical depth. Considerations based on empirical modeling suggest that negative impact occur even at low A. Marina density (5–10 ind. m −2 ). Therefore the spread of A. Marina into former eelgrass areas is critical, since eelgrass recovery may be severely impaired, even when water quality favors eelgrass recolonization.
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Burial of seeds and seedlings by the lugworm Arenicola Marina hampers eelgrass (Zostera Marina) recovery
Journal of Experimental Marine Biology and Ecology, 2011Co-Authors: Thomas Bruun Valdemarsen, Erik Kristensen, Kim Wendelboe, Jonas T Egelund, Mogens FlindtAbstract:Abstract Eelgrass ( Zostera Marina ) used to dominate the vegetation in Odense Fjord, Denmark, and covered > 17 km 2 of the shallow fjord in 1983. Decades of excessive nutrient loading has lead to decreased eelgrass distribution, and only ~ 2 km 2 is covered at present. The state of low eelgrass coverage has not changed despite significant improvements of water quality in the past > 10 years, and lugworms, Arenicola Marina , have colonized the former eelgrass areas (1–8 ind. m −2 ). It was hypothesized that the lack of eelgrass recovery was due to A. Marina , which was investigated by a combined field and laboratory approach. At a study site where eelgrass used to dominate, a seasonal study of lugworm population dynamics and sediment reworking activity was performed. Additionally, density dependent burial of eelgrass seeds and seedlings due to sediment reworking by A. Marina was investigated in mesocosm experiments. Our results indicate that A. Marina may negatively impact eelgrass recovery, since sediment reworking lead to rapid burial of eelgrass seeds and seedlings; within 1–2 months, 95% of seeds and 75% of seedlings were buried below critical depth. Considerations based on empirical modeling suggest that negative impact occur even at low A. Marina density (5–10 ind. m −2 ). Therefore the spread of A. Marina into former eelgrass areas is critical, since eelgrass recovery may be severely impaired, even when water quality favors eelgrass recolonization.
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arenicola Marina polychaeta and organic matter mineralisation in sandy marine sediments in situ and microcosm comparison
Estuarine Coastal and Shelf Science, 2007Co-Authors: Sokratis Papaspyrou, Erik Kristensen, Bjarne ChristensenAbstract:Effects of the polychaete Arenicola Marina on sediment porewater profiles and organic matter mineralisation were studied both in situ and in manipulated laboratory microcosms. Comparison of the results from the two methods showed differences in the shape and magnitude of porewater profiles and solute fluxes. Porewater profiles revealed a significant effect of irrigation on solute transport. The effect was most evident in the homogenised laboratory microcosms where a significant accumulation of porewater solutes with depth was observed in the absence of A. Marina irrigation. In contrast, the limited reactivity of old organic matter stored deep in anoxic in situ sediment resulted in low accumulation of solutes at depth, whereas a rich benthic microalgal community present at the sediment surface contributed to high reaction rates and near-surface solute peaks. Reaction rates were more homogenous with depth and similar or even higher in A. Marina sediment than the control despite a lower organic content in the former. Continuous reworking by A. Marina results in the rapid burial of the small, but reactive and nitrogen-rich, organic pool derived from the benthic microalgae at the sediment surface. Addition of seagrass detritus to the A. Marina sediment resulted in a further increase of reaction rates compared to the unamended A. Marina sediment, while reworking and irrigation activities maintained the organic pool and porewater profiles as low as in the unamended treatment. Benthic respiration in laboratory microcosms was stimulated almost two-fold in the presence of A. Marina. No such stimulation was apparent in situ. Here the stimulated capacity for carbon mineralisation was evident instead as an almost 50% lower sediment organic content in the presence of A. Marina. Despite the strengths and weaknesses of each method, the results are valuable when combined as they clearly demonstrate the effect of irrigation on solute transport and the potential of A. Marina to redistribute and facilitate the removal particulate organic matter via microbial degradation.
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the importance of bacteria and microalgae in the diet of the deposit feeding polychaete arenicola Marina
Ophelia, 2002Co-Authors: Martina Andresen, Erik KristensenAbstract:Abstract The distribution of bacteria and chlorophyll a in sediment around and within Arenicola Marina while feeding on sandy sediment at the shallow Bregnor Bay, Denmark, was examined throughout an annual cycle. Specimens inhabiting homogenized sediment were compared with worms from unmanipulated sediment. Although the feeding pocket was difficult to locate, a low mean grain size of sediment in the gut of A. Marina compared with surrounding unmanipulated sediment indicates selective feeding on particles <500 μm. It appears that A. Marina only occupies one feeding pocket for short time in the densely populated (∼80 ind. m2) sandy sediment at Bregnor Bay. Digestion and assimilation of bacteria and chlorophyll a (i.e. microalgae) during passage of sediment through the gut of A. Marina occur primarily in the stomach. Due to a rapid 50–100% regrowth in the hindgut of A. Marina, assimilation of bacteria must be quantified as the difference in numbers between esophagus and stomach. Assimilation efficiency was s...
Atsushi Ishimatsu - One of the best experts on this subject based on the ideXlab platform.
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cardiac output during exposure to chattonella Marina and environmental hypoxia in yellowtail seriola quinqueradiata
Marine Biology, 2003Co-Authors: K S Lee, Atsushi Ishimatsu, H Sakaguchi, Tatsuya OdaAbstract:The experiments were undertaken to measure, for the first time, cardiac output in yellowtail (Seriola quinqueradiata) during exposure to a harmful red tide flagellate (Chattonella Marina). The responses were compared with those during exposure to environmental hypoxia to evaluate the significance of the drop of arterial oxygen partial pressure (PaO2) in the fish-kill mechan- isms by C. Marina. PaO2 immediately decreased, whereas heart rate (HR) was maintained until shortly before death during exposure to C. Marina. Suffocation developing during the exposure resulted from a decrease in blood oxygen content, but not from lowered blood flow to the tissue. Although exposure to both C. Marina and hypoxia immediately decreased PaO2, arterial oxygen content (CaO2) and pH (pHa) were significantly lower, whereas HR and cardiac output ( _ Q remained significantly higher, for the C. Marina-exposed fish than for hypoxia-exposed fish. Although the drop in PaO2 appears to play a pivotal role in the mechanisms of fish death by C. Marina, other physiological response(s) should also be considered.
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mechanism of superoxide anion generation in the toxic red tide phytoplankton chattonella Marina possible involvement of nad p h oxidase
Biochimica et Biophysica Acta, 2000Co-Authors: Daekyung Kim, Atsushi Ishimatsu, Tatsuya Oda, Atsushi Nakamura, Tarou Okamoto, Nobukazu Komatsu, Takaji Iida, Tsuyoshi MuramatsuAbstract:Red tide phytoplankton Chattonella Marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. Marina, the mechanism of ROS generation in C. Marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. Marina cells showed NAD(P)H-dependent O2− generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. Marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. Marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. Marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. Marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O2− production in C. Marina.
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oxygen radical mediated toxic effects of the red tide flagellate chattonella Marina on vibrio alginolyticus
Marine Biology, 1992Co-Authors: Tatsuya Oda, Atsushi Ishimatsu, M Shimada, Satoshi Takeshita, Tsuyoshi MuramatsuAbstract:Toxic mechanisms of the red tide flagellate, Chattonella Marina, collected in 1985 from Kagoshima Bay, Japan, were studied at the subcellular level. C. Marina was found to reduce ferricytochrome c at a rate related to the concentration of plankton cells. Ca. 50% of the cytochrome c reduction was inhibited by the addition of 100 U superoxide dismutase ml-1. These results suggest that a part of the cytochrome c reduction was caused by a superoxide anion which was extracellulary released from C. Marina. Moreover, a small amount of hydrogen peroxide was detected in the C. Marina suspension using the fluorescence spectrophotometric assay method. The identity of the hydrogen peroxide was confirmed by its reaction with 500 U catalase ml-1. It is thus proposed that C. Marina produces harmful active oxygen radicals and therefore exhibits a toxic effect on surrounding living organisms. In agreement with these results, C. Marina strongly inhibited the proliferation of marine bacteria, Vibrio alginolyticus, in a plankton/bacteria co-culture system. The growth inhibition of bacteria caused by C. Marina was related to the density and the metabolic potential of C. Marina. Ruptured plankton showed no toxic effect on the bacteria. Furthermore, the toxic effect of C. Marina on V. alginolyticus was completely suppressed by the addition of catalase and superoxide dismutase. In addition to these radical-scavenging enzymes, a chemical scavenger, sodium benzoate, also had a protective effect. These results suggest that oxygen radicals are important in the toxic action of C. Marina.
