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

<p>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 <sup>14</sup>C incorporation, and heterotrophic microbial activity, based on <sup>3</sup>H leucine incorporation, compared to the surrounding waters. Similarly, microbial heterotrophic respiration rates obtained from optode‐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.</p>

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>

Soil microbial activity in a Liquidambar plantation unresponsive to CO2-driven increases in primary production

2003 ◽  
Vol 24 (3) ◽  
pp. 263-271 ◽  
Author(s):  
R.L Sinsabaugh ◽  
K Saiya-Cork ◽  
T Long ◽  
M.P Osgood ◽  
D.A Neher ◽  
...  
Keyword(s):  
Primary Production ◽  
Microbial Activity ◽  
Soil Microbial Activity ◽  
Soil Microbial

Biological processes in modelling soil functions – a balancing act between too complex and too simple

2021 ◽  
Author(s):  
Sara König ◽  
Ulrich Weller ◽  
Thomas Reitz ◽  
Bibiana Betancur-Corredor ◽  
Birgit Lang ◽  
...  
Keyword(s):  
Nutrient Cycling ◽  
Microbial Activity ◽  
Community Dynamics ◽  
Spatial Scales ◽  
Simulation Models ◽  
Microbial Processes ◽  
Biological Processes ◽  
Soil Functions ◽  
Management Options ◽  
The Impact

<p>Mechanistic simulation models are an essential tool for predicting soil functions such as nutrient cycling, water filtering and storage, productivity and carbon storage as well as the complex interactions between these functions. Most soil functions are driven or affected by soil organisms. Yet, biological processes are often neglected in soil function models or implicitly described by rate parameters. This can be explained by the high complexity of the soil ecosystem with its dynamic and heterogeneous environment, and by the range of temporal and spatial scales these processes are taking place at. On the other hand, the technical capabilities to explore microbial activity and communities in soil has greatly improved, resulting in new possibilities to understand soil microbial processes on various scales.</p><p>However, to integrate such biological processes in soil modelling, we need to find the right level of detail. Here, we present a systemic soil model approach to simulate the impact of different management options and changing climate on soil functions integrating biological activity on the profile scale. We use stoichiometric considerations to simulate microbial processes involved in different soil functions without explicitly describing community dynamics or functional groups. With this approach we are able to mechanistically describe microbial activity and its impact on the turnover of organic matter and nutrient cycling as driven by agricultural soil management.</p><p>Further, we discuss general challenges and ongoing developments to additionally consider, e.g., microbe-fauna-interactions or microbial feedback with soil structure dynamics.</p>

scholarly journals Impact of Cyclonic Ocean Eddies on Upper Ocean Thermodynamic Response to Typhoon Soudelor

2019 ◽  
Vol 11 (8) ◽  
pp. 938 ◽  
Author(s):  
Jue Ning ◽  
Qing Xu ◽  
Han Zhang ◽  
Tao Wang ◽  
Kaiguo Fan
Keyword(s):  
Vertical Mixing ◽  
Heat Content ◽  
Mesoscale Eddies ◽  
Upper Ocean ◽  
Surface Cooling ◽  
Ocean Eddies ◽  
Horizontal Advection ◽  
Content Change ◽  
Order Of Magnitude ◽  
The Impact

By using multiplatform satellite datasets, Argo observations and numerical model data, the upper ocean thermodynamic responses to Super Typhoon Soudelor are investigated with a focus on the impact of an ocean cyclonic eddy (CE). In addition to the significant surface cooling inside the CE region, an abnormally large rising in subsurface temperature is observed. The maximum warming and heat content change (HCC) reach up to 4.37 °C and 1.73 GJ/m2, respectively. Moreover, the HCC is an order of magnitude larger than that calculated from statistical analysis of Argo profile data in the previous study which only considered the effects caused by typhoons. Meanwhile, the subsurface warming outside the CE is merely 1.74 °C with HCC of 0.39 GJ/m2. Previous studies suggested that typhoon-induced vertical mixing is the primary factor causing subsurface warming but these studies ignored an important mechanism related to the horizontal advection caused by the rotation and movement of mesoscale eddies. This study documents that the eddy-induced horizontal advection has a great impact on the upper ocean responses to typhoons. Therefore, the influence of eddies should be considered when studying the responses of upper ocean to typhoons with pre-existing mesoscale eddies.

scholarly journals Nitrogen Fixation in a Changing Arctic Ocean: An Overlooked Source of Nitrogen?

2020 ◽  
Vol 11 ◽  
Author(s):  
Lisa W. von Friesen ◽  
Lasse Riemann
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Primary Production ◽  
Arctic Ocean ◽  
Current Knowledge ◽  
Carbon Sink ◽  
Spatial Scales ◽  
The Arctic ◽  
Future Research ◽  
The Arctic Ocean

The Arctic Ocean is the smallest ocean on Earth, yet estimated to play a substantial role as a global carbon sink. As climate change is rapidly changing fundamental components of the Arctic, it is of local and global importance to understand and predict consequences for its carbon dynamics. Primary production in the Arctic Ocean is often nitrogen-limited, and this is predicted to increase in some regions. It is therefore of critical interest that biological nitrogen fixation, a process where some bacteria and archaea termed diazotrophs convert nitrogen gas to bioavailable ammonia, has now been detected in the Arctic Ocean. Several studies report diverse and active diazotrophs on various temporal and spatial scales across the Arctic Ocean. Their ecology and biogeochemical impact remain poorly known, and nitrogen fixation is so far absent from models of primary production in the Arctic Ocean. The composition of the diazotroph community appears distinct from other oceans – challenging paradigms of function and regulation of nitrogen fixation. There is evidence of both symbiotic cyanobacterial nitrogen fixation and heterotrophic diazotrophy, but large regions are not yet sampled, and the sparse quantitative data hamper conclusive insights. Hence, it remains to be determined to what extent nitrogen fixation represents a hitherto overlooked source of new nitrogen to consider when predicting future productivity of the Arctic Ocean. Here, we discuss current knowledge on diazotroph distribution, composition, and activity in pelagic and sea ice-associated environments of the Arctic Ocean. Based on this, we identify gaps and outline pertinent research questions in the context of a climate change-influenced Arctic Ocean – with the aim of guiding and encouraging future research on nitrogen fixation in this region.

scholarly journals A Limited Effect of Sub-Tropical Typhoons on Phytoplankton Dynamics

2020 ◽  
Author(s):  
Fei Chai ◽  
Yuntao Wang ◽  
Xiaogang Xing ◽  
Yunwei Yan ◽  
Huijie Xue ◽  
...  
Keyword(s):  
Primary Production ◽  
Vertical Mixing ◽  
Remote Sensing Data ◽  
Upper Ocean ◽  
Northwest Pacific ◽  
Limited Effect ◽  
Significant Drop ◽  
Northwest Pacific Ocean ◽  
Temporal Sampling ◽  
The Impact

Abstract. Typhoons are assumed to stimulate ocean primary production through the upward mixing of nutrients into the surface ocean, based largely on observations of increased surface chlorophyll concentrations following the passage of typhoons. This surface chlorophyll enhancement, seen on occasion by satellites, more often is undetected due to intense cloud coverage. Daily data from a BGC-Argo profiling float revealed the upper-ocean response to Typhoon Trami in the Northwest Pacific Ocean. Temperature and chlorophyll changed rapidly, with a significant drop in sea surface temperature and surge in surface chlorophyll associated with strong vertical mixing, which was only partially captured by satellite observations. However, no net increase in vertically integrated chlorophyll was observed during Typhoon Trami or in its wake. Contrary to the prevailing dogma, the results show that typhoons likely have limited effect on net ocean primary production. Observed surface chlorophyll enhancements during and immediately following typhoons in tropical and subtropical waters are more likely associated with surface entrainment of deep chlorophyll maxima. Moreover, the findings demonstrate that remote sensing data alone can overestimate the impact of storms on primary production in all oceans. Full understanding of the impact of storms on upper ocean productivity can only be achieved with ocean observing robots dedicated to high-resolution temporal sampling in the path of storms.

scholarly journals Response of bacterioplankton activity in an Arctic fjord system to elevated <i>p</i>CO<sub>2</sub>: results from a mesocosm perturbation study

2013 ◽  
Vol 10 (1) ◽  
pp. 297-314 ◽  
Author(s):  
J. Piontek ◽  
C. Borchard ◽  
M. Sperling ◽  
K. G. Schulz ◽  
U. Riebesell ◽  
...  
Keyword(s):  
Primary Production ◽  
Protein Production ◽  
Heterotrophic Bacteria ◽  
Extracellular Enzyme ◽  
Bacterial Activity ◽  
High Pco2 ◽  
Phytoplankton Productivity ◽  
Bacterioplankton Community ◽  
Fjord System ◽  
Arctic Fjord

Abstract. The effect of elevated seawater carbon dioxide (CO2) on the activity of a natural bacterioplankton community in an Arctic fjord system was investigated by a mesocosm perturbation study in the frame of the European Project on Ocean Acidification (EPOCA). A pCO2 range of 175–1085 μatm was set up in nine mesocosms deployed in the Kongsfjorden (Svalbard). The activity of natural extracellular enzyme assemblages increased in response to acidification. Rates of β-glucosidase and leucine-aminopeptidase increased along the gradient of mesocosm pCO2. A decrease in seawater pH of 0.5 units almost doubled rates of both enzymes. Heterotrophic bacterial activity was closely coupled to phytoplankton productivity in this experiment. The bacterioplankton community responded to rising chlorophyll a concentrations after a lag phase of only a few days with increasing protein production and extracellular enzyme activity. Time-integrated primary production and bacterial protein production were positively correlated, strongly suggesting that higher amounts of phytoplankton-derived organic matter were assimilated by heterotrophic bacteria at increased primary production. Primary production increased under high pCO2 in this study, and it can be suggested that the efficient heterotrophic carbon utilisation had the potential to counteract the enhanced autotrophic CO2 fixation. However, our results also show that beneficial pCO2-related effects on bacterial activity can be mitigated by the top-down control of bacterial abundances in natural microbial communities.

Influence of mesoscale eddies on primary production in the South China Sea during spring inter-monsoon period

2014 ◽  
Vol 33 (3) ◽  
pp. 118-128 ◽  
Author(s):  
Zifeng Hu ◽  
Yehui Tan ◽  
Xingyu Song ◽  
Linbin Zhou ◽  
Xiping Lian ◽  
...  
Keyword(s):  
South China Sea ◽  
Primary Production ◽  
South China ◽  
Mesoscale Eddies ◽  
The South China Sea ◽  
The South ◽  
Monsoon Period ◽  
China Sea
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