scholarly journals N2O production and consumption from stable isotopic and concentration data in the Peruvian coastal upwelling system

2017 ◽  
Vol 31 (4) ◽  
pp. 678-698 ◽  
Author(s):  
Annie Bourbonnais ◽  
Robert T. Letscher ◽  
Hermann W. Bange ◽  
Vincent Échevin ◽  
Jennifer Larkum ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Concentration Data ◽  
N2o Production ◽  
Upwelling System ◽  
Production And Consumption ◽  
Stable Isotopic

scholarly journals N2O production in the eastern South Atlantic: Analysis of N2O stable isotopic and concentration data

2014 ◽  
Vol 28 (11) ◽  
pp. 1262-1278 ◽  
Author(s):  
Caitlin H. Frame ◽  
Eric Deal ◽  
Cynthia D. Nevison ◽  
Karen L. Casciotti
Keyword(s):  
South Atlantic ◽  
Concentration Data ◽  
N2o Production ◽  
Stable Isotopic

Modeling the Central California Coastal Upwelling System: Physics, Ecosystems and Resource Management

2002 ◽  
Author(s):  
Francisco P. Chavez ◽  
Richard T. Barber ◽  
Fei Chai ◽  
Yi Chao ◽  
Andrew P. De Vogelaere ◽  
...  
Keyword(s):  
Resource Management ◽  
Coastal Upwelling ◽  
Central California ◽  
Upwelling System

scholarly journals Microbial N2O consumption in and above marine N2O production hotspots

2020 ◽  
Author(s):  
Xin Sun ◽  
Amal Jayakumar ◽  
John C. Tracey ◽  
Elizabeth Wallace ◽  
Colette L. Kelly ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Substrate Affinity ◽  
N2o Production ◽  
Anoxic Waters ◽  
Production And Consumption ◽  
Consumption Rates ◽  
Anoxic Zones ◽  
First Time ◽  
Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

scholarly journals Modeling the impact of climate change on mussel aquaculture in a coastal upwelling system: A critical assessment

2021 ◽  
Vol 775 ◽  
pp. 145020
Author(s):  
Isabel Fuentes-Santos ◽  
Uxío Labarta ◽  
María José Fernández-Reiriz ◽  
Susan Kay ◽  
Solfrid Sætre Hjøllo ◽  
...  
Keyword(s):  
Climate Change ◽  
Coastal Upwelling ◽  
Critical Assessment ◽  
Impact Of Climate Change ◽  
Upwelling System ◽  
System A ◽  
The Impact

scholarly journals Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem

Ocean Science ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 1-11 ◽  
Author(s):  
J. Kämpf
Keyword(s):  
Satellite Data ◽  
Coastal Upwelling ◽  
Phytoplankton Bloom ◽  
Hot Spot ◽  
Marine Ecosystem ◽  
Austral Summer ◽  
Phytoplankton Blooms ◽  
Study Region ◽  
Upwelling System ◽  
Fluorescence Line

Abstract. Satellite-derived chlorophyll a data using the standard NASA-OC3 (ocean colour) algorithm are strongly biased by coloured dissolved organic matter and suspended sediment of river discharges, which is a particular problem for the western Tasmanian shelf. This work reconstructs phytoplankton blooms in the study region using a quadratic regression between OC3 data and chlorophyll fluorescence based on the fluorescence line height (FLH) data. This regression is derived from satellite data of the nearby Bonney upwelling region, which is devoid of river influences. To this end, analyses of 10 years of MODIS-aqua satellite data reveal the existence of a highly productive ecosystem on the western Tasmanian shelf. The region normally experiences two phytoplankton blooms per annum. The first bloom occurs during late austral summer months as a consequence of upwelling-favourable coastal winds. Hence, the western Tasmanian shelf forms a previously unknown upwelling centre of the regional upwelling system, known as Great South Australian Coastal Upwelling System. The second phytoplankton bloom is a classical spring bloom also developing in the adjacent Tasman Sea. The author postulates that this region forms another important biological hot spot for the regional marine ecosystem.

scholarly journals Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

2017 ◽  
Vol 14 (5) ◽  
pp. 1165-1179 ◽  
Author(s):  
Diana Zúñiga ◽  
Celia Santos ◽  
María Froján ◽  
Emilia Salgueiro ◽  
Marta M. Rufino ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediment ◽  
Sediment Trap ◽  
Coastal Upwelling ◽  
Late Summer ◽  
Early Summer ◽  
Marine Diatom ◽  
Photic Zone ◽  
Upwelling System ◽  
Water Column Stratification

Abstract. The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring–early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.

scholarly journals Vertical segregation among pathways mediating nitrogen loss (N<sub>2</sub> and N<sub>2</sub>O production) across the oxygen gradient in a coastal upwelling ecosystem

2017 ◽  
Vol 14 (20) ◽  
pp. 4795-4813 ◽  
Author(s):  
Alexander Galán ◽  
Bo Thamdrup ◽  
Gonzalo S. Saldías ◽  
Laura Farías
Keyword(s):  
Coastal Upwelling ◽  
Nitrite Reduction ◽  
15N Tracer ◽  
Ammonium Oxidation ◽  
N Loss ◽  
N2o Production ◽  
Coastal System ◽  
Central Chile ◽  
N Removal ◽  
Bottom Waters

Abstract. The upwelling system off central Chile (36.5° S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30–50 m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. Incubations were developed using water retrieved from the oxycline (25 m depth) and bottom waters (85 m depth) over the continental shelf off Concepción, Chile. Results of 15N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N2-producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline, where a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40 µmol L−1) relative to the hypoxic bottom waters ( <  20 µmol O2 L−1). Different pathways were responsible for N2O produced in the oxycline and bottom waters, with ammonium oxidation and dissimilatory nitrite reduction, respectively, as the main source processes. Ammonium produced by dissimilatory nitrite reduction to ammonium (DNiRA) could sustain both anammox and nitrification rates, including the ammonium utilized for N2O production. The temporal and vertical variability of δ15N-NO3− confirms that multiple N-cycling processes are modulating the isotopic nitrate composition over the shelf off central Chile during spring and summer. N removal processes in this coastal system appear to be related to the availability and distribution of oxygen and particles, which are a source of organic matter and the fuel for the production of other electron donors (i.e. ammonium) and acceptors (i.e. nitrate and nitrite) after its remineralization. These results highlight the links between several pathways involved in N loss. They also establish that different mechanisms supported by alternative N substrates are responsible for substantial accumulation of N2O, which are frequently observed as hotspots in the oxycline and bottom waters. Considering the extreme variation in oxygen observed in several coastal upwelling systems, these findings could help to understand the ecological and biogeochemical implications due to global warming where intensification and/or expansion of the oceanic OMZs is projected.

scholarly journals Abiotic ammonification and gross ammonium photoproduction in the upwelling system off central Chile (36° S)

2012 ◽  
Vol 9 (12) ◽  
pp. 18479-18518
Author(s):  
A. Rain-Franco ◽  
C. Muñoz ◽  
C. Fernandez
Keyword(s):  
Organic Matter ◽  
Coastal Upwelling ◽  
Archaeal Community ◽  
Simultaneous Occurrence ◽  
Diatom Species ◽  
Chaetoceros Muelleri ◽  
Central Chile ◽  
Upwelling System ◽  
Simulated Solar Radiation ◽  
Radiation Conditions

Abstract. We investigated the production of ammonium via photodegradation of dissolved organic matter (DOM) in the coastal upwelling system off central Chile (36° S). Photoammonification experiments were carried out using exudates obtained from representative diatom species (Chaetoceros muelleri and Thalassiosira minuscule) and natural marine DOM under simulated solar radiation conditions. Additionally, we evaluated the use of photoproduced ammonium by natural microbial communities and separated ammonium oxidizing archaea and bacteria by using GC-7 as an inhibitor of the archaeal community. We found photoammonification operating at two levels: via the transformation of DOM by UV radiation (abiotic ammonification) and via the simultaneous occurrence of abiotic phototransformation and biological remineralization of DOM into NH4+ (referred as gross photoproduction of NH4+). The maximum rates of abiotic ammonification reached 0.057 μmol L−1 h−1, whereas maximum rates of gross photoproduction reached 0.746 μmol L−1 h−1. Our results also suggest that ammonium oxidizing archaea could dominate the biotic remineralization induced by photodegradation of organic matter and consequently play an important role in the local N cycle. Abiotic ammonium photoproduction in coastal upwelling systems could support between 7 and 50% of the spring-summer phytoplankton NH4+ demand. Surprisingly, gross ammonium photoproduction (remineralization induced by abiotic ammonification) might support 50 to 180% of spring-summer phytoplankton NH4+ assimilation.

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