The Experts below are selected from a list of 83730 Experts worldwide ranked by ideXlab platform
P. Stief - One of the best experts on this subject based on the ideXlab platform.
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stimulation of microbial nitrogen cycling in Aquatic Ecosystems by benthic macrofauna mechanisms and environmental implications
Biogeosciences, 2013Co-Authors: P. StiefAbstract:Invertebrate animals that live at the bottom of Aquatic Ecosystems (i.e., benthic macrofauna) are impor- tant mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macro- fauna stimulates microbial nutrient dynamics through differ- ent types of animal-microbe interactions, which potentially affect the trophic status of Aquatic Ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of Aquatic Ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammo- nium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrifica- tion and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments is enhanced more strongly than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow Aquatic Ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on ben- thic microbes apparently has small or neutral effects on ni- trogen cycling. Animal-microbe symbioses provide abun- dant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies reveal that ecosys- tem engineering, grazing, and symbioses of benthic macro- fauna significantly enhance nitrous oxide emission from shallow Aquatic Ecosystems. The beneficial effect of benthic macrofauna on fixed nitro- gen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates Aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macro- fauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of ni- trogen.
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Stimulation of microbial nitrogen cycling in Aquatic Ecosystems by benthic macrofauna: mechanisms and environmental implications
2013Co-Authors: P. StiefAbstract:Abstract. Invertebrate animals that live at the bottom of Aquatic Ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal–microbe interactions, which potentially affect the trophic status of Aquatic Ecosystems. This review contrasts three types of animal–microbe interactions in the benthos of Aquatic Ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments often is enhanced even more than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow Aquatic Ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies revealed that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow Aquatic Ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification–denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates Aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.
M I Gladyshev - One of the best experts on this subject based on the ideXlab platform.
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production of epa and dha in Aquatic Ecosystems and their transfer to the land
Prostaglandins & Other Lipid Mediators, 2013Co-Authors: M I Gladyshev, Nadezhda N Sushchik, Olesia N MakhutovaAbstract:Most omnivorous animals, including humans, have to some degree relied on physiologically important polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from food. Only some taxa of microalgae, rather than higher plants can synthesize de novo high amounts of EPA and DHA. Once synthesized by microalgae, PUFA are transferred through trophic chain to organisms of higher levels. Thus, Aquatic Ecosystems play the unique role in the Biosphere as the principal source of EPA and DHA for most omnivorous animals, including inhabitants of terrestrial Ecosystems. PUFA are transferred from Aquatic to terrestrial Ecosystems through riparian predators, drift of carrion and seaweeds, emergence of amphibiotic insects, and water birds. The essential PUFA are transferred through trophic chains with about twice higher efficiency than bulk carbon. Thereby, PUFA are accumulated, rather than diluted in biomass of organisms of higher trophic levels, e.g., in fish. Mankind is faced with a severe deficiency of EPA and DHA in diet. Although additional sources of PUFA supply for humans, such as aquaculture, biotechnology of microorganisms and transgenic terrestrial oil-seed producing plants are developed, natural fish production of Aquatic Ecosystems will remain one of the main sources of EPA and DHA for humans. Aquatic Ecosystems have to be protected from anthropogenic impacts, such as eutrophication, pollution and warming, which reduce PUFA production.
Val H Smith - One of the best experts on this subject based on the ideXlab platform.
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Enhanced dissolved organic carbon production in Aquatic Ecosystems in response to elevated atmospheric CO2
Biogeochemistry, 2014Co-Authors: Chao Song, Ford Ballantyne, Val H SmithAbstract:Although Aquatic Ecosystems are a major carbon reservoir, how their carbon dynamics will respond to increasing concentrations of atmospheric CO2 is not well understood. The availability of essential nutrients has the potential to modify carbon fluxes under elevated CO2 by altering carbon processing and storage in the biota. Here, we describe a semi-continuous culture experiment with natural phytoplankton and bacteria assemblages designed to investigate (1) how carbon dynamics in Aquatic Ecosystems respond to continuously elevated atmospheric CO2, and (2) whether carbon fluxes resulting from elevated CO2 are modified by changes in inorganic nitrogen and phosphorus availability. Our results showed that elevated CO2 led to significant increases in photosynthetic carbon uptake, despite a decrease in the algal chlorophyll a concentrations and no significant change in total algal biovolume. This enhancement of inorganic carbon uptake was accompanied by a significant increase in dissolved organic carbon (DOC) production. Concurrent increases in the C/N and C/P ratios of dissolved organic matter also suggested that DOC stability increased. Nutrient availability, especially nitrogen availability, had strong effects on inorganic carbon uptake and biomass carbon pools. In contrast, CO2-enhanced DOC production was not significantly affected by varying concentrations of inorganic nitrogen and phosphorus. Our study underscores the importance of DOC as a potential carbon sink in Aquatic Ecosystems. The observed responses to changes in CO2 and nutrient availability could have important implications for long-term carbon cycling in Aquatic Ecosystems, and highlight the potential buffering capacity of Aquatic Ecosystems to future environmental change.
Helle Ploug - One of the best experts on this subject based on the ideXlab platform.
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microbial ecology of organic aggregates in Aquatic Ecosystems
Aquatic Microbial Ecology, 2002Co-Authors: Meinhard Simon, Hanspeter Grossart, Bernd Schweitzer, Helle PlougAbstract:Macroscopic organic aggregates, which are >500 µm and known as marine and lake snow, are important components in the turnover, decomposition and sinking flux of both organic and inorganic matter and elements in Aquatic Ecosystems. They are composed of various organic and inorganic materials depending largely on the given system and environmental conditions. The sys- tems include the pelagic limnetic, the neritic and oceanic marine region, as well as shallow turbid environments, e.g. rivers, the littoral zone of lakes, estuaries and tidally affected coastal areas with intense turbulence and a high load of suspended matter. Aggregate abundance and size vary greatly among these systems. Macroaggregates are heavily colonized by bacteria and other heterotrophic microbes and greatly enriched in organic and inorganic nutrients as compared to the surrounding water. During the last 15 yr, many studies have been carried out to examine various aspects of the formation of aggregates, their microbial colonization and decomposition, nutrient recycling and their significance for the sinking flux. They have been identified as hot-spots of the microbial decomposi- tion of organic matter. Further, microaggregates, which are <5 to 500 µm in size and stained by different dyes, such as transparent exopolymer particles (TEP) and Coomassie blue-stained particles, have been discovered and shown also to be important in the formation and decomposition of macroaggregates. In this review we give an overview of the present state of the microbial ecology of macro- and microaggregates, including the mentioned points but highlighting in particular the recent findings on the bacterial colonization of aggregates using molecular tools, their microbial decomposition and mineralization, and the significance of protozoans and metazoans for the colo- nization and decomposition of macroaggregates. Today it is evident that not only the aggregates but also their surroundings are sites and hot-spots of microbial processes, with the plume of solutes leak- ing out of the aggregates and greatly extending the volume of the intense decomposition processes. This microheterogeneity has important implications for the spatial and temporal dynamics of the organic-matter field in Aquatic Ecosystems and for our understanding of how heterotrophic organisms are involved in the decomposition of organic matter. The significance of aggregate-associated micro- bial processes as key processes and also for the overall decomposition and flux of organic matter- varies greatly among the various systems, and is greatly affected by the total amount of suspended particulate matter. A conclusion from the presented studies and results is that the significance of bac- teria for the formation and decomposition of aggregates appears to be much greater than previously estimated. For a better understanding of the functioning of Aquatic Ecosystems it is of great impor- tance to include aggregate-associated processes in ecosystem modeling approaches.
Hanspeter Grossart - One of the best experts on this subject based on the ideXlab platform.
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Fungi in Aquatic Ecosystems
Nature Reviews Microbiology, 2019Co-Authors: Hanspeter Grossart, Maiko Kagami, Christian Wurzbacher, Michael Cunliffe, Silke Wyngaert, Keilor Rojas-jimenezAbstract:In this Review, Grossart and colleagues conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring Aquatic food webs. They focus on currently unexplored Aquatic fungal diversity, highlighting poorly understood Ecosystems, including emerging artificial Aquatic habitats. Fungi are phylogenetically and functionally diverse ubiquitous components of almost all Ecosystems on Earth, including Aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic Ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many Aquatic systems, yet a conceptual framework is still missing. In this Review, we conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring Aquatic food webs. We focus on currently unexplored fungal diversity, highlighting poorly understood Ecosystems, including emerging artificial Aquatic habitats.
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fungi in Aquatic Ecosystems
Nature Reviews Microbiology, 2019Co-Authors: Hanspeter Grossart, Silke Van Den Wyngaert, Maiko Kagami, Christian Wurzbacher, Michael Cunliffe, Keilor RojasjimenezAbstract:Fungi are phylogenetically and functionally diverse ubiquitous components of almost all Ecosystems on Earth, including Aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic Ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many Aquatic systems, yet a conceptual framework is still missing. In this Review, we conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring Aquatic food webs. We focus on currently unexplored fungal diversity, highlighting poorly understood Ecosystems, including emerging artificial Aquatic habitats.
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microbial ecology of organic aggregates in Aquatic Ecosystems
Aquatic Microbial Ecology, 2002Co-Authors: Meinhard Simon, Hanspeter Grossart, Bernd Schweitzer, Helle PlougAbstract:Macroscopic organic aggregates, which are >500 µm and known as marine and lake snow, are important components in the turnover, decomposition and sinking flux of both organic and inorganic matter and elements in Aquatic Ecosystems. They are composed of various organic and inorganic materials depending largely on the given system and environmental conditions. The sys- tems include the pelagic limnetic, the neritic and oceanic marine region, as well as shallow turbid environments, e.g. rivers, the littoral zone of lakes, estuaries and tidally affected coastal areas with intense turbulence and a high load of suspended matter. Aggregate abundance and size vary greatly among these systems. Macroaggregates are heavily colonized by bacteria and other heterotrophic microbes and greatly enriched in organic and inorganic nutrients as compared to the surrounding water. During the last 15 yr, many studies have been carried out to examine various aspects of the formation of aggregates, their microbial colonization and decomposition, nutrient recycling and their significance for the sinking flux. They have been identified as hot-spots of the microbial decomposi- tion of organic matter. Further, microaggregates, which are <5 to 500 µm in size and stained by different dyes, such as transparent exopolymer particles (TEP) and Coomassie blue-stained particles, have been discovered and shown also to be important in the formation and decomposition of macroaggregates. In this review we give an overview of the present state of the microbial ecology of macro- and microaggregates, including the mentioned points but highlighting in particular the recent findings on the bacterial colonization of aggregates using molecular tools, their microbial decomposition and mineralization, and the significance of protozoans and metazoans for the colo- nization and decomposition of macroaggregates. Today it is evident that not only the aggregates but also their surroundings are sites and hot-spots of microbial processes, with the plume of solutes leak- ing out of the aggregates and greatly extending the volume of the intense decomposition processes. This microheterogeneity has important implications for the spatial and temporal dynamics of the organic-matter field in Aquatic Ecosystems and for our understanding of how heterotrophic organisms are involved in the decomposition of organic matter. The significance of aggregate-associated micro- bial processes as key processes and also for the overall decomposition and flux of organic matter- varies greatly among the various systems, and is greatly affected by the total amount of suspended particulate matter. A conclusion from the presented studies and results is that the significance of bac- teria for the formation and decomposition of aggregates appears to be much greater than previously estimated. For a better understanding of the functioning of Aquatic Ecosystems it is of great impor- tance to include aggregate-associated processes in ecosystem modeling approaches.