scholarly journals Carbon fluxes through bacterial communities on glacier surfaces

2010 ◽  
Vol 51 (56) ◽  
pp. 32-40 ◽  
Author(s):  
Alexandre M. Anesio ◽  
Birgit Sattler ◽  
Christine Foreman ◽  
Jon Telling ◽  
Andy Hodson ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Community Respiration ◽  
Organic C ◽  
C Cycle ◽  
Cryoconite Hole ◽  
Eukaryotic Organisms ◽  
Doubling Times

AbstractThere is very little information about the activity of microbial communities on the surface of glaciers, though there is an increasing body of evidence to show that they strongly influence the biogeochemistry of these habitats. We measured bacterial abundance and production in cryoconite holes on Arctic, Antarctic and Alpine glaciers in order to estimate the role of heterotrophic bacteria within the carbon budget of glacial ecosystems. Our results demonstrate an active bacterial community on the surface of glaciers with doubling times that vary from a few hours to hundreds of days depending on the glacier and position (water or sediments) within the cryoconite hole. However, bacterial production is only ∼2–3% of the published literature values of community respiration from similar habitats, indicating that other types of microbes (e.g. eukaryotic organisms) may also play a role in the C cycle of glaciers. We estimate that only up to 7% of the organic C in cryoconite sediments is utilized by the heterotrophic bacterial community annually, suggesting that the surface of glaciers can accumulate organic carbon, and that this C may be important for biogeochemical activity downstream to adjacent ecosystems.

scholarly journals Fe and C co-limitation of heterotrophic bacteria in the naturally fertilized region off the Kerguelen Islands

2015 ◽  
Vol 12 (6) ◽  
pp. 1983-1992 ◽  
Author(s):  
I. Obernosterer ◽  
M. Fourquez ◽  
S. Blain
Keyword(s):  
Trace Metal ◽  
Bacterial Production ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Kerguelen Islands ◽  
High Nutrient ◽  
Limiting Nutrient ◽  
Heterotrophic Metabolism ◽  
Heterotrophic Production

Abstract. It has been univocally shown that iron (Fe) is the primary limiting nutrient for phytoplankton metabolism in high-nutrient, low-chlorophyll (HNLC) waters, yet the question of how this trace metal affects heterotrophic microbial activity is far less understood. We investigated the role of Fe for bacterial heterotrophic production and growth at three contrasting sites in the naturally Fe-fertilized region east of the Kerguelen Islands and at one site in HNLC waters during the KEOPS2 (Kerguelen Ocean and Plateau Compared Study 2) cruise in spring 2011. We performed dark incubations of natural microbial communities amended either with iron (Fe, as FeCl3) or carbon (C, as trace-metal clean glucose), or a combination of both, and followed bacterial abundance and heterotrophic production for up to 7 days. Our results show that single and combined additions of Fe and C stimulated bulk and cell-specific bacterial production at the Fe-fertilized sites, while in HNLC waters only combined additions resulted in significant increases in these parameters. Bacterial abundance was enhanced in two out of the three experiments performed in Fe-fertilized waters but did not respond to Fe or C additions in HNLC waters. Our results provide evidence that both Fe and C are present at limiting concentrations for bacterial heterotrophic activity in the naturally fertilized region off the Kerguelen Islands in spring, while bacteria were co-limited by these elements in HNLC waters. These results shed new light on the role of Fe in bacterial heterotrophic metabolism in regions of the Southern Ocean that receive variable Fe inputs.

Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor

1990 ◽  
Vol 36 (12) ◽  
pp. 859-863 ◽  
Author(s):  
James A. Novitsky
Keyword(s):  
Bacterial Community ◽  
Water Column ◽  
Sediment Surface ◽  
Metabolic Inhibitor ◽  
Optimum Conditions ◽  
Bacterial Populations ◽  
Protozoan Grazing ◽  
Large Numbers ◽  
Doubling Times

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.

Bacterioplankton Density and Activity in Benthic Nepheloid Layers of Lake Michigan and Lake Superior

1991 ◽  
Vol 48 (5) ◽  
pp. 923-932 ◽  
Author(s):  
Randall E. Hicks ◽  
Christopher J. Owen
Keyword(s):  
Lake Michigan ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Lake Superior ◽  
Field Measurements ◽  
Depth Interval ◽  
Nepheloid Layer ◽  
Dividing Cells ◽  
Doubling Times ◽  
Benthic Nepheloid Layer

Benthic nepheloid layers were observed in Lake Michigan and Lake Superior during July 1988 using the Johnson-Sea-Link II submersible. A particularly well-defined benthic nepheloid layer was present in Whitefish Bay, Lake Superior, where particle concentrations increased 10 times over the bottom 30 m. Bacterial abundance, however, increased only 1.5 times in the same depth interval and a maximum of only 16% 1 m above the sediment in both lakes when the sediment boundary layer was deliberately resuspended. Bacterial abundance was greater in Lake Michigan than in Lake Superior. Bacterioplankton abundance and the frequency of dividing cells were both related to temperature and organic carbon concentrations. The range of individual cell volumes (0.024–0.042 μm3) was similar in both lakes, regardless of depth. Less than 5% of the heterotrophic bacteria were actively dividing and only 2.0–3.4% of the bacterioplankton in the epilimnion and hypolimnion were synthetically active in both lakes. Bacterioplankton doubling times, estimated from field measurements of the frequency of dividing cells, increased from 29 h at 5 m to > 230 h at 310 m in the Caribou Basin of Lake Superior. The abundance, cell size, and activity of heterotrophic bacterioplankton in the deep hypolimnia of Lake Michigan and Lake Superior were unaffected by the presence of a benthic nepheloid layer.

scholarly journals Contrasting patterns of carbon cycling and dissolved organic matter processing in two phytoplankton–bacteria communities

2021 ◽  
Vol 18 (24) ◽  
pp. 6589-6616
Author(s):  
Samu Elovaara ◽  
Eeva Eronen-Rasimus ◽  
Eero Asmala ◽  
Tobias Tamelander ◽  
Hermanni Kaartokallio
Keyword(s):  
Primary Production ◽  
Bacterial Production ◽  
Bacterial Biomass ◽  
Community Respiration ◽  
Exponential Growth Phase ◽  
Bacterial Respiration ◽  
Organic C ◽  
Optical Signals ◽  
C Cycle ◽  
Microbial Consumption

Abstract. Microbial consumption of phytoplankton-derived organic carbon in the pelagic food web is an important component of the global C cycle. We studied C cycling in two phytoplankton–bacteria systems (non-axenic cultures of a dinoflagellate Apocalathium malmogiense and a cryptophyte Rhodomonas marina) in two complementary experiments. In the first experiment we grew phytoplankton and bacteria in nutrient-replete conditions and followed C processing at early exponential growth phase and twice later when the community had grown denser. Cell-specific primary production and total community respiration were up to 4 and 7 times higher, respectively, in the A. malmogiense treatments. Based on the optical signals, accumulating dissolved organic C (DOC) was degraded more in the R. marina treatments, and the rate of bacterial production to primary production was higher. Thus, the flow of C from phytoplankton to bacteria was relatively higher in R. marina treatments than in A. malmogiense treatments, which was further supported by faster 14C transfer from phytoplankton to bacterial biomass. In the second experiment we investigated consumption of the phytoplankton-derived DOC by bacteria. DOC consumption and transformation, bacterial production, and bacterial respiration were all higher in R. marina treatments. In both experiments A. malmogiense supported a bacterial community predominated by bacteria specialized in the utilization of less labile DOC (class Bacteroidia), whereas R. marina supported a community predominated by copiotrophic Alpha- and Gammaproteobacteria. Our findings suggest that large dinoflagellates cycle relatively more C between phytoplankton biomass and the inorganic C pool, whereas small cryptophytes direct relatively more C to the microbial loop.

scholarly journals Natural Assemblages of Marine Proteobacteria and Members of the Cytophaga-Flavobacter Cluster Consuming Low- and High-Molecular-Weight Dissolved Organic Matter

2000 ◽  
Vol 66 (4) ◽  
pp. 1692-1697 ◽  
Author(s):  
Matthew T. Cottrell ◽  
David L. Kirchman
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Bacterial Community ◽  
Dissolved Organic Matter ◽  
Relative Abundance ◽  
Heterotrophic Bacteria ◽  
Phylogenetic Groups ◽  
Whole Cells ◽  
Biogeochemical Models

ABSTRACT We used a method that combines microautoradiography with hybridization of fluorescent rRNA-targeted oligonucleotide probes to whole cells (MICRO-FISH) to test the hypothesis that the relative contributions of various phylogenetic groups to the utilization of dissolved organic matter (DOM) depend solely on their relative abundance in the bacterial community. We found that utilization of even simple low-molecular-weight DOM components by bacteria differed across the major phylogenetic groups and often did not correlate with the relative abundance of these bacterial groups in estuarine and coastal environments. The Cytophaga-Flavobacter cluster was overrepresented in the portion of the assemblage consuming chitin,N-acetylglucosamine, and protein but was generally underrepresented in the assemblage consuming amino acids. The amino acid-consuming assemblage was usually dominated by the α subclass of the class Proteobacteria, although the representation of α-proteobacteria in the protein-consuming assemblages was about that expected from their relative abundance in the entire bacterial community. In our experiments, no phylogenetic group dominated the consumption of all DOM, suggesting that the participation of a diverse assemblage of bacteria is essential for the complete degradation of complex DOM in the oceans. These results also suggest that the role of aerobic heterotrophic bacteria in carbon cycling would be more accurately described by using three groups instead of the single bacterial compartment currently used in biogeochemical models.

scholarly journals The role of soil in regulation of climate

2021 ◽  
Vol 376 (1834) ◽  
pp. 20210084 ◽  
Author(s):  
Rattan Lal ◽  
Curtis Monger ◽  
Luke Nave ◽  
Pete Smith
Keyword(s):  
Land Use ◽  
Management Practices ◽  
Ghg Emissions ◽  
Organic C ◽  
Soil C ◽  
C Cycle ◽  
C Stocks ◽  
C Stock ◽  
Land Use And Management

The soil carbon (C) stock, comprising soil organic C (SOC) and soil inorganic C (SIC) and being the largest reservoir of the terrestrial biosphere, is a critical part of the global C cycle. Soil has been a source of greenhouse gases (GHGs) since the dawn of settled agriculture about 10 millenia ago. Soils of agricultural ecosystems are depleted of their SOC stocks and the magnitude of depletion is greater in those prone to accelerated erosion by water and wind and other degradation processes. Adoption of judicious land use and science-based management practices can lead to re-carbonization of depleted soils and make them a sink for atmospheric C. Soils in humid climates have potential to increase storage of SOC and those in arid and semiarid climates have potential to store both SOC and SIC. Payments to land managers for sequestration of C in soil, based on credible measurement of changes in soil C stocks at farm or landscape levels, are also important for promoting adoption of recommended land use and management practices. In conjunction with a rapid and aggressive reduction in GHG emissions across all sectors of the economy, sequestration of C in soil (and vegetation) can be an important negative emissions method for limiting global warming to 1.5 or 2°C This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

scholarly journals Contrasting patterns of carbon cycling and DOM processing in two phytoplankton-bacteria communities

2021 ◽  
Author(s):  
Samu Markku Elovaara ◽  
Eeva Liisa Eronen-Rasimus ◽  
Eero Jooseppi Asmala ◽  
Tobias Tamelander ◽  
Hermanni Pekka Kaartokallio
Keyword(s):  
Primary Production ◽  
Bacterial Production ◽  
Bacterial Biomass ◽  
Community Respiration ◽  
Exponential Growth Phase ◽  
Bacterial Respiration ◽  
Organic C ◽  
Optical Signals ◽  
C Cycle ◽  
Microbial Consumption

Abstract. Microbial consumption of phytoplankton-derived organic carbon in the pelagic food web is an important component of the global C cycle. We studied C cycling in two phytoplankton-bacteria systems (non-axenic cultures of a dinoflagellate Apocalathium malmogiense and a cryptophyte Rhodomonas marina) in two experiments. In the first experiment we grew phytoplankton and bacteria in nutrient replete conditions and followed C processing at early exponential growth phase and at two later phases. Primary production and total community respiration were up to 4 and 7 times higher, respectively, in the A. malmogiense treatments. Based on the optical signals, accumulating dissolved organic C (DOC) was degraded more in the R. marina treatments and the rate of bacterial production to primary production was higher. Thus, the flow of C from phytoplankton to bacteria was relatively higher in R. marina treatments than in A. malmogiense treatments which was further supported by faster 14C transfer from phytoplankton to bacterial biomass. In the second experiment we investigated consumption of the phytoplankton-derived DOC by bacteria. DOC consumption and transformation, bacterial production and bacterial respiration were all higher in R. marina treatments. In both experiments A. malmogiense supported a bacterial community predominated by bacteria specialized in the utilization of less labile DOC (class Bacteroidia) whereas R. marina supported a community predominated by copiotrophic Alpha- and Gammaproteobacteria. Our findings suggest that large dinoflagellates cycle relatively more C between phytoplankton biomass and the inorganic C pool whereas small cryptophytes direct relatively more C to the microbial loop.

scholarly journals Reference carbon cycle dataset for typical Chinese forests via colocated observations and data assimilation

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Honglin He ◽  
Rong Ge ◽  
Xiaoli Ren ◽  
Li Zhang ◽  
Qingqing Chang ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Global Climate ◽  
Meteorological Data ◽  
C Sequestration ◽  
Research Network ◽  
Soil Biology ◽  
Area Index ◽  
Ecosystem Research ◽  
Organic C ◽  
C Cycle

AbstractChinese forests cover most of the representative forest types in the Northern Hemisphere and function as a large carbon (C) sink in the global C cycle. The availability of long-term C dynamics observations is key to evaluating and understanding C sequestration of these forests. The Chinese Ecosystem Research Network has conducted normalized and systematic monitoring of the soil-biology-atmosphere-water cycle in Chinese forests since 2000. For the first time, a reference dataset of the decadal C cycle dynamics was produced for 10 typical Chinese forests after strict quality control, including biomass, leaf area index, litterfall, soil organic C, and the corresponding meteorological data. Based on these basic but time-discrete C-cycle elements, an assimilated dataset of key C cycle parameters and time-continuous C sequestration functions was generated via model-data fusion, including C allocation, turnover, and soil, vegetation, and ecosystem C storage. These reference data could be used as a benchmark for model development, evaluation and C cycle research under global climate change for typical forests in the Northern Hemisphere.

scholarly journals Functional Characterization of Spliceosomal Introns and Identification of U2, U4, and U5 snRNAs in the Deep-Branching Eukaryote Entamoeba histolytica

2007 ◽  
Vol 6 (6) ◽  
pp. 940-948 ◽  
Author(s):  
Carrie A. Davis ◽  
Michael P. S. Brown ◽  
Upinder Singh
Keyword(s):  
Entamoeba Histolytica ◽  
Splice Site ◽  
Expressed Sequence Tag ◽  
Functional Characterization ◽  
Molecular Evidence ◽  
Spliceosomal Introns ◽  
Accurate Expression ◽  
Eukaryotic Organisms

ABSTRACT Pre-mRNA splicing is essential to ensure accurate expression of many genes in eukaryotic organisms. In Entamoeba histolytica, a deep-branching eukaryote, approximately 30% of the annotated genes are predicted to contain introns; however, the accuracy of these predictions has not been tested. In this study, we mined an expressed sequence tag (EST) library representing 7% of amoebic genes and found evidence supporting splicing of 60% of the testable intron predictions, the majority of which contain a GUUUGU 5′ splice site and a UAG 3′ splice site. Additionally, we identified several splice site misannotations, evidence for the existence of 30 novel introns in previously annotated genes, and identified novel genes through uncovering their spliced ESTs. Finally, we provided molecular evidence for the E. histolytica U2, U4, and U5 snRNAs. These data lay the foundation for further dissection of the role of RNA processing in E. histolytica gene expression.

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