scholarly journals Food quality determines sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

2012 ◽  
Vol 9 (8) ◽  
pp. 11331-11374 ◽  
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 day) responses of sediment communities to deposition of nitrogen-rich marine (Thallassiosira 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 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 First in situ estimations of small phytoplankton carbon and nitrogen uptake rates in the Kara, Laptev, and East Siberian seas

2018 ◽  
Vol 15 (18) ◽  
pp. 5503-5517 ◽  
Author(s):  
P. Sadanandan Bhavya ◽  
Jang Han Lee ◽  
Ho Won Lee ◽  
Jae Joong Kang ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Nitrogen Uptake ◽  
Isotope Labeling ◽  
N Uptake ◽  
The Arctic ◽  
Carbon And Nitrogen ◽  
Uptake Rates ◽  
Small Phytoplankton ◽  
C And N

Abstract. Carbon and nitrogen uptake rates by small phytoplankton (0.7–5 µm) in the Kara, Laptev, and East Siberian seas in the Arctic Ocean were quantified using in situ isotope labeling experiments; this research, which was novel and part of the NABOS (Nansen and Amundsen Basins Observational System) program, took place from 21 August to 22 September 2013. The depth-integrated carbon (C), nitrate (NO3-), and ammonium (NH4+) uptake rates by small phytoplankton ranged from 0.54 to 15.96 mg C m−2 h−1, 0.05 to 1.02 mg C m−2 h−1, and 0.11 to 3.73 mg N m−2 h−1, respectively. The contributions of small phytoplankton towards the total C, NO3-, and NH4+ varied from 25 % to 89 %, 31 % to 89 %, and 28 % to 91 %, respectively. The turnover times for NO3- and NH4+ by small phytoplankton found in the present study indicate the longer residence times (years) of the nutrients in the deeper waters, particularly for NO3-. Additionally, the relatively higher C and N uptake rates by small phytoplankton obtained in the present study from locations with less sea ice concentration indicate the possibility that small phytoplankton thrive under the retreat of sea ice as a result of warming conditions. The high contributions of small phytoplankton to the total C and N uptake rates suggest the capability of small autotrophs to withstand the adverse hydrographic conditions introduced by climate change.

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 Salinity-dependent algae uptake and subsequent carbon and nitrogen metabolisms of two intertidal foraminifera (<i>Ammonia tepida</i> and <i>Haynesina germanica</i>)

2020 ◽  
Vol 17 (13) ◽  
pp. 3723-3732
Author(s):  
Michael Lintner ◽  
Bianca Biedrawa ◽  
Julia Wukovits ◽  
Wolfgang Wanek ◽  
Petra Heinz
Keyword(s):  
Feeding Activity ◽  
N Uptake ◽  
Isotope Ratio Mass Spectrometry ◽  
Trophic Levels ◽  
Food Uptake ◽  
Biomass Turnover ◽  
Feeding Experiments ◽  
C And N ◽  
C And N Cycling ◽  
Marine Protists

Abstract. Benthic foraminifera are abundant marine protists which play an important role in the transfer of energy in the form of organic matter and nutrients to higher trophic levels. Due to their aquatic lifestyle, factors such as water temperature, salinity and pH are key drivers controlling biomass turnover through foraminifera. In this study the influence of salinity on the feeding activity of foraminifera was tested. Two species, Ammonia tepida and Haynesina germanica, were collected from a mudflat in northern Germany (Friedrichskoog) and cultured in the laboratory at 20 ∘C and a light–dark cycle of 16:08 h. A lyophilized algal powder from Dunaliella tertiolecta, which was isotopically enriched with 13C and 15N, was used as a food source. The feeding experiments were carried out at salinity levels of 11, 24 and 37 practical salinity units (PSU) and were terminated after 1, 5 and 14 d. The quantification of isotope incorporation was carried out by isotope ratio mass spectrometry. Ammonia tepida exhibited a 10-fold higher food uptake compared to H. germanica. Furthermore, in A. tepida the food uptake increased with increasing salinity but not in H. germanica. Over time (from 1–5 to 14 d) food C retention increased relative to food N in A. tepida while the opposite was observed for H. germanica. This shows that if the salinity in the German Wadden Sea increases, A. tepida is predicted to exhibit a higher C and N uptake and turnover than H. germanica, with accompanying changes in C and N cycling through the foraminiferal community. The results of this study show how complex and differently food C and N processing of foraminiferal species respond to time and to environmental conditions such as salinity.

Effects of green manures on soil organic matter and wheat yields and N nutrition

2001 ◽  
Vol 81 (4) ◽  
pp. 371-382 ◽  
Author(s):  
A. N’Dayegamiye ◽  
Thi Sen Tran
Keyword(s):  
Organic Matter ◽  
Green Manure ◽  
Microbial Respiration ◽  
N Uptake ◽  
Green Manures ◽  
Manure Application ◽  
N Nutrition ◽  
C And N ◽  
Heavy Fractions ◽  
Fertilizer Rates

A field study was conducted for 5 yr (1993-1997) to evaluate the effects of green manure residues applied to the soil in 1993 and 1995, on wheat (Triticum aestivum L.) yields and N nutrition as subsequent crop in 1994, 1996 and 1997. The effect of green manure application was also evaluated on soil microbial activity (CO2), on C and N contents of whole soil and on labile (LF) and heavy fractions (HF) of organic matter (OM). The experiment was initiated on a Le Bras silt loam (Humic Gleysol). The green manures, as a main factor, were clover (Trifolium pratense L.), buckwheat (Fagapyrum esculentum L.), millet (Echinicloa crus galli L.), mustard (Brassica hirta Moench), and colza (Brassica campestris L.), and there was a control without green manure. The sub-factors consisted of four N fertilizer rates for wheat in the subsequent years at 0, 30, 60 and 90 kg N ha–1. Broadcast application of 15N- labelled NH4NO3 was made in 90 kg N ha–1 fertilizer treatments. Two green manure applications did not influence the C and N contents of densimetric fractions of OM (LF and HF), but significantly increased those of whole soil, and microbial respiration (CO2). Green manures significantly increased wheat yields and N uptake in 1994 and 1996. Levels of N derived from fertilizer (Ndff) were lower in all green manure treatments as compared to the control, which indicates that the proportion of N derived from soil and green manures (% Ndfs) was higher in these treatments. The contribution of N from green manure varied in the following order: buckwheat < clover < mustard < millet < colza. With the exception of the clover treatment (< 100%), the N recoveries from the other green manure N (NRGM) ranged from 23 to 34% and from 19 to 36% for 1994 and 1996, respectively. Green manure application provided 15 to 24 kg N ha–1 in 1994 and from 16 to 36 kg N ha–1 in 1996 and this contribution accounted for 25 to 31% of the total wheat N uptake. Significant green manure effects on wheat yield and N nutrition were primarily due to the improvement of soil properties and to high N recoveries from the green manure. In the cold temperate climate of Québec, green manure incorporation into soil in late summer or early fall of the preceding year allowed N synchronization with wheat N needs in subsequent cropping seasons. Nitrogen fertilizer rates could be reduced after the incorporation of green manures having high yields and N contents in the previous season. Key words: Green manure, wheat yields and N uptake, N recoveries, microbial respiration, labile and heavy fractions of OM, C and N contents

scholarly journals Nitrate uptake and carbon exudation – do plant roots stimulate or inhibit denitrification?

2020 ◽  
Author(s):  
Pauline Sophie Rummel ◽  
Reinhard Well ◽  
Birgit Pfeiffer ◽  
Klaus Dittert ◽  
Sebastian Floßmann ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Plant Growth ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Root Exudation ◽  
Mineral N ◽  
Double Labeling ◽  
Organic C ◽  
C And N

Abstract Background and aims Plant growth affects soil moisture, mineral N and organic C availability in soil, all of which influence denitrification. With increasing plant growth, root exudation may stimulate denitrification, while N uptake restricts nitrate availability. Methods We conducted a double labeling pot experiment with either maize (Zea mays L.) or cup plant (Silphium perfoliatum L.) of the same age but differing in size of their shoot and root systems. The 15N gas flux method was applied to directly quantify N2O and N2 fluxes in situ. To link denitrification with available C in the rhizosphere, 13CO2 pulse labeling was used to trace C translocation from shoots to roots and its release by roots into the soil. Results Plant water and N uptake were the main factors controlling daily N2O + N2 fluxes, cumulative N emissions, and N2O production pathways. Accordingly, pool-derived N2O + N2 emissions were 30–40 times higher in the treatment with highest soil NO3− content and highest soil moisture. CO2 efflux from soil was positively correlated with root dry matter, but we could not detect any relationship between root-derived C and N2O + N2 emissions. Conclusions Root-derived C may stimulate denitrification under small plants, while N and water uptake become the controlling factors with increasing plant and root growth.

Influence of carbon and nitrogen on cellulose and lignin degradation in forest soils

1995 ◽  
Vol 25 (8) ◽  
pp. 1231-1236 ◽  
Author(s):  
James A. Entry ◽  
Carole B. Backman
Keyword(s):  
Organic Matter ◽  
Soil Type ◽  
Fungal Biomass ◽  
Lignin Degradation ◽  
Cellulose Degradation ◽  
Bacterial Biomass ◽  
Terrestrial Ecosystems ◽  
Organic Matter Decomposition ◽  
Decomposition Rates ◽  
C And N

The concentration of lignin in plant tissue is a major factor controlling organic matter decomposition rates in terrestrial ecosystems. Microcosms were used to determine the influence of C and N additions on active bacterial and active fungal biomass, cellulose degradation, and lignin degradation at 4, 8, and 12 weeks in soils from the Tuskeege National Forest in southern Alabama. Active bacterial and active fungal biomass was determined by direct microscopy; cellulose and lignin degradation were measured radiometrically. The experimental design was a 33 latin square. Treatments were as follows: soil type, soil C (soils amended with the equivalent of 0, 400, or 800 kg C•ha−1 as cellulose), and soil N (soils amended with the equivalent of 0, 250, or 500 kg N•ha−1 as NH4NO3). Active bacterial biomass, active fungal biomass, and cellulose and lignin degradation did not differ with soil type. Active bacterial biomass was not affected by N or C additions. As C and N concentrations increased, active fungal biomass as well as cellulose and lignin degradation increased. The concentration of C and N (together) in the soil correlated with both cellulose and lignin degradation (r2 = 0.76, p < 0.001; r2 = 0.44, p < 0.001, respectively). Active fungal biomass correlated curvilinearly with both cellulose and lignin degradation (r2 = 0.38, p < 0.001; r2 = 0.33, p < 0.001, respectively). The lignin:N ratio is often used to predict organic matter decomposition rates in terrestrial ecosystems. These results lead us to conclude that a cellulose:lignin:N ratio may be a more accurate predictor of organic matter decomposition rates than C:N ratio or lignin:N ratios.

scholarly journals Salinity-depending carbon and nitrogen uptake of two intertidal foraminifera (<i>Ammonia tepida</i> and <i>Haynesina germanica</i>)

2019 ◽  
Author(s):  
Michael Lintner ◽  
Bianca Biedrawa ◽  
Julia Wukovits ◽  
Wolfgang Wanek ◽  
Petra Heinz
Keyword(s):  
Feeding Activity ◽  
N Uptake ◽  
Isotope Ratio Mass Spectrometry ◽  
Trophic Levels ◽  
Food Uptake ◽  
Biomass Turnover ◽  
Feeding Experiments ◽  
C And N ◽  
C And N Cycling ◽  
Marine Protists

Abstract. Benthic foraminifera are abundant marine protists which play an important role in the transfer of energy in the form of organic matter and nutrients to higher trophic levels. Due to their aquatic lifestyle, factors such as water temperature, salinity and pH are key drivers controlling biomass turnover through foraminifera. In this study the influence of salinity on the feeding activity of foraminifera was tested. Two species, Ammonia tepida and Haynesina germanica, were collected from a mudflat in northern Germany (Friedrichskoog) and cultured in the laboratory at 20 °C and a light/dark cycle of 16:8 h. A lyophilized algal powder from Dunaliella tertiolecta, which was isotopically enriched with 13C and 15N, was used as a food source. The feeding experiments were carried out at salinity levels of 11, 24 and 37 practical salinity units (PSU) and were terminated after 1, 5 and 14 days. The quantification of isotope incorporation was carried out by isotope ratio mass spectrometry. Ammonia tepida exhibited a 10-fold higher food uptake compared to H. germanica. Furthermore, in A. tepida the food uptake increased with increasing salinity but not in H. germanica. Over time (from 1–5 d to 14 d) food C retention increased relative to food N in A. tepida while the opposite was observed for H. germanica. This shows, that if the salinity in the German Wadden Sea increases, A. tepida is predicted to exhibit a higher C and N uptake and turnover than H. germanica, with accompanying changes in C and N cycling through the foraminiferal community. The results of this study show how complex and differently food C and N processing of foraminiferal species respond to time and to environmental conditions such as salinity.

Relating particulate organic matter-nitrogen (POM-N) and non-POM-N with pulse crop residues, residue management and cereal N uptake

Agronomie ◽  
2002 ◽  
Vol 22 (7-8) ◽  
pp. 777-787 ◽  
Author(s):  
Graeme D. Schwenke ◽  
Warwick L. Felton ◽  
David F. Herridge ◽  
Dil F. Khan ◽  
Mark B. Peoples
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Crop Residues ◽  
N Uptake ◽  
Residue Management ◽  
Pulse Crop
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