Utilisation de la scanographie pour l'étude des sédiments : influence des paramètres physiques, chimiques et biologiques sur la mesure des intensités tomographiques

2003 ◽  
Vol 40 (7) ◽  
pp. 937-948 ◽  
Author(s):  
Laure de Montety ◽  
Bernard Long ◽  
Gaston Desrosiers ◽  
Jean-François Crémer ◽  
Jacques Locat ◽  
...  
Keyword(s):  
Flash Flood ◽  
Fine Fraction ◽  
Benthic Fauna ◽  
Sediment Layer ◽  
Relative Importance ◽  
Benthic Organisms ◽  
Ct Scanner ◽  
Biogenic Structures ◽  
Non Destructive ◽  
Surface Sediment Layer

In July 1996, a flash flood resulted in the input of 9 million m3 of sediment toward the Bay of Ha! Ha!, leading to the elimination, partly or totally, of the benthic fauna of the bay. In this study, the CT scanner has been used in a highly perturbed environment, the Bay of Ha! Ha!, to both assess (i) the relationships between the variations of tomographic intensities and the sedimentologic parameters of the sedimentary column and (ii) to quantify the biogenic structures resulting from the activity of benthic organisms. Compaction, CaCO3 contents, and granulometry of sediments are the most important influences on the variation of tomographic intensities. The scanner allowed the study and quantification, in a non destructive way, of the sediment occupation by biogenic structures and, more particularly, allowed to further assess most of the relative importance of the fine fraction of biogenic structures (0.250–1 mm) in the surface sediment layer (0–5 cm). Sediment occupation by biogenic structures reached maximal values at the upper part of the sedimentary column and decreased with depth. If sedimentary reworking leads to an increase in the sediment porosity, destabilization generated by the activity of organisms is balanced by the consolidation of the wall of the biogenic structures. Bioturbation resulting from the activity of benthic organisms into the sediments has a significant role on the sedimentary structure and biogeochemical processes. It is therefore necessary to quantify the volume of sediments occupied by biogenic structures to assess the activity of benthic organisms in the sedimentary column.

scholarly journals On the possible presence of oxygen in the upper sediment layer of the hydrogen sulfide zone in the Black Sea

2019 ◽  
Vol 59 (1) ◽  
pp. 166-169
Author(s):  
P. A. Stunzhas ◽  
M. B. Gulin ◽  
A. G. Zatsepin ◽  
E. A. Ivanova
Keyword(s):  
Black Sea ◽  
Benthic Fauna ◽  
Water Layer ◽  
Bottom Layer ◽  
The Black Sea ◽  
Depth Range ◽  
Sediment Layer ◽  
Bottom Water Layer ◽  
Long Time ◽  
Eukaryotic Organisms

In the northeastern Black Sea the search was performed for living eukaryotic organisms (micro- and meiobenthos) in hypoxic and anoxic conditions as well as measurement of O2 in the bottom water layer and in the upper layer of sediments. The results have shown the presence of a deep maximum abundance of zoobenthos in a depth range of 215–244 m. This aggregation of benthic fauna occupies a layer of 30 m along the vertical. In general, the proportion of active meiobenthos was no greater than 1.5% of the total number of organisms recorded from the sample.The presence of aerobic benthos near the upper boundary of the H2S zone can be explained by: sliding down of sediments from a higher depth; quasi-periodic O2 supply due to fluctuations in the position of the isopycna and/or sinking of waters downslope in the bottom Ekman layer. Also, in the case of physical entry of oxygen into the bottom layer, it can remain for a relatively long time in the upper part of the H2S zone due to the lack of deep Mn+2 flux and reaction with it.

scholarly journals Macro benthic fauna in relation to limnological variables in a migratory bird visiting lake at Jahangirnagar University, Bangladesh

2018 ◽  
Vol 4 (2) ◽  
pp. 99-106
Author(s):  
S Sharmin ◽  
SH Rahman ◽  
MN Naser ◽  
S Hoque
Keyword(s):  
Water Temperature ◽  
Diversity Index ◽  
Winter Season ◽  
Benthic Fauna ◽  
Migratory Bird ◽  
Soil Parameters ◽  
Benthic Organisms ◽  
Wiener Diversity Index ◽  
Water Ph ◽  
Temperature Water

The abundance of macro benthic organisms was observed from a migratory bird visiting lake in Jahangirnagar University, Savar for a period from July 2016 to June 2017. A total of 22 species belonging to three phyla (viz. Mollusca, Annelida and Arthropoda) and 14 families was recorded with maximum abundance in summer season and minimum in winter season. Molluscan population (37%) was dominant in benthos, followed by Annelida (31%) and Arthropoda (28%). Average values of water temperature, dissolved oxygen and water pH were within standard permissible ranges in the aquatic habitats of the country. Water and soil parameters were in suitable ranges for the growth and abundance of benthos. Correlation indicated that Mollusca and Annelida were closely dependent on water temperature, water pH, water depth, soil organic carbon and soil organic matters, whereas Arthropoda had less dependency on them. In the present study lower Shanon-Wiener diversity index (2.55-2.92) and low species richness (18-24) clearly demonstrated that the lake is moderately polluted. J. Biodivers. Conserv. Bioresour. Manag. 2018, 4(2): 99-106

Habitat, benthic prey, and distribution of juvenile lake sturgeon (Acipenser fulvescens) in northern Ontario rivers

1997 ◽  
Vol 54 (12) ◽  
pp. 2866-2871 ◽  
Author(s):  
Wayne B Chiasson ◽  
David LG Noakes ◽  
F William H. Beamish
Keyword(s):  
Trophic Status ◽  
Anthropogenic Activities ◽  
Temporal Distribution ◽  
Benthic Fauna ◽  
Lake Sturgeon ◽  
Acipenser Fulvescens ◽  
Benthic Organisms ◽  
Foraging Success ◽  
Northern Ontario ◽  
Northern Rivers

The spatial and temporal distribution and relative abundance of juvenile lake sturgeon (Acipenser fulvescens) and benthic macroinvertebrates were examined in the Mattagami and Groundhog rivers, tributaries of the Moose River in northern Ontario, Canada. Relative density and diversity of the benthic fauna were low, the most common taxa being Ablabesmyia sp. (Diptera) and Hexagenia sp. (Ephemeroptera). Benthic organisms were most abundant in substrate dominated by sand and clay. An appreciable portion of the riverbed was strewn with wood chips and was particularly depauperate of macrobenthos. Lake sturgeon foraged exclusively on the benthos, especially taxa of Ephemeroptera, Diptera, and Trichoptera. Hexagenia was the only prey species in greater density in sturgeon stomachs than in the benthos. The largest concentration of juvenile lake sturgeon was found adjacent to substrate dominated by sand and clay. Gillnet catches of lake sturgeon suggest that they are more active at night, which may enhance their foraging success. In these northern rivers, the trophic status of juvenile lake sturgeon is marginalized by an impoverished food supply, in part the consequence of habitat loss resulting from anthropogenic activities.

scholarly journals Methane formation and consumption by sediments in a cross-channel profile of a small river impoundment

2019 ◽  
Vol 78 (2) ◽  
Author(s):  
Adam Bednařík ◽  
Martin Blaser ◽  
Martin Rulik
Keyword(s):  
Nitrogen Content ◽  
Surface Sediment ◽  
Methane Formation ◽  
Organic Carbon Content ◽  
Sediment Layer ◽  
Carbon And Nitrogen ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Carbon And Nitrogen Content ◽  
Surface Sediment Layer

Rivers are a natural source of methane (CH4) into the atmosphere and may contribute significantly to total CH4 emissions. Even though the details of sources of CH4 in rivers are not fully understood, weirs have been recognized as a hotspot of CH4 emissions. In this study, we investigated CH4 production and consumption in air-exposed river sediments along a cross-channel transect located upstream of a weir. Stable carbon isotopes were used for determination of individual methanogenic pathways. In order to understand the relationship between physicochemical and biological processes, additional parameters such as organic matter, grain median size, and carbon and nitrogen content were characterized as well. Generally, samples from the surface sediment layer (0-10 cm) had higher CH4 production than sediments from the deeper layer (10-20 cm) during the incubation experiments. Sediments near the bank zones and in the mid-channel were characterized by the highest organic carbon content (6.9 %) as well the highest methanogenic activity (2.5 mmol g-1 DW d-1). The CH4 production was predominated by H2/CO2 dependent methanogenesis in the surface sediment layer (0-10 cm), while the proportion of acetoclastic and hydrogenotrophic methanogenesis in the deeper sediment layer (10-20 cm) was balanced. The CH4 oxidation potential of sediments showed the same spatial pattern as observed for the CH4 production. Our results showed high spatial variability of sediment CH4 production and oxidation in the cross-channel profile upstream of the weir, whereas the highest CH4 dynamics were observed in the littoral zones. This variability was closely linked with the carbon and nitrogen content in the sediment samples.

Crue éclair de juillet 1996 dans la région du Saguenay (Québec). 2. Impacts sur les sédiments et le biote de la baie des Ha! Ha! et du fjord du Saguenay

1999 ◽  
Vol 56 (11) ◽  
pp. 2136-2147 ◽  
Author(s):  
Émilien Pelletier ◽  
Bruno Deflandre ◽  
Christian Nozais ◽  
Guglielmo Tita ◽  
Gaston Desrosiers ◽  
...  
Keyword(s):  
Flash Flood ◽  
Biological Indicators ◽  
Average Density ◽  
Benthic Habitat ◽  
Sediment Layer ◽  
Pioneer Species ◽  
The North ◽  
Geological Processes ◽  
Saguenay Fjord ◽  
Interstitial Waters

Several million tons of sediments and various debris were transported to the north arm of the Saguenay Fjord and the Baie des Ha! Ha! following the torrential rains and accompanying flash flood of July 1996 in the Saguenay region (Québec). The flood deposits covered the indigenous sediments and buried the benthic community. The objective of this work is to determine the best chemical and biological indicators of the changes that occurred in the benthic habitat of the fjord. The new sediment layer is poor in organic matter but rich in detrital carbonates and contains low mercury and lead concentrations reflecting the absence of industrial contamination. Ongoing geological processes leading to the re-establishment of steady-state conditions were evidenced by measurements of porosity, redox potential (Eh), and salinity of interstitial waters taken a few weeks and a few months after the events. The meiofauna were severely affected with a massive reduction of the average density of organisms relative to values recorded before the flood, but recolonisation was already in progress 1 year after the flood. Important losses of macrobenthic species were recorded in 1997 relative to 1996. However, the abundance and the diversity of the polycheate taxa were higher in 1997, indicating a recolonisation of the new sediment layer by pioneer species.

scholarly journals Measurement of snow density and microstructure using computed tomography

2002 ◽  
Vol 48 (161) ◽  
pp. 312-316 ◽  
Author(s):  
Chris C. Lundy ◽  
Michael Q. Edens ◽  
Robert L. Brown
Keyword(s):  
Computed Tomography ◽  
Plane Surface ◽  
Ct Images ◽  
Two Dimensional ◽  
Ct Scanner ◽  
Cross Sectional ◽  
Thin Sections ◽  
Kinetic Growth ◽  
Similar Images ◽  
Non Destructive

AbstractIn the past, two-dimensional images of internal snow structure have been obtained through plane surface sections or thin sections. These techniques are time-consuming and necessarily destroy the snow specimen. Computed tomography (CT) allows similar images to be obtained, but in a more efficient and non-destructive manner. To demonstrate the methodology, a CT scanner was used to obtain cross-sectional images over time of a snow sample undergoing kinetic-growth metamorphism. Densities calculated from the CT images correlated well to density measured using a traditional method. A procedure was developed that allows the CT image to be converted to binary in an objective manner. Employing innovative stereological software, the microstructural properties (grain diameter, bond diameter, neck length and intercept length) of the snow were then measured from the two-dimensional CT images. The presented methodology provides significant improvements over previous techniques, requiring less time and labor to obtain high-quality microstructural data.

Study on the concentration, flux, occurrence and retention processes of total phosphorus in Dahuofang reservoir

2021 ◽  
Author(s):  
Guoxian Huang ◽  
Xinghua Li ◽  
Mingdong Sun ◽  
Kun Lei
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Total Phosphorus ◽  
Surface Sediment ◽  
Retention Rate ◽  
Sediment Layer ◽  
Overlying Water ◽  
Large Reservoir ◽  
Dahuofang Reservoir ◽  
Surface Sediment Layer

<p>Dahuofang reservoir (DHFR) is one of the most important drinking water sources in Liaoning province, China. The processes of total phosphorus (TP) concentration, flux and retention rate are very important to the water quality management and drinking water safety for the reservoir. Based on the monitoring data of meteorology, hydrology, water quality and sediment, etc. at the controlled stations of Dahuofang catchment during 1992-2017, The suspended sediment centration(SSC) and TP concentration variation and differences from upper to lower reach of DHFR  during floods in 2010 and 2013 are analyzed and compared respectively. Based  on the  mass balance equation of TP and the related fluxes formula at the different boundaries, the stocking processes in both the overlying water and the active surface sediment layer are solved. The results revealed the TP accumulation variation in the overlying water and the surface sediment layer, together with the controlling mechanism of TP concentration in overlying water under different floods events. Moreover, the results discovered that the combination of flood and dry hydrological rhythms is very important to maintain the dynamic balance of accumulated sediment and TP in the reservoir. The study does not only provide the effective calculation method forthe TP flux, accumulation and retention rate in the large reservoir, but also partly supply a new eyesight on the sediment nutrient control and related continuable management  for large reservoirs in north China.</p>

scholarly journals Microplastic Contamination in Freshwater Environments: A Review, Focusing on Interactions with Sediments and Benthic Organisms

Environments ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 30 ◽  
Author(s):  
Arianna Bellasi ◽  
Gilberto Binda ◽  
Andrea Pozzi ◽  
Silvia Galafassi ◽  
Pietro Volta ◽  
...  
Keyword(s):  
Benthic Fauna ◽  
Data Retrieval ◽  
Future Trends ◽  
Benthic Organisms ◽  
Transfer Processes ◽  
Analysis Strategies ◽  
The World ◽  
Global Concern ◽  
Negative Impacts ◽  
A Site

Plastic is one of the most commonly produced and used materials in the world due to its outstanding features. However, the worldwide use of plastics and poor waste management have led to negative impacts on ecosystems. Plastic degradation in the environment leads to the generation of plastic particles with a size of <5 mm, which are defined as microplastics (MPs). These represent a global concern due to their wide dispersion in water environments and unclear potential ecotoxicological effects. Different studies have been performed with the aim of evaluating the presence and impacts of MPs in the marine environment. However, the presence of MPs in freshwater systems is still poorly investigated, making data retrieval a difficult task. The purpose of this review is to identify the main aspects concerning MPs pollution sources in lakes and rivers, with a focus on freshwater sediments as a site of accumulation and as the habitat of benthic organisms, which are key components of food webs and play a fundamental role in energy/contaminant transfer processes, but are still poorly considered. Through this review, the sources and fate of MPs in freshwater are analysed, ecotoxicological studies focused on sediments and benthic fauna are exposed, the most frequently used sampling and analysis strategies are reported, and future trends of MPs analysis in this field are proposed.

Feeding ecology of the southern thorny skate,Amblyraja doellojuradoion the Argentine Continental Shelf

2013 ◽  
Vol 93 (8) ◽  
pp. 2207-2216 ◽  
Author(s):  
G.E. Delpiani ◽  
M.C. Spath ◽  
D.E. Figueroa
Keyword(s):  
Continental Shelf ◽  
Generalized Linear Models ◽  
Feeding Ecology ◽  
Sexual Maturity ◽  
Linear Models ◽  
Feeding Habits ◽  
Benthic Fauna ◽  
Relative Importance ◽  
The North ◽  
Index Of Relative Importance

The feeding ecology of the southern thorny skate,Amblyraja doellojuradoi, on the Argentine Continental Shelf was evaluated using generalized linear models.Amblyraja doellojuradoipreyed mainly on crabs (85.41% index of relative importance (IRI)) and to a lesser extent on polychaetes (4.98% IRI), teleosts (3.28% IRI), isopods (2.03% IRI), other crustaceans (1.52% IRI) and other invertebrates (2.78% IRI). As individuals increased in size, the consumption of crabs also increased and the consumption of polychaetes and other invertebrates decreased. The study area was divided into a northern (36°–43°S) and a southern (43°–50°S) region. Regarding the latitude of capture, it was observed thatA. doellojuradoimainly fed on crabs in the north and on fish, isopods and other crustaceans in the south. Females ofA. doellojuradoihad a stronger preference for fish and isopods than males. As to sexual maturity, immatures fed more on polychaetes and other crustaceans than did mature. The ontogenetic change in feeding habits could be attributed to body size and an increasing ability to capture larger prey, rather than to food availability. However, this point cannot be confirmed because little is known about the benthic fauna of this area.

scholarly journals Advances in deepsea paleoecology: introduction to the symposium

1992 ◽  
Vol 6 ◽  
pp. 214-214
Author(s):  
W. Miller
Keyword(s):  
Large Scale ◽  
Ecosystem Dynamics ◽  
Future Research ◽  
Small Scale ◽  
Time Averaging ◽  
Benthic Organisms ◽  
Research Issues ◽  
Shallow Marine ◽  
Biogenic Structures

This symposium will cover new developments in the ecology and paleoecology of deepsea organisms, based largely on advances in the study of protists, metazoan associations, and biogenic sedimentary structures. Bringing together ecologists and paleoecologists will establish a bridge between workers who have devoted their attention exclusively to the modern biota and those who have only considered fossil evidence from pelagic, turbidite, and related deep basinal rock sequences. Contributors will emphasize patterns and processes from historical or developmental perspectives as well as from experimental or actualistic perspectives, and will attempt to identify the promising directions for future research.Specifically, attention will be focused on benthic organisms and associations, and on biogenic structures, because these entities make up ecologic patterns that are most accessible to study by both biologists and paleontologists. On the biologic side, contributors will review the significance of new discoveries and theories, present summaries of path breaking work on foraminiferids and xenophyophores, and characterize modern organism-sediment interactions and trace associations. Paleontologists will emphasize processes requiring large areas of seafloor and long time spans in their review of the origins of deepsea communities and ichnofacies, large-scale dispersal patterns, long-term ecosystem dynamics, and taphonomy and time-averaging of deepsea fossil deposits. This is the first attempt to bring ecologic and paleoecologic efforts into closer coordination in order to identify the most significant themes in the historical biology of deepwater marine organisms.Some examples of research issues amenable to this kind of coordinated approach include: 1) origination of deepsea inhabitants from shallow marine sources vs. elaboration and diversification of taxa already established in deepwater; 2) importance of small-scale, frequent disturbance vs. large-scale, rare events (turbidity currents, anoxia episodes) in shaping the deepsea biota; 3) taxonomic replacements and invasions at varied spatiotemporal scales; 4) biotic interactions vs. environmental pacing as mechanisms producing community structure; 5) evolutionary importance of allochthonous vs. autochthonous food supplies; 6) relationships between trace fossil assemblages and the development of deepsea ecosystems; 7) the nature and history of linkages between deepsea ecologic systems, and terrestrial and shallow marine systems; and 8) preservation potential of the dominant benthic organisms, and their symbionts or traces, and its implications in paleoecologic reconstructions. In general, combining biologic and paleontologic information should result in more realistic and useful interpretations of ancient biotas (rather than simply the description of more unique fossil finds), as well as an increased awareness of the long-term development of the modern biota (rather than attention directed exclusively to living organisms, short-term processes, and small-scale patterns).

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