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Peter Stief - One of the best experts on this subject based on the ideXlab platform.

  • Chironomus Plumosus larvae increase fluxes of denitrification products and diversity of nitrate reducing bacteria in freshwater sediment
    Systematic and Applied Microbiology, 2014
    Co-Authors: Morten Poulsen, Andreas Schramm, Michael Vedel Wegener Kofoed, Lone Heimann Larsen, Peter Stief
    Abstract:

    Abstract Benthic invertebrates affect microbial processes and communities in freshwater sediment by enhancing sediment-water solute fluxes and by grazing on bacteria. Using microcosms, the effects of larvae of the widespread midge Chironomus Plumosus on the efflux of denitrification products (N 2 O and N 2  + N 2 O) and the diversity and abundance of nitrate- and nitrous-oxide-reducing bacteria were investigated. Additionally, the diversity of actively nitrate- and nitrous-oxide-reducing bacteria was analyzed in the larval gut. The presence of larvae increased the total effluxes of N 2 O and N 2  + N 2 O up to 8.6- and 4.2-fold, respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N 2 O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG , nor nosZ was different in sediments with and without larvae. Hence, C. Plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut.

  • control of nitrous oxide emission from Chironomus Plumosus larvae by nitrate and temperature
    Limnology and Oceanography, 2010
    Co-Authors: Morten Poulsen, Peter Stief, Lubos Polerecky, Andreas Schramm
    Abstract:

    Aquatic invertebrates that ingest large numbers of bacteria produce substantial amounts of the greenhouse gas N 2 0 because of incomplete denitrification in their anoxic gut. We investigated the influence of two key environmental factors, temperature and NO ― 3 availability, on N 2 O emission from larvae of Chironomus Plumosus in field and laboratory experiments. Larvae collected from lake sediments emitted between 2 and 73 pmol N 2 O ind. ―1 h ―1 during the warm season, but took up maximally —27 pmol N 2 0 ind. ―1 h ―1 during winter. Larvae kept in laboratory microcosms emitted between 14 and 122 pmol N 2 0 ind. ―1 h ―1 , and N 2 0 uptake was never observed. For both types of larvae, the rate of N 2 O emission was stimulated by temperature (when the NO 3 concentration in the water column was higher than 25-50 μmol L ―1 ) and by NO ― 3 (when the temperature was higher than 4―10°C). Modeling based on experimentally determined ventilation parameters and sedimentary O 2 and NO ― 3 turnover rates predicted that NO ― 3 concentrations inside the burrow and in the sediment surrounding the burrow fluctuated and were on average lower than those in the water column. In contrast, NO ― 3 concentrations measured in the gut and hemolymph of the microcosm-incubated larvae were at least as high as in the water column. This suggests that N 2 O emission from C. Plumosus larvae is controlled by NO ― 3 availability in the water column, but is decoupled, by a hitherto unknown mechanism, from NO ― 3 present in the immediate surroundings of the larva.

  • The gut microenvironment of sediment-dwelling Chironomus Plumosus larvae as characterised with O2, pH, and redox microsensors.
    Journal of comparative physiology. B Biochemical systemic and environmental physiology, 2006
    Co-Authors: Peter Stief, Gundula Eller
    Abstract:

    We devised a set-up in which microsensors can be used for characterising the gut microenvironment of aquatic macrofauna. In a small flow cell, we measured microscale gradients through dissected guts (O(2), pH, redox potential [E ( h )]), in the haemolymph (O(2)), and towards the body surface (O(2)) of Chironomus Plumosus larvae. The gut microenvironment was compared with the chemical conditions in the lake sediment in which the animals reside and feed. When the dissected guts were incubated at the same nominal O(2) concentration as in haemolymph, the gut content was completely anoxic and had pH and E ( h ) values slightly lower than in the ambient sediment. When the dissected guts were artificially oxygenated, the volumetric O(2)-consumption rates of the gut content were at least 10x higher than in the sediment. Using these potential O(2)-consumption rates in a cylindrical diffusion-reaction model, it was predicted that diffusion of O(2) from the haemolymph to the gut could not oxygenate the gut content under in vivo conditions. Additionally, the potential O(2)-consumption rates were so high that the intake of dissolved O(2) along with feeding could be ruled out to oxygenate the gut content. We conclude that microorganisms present in the gut of C. Plumosus cannot exhibit an aerobic metabolism. The presented microsensor technique and the data analysis are applicable to guts of other macrofauna species with cutaneous respiration.

Mohai Shen - One of the best experts on this subject based on the ideXlab platform.

  • influence of carbon nanotubes with preloaded and coexisting dissolved organic matter on the bioaccumulation of polycyclic aromatic hydrocarbons to Chironomus Plumosus larvae in sediment
    Environmental Toxicology and Chemistry, 2014
    Co-Authors: Mohai Shen, Xinghui Xia, Xiuli Zhao, Yawei Zhai, Xiaotian Zhang, Pu Zhang
    Abstract:

    The ubiquity of dissolved organic matter (DOM) in an aqueous environment may have influence on the carbonaceous material's impact on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to benthonic organisms in contaminated sediment. In the present study, 1 multiwalled carbon nanotube (MWNT); 2 types of DOM (fulvic acid and tannic acid), and 2 PAHs (pyrene and chrysene) were selected to study the influence of MWNT with preloaded and coexisting DOM on the bioaccumulation of PAHs to Chironomus Plumosus larvae in sediment. Moreover, the freely dissolved concentrations of PAHs were measured to explore the influence mechanisms. The results showed that despite the presence or absence of preloaded or coexisting DOM, the presence of 1% MWNT in sediments suppressed the biota-sediment accumulation factor (BSAF) and elevated the water-based bioaccumulation factor (BAF) of PAHs. However, the BSAF and BAF values generally decreased with the increase of 2 forms of both DOM; this was caused by the combined impact of DOM and MWNT on the freely dissolved concentrations of PAHs and the ingestion behavior of benthic organisms. Environ Toxicol Chem 2014;33:182–189. © 2013 SETAC

  • effects of carbon nanotubes chars and ash on bioaccumulation of perfluorochemicals by Chironomus Plumosus larvae in sediment
    Environmental Science & Technology, 2012
    Co-Authors: Xinghui Xia, Xiuli Zhao, Xi Chen, Huiting Chen, Mohai Shen
    Abstract:

    This study examined the effect of five types of carbonaceous materials (CMs) in sediment on bioaccumulation of perfluorochemicals (PFCs) by Chironomus Plumosus larvae. The CMs included two multiwalled carbon nanotubes (MWCNT10 and MWCNT50), maize straw- and willow-derived chars, and maize straw-origin ash. The PFCs included perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA). The CMs with different concentrations (0–1.5% dry weight) were amended into sediments spiked with PFCs and aged for 60 d. The uptake rate constants (ks) for each PFC to larvae differed with different CM amendments (p 0.05). Decreasing PFC concentration in larvae (CB) was found with increasing CM concentration (fCM) in the sediments, and a linear positive correlation existed between 1/CB and fCM (p < 0.05). The effect of CMs o...

  • influences of multiwalled carbon nanotubes and plant residue chars on bioaccumulation of polycyclic aromatic hydrocarbons by Chironomus Plumosus larvae in sediment
    Environmental Toxicology and Chemistry, 2012
    Co-Authors: Mohai Shen, Xinghui Xia, Fan Wang, Pu Zhang, Xiuli Zhao
    Abstract:

    Carbonaceous materials (CMs), including carbon nanotubes (CNTs), and black carbon have been suggested as potential remediation materials for hydrophobic organic contaminants (HOCs) in sediments or soils. However, the concentration-dependent and potential effects of CMs on the decrease in HOC bioavailability are not well understood. In this research, the effects of two types of multiwalled CNTs (MWNT-1 and MWNT-2) and chars (char-stalk produced from stalk and char-wood from wood) on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), including phenanthrene, pyrene, and chrysene, in the benthic organism Chironomus Plumosus larvae were studied. When CM content was 1.5% or less in sediments, biota-sediment accumulation factor (BSAF) values for PAHs decreased sharply as CM increased. However, when char and MWNT-1 content was greater than 1.5% in sediments, reduction rates of BSAF were slight. Furthermore, when MWNT-2 content was greater than 1.5%, BSAF values were elevated. This indicated that the MWNT-associated PAHs may have been absorbed by larvae through particle ingestion, and suggested that some CNTs may not be suitable for the remediation of HOC-contaminated sediments because they probably could increase the exposure risk of PAHs to benthic organisms, possibly because of their unique structure. Environ. Toxicol. Chem. 2012;31:202–209. © 2011 SETAC

Morten Poulsen - One of the best experts on this subject based on the ideXlab platform.

  • Chironomus Plumosus larvae increase fluxes of denitrification products and diversity of nitrate reducing bacteria in freshwater sediment
    Systematic and Applied Microbiology, 2014
    Co-Authors: Morten Poulsen, Andreas Schramm, Michael Vedel Wegener Kofoed, Lone Heimann Larsen, Peter Stief
    Abstract:

    Abstract Benthic invertebrates affect microbial processes and communities in freshwater sediment by enhancing sediment-water solute fluxes and by grazing on bacteria. Using microcosms, the effects of larvae of the widespread midge Chironomus Plumosus on the efflux of denitrification products (N 2 O and N 2  + N 2 O) and the diversity and abundance of nitrate- and nitrous-oxide-reducing bacteria were investigated. Additionally, the diversity of actively nitrate- and nitrous-oxide-reducing bacteria was analyzed in the larval gut. The presence of larvae increased the total effluxes of N 2 O and N 2  + N 2 O up to 8.6- and 4.2-fold, respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N 2 O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG , nor nosZ was different in sediments with and without larvae. Hence, C. Plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut.

  • control of nitrous oxide emission from Chironomus Plumosus larvae by nitrate and temperature
    Limnology and Oceanography, 2010
    Co-Authors: Morten Poulsen, Peter Stief, Lubos Polerecky, Andreas Schramm
    Abstract:

    Aquatic invertebrates that ingest large numbers of bacteria produce substantial amounts of the greenhouse gas N 2 0 because of incomplete denitrification in their anoxic gut. We investigated the influence of two key environmental factors, temperature and NO ― 3 availability, on N 2 O emission from larvae of Chironomus Plumosus in field and laboratory experiments. Larvae collected from lake sediments emitted between 2 and 73 pmol N 2 O ind. ―1 h ―1 during the warm season, but took up maximally —27 pmol N 2 0 ind. ―1 h ―1 during winter. Larvae kept in laboratory microcosms emitted between 14 and 122 pmol N 2 0 ind. ―1 h ―1 , and N 2 0 uptake was never observed. For both types of larvae, the rate of N 2 O emission was stimulated by temperature (when the NO 3 concentration in the water column was higher than 25-50 μmol L ―1 ) and by NO ― 3 (when the temperature was higher than 4―10°C). Modeling based on experimentally determined ventilation parameters and sedimentary O 2 and NO ― 3 turnover rates predicted that NO ― 3 concentrations inside the burrow and in the sediment surrounding the burrow fluctuated and were on average lower than those in the water column. In contrast, NO ― 3 concentrations measured in the gut and hemolymph of the microcosm-incubated larvae were at least as high as in the water column. This suggests that N 2 O emission from C. Plumosus larvae is controlled by NO ― 3 availability in the water column, but is decoupled, by a hitherto unknown mechanism, from NO ― 3 present in the immediate surroundings of the larva.

Andreas Schramm - One of the best experts on this subject based on the ideXlab platform.

  • Chironomus Plumosus larvae increase fluxes of denitrification products and diversity of nitrate reducing bacteria in freshwater sediment
    Systematic and Applied Microbiology, 2014
    Co-Authors: Morten Poulsen, Andreas Schramm, Michael Vedel Wegener Kofoed, Lone Heimann Larsen, Peter Stief
    Abstract:

    Abstract Benthic invertebrates affect microbial processes and communities in freshwater sediment by enhancing sediment-water solute fluxes and by grazing on bacteria. Using microcosms, the effects of larvae of the widespread midge Chironomus Plumosus on the efflux of denitrification products (N 2 O and N 2  + N 2 O) and the diversity and abundance of nitrate- and nitrous-oxide-reducing bacteria were investigated. Additionally, the diversity of actively nitrate- and nitrous-oxide-reducing bacteria was analyzed in the larval gut. The presence of larvae increased the total effluxes of N 2 O and N 2  + N 2 O up to 8.6- and 4.2-fold, respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N 2 O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG , nor nosZ was different in sediments with and without larvae. Hence, C. Plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut.

  • control of nitrous oxide emission from Chironomus Plumosus larvae by nitrate and temperature
    Limnology and Oceanography, 2010
    Co-Authors: Morten Poulsen, Peter Stief, Lubos Polerecky, Andreas Schramm
    Abstract:

    Aquatic invertebrates that ingest large numbers of bacteria produce substantial amounts of the greenhouse gas N 2 0 because of incomplete denitrification in their anoxic gut. We investigated the influence of two key environmental factors, temperature and NO ― 3 availability, on N 2 O emission from larvae of Chironomus Plumosus in field and laboratory experiments. Larvae collected from lake sediments emitted between 2 and 73 pmol N 2 O ind. ―1 h ―1 during the warm season, but took up maximally —27 pmol N 2 0 ind. ―1 h ―1 during winter. Larvae kept in laboratory microcosms emitted between 14 and 122 pmol N 2 0 ind. ―1 h ―1 , and N 2 0 uptake was never observed. For both types of larvae, the rate of N 2 O emission was stimulated by temperature (when the NO 3 concentration in the water column was higher than 25-50 μmol L ―1 ) and by NO ― 3 (when the temperature was higher than 4―10°C). Modeling based on experimentally determined ventilation parameters and sedimentary O 2 and NO ― 3 turnover rates predicted that NO ― 3 concentrations inside the burrow and in the sediment surrounding the burrow fluctuated and were on average lower than those in the water column. In contrast, NO ― 3 concentrations measured in the gut and hemolymph of the microcosm-incubated larvae were at least as high as in the water column. This suggests that N 2 O emission from C. Plumosus larvae is controlled by NO ― 3 availability in the water column, but is decoupled, by a hitherto unknown mechanism, from NO ― 3 present in the immediate surroundings of the larva.

Pu Zhang - One of the best experts on this subject based on the ideXlab platform.

  • influence of carbon nanotubes with preloaded and coexisting dissolved organic matter on the bioaccumulation of polycyclic aromatic hydrocarbons to Chironomus Plumosus larvae in sediment
    Environmental Toxicology and Chemistry, 2014
    Co-Authors: Mohai Shen, Xinghui Xia, Xiuli Zhao, Yawei Zhai, Xiaotian Zhang, Pu Zhang
    Abstract:

    The ubiquity of dissolved organic matter (DOM) in an aqueous environment may have influence on the carbonaceous material's impact on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to benthonic organisms in contaminated sediment. In the present study, 1 multiwalled carbon nanotube (MWNT); 2 types of DOM (fulvic acid and tannic acid), and 2 PAHs (pyrene and chrysene) were selected to study the influence of MWNT with preloaded and coexisting DOM on the bioaccumulation of PAHs to Chironomus Plumosus larvae in sediment. Moreover, the freely dissolved concentrations of PAHs were measured to explore the influence mechanisms. The results showed that despite the presence or absence of preloaded or coexisting DOM, the presence of 1% MWNT in sediments suppressed the biota-sediment accumulation factor (BSAF) and elevated the water-based bioaccumulation factor (BAF) of PAHs. However, the BSAF and BAF values generally decreased with the increase of 2 forms of both DOM; this was caused by the combined impact of DOM and MWNT on the freely dissolved concentrations of PAHs and the ingestion behavior of benthic organisms. Environ Toxicol Chem 2014;33:182–189. © 2013 SETAC

  • influences of multiwalled carbon nanotubes and plant residue chars on bioaccumulation of polycyclic aromatic hydrocarbons by Chironomus Plumosus larvae in sediment
    Environmental Toxicology and Chemistry, 2012
    Co-Authors: Mohai Shen, Xinghui Xia, Fan Wang, Pu Zhang, Xiuli Zhao
    Abstract:

    Carbonaceous materials (CMs), including carbon nanotubes (CNTs), and black carbon have been suggested as potential remediation materials for hydrophobic organic contaminants (HOCs) in sediments or soils. However, the concentration-dependent and potential effects of CMs on the decrease in HOC bioavailability are not well understood. In this research, the effects of two types of multiwalled CNTs (MWNT-1 and MWNT-2) and chars (char-stalk produced from stalk and char-wood from wood) on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), including phenanthrene, pyrene, and chrysene, in the benthic organism Chironomus Plumosus larvae were studied. When CM content was 1.5% or less in sediments, biota-sediment accumulation factor (BSAF) values for PAHs decreased sharply as CM increased. However, when char and MWNT-1 content was greater than 1.5% in sediments, reduction rates of BSAF were slight. Furthermore, when MWNT-2 content was greater than 1.5%, BSAF values were elevated. This indicated that the MWNT-associated PAHs may have been absorbed by larvae through particle ingestion, and suggested that some CNTs may not be suitable for the remediation of HOC-contaminated sediments because they probably could increase the exposure risk of PAHs to benthic organisms, possibly because of their unique structure. Environ. Toxicol. Chem. 2012;31:202–209. © 2011 SETAC