Organic matter transport by cyclonic eddies formed in eastern boundary upwelling system supports heterotrophy in the open oligotrophic ocean

2021 ◽  
Author(s):  
Quentin Devresse ◽  
Kevin W Becker ◽  
Anja Engel
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Microbial Activity ◽  
Mesoscale Eddies ◽  
Open Ocean ◽  
Cyclonic Eddy ◽  
Positive Anomaly ◽  
Eastern Boundary ◽  
Biogeochemical Parameters ◽  
Epipelagic Layer

<p>Mesoscale eddies formed in Eastern boundary upwelling systems are elementary components of ocean circulation and play important roles in the offshore transport of organic carbon and nutrients. Yet, most of our knowledge about this lateral transport and its influence on biogeochemical cycles relies on modelling studies and satellite observations, while in situ measurements of biogeochemical parameters are scarce. For example, little is known about the effects of mesoscale eddies on organic carbon distribution, microbial activity, and organic matter (OM) turnover in the open oligotrophic ocean. To address this gap, we investigated the horizontal and vertical variability of phytoplankton and bacterial activity as well as dissolved organic carbon along a zonal corridor of the westward propagation of eddies between the Cape Verde Islands and Mauretania in the Eastern Tropical North Atlantic (ETNA). We additionally collected samples from a cyclonic eddy along this transect at high spatial resolution. Our results indicate a strong impact of cyclonic eddies on both microbial abundance and metabolic activity in the epipelagic layer (0–200 m). Generally, all determined parameters (bacterial abundance, heterotrophic respiration rates, bacterial biomass production, bacterial growth efficiency, bacterial carbon demand and net primary production) were higher in the eddy than in the stations along the meridional transect. Along the transect, microbial biomass and activity rates were gradually decreasing from the coast to the open ocean. We further observed high variability of biogeochemical parameters within the eddy with elevates microbial abundances as well as process rates in the south-western periphery. This can be explained by the rotational flow of the cyclonic eddy, which perturbs local OM and nutrient distribution via azimuthal advection. The local positive anomaly of microbial activity in the cyclonic eddy compared to all other stations including the near coast ones results from eddy pumping of nutrient into the epipelagic layer that promotes growth of phytoplankton. Overall, our study supports that cyclonic eddies are important vehicles for the transport of fresh OM that fuel heterotrophic activity the open ocean, highlighting the coupling between productive EBUS and the adjacent oligotrophic ETNA.</p>

EFFECT OF LONG-TERM PIG SLURRY AND SOLID CATTLE MANURE APPLICATION ON SOIL CHEMICAL AND BIOLOGICAL PROPERTIES

1989 ◽  
Vol 69 (1) ◽  
pp. 39-47 ◽  
Author(s):  
A. NDAYEGAMIYE ◽  
D. CÔTÉ
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Microbial Activity ◽  
Humic Acids ◽  
Organic Matter Content ◽  
Biological Properties ◽  
Matter Content ◽  
Cattle Manure ◽  
Pig Slurry

Chemical and biological properties were evaluated in 1987 on an acidic silty loam soil following a long-term field study established in 1978 and cultivated with silage corn. Treatments included a control, solid cattle manure (20, 40 and 60 Mg ha−1 FYM) and pig slurry (60, 120 m3 ha−1 SLU) applied every 2 yr and annually, respectively. No fertilizer was applied. The results of this study have shown that neither treatment significantly affected soil pH values, total-N contents and C:N ratios compared to the control. The cation exchange capacity (CEC) of the soil was significantly higher with FYM treatment than with control or SLU application. The highest rates of FYM and SLU have also increased (P < 0.05) soil organic carbon, microbial activity and potentially mineralizable nitrogen. The soil microflora populations (bacteria, fungi, actinomycetes, ammonifiers and nitrifiers) were greatly improved by both treatments. There were no significant differences in organic matter content or the relative amount of humic and fulvic acids between FYM and SLU plots. In spite of these results, FYM application (40 and 60 Mg ha−1) did affect more significantly the distribution of organic carbon in HA and the E4/E6 quotients than SLU additions. Humic acids extracted from SLU amended soils had a lower C content and lower E4/E6 ratios than humic acids from FYM soils. Long-term SLU application did not contribute to decreased organic matter content, CEC and humic acids yield, probably because of optimal organic residues returned to the soil by the corn crops. The FYM application generally improved soil chemical and biological properties. For a sustainable soil productivity, long-term SLU application should then be avoided in rotation in which small amounts of plant residues are returned, especially on soils with low organic matter contents. Key words: Organic matter, microbial activity, nitrogen mineralization potential, CEC, solid cattle manure, pig slurry

scholarly journals Is microbial activity in tropical forests limited by phosphorus availability? Evidence from a tropical forest in China

2019 ◽  
Author(s):  
Taiki Mori ◽  
Xiankai Lu ◽  
Cong Wang ◽  
Qinggong Mao ◽  
Senhao Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Microbial Activity ◽  
Tropical Forests ◽  
Microbial Respiration ◽  
P Fertilization ◽  
Soil Microbial ◽  
Prevailing Paradigm ◽  
P Addition

AbstractThe prevailing paradigm for soil microbial activity in tropical forests is that microbial activity is limited by phosphorus (P) availability. Thus, exogenous P addition should increase rates of organic matter decomposition. Studies have also confirmed that soil respiration is accelerated when P is added experimentally. However, we hypothesize that the increased rates of soil microbial respiration could be due to the release of organic material from the surface of soil minerals when P is added, because P is more successful at binding to soil particles than organic compounds. In this study, we demonstrate that P addition to soil is associated with significantly higher dissolved organic carbon (DOC) content in a tropical evergreen forest in southern China. Our results indicate that P fertilization stimulated soil respiration but suppressed litter decomposition. Results from a second sorption experiment revealed that the recovery ratio of added DOC in the soil of a plot fertilized with P for 9 years was larger than the ratio in the soil of a non-fertilized plot, although the difference was small. We also conducted a literature review on the effects of P fertilization on the decomposition rates of litter and soil organic matter at our study site. Previous studies have consistently reported that P addition led to higher response ratios of soil microbial respiration than litter decomposition. Therefore, experiments based on P addition cannot be used to test whether microbial activity is P-limited in tropical forest soils, because organic carbon desorption occurs when P is added. Our findings suggest that the prevailing paradigm on the relationship between P and microbial activity in tropical forest soils should be re-evaluated.

scholarly journals Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation

2010 ◽  
Vol 7 (6) ◽  
pp. 1973-1982 ◽  
Author(s):  
I. Tsandev ◽  
C. Rabouille ◽  
C. P. Slomp ◽  
P. Van Cappellen
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Sea Level ◽  
Deep Sea ◽  
Oxygen Demand ◽  
Coupled Model ◽  
Submarine Canyon ◽  
Open Ocean ◽  
Oxygen Levels ◽  
Organic Carbon Burial

Abstract. The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

Interactions among sediments, organic matter, and microbial activity in the hyporheic zone of an intermittent stream

1999 ◽  
Vol 56 (3) ◽  
pp. 487-495 ◽  
Author(s):  
Mohamed Chafiq ◽  
Janine Gibert ◽  
Cécile Claret
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Microbial Activity ◽  
Bacterial Biomass ◽  
Hydrolytic Activity ◽  
Subsurface Water ◽  
Surface Discharge ◽  
Intermittent Stream ◽  
Fine Sediments

Interactions between surface and subsurface water in intermittent streams are poorly understood. We predicted that surface discharge patterns would influence retention and transport of fine sediments and particulate organic matter in a first-order intermittent stream, which in turn would affect microbial activity at different depths in the sediment. We measured sediments, dissolved and particulate organic carbon, and microbial and bacterial biomass and activity at three depths (surface and 20 and 40 cm) over a period spanning low and high flows at five stations on an intermittent stream. Discharge influenced physicochemical and sediment characteristics at the upstream stations with coarse substratum. In the finer sediments of the lower reaches, an active hyporheic microbial assemblage primarily governed sediment and organic dynamics. With decreasing discharge and increasing retention of fine sediments and particulate organic carbon, greater microbial hydrolytic activity in bed-sediments occurred downstream. Dissolved oxygen, organic carbon, fine sediments, microbial biomass, hydrolytic activity, and bacterial biomass declined with depth, and changed over time, apparently in response to varying discharge. We conclude that discharge and substratum particle size may interact to control organic dynamics and hyporheic microbial activity in a 1st order stream.

Variations of microbial activity and diversity in mesoscale eddies formed in the Eastern boundary upwelling system off West Africa

2020 ◽  
Author(s):  
Kevin W. Becker ◽  
Quentin Devresse ◽  
Anja Engel
Keyword(s):  
Nucleic Acid ◽  
Primary Production ◽  
Microbial Activity ◽  
Heterotrophic Bacteria ◽  
Spatial Scales ◽  
Mesoscale Eddies ◽  
Upper Ocean ◽  
Patchy Distribution ◽  
Eastern Boundary ◽  
Eukaryotic Phytoplankton

&lt;p&gt;Mesoscale eddies formed at Eastern boundary upwelling systems (EBUS) are important vehicles for nutrients and carbon to the open oligotrophic ocean that influence the biogeochemistry on relatively small spatial scales (on the order of 100 km). They impact upper-ocean chemistry and biology through a number of processes. For example, in cyclonic eddies upward nutrient supply to the euphotic zone typically results in intensified primary productivity and changes in community structure, both of which affect export fluxes of carbon to the deep ocean. Therefore, the factors that control the (sub)mesoscale dynamics of the upper ocean are essential to understanding the efficiency of the biological carbon pump. However, the governing dynamical processes are largely unknown, and so is the overall biogeochemical and ecosystem response. To investigate the horizontal and vertical variability of phytoplankton and heterotrophic bacteria within and around mesoscale eddies, we collected samples along a zonal corridor of the westward propagation of eddies between the Cape Verde Islands and Mauretania as well as from a cyclonic eddy along this transect at high spatial resolution. In the eddy, we generally observed enhanced primary production, based on &lt;sup&gt;14&lt;/sup&gt;C incorporation, and heterotrophic microbial activity, based on &lt;sup&gt;3&lt;/sup&gt;H leucine incorporation, compared to the surrounding waters. Similarly, microbial heterotrophic respiration rates obtained from optode&amp;#8208;based oxygen consumption measurements during dark incubations were highest inside the eddy. However, the detailed eddy survey revealed a patchy distribution of all microbial process rates. The rates were highest in the Northern and Western periphery of the eddy where depth-integrated primary and heterotrophic production were more than three times higher than in the eddy core. The patchy distribution was also apparent from flow cytometry data, which showed higher relative abundances of larger eukaryotic phytoplankton (nanoplankton) compared to picoplankton in the most productive regions of the eddy. The higher activities were additionally accompanied by a higher relative abundance of high nucleic acid containing bacteria, which are considered the more active members of the given community compared to low nucleic acid-containing bacteria. The enhanced primary production, particularly in the Northern and Western eddy peripheries, will fuel export production particularly in these regions. To gain further insight into the organic carbon dynamics, data on the spatial distribution and the lateral and vertical fluxes of dissolved and particulate organic matter are currently underway. While our data confirm previous studies of enhanced biological activity within eddies formed in EBUS regions, it also indicates that the effect of variable phytoplankton and heterotrophic bacterial distributions and activity within an eddy leads to consequences for the spatial and temporal representativeness of measurements from only a few samples. This study thus contributes to a more comprehensive view on the functioning of eddy dynamics and it will facilitate modelling efforts on the role that eddies play in the ocean carbon budget.&lt;/p&gt;

Soil organic carbon under lockdown: Fresh plant litter as the nucleus for persistent carbon

2021 ◽  
Author(s):  
Kristina Witzgall ◽  
Alix Vidal ◽  
David Schubert ◽  
Carmen Höschen ◽  
Steffen Schweizer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Microbial Activity ◽  
Soil Structure ◽  
Fungal Growth ◽  
Plant Litter ◽  
Soil Matrix ◽  
Plant Soil

Abstract The largest terrestrial organic carbon pool, carbon in soils, is regulated by the intricate connection between plant carbon inputs, microbial activity, and soil matrix. This is manifested by how microorganisms, the key players in transforming plant-derived carbon into soil organic carbon, are controlled by the physical arrangement of organic and inorganic soil particles. We studied the role of soil structure on the fate of litter-derived organic matter and we propose that the persistence of soil carbon pools is directly determined at plant–soil interfaces. We show that while microbial activity and fungal growth is controlled by soil structure, occlusion of organic matter into aggregates and formation of organo-mineral associations occur in concert on litter surfaces regardless of soil structure. These two mechanisms—the two most prominent processes contributing to the persistence of organic matter—occur directly at fresh litter that constitutes a key nucleus in the build-up of soil carbon persistence.

scholarly journals Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation

2010 ◽  
Vol 7 (1) ◽  
pp. 879-903 ◽  
Author(s):  
I. Tsandev ◽  
C. Rabouille ◽  
C. P. Slomp ◽  
P. Van Cappellen
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Sea Level ◽  
Deep Sea ◽  
Oxygen Demand ◽  
Coupled Model ◽  
Submarine Canyon ◽  
Open Ocean ◽  
Oxygen Levels ◽  
Organic Carbon Burial

Abstract. The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep sea-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

scholarly journals Particulate organic matter as a functional soil component for persistent soil organic carbon

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kristina Witzgall ◽  
Alix Vidal ◽  
David I. Schubert ◽  
Carmen Höschen ◽  
Steffen A. Schweizer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Microbial Activity ◽  
Particulate Organic Matter ◽  
Soil Structure ◽  
Plant Litter ◽  
Carbon Substrate ◽  
Soil Matrix

AbstractThe largest terrestrial organic carbon pool, carbon in soils, is regulated by an intricate connection between plant carbon inputs, microbial activity, and the soil matrix. This is manifested by how microorganisms, the key players in transforming plant-derived carbon into soil organic carbon, are controlled by the physical arrangement of organic and inorganic soil particles. Here we conduct an incubation of isotopically labelled litter to study effects of soil structure on the fate of litter-derived organic matter. While microbial activity and fungal growth is enhanced in the coarser-textured soil, we show that occlusion of organic matter into aggregates and formation of organo-mineral associations occur concurrently on fresh litter surfaces regardless of soil structure. These two mechanisms—the two most prominent processes contributing to the persistence of organic matter—occur directly at plant–soil interfaces, where surfaces of litter constitute a nucleus in the build-up of soil carbon persistence. We extend the notion of plant litter, i.e., particulate organic matter, from solely an easily available and labile carbon substrate, to a functional component at which persistence of soil carbon is directly determined.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

scholarly journals Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island, Korea, based on absorption and fluorescence spectroscopy

2021 ◽  
Author(s):  
Jeonghyun Kim ◽  
Yeseul Kim ◽  
Sung Eun Park ◽  
Tae-Hoon Kim ◽  
Bong-Guk Kim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Matter ◽  
Coastal Water ◽  
Coastal Region ◽  
Principal Component ◽  
Distribution Patterns ◽  
Organic Pollution ◽  
Jeju Island

AbstractIn Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and behaviours of dissolved organic matter (DOM) in the coastal water are still unknown. To decipher characteristics of organic pollution, we compared physicochemical parameters with spectral optical properties near the coastal aquafarms in Jeju Island. Absorption spectra were measured to calculate the absorption coefficient, spectral slope coefficient, and specific UV absorbance. Fluorescent DOM was analysed using fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured using high-temperature catalytic oxidation. The DOC concentration near the discharge outlet was twice higher than that in natural groundwater, and the TDN concentration exponentially increased close to the outlet. These distribution patterns indicate that aquafarms are a significant source of DOM. Herein, principal component analysis was applied to categorise the DOM origins. There were two distinct groups, namely, aquaculture activity for TDN with humic-like and high molecular weights DOM (PC1: 48.1%) and natural biological activity in the coastal water for DOC enrichment and protein-like DOM (PC2: 18.8%). We conclude that the aquafarms significantly discharge organic nitrogen pollutants and provoke in situ production of organic carbon. Furthermore, these findings indicate the potential of optical techniques for the efficient monitoring of anthropogenic organic pollutants from aquafarms worldwide.

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