scholarly journals The trophic biology of the holothurian <i>Molpadia musculus</i>: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

2010 ◽  
Vol 7 (8) ◽  
pp. 2419-2432 ◽  
Author(s):  
T. Amaro ◽  
S. Bianchelli ◽  
D. S. M. Billett ◽  
M. R. Cunha ◽  
A. Pusceddu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Submarine Canyon ◽  
Gut Contents ◽  
Digestion Rate ◽  
In Situ Experiments ◽  
Total Digestion ◽  
Organic Matter Cycling

Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

scholarly journals The trophic biology of the holothurian <i>Molpadia musculus</i> at 3500 m in the Nazaré Canyon (NE Atlantic)

2010 ◽  
Vol 7 (2) ◽  
pp. 3061-3094
Author(s):  
T. Amaro ◽  
S. Bianchelli ◽  
D. S. M. Billett ◽  
M. R. Cunha ◽  
A. Pusceddu ◽  
...  
Keyword(s):  
Deep Sea ◽  
Ecosystem Functioning ◽  
Gut Contents ◽  
Biogeochemical Processes ◽  
Ne Atlantic ◽  
Digestion Rate ◽  
Faecal Material ◽  
Sediment Samples ◽  
Very High

Abstract. Megafaunal organisms play a key role in the deep-sea ecosystem functioning. At 3500 m depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were found. Sediment samples and holothurians were collected by ROV and experiments were conducted in situ in incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian gut contents, conversely, protein concentrations were higher than the other compounds and decreased significantly as the material passed through the digestive tract. About 33±1% of the proteins were digested already in the mid gut, with a final digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, biopolymeric C digestion rate was on average 62±3%. We also calculated that the entire holothurians' population could remove from the sediment about 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1. These results suggest that the M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes of the Nazaré Canyon.

scholarly journals Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

2013 ◽  
Vol 10 (1) ◽  
pp. 67-80 ◽  
Author(s):  
W. R. Hunter ◽  
A. Jamieson ◽  
V. A. I. Huvenne ◽  
U. Witte
Keyword(s):  
Organic Matter ◽  
Feeding Activity ◽  
N Uptake ◽  
Bacterial Biomass ◽  
Submarine Canyon ◽  
Stable Isotope Labelling ◽  
C And N ◽  
13C Label ◽  
Experimental Treatments

Abstract. The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3–7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0–1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal–bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

scholarly journals The Role of Electron Microscopy in Materials Science

1982 ◽  
Vol 35 (6) ◽  
pp. 727 ◽  
Author(s):  
PB Hirsch
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Optical Techniques ◽  
Bulk Properties ◽  
In Situ Experiments ◽  
Powerful Means ◽  
Appropriate Scale ◽  
Powerful Electron

The properties of the materials in a component or a device depend on structure and composition often on a scale of 10-10 to 10-6 m. Electron microscopy and microanalytical techniques provide a powerful means for determining the structure and composition on the appropriate scale, lead to an understanding of basic mechanisms, and by correlation or in situ experiments to explanations of bulk properties. Examples are given of the application of a variety of powerful electron optical techniques to a number of materials problems.

scholarly journals In Situ Experiments To Reveal the Role of Surface Feature Sidewalls in the Cassie–Wenzel Transition

Langmuir ◽  
2014 ◽  
Vol 30 (50) ◽  
pp. 15162-15170 ◽  
Author(s):  
René Hensel ◽  
Andreas Finn ◽  
Ralf Helbig ◽  
Sebastian Killge ◽  
Hans-Georg Braun ◽  
...  
Keyword(s):  
Surface Feature ◽  
In Situ Experiments

scholarly journals Halogens in pore water of peat bogs – the role of peat decomposition and dissolved organic matter

2006 ◽  
Vol 3 (1) ◽  
pp. 53-64 ◽  
Author(s):  
H. Biester ◽  
D. Selimović ◽  
S. Hemmerich ◽  
M. Petri
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Pore Water ◽  
Peat Bogs ◽  
Pore Waters ◽  
Peat Pore Water ◽  
Icp Ms ◽  
Halogen Species

Abstract. Halogens are strongly enriched in peat and peatlands and such they are one of their largest active terrestrial reservoir. The enrichment of halogens in peat is mainly attributed to the formation of organohalogens and climatically controlled humification processes. However, little is known about release of halogens from the peat substrate and the distribution of halogens in the peat pore water. In this study we have investigated the distribution of chlorine, bromine and iodine in pore water of three pristine peat bogs located in the Magellanic Moorlands, southern Chile. Peat pore waters were collected using a sipping technique, which allows in situ sampling down to a depth greater than 6m. Halogens and halogen species in pore water were determined by ion-chromatography (IC) (chlorine) and IC-ICP-MS (bromine and iodine). Results show that halogen concentrations in pore water are 15–30 times higher than in rainwater. Mean concentrations of chlorine, bromine and iodine in pore water were 7–15 mg l−1, 56–123 μg l−1, and 10–20 μg l−1, which correspond to mean proportions of 10–15%, 1–2.3% and 0.5–2.2% of total concentrations in peat, respectively. Organobromine and organoiodine were the predominant species in pore waters, whereas chlorine in pore water was mostly chloride. Advection and diffusion of halogens were found to be generally low and halogen concentrations appear to reflect release from the peat substrate. Release of bromine and iodine from peat depend on the degree of peat degradation, whereas this relationship is weak for chlorine. Relatively higher release of bromine and iodine was observed in less degraded peat sections, where the release of dissolved organic carbon (DOC) was also the most intensive. It has been concluded that the release of halogenated dissolved organic matter (DOM) is the predominant mechanism of iodine and bromine release from peat.

Finite Element Model of a Cell Incorporating Cell Membrane, Cytoskeletal Structure and Intracellular Fluid Pressure

2002 ◽  
Author(s):  
Vidyashankar Venkatesan ◽  
Nilay Mukherjee
Keyword(s):  
Finite Element ◽  
Compressive Loading ◽  
Fluid Pressure ◽  
Element Model ◽  
Structural Components ◽  
Element Analysis ◽  
In Situ Experiments ◽  
A Cell

Compressive loading is intrinsic to certain tissues in our body like articular cartilage and bone (1). In situ experiments in cartilage suggest that chondrocytes can undergo significant deformation due to compressive loading on the tissue (2). In situ and isolated cell experiments have concluded that cells are quite resilient to compressive loading, aspiration etc. and exhibit a moduli in the range of 0.6 to 2 kPa (3). However, few studies have attempted to understand the compressive behavior of cells in terms of its structural components. The structural components of a cell consist of a membrane and a dense network of at least three elements (actin, microtubules and intermediate filaments). Using finite element analysis techniques we wanted to explore the role of these structural components in determining the ability of the cell to withstand compression.

scholarly journals Ooids forming in situ within microbial mats (Kiritimati atoll, central Pacific)

PalZ ◽  
2021 ◽  
Author(s):  
Pablo Suarez-Gonzalez ◽  
Joachim Reitner
Keyword(s):  
Organic Matter ◽  
Microbial Communities ◽  
Microbial Mats ◽  
Formation Processes ◽  
Central Pacific ◽  
Environmental Processes ◽  
Definition Of ◽  
First Time

AbstractOoids (subspherical particles with a laminated cortex growing around a nucleus) are ubiquitous in the geological record since the Archean and have been widely studied for more than two centuries. However, various questions about them remain open, particularly about the role of microbial communities and organic matter in their formation and development. Although ooids typically occur rolling around in agitated waters, here, we describe for the first time aragonite ooids forming statically within microbial mats from hypersaline ponds of Kiritimati (Kiribati, central Pacific). Subspherical particles had been previously observed in these mats and classified as spherulites, but these particles grow around autochthonous micritic nuclei, and many of them have laminated cortices, with alternating radial fibrous laminae and micritic laminae. Thus, they are compatible with the definition of the term ‘ooid’ and are in fact very similar to many modern and fossil examples. Kiritimati ooids are more abundant and developed in some ponds and in some particular layers of the microbial mats, which leads to the discussion and interpretation of their formation processes as product of mat evolution, through a combination of organic and environmental factors. Radial fibrous laminae are formed during periods of increased supersaturation, either by metabolic or environmental processes. Micritic laminae are formed in closer association with the mat exopolymer (EPS) matrix, probably during periods of lower supersaturation and/or stronger EPS degradation. Therefore, this study represents a step forward in the understanding of ooid development as influenced by microbial communities, providing a useful analogue for explaining similar fossil ooids.

scholarly journals Influence of condensation domains on activity and specificity of adenylation domains

2021 ◽  
Author(s):  
Janik Kranz ◽  
Sebastian L. Wenski ◽  
Alexnder A. Dichter ◽  
Helge B. Bode ◽  
Kenan A. J. Bozhueyuek
Keyword(s):  
Structural Features ◽  
Peptide Synthetases ◽  
In Situ Experiments ◽  
The Subject ◽  
New Perspective ◽  
Condensation Domain

Many clinically used natural products are produced by non-ribosomal peptide synthetases (NRPSs), which due to their modular nature should be accessible to modification and engineering approaches. While the adenylation domain (A) plays the key role in substrate recognition and activation, the condensation domain (C) which is responsible for substrate linkage and stereochemical filtering recently became the subject of debate - with its attributed role as a "gatekeeper" being called into question. Since we have thoroughly investigated different combinations of C-A didomains in a series of in vitro, in vivo, and in situ experiments suggesting an important role to the C-A interface for the activity and specificity of the downstream A domain and not the C domain as such, we would like to contribute to this discussion. The role of the C-A interface, termed 'extended gatekeeping', due to structural features of the C domains, can also be transferred to other NRPSs by engineering, was finally investigated and characterised in an in silico approach on 30 wild-type and recombinant C-A interfaces. With these data, we not only would like to offer a new perspective on the specificity of C domains, but also to revise our previously established NRPS engineering and construction rules.

scholarly journals Bioturbation, ecosystem functioning and community structure

2002 ◽  
Vol 6 (6) ◽  
pp. 999-1005 ◽  
Author(s):  
C. L. Biles ◽  
D. M. Paterson ◽  
R. B. Ford ◽  
M. Solan ◽  
D. G. Raffaelli
Keyword(s):  
Community Structure ◽  
Water Column ◽  
Ecosystem Functioning ◽  
Nutrient Concentration ◽  
Nutrient Release ◽  
Nutrient Concentrations ◽  
Infaunal Community ◽  
Significant Difference ◽  
In Situ Experiments

Abstract. The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. In situ and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and in situ experiments to generate flow conditions produced a significant increase in ammonia (NH4-N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH4-N production through modifying bioturbation of the sediment. Keywords: bioturbation, community structure, ccosystem functioning, estuaries, flow, infauna

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