Heterotrophic activities of bacterioneuston and bacterioplankton

1976 ◽  
Vol 22 (12) ◽  
pp. 1699-1709 ◽  
Author(s):  
A. S. Dietz ◽  
L. J. Albright ◽  
T. Tuominen
Keyword(s):  
Organic Carbon ◽  
Glucose Concentration ◽  
Natural Waters ◽  
Heterotrophic Bacteria ◽  
Bulk Water ◽  
Surface Microlayer ◽  
Near Surface ◽  
Heterotrophic Activity ◽  
Order Of Magnitude ◽  
Viable Bacteria

Numbers of viable bacteria as indicated by colony-forming units (CFU), microbial adenosine triphosphate levels, dissolved organic carbon (DOC), particulate organic carbon and nitrogen (POC and PON), glucose concentration, heterotrophic potential (Vmax) and in situ heterotrophic activity (Vn) of near-surface microlayer samples (70–80 μm depth), the neuston, and bulk column water samples (0.2–1.5 m depth), the plankton, of several natural waters were compared. DOC and glucose concentration values of near-surface and bulk water were similar, whereas POC and PON values of the near-surface were normally one order of magnitude greater than those of bulk water. Viable counts were generally greater in the neuston, but ATP levels were greater in the plankton. Comparative values of total heterotrophic potentials and heterotrophic activities fluctuated greatly. Heterotrophic potential per CFU of the neuston was 33% of that of the plankton; neuston heterotrophic activity per CFU was 10% of that of the plankton. These data suggest that neustonic heterotrophic bacteria are not as metabolically active as their planktonic counterparts and that they are under greater stress at the near-surface than in the column water.

scholarly journals Bacterioneuston in Lake Baikal: Abundance, Spatial and Temporal Distribution

2018 ◽  
Vol 15 (11) ◽  
pp. 2587 ◽  
Author(s):  
Agnia Galachyants ◽  
Irina Tomberg ◽  
Elena Sukhanova ◽  
Yulia Shtykova ◽  
Maria Suslova ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Lake Baikal ◽  
Direct Relationship ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Surface Microlayer ◽  
Suspended Particulate ◽  
Total Bacterial Abundance

An aquatic surface microlayer covers more than 70% of the world’s surface. Our knowledge about the biology of the surface microlayer of Lake Baikal, the most ancient lake on Earth with a surface area of 31,500 km2, is still scarce. The total bacterial abundance, the number of cultured heterotrophic temporal bacteria, and the spatial distribution of bacteria in the surface microlayer and underlying waters of Lake Baikal were studied. For the first time, the chemical composition of the surface microlayer of Lake Baikal was determined. There were significant differences and a direct relationship between the total bacterial abundance in the surface microlayer and underlying waters of Lake Baikal, as well as between the number of cultured heterotrophic bacteria in studied water layers in the period of summer stratification. In the surface microlayer, the share of cultured heterotrophic bacteria was higher than in the underlying waters. The surface microlayer was characterized by enrichment with PO43−, total organic carbon and suspended particulate matter compared to underlying waters. A direct relationship was found between the number of bacteria in the surface microlayer and environmental factors, including temperature, total organic carbon and suspended particulate matter concentration.

scholarly journals Fine-scale variability in methanol uptake and oxidation: from the microlayer to 1000 m

2012 ◽  
Vol 9 (8) ◽  
pp. 2961-2972 ◽  
Author(s):  
J. L. Dixon ◽  
P. D. Nightingale
Keyword(s):  
Methanol Oxidation ◽  
Heterotrophic Bacteria ◽  
Growth Efficiency ◽  
Cellular Growth ◽  
Bacterial Growth Efficiency ◽  
Leucine Incorporation ◽  
Surface Microlayer ◽  
Near Surface ◽  
Sea Surface Microlayer ◽  
Uptake Rates

Abstract. The aim of this research was to make the first depth profiles of the microbial assimilation of methanol carbon and its oxidation to carbon dioxide and use as an energy source from the microlayer to 1000 m. Some of the highest reported methanol oxidation rate constants of 0.5–0.6 d−1 were occasionally found in the microlayer and immediately underlying waters (10 cm depth), albeit these samples also showed the greatest heterogeneity compared to other depths down to 1000 m. Methanol uptake into the particulate phase was exceptionally low in microlayer samples, suggesting that any methanol utilised by microbes in this environment is for energy generation. The sea surface microlayer and 10 cm depth also showed a higher proportion of bacteria with a low DNA content, and bacterial leucine uptake rates in surface microlayer samples were either less than or the same as those in the underlying 10 cm layer. The average methanol oxidation and particulate rates were however statistically the same throughout the depths sampled, although the latter were highly variable in the near-surface 0.25–2 m compared to deeper depths. The statistically significant relationship demonstrated between uptake of methanol into particles and bacterial leucine incorporation suggests that many heterotrophic bacteria could be using methanol carbon for cellular growth. On average, methanol bacterial growth efficiency (BGEm) in the top 25 m of the water column is 6% and decreases with depth. Although, for microlayer and 10 cm-depth samples, BGEm is less than the near-surface 25–217 cm, possibly reflecting increased environmental UV stress resulting in increased maintenance costs, i.e. energy required for survival. We conclude that microbial methanol uptake rates, i.e. loss from seawater, are highly variable, particularly close to the seawater surface, which could significantly impact upon seawater concentrations and hence the air–sea flux.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

Ultra-Low Resistance Ni-Based Contacts to n-InP: the Dependence of Contact Resistivity on the Condition of the Metal-Semiconductor Interface

1993 ◽  
Vol 318 ◽  
Author(s):  
Navid S. Fatemi ◽  
Victor G. Weizer
Keyword(s):  
Deposition Process ◽  
Atomic Ratio ◽  
Contact Resistivity ◽  
Semiconductor Interface ◽  
Near Surface ◽  
Process Use ◽  
Fold Reduction ◽  
Specific Contact ◽  
Order Of Magnitude ◽  
First Time

ABSTRACTNear-theoretical-minimum values of specific contact resistivity, ρc (in the mid-to-low E-8 Ω-cm2 range) have been achieved for Ni-based contacts to moderately doped (2E18 cm−3) n-type InP. In each case these values are an order of magnitude lower than those previously achieved. These ultra-low resistivities are shown to result when the metallurgical interaction rate between the contact metal and the semiconductor is sufficiently reduced. Several methods of reducing the metal-InP reaction rate and thus achieving lowered resistivity values are demonstrated. We show, for instance, that the introduction of a thin (100Å) Au layer at the metal-InP interface retards metal-semiconductor intermixing during sintering and results in a ten-fold reduction in pc. Another method consists of ensuring the perfection of the near-surface InP lattice prior to and during contact deposition process. Use of this technique has enabled us to fabricate, for the first time, Ni-only contacts with pc values in the low E-8 Ω-cm2 range. We present an explanation for these observations that is based upon the magnitude of the In-to-P atomic ratio at the metal-InP interface.

scholarly journals Enhanced heterotrophic activity in the surface microlayer of the Mediterranean Sea

2005 ◽  
Vol 39 ◽  
pp. 293-302 ◽  
Author(s):  
I Obernosterer ◽  
P Catala ◽  
T Reinthaler ◽  
GJ Herndl ◽  
P Lebaron
Keyword(s):  
Mediterranean Sea ◽  
Surface Microlayer ◽  
Heterotrophic Activity ◽  
The Mediterranean

scholarly journals Particulate barium tracing of significant mesopelagic carbon remineralisation in the North Atlantic

2018 ◽  
Vol 15 (8) ◽  
pp. 2289-2307 ◽  
Author(s):  
Nolwenn Lemaitre ◽  
Hélène Planquette ◽  
Frédéric Planchon ◽  
Géraldine Sarthou ◽  
Stéphanie Jacquet ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
North Atlantic ◽  
Deep Convection ◽  
Sediment Traps ◽  
Heterotrophic Activity ◽  
Physical Forcing ◽  
The North ◽  
Poc Export ◽  
Order Of Magnitude ◽  
The North Atlantic

Abstract. The remineralisation of sinking particles by prokaryotic heterotrophic activity is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May–June 2014) using the particulate biogenic barium (excess barium; Baxs) proxy. Important mesopelagic (100–1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure, and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L−1), which was attributed to an intense bloom averaging 6 mg chl a m−3 between January and June 2014 and by an intense 1500 m deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. In comparison, the temperate province, characterized by the lowest Baxs content (391 pmol L−1), was sampled during the bloom period and phytoplankton appear to be dominated by small and calcifying species, such as coccolithophorids. The Baxs content, related to oxygen consumption, was converted into a remineralisation flux using an updated relationship, proposed for the first time in the North Atlantic. The estimated fluxes were of the same order of magnitude as other fluxes obtained using independent methods (moored sediment traps, incubations) in the North Atlantic. Interestingly, in the subpolar and subtropical provinces, mesopelagic POC remineralisation fluxes (up to 13 and 4.6 mmol C m−2 d−1, respectively) were equalling and occasionally even exceeding upper-ocean POC export fluxes, deduced using the 234Th method. These results highlight the important impact of the mesopelagic remineralisation on the biological carbon pump of the studied area with a near-zero, deep (> 1000 m) carbon sequestration efficiency in spring 2014.

scholarly journals Biochemical characteristics and bacterial community structure of the sea surface microlayer in the South Pacific Ocean

2007 ◽  
Vol 4 (4) ◽  
pp. 2809-2844 ◽  
Author(s):  
I. Obernosterer ◽  
P. Catala ◽  
R. Lami ◽  
J. Caparros ◽  
J. Ras ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Pacific Ocean ◽  
Organic Carbon ◽  
South Pacific ◽  
Leucine Incorporation ◽  
Surface Microlayer ◽  
South Pacific Ocean ◽  
Subsurface Waters ◽  
Card Fish

Abstract. The chemical and biological characteristics of the surface microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7), and POC:PON ratios were consistently higher in the surface microlayer as compared to subsurface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and heterotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface microlayer had close similarity (>76%) to those in subsurface waters. By contrast, bacterial heterotrophic production (3H-leucine incorporation) was consistently lower in the surface microlayer than in subsurface waters. By applying CARD-FISH and microautoradiography, we observed that Bacteroidetes and Gammaproteobacteria dominated leucine uptake in the surface microlayer, while in subsurface waters Bacteroidetes and Alphaproteobacteria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface microlayer closely resembles that of the surface waters of the open ocean. However, even short time periods in the surface microlayer result in differences in bacterial groups accounting for leucine incorporation, probably as a response to the differences in the physical and chemical nature of the two layers.

scholarly journals Simulating the Impact of the Internal Structure of Phytoplankton on the Bulk Particulate Backscattering Ratio using a Two-Layered Spherical Geometry for Cells

2018 ◽  
Author(s):  
Lucile Duforêt-Gaurier ◽  
David Dessailly ◽  
William Moutier ◽  
Hubert Loisel
Keyword(s):  
Coastal Waters ◽  
Natural Waters ◽  
Heterotrophic Bacteria ◽  
Relative Concentration ◽  
Spherical Geometry ◽  
The Third ◽  
Study Case ◽  
Coated Spheres ◽  
The Impact ◽  
Phytoplankton Cells

The bulk backscattering ratio ($\tilde{b_{bp}}$) is commonly used as a descriptor of the bulk real refractive index of the particulate assemblage in natural waters. Based on numerical simulations, we analyze the impact of heterogeneity of phytoplankton cells on $\tilde{b_{bp}}$. $\tilde{b_{bp}}$ is modeled considering viruses, heterotrophic bacteria, phytoplankton, detritus, and minerals. Three study cases are defined according to the relative abundance of these different components. Two study cases represent typical situations in open ocean, outside (No-B/No-M) and inside bloom (B/No-M). The third study case is typical of coastal waters with the presence of minerals. Phytoplankton cells are modeled by a two-layered spherical geometry representing a chloroplast surrounding the cytoplasm. The $\tilde{b_{bp}}$ values are higher when heterogeneity is considered because the contribution of coated spheres to backscattering is higher than homogeneous spheres. The impact of heterogeneity is however strongly conditioned by the hyperbolic slope $\xi$ of the particle size distribution. Even if the relative concentration of phytoplankton is small (<1%), $\tilde{b_{bp}}$ increases by about 60% (for $\xi=4.3$ and for the No-B/No-M water body), when the heterogeneity is taken into account, in comparison with a particulate population only composed by homogeneous spheres. As expected, heterogeneity has a much smaller impact (about 5$\%$ for $\xi=4.3$) on $\tilde{b_{bp}}$ when minerals are added.

scholarly journals Детекторы на основе низкобарьерных диодов Мотта и их характеристики в диапазоне 150-250 GHz

2019 ◽  
Vol 45 (5) ◽  
pp. 56
Author(s):  
П.В. Волков ◽  
Н.В. Востоков ◽  
А.В. Горюнов ◽  
Л.М. Кукин ◽  
В.В. Паршин ◽  
...  
Keyword(s):  
Performance Characteristics ◽  
Near Surface ◽  
Millimeter Wavelength ◽  
Constant Bias ◽  
Order Of Magnitude

AbstractThe characteristics of millimeter-wavelength detectors based on planar Mott diodes with near-surface δ-doping operating without a constant bias are discussed. These detectors have a volt–watt sensitivity of ~1000 V/W with NEP ~ 10 pW/Hz^1/2 in the 150–250 GHz range. The obtained estimates reveal the possibility of an additional order-of-magnitude enhancement of the performance characteristics of detectors with smaller areas of the diode barrier contact.

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