scholarly journals The contribution of tephra constituents during biogenic silica determination: implications for soil and paleoecological studies

2015 ◽  
Vol 12 (4) ◽  
pp. 3505-3545 ◽  
Author(s):  
W. Clymans ◽  
L. Barão ◽  
N. Van der Putten ◽  
S. Wastegård ◽  
G. Gísladóttir ◽  
...  
Keyword(s):  
Biogenic Silica ◽  
Environmental Changes ◽  
Biological Effects ◽  
Volcanic Glass ◽  
Alkaline Media ◽  
Nano Crystalline ◽  
Glass Shard ◽  
Dissolution Properties ◽  
Highly Sensitive ◽  
Alkaline Dissolution

Abstract. Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by paleoecologists to study environmental changes. Alkaline extractions are typically used to measure BSi in both terrestrial and aquatic environments. The dissolution properties of volcanic glass in tephra deposits and their nano-crystalline weathering products are hypothesized to overlap those of BSi, however, data to support this behavior are lacking. The understanding that the Si-bearing fractions that dissolve in alkaline media (SiAlk) do not necessarily correspond to BSi, question the applicability of BSi as a proxy. Here, analysis of 15 samples reported as tephra-containing allows us to reject the hypothesis that tephra constituents produce an identical dissolution signal to that of BSi during alkaline extraction. We found that dissolution of volcanic glass shards is incomplete during alkaline dissolution. Simultaneous measurement of Al and Si used here during alkaline dissolution provides an important parameter to enable us to separate glass shard dissolution from dissolution of BSi and other Si-bearing fractions. The contribution from volcanic glass shard (between 0.2–4 wt.% SiO2), the main constituent of distal tephra, during alkaline dissolution can be substantial depending on the total SiAlk. Hence, soils and lake sediments with low BSi concentrations are highly sensitive to the additional dissolution from tephra constituents and its weathering products. We advise evaluation of the potential for volcanic or other non-biogenic contributions for all types of studies using BSi as an environmental proxy.

scholarly journals The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies

2015 ◽  
Vol 12 (12) ◽  
pp. 3789-3804 ◽  
Author(s):  
W. Clymans ◽  
L. Barão ◽  
N. Van der Putten ◽  
S. Wastegård ◽  
G. Gísladóttir ◽  
...  
Keyword(s):  
Biogenic Silica ◽  
Environmental Changes ◽  
Biological Effects ◽  
Volcanic Glass ◽  
Alkaline Media ◽  
Glass Shard ◽  
Dissolution Properties ◽  
Highly Sensitive ◽  
Alkaline Dissolution ◽  
Glass Shards

Abstract. Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by palaeoecologists to study environmental changes. Alkaline extractions are typically used to measure BSi in both terrestrial and aquatic environments. The dissolution properties of volcanic glass in tephra deposits and their nanocrystalline weathering products are hypothesized to overlap those of BSi; however, data to support this behaviour are lacking. The potential that Si-bearing fractions dissolve in alkaline media (SiAlk) that do not necessarily correspond to BSi brings the applicability of BSi as a proxy into question. Here, analysis of 15 samples reported as tephra-containing allows us to reject the hypothesis that tephra constituents produce an identical dissolution signal to that of BSi during alkaline extraction. We found that dissolution of volcanic glass shards is incomplete during alkaline dissolution. Simultaneous measurement of Al and Si used here during alkaline dissolution provides an important parameter to enable us to separate glass shard dissolution from dissolution of BSi and other Si-bearing fractions. The contribution from volcanic glass shards (between 0.2 and 4 wt % SiO2), the main constituent of distal tephra, during alkaline dissolution can be substantial depending on the total SiAlk. Hence, soils and lake sediments with low BSi concentrations are highly sensitive to the additional dissolution from tephra constituents and its weathering products. We advise evaluation of the potential for volcanic or other non-biogenic contributions for all types of studies using BSi as an environmental proxy.

Sedimentological and Biological Changes Associated with the Construction of the Oil Terminal of Antifer, France

1984 ◽  
Vol 16 (3-4) ◽  
pp. 399-406
Author(s):  
Y Monbet
Keyword(s):  
Grain Size ◽  
Environmental Changes ◽  
Biological Effects ◽  
Standing Stock ◽  
Natural Populations ◽  
Benthic Fauna ◽  
Field Investigations ◽  
Mean Grain Size ◽  
To Receive ◽  
Principal Species

A study was conducted to gain insight on actual sedimentological and biological effects associated with the construction of an oil Terminal designed to receive 500 000 d.w.t. tankers. Field investigations and subsequent laboratory analyses were organized to evaluate the nature and magnitude of environmental changes on benthic macrofauna, three years after the end of the construction. Sediments were found to decrease dramatically in medium grain size in area sheltered by the newly built breakwater. Increase of percentage of silt and clays (90 % against 20 %) was observed leeward of the jetty. The benthic fauna showed significant modifications. Although the same community (Pectinaria kareni Abra alba) recolonized the bottom after the dredging of up to 30 × 106 m3 of sediments, increase in abundance occured. Biomass remained at a constant level and decrease of diversity was observed. Considering the rate of siltation, and assuming a constant siltation rate equal to the rate observed from 1975 to 1978, a simple regressive model relating biomass to mean grain size of sediments has been developped. This model allowed the prediction of biomass and production of the two principal species for the period 1978 – 1981. Continuous siltation within the harbor leads to a maximum of biomass from years after the end of the construction, followed by a decrease of standing stock. This process may be explained by the respective tolerance of the two principal species to increase silt contant and also probably by the accumulation of organic matter which may impede the development of natural populations.

scholarly journals Miocene and Pliocene Silicic Coromandel Volcanic Zone Tephras from ODP Site 1124-C: Petrogenetic Applications and Temporal Evolution

2021 ◽  
Author(s):  
◽  
Matthew Thomas Stevens
Keyword(s):  
Trace Element ◽  
Mantle Wedge ◽  
Major Element ◽  
Volcanic Glass ◽  
Fractional Crystallisation ◽  
Volcanic Zone ◽  
Arc Magmas ◽  
Glass Shard ◽  
Tephra Layers ◽  
Glass Shards

<p>The Coromandel Volcanic Zone (CVZ) was the longest-lived area of volcanism in New Zealand hosting the commencement of large explosive rhyolitic and ignimbrite forming eruptions. The NW trending Coromandel Peninsula is the subaerial remnant of the Miocene-Pliocene CVZ, which is regarded as a tectonic precursor to the Taupo Volcanic Zone (TVZ), currently the most dynamic and voluminous rhyolitic volcanic centre on Earth. This study presents new single glass shard major and trace element geochemical analyses for 72 high-silica volcanic tephra layers recovered from well-dated deep-sea sediments of the SW Pacific Ocean by the Ocean Drilling Program (ODP) Leg 181. ODP Site 1124, ~720 km south and east from the CVZ, penetrated sediments of the Rekohu Drift yielding an unprecedented record of major explosive volcanic eruptions owing to the favourable location and preservation characteristics at this site. This record extends onshore eruptive sequences of CVZ explosive volcanism that are obscured by poor exposure, alteration, and erosion and burial by younger volcanic deposits. Tephra layers recovered from Site 1124 are well-dated through a combination of biostratigraphic and palaeomagnetic methods allowing the temporal geochemical evolution of the CVZ to be reconstructed in relation to changes in the petrogenesis of CVZ arc magmas from ~ 10 to 2 Ma. This thesis establishes major and trace element geochemical "fingerprints" for all Site 1124-C tephras using well-established (wavelength dispersive electron probe microanalysis) and new (laser ablation inductively coupled plasma mass spectrometry) in situ single glass shard microanalytical techniques. Trace element analysis of Site 1124-C glass shards (as small as 20 um) demonstrate that trace element signatures offer a more specific, unequivocal characterisation for distinguishing (and potentially correlating) between tephras with nearly identical major element compositions. The Site 1124-C core contains 72 unaltered Miocene-Pliocene volcanic glass-shard-bearing laminae > 1 cm thick that correspond to 83 or 84 geochemical eruptive units. Revised eruptive frequencies based on the number of geochemical eruptive units identified represent at least one eruption every 99 kyr for the late Miocene and one per 74 kyr for the Pliocene. The frequency of tephra deposition throughout the history of the CVZ has not been constant, rather reflecting pulses of major explosive eruptions resulting in closely clustered groups of tephra separated by periods of reduced activity, relative volcanic quiescence or non-tephra deposition. As more regular activity became prevalent in the Pliocene, it was accompanied by more silicic magma compositions. Rhyolitic volcanic glass shards are characterised by predominantly calc-alkaline and minor high-K enriched major element compositions. Major element compositional variability of the tephras deposited between 10 Ma and 2 Ma reveals magma batches with pre-eruptive compositional gradients implying a broad control by fractional crystallisation. Trace element characterisation of glass shards reveals the role of magmatic processes that are not readily apparent in the relatively homogeneous major element compositions. Multi-element diagrams show prominent negative Sr and Ti anomalies against primitive mantle likely caused by various degrees of plagioclase and titanomagnetite fractional crystallisation in shallow magma chambers. Relative Nb depletion, characteristic of arc volcanism, is moderate in CVZ tephras. HFSEs (e.g. Nb, Zr, Ti) and HREEs (e.g. Yb, Lu) remain immobile during slab fluid flux suggesting they are derived from the mantle wedge. LILE (e.g. Rb, Cs, Ba, Sr) and LREE (e.g. La, Ce) enrichments are consistent with slab fluid contribution. B/La and Li/Y ratios can be used as a proxy for the flux of subducting material to the mantle wedge, they suggest there is a strong influence from this component in the generation of CVZ arc magmas, potentially inducing melting. CVZ tephra show long-term coherent variability in trace element geochemistry. Post ~ 4 Ma tephras display a more consistent, less variable, chemical fingerprint that persists up to and across the CVZ/TVZ transition at ~ 2 Ma. Initiation of TVZ volcanism may have occurred earlier than is presently considered, or CVZ to TVZ volcanism may have occurred without significant changes in magma generation processes.</p>

scholarly journals Bioluminescence dynamics in single germinating bacterial spores reveal metabolic heterogeneity

2020 ◽  
Vol 17 (170) ◽  
pp. 20200350
Author(s):  
Zak Frentz ◽  
Jonathan Dworkin
Keyword(s):  
Cell Fate ◽  
Quantitative Measurement ◽  
Environmental Changes ◽  
Reducing Power ◽  
Extreme Case ◽  
Bacterial Bioluminescence ◽  
Highly Sensitive ◽  
Germination Timing ◽  
Metabolic Heterogeneity ◽  
Spore Forming Bacteria

Spore-forming bacteria modulate their metabolic rate by over five orders of magnitude as they transition between dormant spores and vegetative cells and thus represent an extreme case of phenotypic variation. During environmental changes in nutrient availability, clonal populations of spore-forming bacteria exhibit individual differences in cell fate, the timing of phenotypic transitions and gene expression. One potential source of this variability is metabolic heterogeneity, but this has not yet been measured, as existing single-cell methods are not easily applicable to spores due to their small size and strong autofluorescence. Here, we use the bacterial bioluminescence system and a highly sensitive microscope to measure metabolic dynamics in thousands of B. subtilis spores as they germinate. We observe and quantitate large variations in the bioluminescence dynamics across individual spores that can be decomposed into contributions from variability in germination timing, the amount of endogenously produced luminescence substrate and the intracellular reducing power. This work shows that quantitative measurement of spore metabolism is possible and thus it opens avenues for future study of the thermodynamic nature of dormant states.

scholarly journals Characterization of oxidative stress biomarkers in a freshwater anomuran crab

2017 ◽  
Vol 78 (1) ◽  
pp. 61-67 ◽  
Author(s):  
A. C. P. Borges ◽  
J. F. G. Piassão ◽  
M. O. Paula ◽  
S. Sepp ◽  
C. F. S. Bez ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Seasonal Variations ◽  
Environmental Changes ◽  
Oxidative Stress Biomarkers ◽  
Stress Biomarkers ◽  
Physicochemical Variables ◽  
Highly Sensitive ◽  
Freshwater Crustacean ◽  
Environmental Responses ◽  
Oxidative Biomarkers

Abstract In general, environmental responses at level of populations or communities are preceded by alterations at lower biological levels which can be efficiently detected by the analysis of biomarkers. We analyzed the oxidative biomarkers TBARS and Catalase in Aegla singularis, a freshwater crustacean highly sensitive to environmental changes. The objective was to address if are differences in these biomarkers related to the gender as well if they are influenced by seasonal or water physicochemical variables. The results showed differences in biomarkers profile related to the gender. In female crabs were not sensitive to seasonal variations throughout the study period. However, in males the biomarkers evaluated were higher in the winter as compared to remaining seasons and showed tendency of negative correlation with water temperature and pH. This study highlights that gender, seasonal variations and physicochemical variables can influence oxidative stress biomarkers in A. singularis. Female crabs probably are better suited as a model for biomarker application in environmental studies, because their insensibility to seasonal variations can facilitate the observations of responses related specifically to environmental disturbances.

scholarly journals Evolutionary heritage shapes tree distributions along an Amazon-to-Andes elevation gradient

2020 ◽  
Author(s):  
Andy R. Griffiths ◽  
Miles R. Silman ◽  
William Farfán Rios ◽  
Kenneth J. Feeley ◽  
Karina García Cabrera ◽  
...  
Keyword(s):  
Census Data ◽  
Environmental Changes ◽  
Elevation Gradient ◽  
Cloud Base ◽  
Valuable Insight ◽  
Montane Forests ◽  
Peruvian Andes ◽  
Habitat Specialisation ◽  
Tropical Montane Forests ◽  
Highly Sensitive

ABSTRACTUnderstanding how evolutionary constraints shape the elevational distributions of tree lineages provides valuable insight into the future of tropical montane forests under global change. With narrow elevational ranges, high taxonomic turnover, frequent habitat specialisation, and exceptional levels of endemism, tropical montane forests and trees are predicted to be highly sensitive to environmental change. Using plot census data from a gradient traversing >3000 m in elevation on the Amazonian flank of the Peruvian Andes, we employ phylogenetic approaches to assess the influence of evolutionary heritage on distribution trends of trees at the genus level. We find that closely related lineages tend to occur at similar mean elevations, with sister genera pairs occurring a mean 254 m in elevation closer to each other than the mean elevational difference for all genera pairs. We also demonstrate phylogenetic clustering both above and below 1750 m a.s.l, corresponding roughly to the cloud-base ecotone. Belying these general trends, some lineages occur across many different elevations. However, these highly plastic lineages are not phylogenetically clustered. Overall, our findings suggest that tropical montane forests are home to unique tree lineage diversity, constrained by their evolutionary heritage and vulnerable to substantial losses under environmental changes, such as rising temperatures or an upward shift of the cloud base.

scholarly journals Biodegradation Effect of some Bacterial Isolates on some Endocrine Disruptors (EDCS)

2018 ◽  
Vol 29 (2) ◽  
pp. 43
Author(s):  
Amna Mohmmed Ali Al-Hashimi
Keyword(s):  
Biological Effects ◽  
Chemical Compounds ◽  
Diffusion Method ◽  
Bacterial Isolates ◽  
Physical Conditions ◽  
Natural Hormone ◽  
Highly Sensitive ◽  
Wide Range ◽  
Proteus Penneri ◽  
Degradation Effect

EDCs raised a certain concern for living health began since last century, via interfere with natural hormone functions and produce reversible or irreversible biological effects. Bisphenol (BPA) is an organic compound that causing human health risks. Different bacterial spp. has biodegradation ability for wide range of EDC. 4 bacterial spp. were isolated and worked on (Pseudomonas auroginosa, Pseudomona lutoi, Proteus penneri, and E.coli). The effect of substrate tolerate bisphenol (5 mg/ ml) using the well diffusion method were investigated. The biodegradation effect of bacterial isolated on breakdown bisphenol and its derivatives using UV vis spectrophotometer were studied and comparing in various incubation time and temperature to assess the effect of the physical conditions on the bacterial ability of bisphenol degradation. Proteus penneri showed a significant ability to resistance to para-phenol and meta-phenol, while highly sensitive to ortho- aminophenol and para- creso, Pseudomonas aeroginosa and Pseudomonas lutiola sensitive to meta- aminophenol, while resist to degraded three phenol compounds (para, ortho aminophenol, and para crysol). Data showed a significant effect for ps. Lutiola after 15 days of incubation followed by p. penorri and E.coli. to degraded phenol chemical compounds. Data demonstaed that bacterial spp. ps. Lutiola has an obvious degradation effect for bisphenol compound after 15 days of incubation however, Sp. euroginosa showed an absolutely different behavior toward bisphenol which showed an raising absorbance after the 15 days of incubation. The ability of different local bacterial isolated to breakdown the phenol and its derivitives in surface water was investigated .

scholarly journals Effects of Ocean Acidification on Marine Biodiversity and Ecosystem Function

2011 ◽  
Author(s):  
James P. Barry ◽  
Stephen Widdicombe
Keyword(s):  
Ocean Acidification ◽  
Ecosystem Function ◽  
Environmental Changes ◽  
Biological Effects ◽  
Marine Ecosystems ◽  
Fishing Effort ◽  
Elemental Cycling ◽  
Biodiversity And Ecosystem Function ◽  
The Stability ◽  
And Function

The biodiversity of the oceans, including the striking variation in life forms from microbes to whales and ranging from surface waters to hadal trenches, forms a dynamic biological framework enabling the flow of energy that shapes and sustains marine ecosystems. Society relies upon the biodiversity and function of marine systems for a wide range of services as basic as producing the seafood we consume or as essential as generating much of the oxygen we breathe. Perhaps most obvious is the global seafood harvest totalling over 100 Mt yr–1 (82 and 20 Mt in 2008 for capture and aquaculture, respectively; FAO 2009) from fishing effort that expands more broadly and deeper each year as fishery stocks are depleted (Pauly et al. 2003). Less apparent ecosystem services linked closely to biodiversity and ecosystem function are waste processing and improved water quality, elemental cycling, shoreline protection, recreational opportunities, and aesthetic or educational experiences (Cooley et al. 2009). There is growing concern that ocean acidification caused by fossil fuel emissions, in concert with the effects of other human activities, will cause significant changes in the biodiversity and function of marine ecosystems, with important consequences for resources and services that are important to society. Will the effects of ocean acidification on ecosystems be similar to those arising from other environmental perturbations observed during human or earth history? Although changes in biodiversity and ecosystem function due to ocean acidification have not yet been widely observed, their onset may be difficult to detect amidst the variability associated with other human and non-human factors, and the greatest impacts are expected to occur as acidification intensifies through this century. In theory, large and rapid environmental changes are expected to decrease the stability and productivity of ecosystems due to a reduction in biodiversity caused by the loss of sensitive species that play important roles in energy flow (i.e. food web function) or other processes (e.g. ecosystem engineers; Cardinale et al. 2006). In practice, however, most research concerning the biological effects of ocean acidification has focused on aspects of the performance and survival of individual species during short-term studies, assuming that a change in individual performance will influence ecosystem function.

scholarly journals Si cycling in transition zones: a study of Si isotopes and biogenic silica accumulation in the Chesapeake Bay through the Holocene

2019 ◽  
Vol 146 (2) ◽  
pp. 145-170
Author(s):  
Carla K. M. Nantke ◽  
Patrick J. Frings ◽  
Johanna Stadmark ◽  
Markus Czymzik ◽  
Daniel J. Conley
Keyword(s):  
Land Use ◽  
Chesapeake Bay ◽  
Biogenic Silica ◽  
Environmental Changes ◽  
Land Use Changes ◽  
Sediment Cores ◽  
Global Scale ◽  
Silicon Isotope ◽  
Coastal Zones ◽  
Local Climate

AbstractSi fluxes from the continents to the ocean are a key element of the global Si cycle. Due to the ability of coastal ecosystems to process and retain Si, the ‘coastal filter’ has the potential to alter Si fluxes at a global scale. Coastal zones are diverse systems, sensitive to local environmental changes, where Si cycling is currently poorly understood. Here, we present the first palaeoenvironmental study of estuarine biogenic silica (BSi) fluxes and silicon isotope ratios in diatoms (δ30Sidiatom) using hand-picked diatom frustules in two sediment cores (CBdist and CBprox) from the Chesapeake Bay covering the last 12000 and 8000 years, respectively. Constrained by the well-understood Holocene evolution of the Chesapeake Bay, we interpret variations in Si cycling in the context of local climate, vegetation and land use changes. δ30Sidiatom varies between + 0.8 and + 1.7‰ in both sediment cores. A Si mass balance for the Chesapeake Bay suggests much higher rates of Si retention (~ 90%) within the system than seen in other coastal systems. BSi fluxes for both sediment cores co-vary with periods of sea level rise (between 9500 and 7500 a BP) and enhanced erosion due to deforestation (between 250 and 50 a BP). However, differences in δ30Sidiatom and BSi flux between the sites emphasize the importance of the seawater/freshwater mixing ratios and locally variable Si inputs from the catchment. Further, we interpret variations in δ30Sidiatom and the increase in BSi fluxes observed since European settlement (~ 250 a BP) to reflect a growing human influence on the Si cycle in the Chesapeake Bay. Thereby, land use change, especially deforestation, in the catchment is likely the major mechanism.

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