scholarly journals Microbial mats as shelter microhabitat for amphipods in an intermittent karstic spring

2018 ◽  
pp. 7 ◽  
Author(s):  
Petar Žutinić ◽  
Ines Petrić ◽  
Sanja Gottstein ◽  
Marija Gligora Udovič ◽  
Koraljka Kralj Borojević ◽  
...  
Keyword(s):  
Microbial Mats ◽  
High Water ◽  
Microbial Mat ◽  
Flow Conditions ◽  
Temporary Stream ◽  
Strong Current ◽  
Cyanobacterial Species ◽  
Animal Activity ◽  
Winter Sample ◽  
Representative Samples

Microbial mats represent complex communities where cyanobacteria and diatoms as key organisms provide shelter for diverse assemblages of aquatic invertebrates, like the small stygophilous amphipod Synurella ambulans. Studies addressing such communities in the karst springs have rarely examined springheads, and have ignored intermittent springs. During high flow conditions the stygophilic crustaceans are flushed to the surface of a temporary stream Krčić where microbial mats prevent their drift and enables their successful retreat into underground in the periods of drought. The objective of this study was to characterize the microbial mat community of the Krčić Spring as a shelter for S. ambulans during strong current and high water level. Representative samples for diatom and cyanobacterial species identification and composition, as well as the fresh mat material for potential animal activity and cyanobacterial phylogenetic analysis were collected. The most dominant diatom was Achnanthidium minutissimum, whilst Fragilaria capucina, Meridion circulare, Navicula cryptocephala and Nitzschia palea had abundance greater than 0.5%. Morphological observations of cyanobacteria revealed that Phormidium favosum was the most dominant, with Hydrocoleum muscicola as a subdominant. Cyanobacterial phylogenetic relationship revealed two distinct clusters: (i) "Phormidium cluster", confirming morphological observations in both winter and spring samples, and (ii) "Wilmottia cluster", a first report for Croatia and found exclusively in the winter sample. Laboratory observations revealed a small stygophilic amphipod S. ambulans, hiding and feeding inside the pockets of fresh microbial mat. The intermittent Krčić Spring as a predator-free and competitor-free ecosystem provides a spatiotemporal conformity between microbial mat and stygophilous amphipod.

scholarly journals Structure and cyanobacterial species composition of microbial mats in an Arabian Desert stream

2013 ◽  
Vol 7 (15) ◽  
pp. 1434-1442 ◽  
Author(s):  
M M Abed Raeid ◽  
J Barry Michael ◽  
Al Kindi Sumaiya ◽  
Golubic Stjepko
Keyword(s):  
Species Composition ◽  
Microbial Mats ◽  
Cyanobacterial Species ◽  
Desert Stream

scholarly journals Sterol preservation in hypersaline microbial mats

2020 ◽  
Vol 17 (3) ◽  
pp. 649-666
Author(s):  
Yan Shen ◽  
Volker Thiel ◽  
Pablo Suarez-Gonzalez ◽  
Sebastiaan W. Rampen ◽  
Joachim Reitner
Keyword(s):  
Microbial Mats ◽  
Abiotic Factors ◽  
Total Sterol ◽  
Microbial Transformation ◽  
Microbial Mat ◽  
Hypersaline Lake ◽  
Central Pacific ◽  
Significant Drop ◽  
Subaerial Exposure ◽  
Benthic Ecosystems

Abstract. Microbial mats are self-sustaining benthic ecosystems composed of highly diverse microbial communities. It has been proposed that microbial mats were widespread in Proterozoic marine environments, prior to the emergence of bioturbating organisms at the Precambrian–Cambrian transition. One characteristic feature of Precambrian biomarker records is that steranes are typically absent or occur in very low concentrations. This has been explained by low eukaryotic source inputs, or degradation of primary produced sterols in benthic microbial mats (“mat-seal effect”). To better understand the preservational pathways of sterols in microbial mats, we analyzed freely extractable and carbonate-bound lipid fractions as well as decalcified extraction residues in different layers of a recent calcifying mat (∼1500 years) from the hypersaline Lake 2 on the island of Kiritimati, central Pacific. A variety of C27–C29 sterols and distinctive C31 4α-methylsterols (4α-methylgorgosterol and 4α-methylgorgostanol, biomarkers for dinoflagellates) were detected in freely extractable and carbonate-bound lipid pools. These sterols most likely originated from organisms living in the water column and the upper mat layers. This autochthonous biomass experienced progressive microbial transformation and degradation in the microbial mat, as reflected by a significant drop in total sterol concentrations, up to 98 %, in the deeper layers, and a concomitant decrease in total organic carbon. Carbonate-bound sterols were generally low in abundance compared to the freely extractable portion, suggesting that incorporation into the mineral matrix does not play a major role in the preservation of eukaryotic sterols in this mat. Likewise, pyrolysis of extraction residues suggested that sequestration of steroid carbon skeletons into insoluble organic matter was low compared to hopanoids. Taken together, our findings argue for a major mat-seal effect affecting the distribution and preservation of steroids in the mat studied. This result markedly differs from recent findings made for another microbial mat growing in the nearby hypersaline Lake 22 on the same island, where sterols showed no systematic decrease with depth. The observed discrepancies in the taphonomic pathways of sterols in microbial mats from Kiritimati may be linked to multiple biotic and abiotic factors including salinity and periods of subaerial exposure, implying that caution has to be exercised in the interpretation of sterol distributions in modern and ancient microbial mat settings.

scholarly journals Formation of Kinneyia via shear-induced instabilities in microbial mats

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120362 ◽  
Author(s):  
Katherine Thomas ◽  
Stephan Herminghaus ◽  
Hubertus Porada ◽  
Lucas Goehring
Keyword(s):  
Microbial Mats ◽  
Flow Speed ◽  
Glass Beads ◽  
Flowing Water ◽  
Flow Conditions ◽  
Theoretical Predictions ◽  
Laboratory Analogue ◽  
Littoral Habitats ◽  
Over Time ◽  
Ripple Pattern

Kinneyia are a class of microbially mediated sedimentary fossils. Characterized by clearly defined ripple structures, Kinneyia are generally found in areas that were formally littoral habitats and covered by microbial mats. To date, there has been no conclusive explanation of the processes involved in the formation of these fossils. Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin–Helmholtz-type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time. Theoretical predictions show that the ripple instability has a wavelength proportional to the thickness of the film. Experiments carried out using viscoelastic films confirm this prediction. The ripple pattern that forms has a wavelength roughly three times the thickness of the film. This behaviour is independent of the viscosity of the film and the flow conditions. Laboratory-analogue Kinneyia were formed via the sedimentation of glass beads, which preferentially deposit in the troughs of the ripples. Well-ordered patterns form, with both honeycomb-like and parallel ridges being observed, depending on the flow speed. These patterns correspond well with those found in Kinneyia, with similar morphologies, wavelengths and amplitudes being observed.

Mobility of Herbicides in Soil Columns Under Saturated- and Unsaturated-Flow Conditions

Weed Science ◽  
1982 ◽  
Vol 30 (6) ◽  
pp. 579-584 ◽  
Author(s):  
Jerome B. Weber ◽  
David M. Whitacre
Keyword(s):  
Unsaturated Flow ◽  
Sandy Loam ◽  
High Water ◽  
Loamy Sand ◽  
Silt Loam ◽  
Flow Conditions ◽  
Soil Columns ◽  
Saturated Flow

Under unsaturated-flow conditions, bromacil (5-bromo-3-sec-butyl-6-methyluracil) was considerably more mobile than buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxyl-1-methyl-2-imidazolidinone}. Because of their high water solubilities, both herbicides were much more mobile than atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), prometon [2,4-bis (isopropylamino)-6-methoxy-s-triazine], or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea]. Under saturated-flow conditions, buthidazole was leached through Lakeland loamy sand in slightly greater amounts than tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or CN-10-3510 (formerly VEL 3510) {1-β,β-dimethoxyl-1-methyl-3-[5-(1,1-dimethylethyl)-1,3, 4-thiadiazol-2-yl] urea}. Distribution of the three herbicides in the leached soil was similar and relatively uniform. In Lakeland loamy sand, 30 times as much tebuthiuron was leached under saturated-flow conditions as under unsaturated-flow conditions. Intermittent saturated-unsaturated-flow conditions resulted in four times as much leaching of tebuthiuron as unsaturated flow alone. Only one-tenth as much tebuthiuron leached under intermittent saturated-unsaturated-flow conditions as under saturated-flow conditions. Tebuthiuron added to Lakeland soil and oven-dried was retained in significantly greater amounts than when added to moist Lakeland soil. Low amounts of tebuthiuron leached through Lakeland loamy sand, Portsmouth sandy loam, and Rains silt loam, but high amounts leached through Davidson clay. Greater amounts of the herbicide were retained in the surface zones of the three former soils, but the inverse was the case for the Davidson soil.

scholarly journals Responses of a Thermophilic Synechococcus Isolate from the Microbial Mat of Octopus Spring to Light

2007 ◽  
Vol 73 (13) ◽  
pp. 4268-4278 ◽  
Author(s):  
Oliver Kilian ◽  
Anne-Soisig Steunou ◽  
Fariba Fazeli ◽  
Shaun Bailey ◽  
Devaki Bhaya ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Microbial Mats ◽  
Carbon Fixation ◽  
Fluorescence Emission ◽  
Transcript Abundance ◽  
High Light ◽  
Microbial Mat ◽  
Fluorescence Emission Spectra ◽  
Thermophilic Cyanobacteria ◽  
Genes Encoding

ABSTRACT Thermophilic cyanobacteria of the genus Synechococcus are major contributors to photosynthetic carbon fixation in the photic zone of microbial mats in Octopus Spring, Yellowstone National Park. Synechococcus OS-B′ was characterized with regard to the ability to acclimate to a range of different light irradiances; it grows well at 25 to 200 μmol photons m−2 s−1 but dies when the irradiance is increased to 400 μmol photons m−2 s−1. At 200 μmol photons m−2 s−1 (high light [HL]), we noted several responses that had previously been associated with HL acclimation of cyanobacteria, including cell bleaching, reduced levels of phycobilisomes and chlorophyll, and elevated levels of a specific carotenoid. Synechococcus OS-B′ synthesizes the carotenoids zeaxanthin and β,β-carotene and a novel myxol-anhydrohexoside. Interestingly, 77-K fluorescence emission spectra suggest that Synechococcus OS-B′ accumulates very small amounts of photosystem II relative to that of photosystem I. This ratio further decreased at higher growth irradiances, which may reflect potential photodamage following exposure to HL. We also noted that HL caused reduced levels of transcripts encoding phycobilisome components, particularly that for CpcH, a 20.5-kDa rod linker polypeptide. There was enhanced transcript abundance of genes encoding terminal oxidases, superoxide dismutase, tocopherol cyclase, and phytoene desaturase. Genes encoding the photosystem II D1:1 and D1:2 isoforms (psbAI and psbAII/psbAIII, respectively) were also regulated according to the light regimen. The results are discussed in the context of how Synechococcus OS-B′ may cope with high light irradiances in the high-temperature environment of the microbial mat.

scholarly journals [FeFe] Hydrogenase Genetic Diversity Provides Insight into Molecular Adaptation in a Saline Microbial Mat Community

2009 ◽  
Vol 75 (13) ◽  
pp. 4620-4623 ◽  
Author(s):  
Eric S. Boyd ◽  
John R. Spear ◽  
John W. Peters
Keyword(s):  
Genetic Diversity ◽  
Environmental Conditions ◽  
Microbial Mats ◽  
Microbial Mat ◽  
Molecular Adaptation ◽  
Degenerate Primers ◽  
Insight Into

ABSTRACT Degenerate primers for the [FeFe] hydrogenase (hydA) were developed and used in PCRs to examine hydA in microbial mats that inhabit saltern evaporative ponds in Guerrero Negro (GN), Mexico. A diversity of deduced HydA was discovered that revealed unique variants, which may reflect adaptation to the environmental conditions present in GN.

Development and Validation of Enthalpy-Porosity Method for Artificial Ground Freezing Under Seepage Conditions

2018 ◽  
Author(s):  
Mahmoud A. Alzoubi ◽  
Agus P. Sasmito
Keyword(s):  
Seepage Flow ◽  
High Water ◽  
Flow Conditions ◽  
Ground Structure ◽  
Reliable Prediction ◽  
Closure Time ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
Development And Validation

Groundwater flow has an undesirable effect on ice growth in artificial ground freezing (AGF) process: high water flow could hinder the hydraulic sealing between two freeze pipes. Therefore, a reliable prediction of the multiphysics ground behavior under seepage flow conditions is compulsory. This paper describes a mathematical model that considers conservation of mass, momentum, and energy. The model has been derived, validated, and implemented to simulate the multiphase heat transfer between freeze pipes and surrounded porous ground structure with and without the presence of groundwater seepage. The paper discusses, also, the influence of the coolant’s temperature, the spacing between two freeze pipes, and the seepage temperature on time needed to create a closed, frozen wall. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.

scholarly journals Radiocarbon Dating of Recent Intertidal Microbial Mats on Atoll Rims

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1603-1616 ◽  
Author(s):  
Jean Trichet ◽  
Christine Hatté ◽  
Michel Fontugne
Keyword(s):  
Southern Hemisphere ◽  
Radiocarbon Dating ◽  
Microbial Mats ◽  
French Polynesia ◽  
Microbial Mat ◽  
Accumulation Process ◽  
Reservoir Effect ◽  
Activity Measurements ◽  
Effect Estimation

Microbial mats (koparain Polynesian) that develop in shallow brackish to hypersaline ponds on the rims of atolls were investigated for their accumulation process and rate. Two sequences of ∼30-cm-deep kopara, composed of 7 and 5 layers distinguished by their colors and sedimentological facies were collected in 1996 from the Tetiaroa atoll, French Polynesia. The combination of radiocarbon activity measurements on both organic and carbonate constituents, reservoir effect estimation, and comparison with the Southern Hemisphere atmospheric bomb-peak14C record allowed us to establish a fine chronology of the layer successions documenting the mode of formation, erosion, and restoration of these microbial mat deposits.

Sign in / Sign up

Export Citation Format

Share Document