Effect of seasonal changes in bottom water oxygenation on sediment N oxides and N2O cycling in the coastal upwelling regime off central Chile (36.5°S)

2007 ◽  
Vol 75 (3) ◽  
pp. 561-575 ◽  
Author(s):  
Laura Farías ◽  
Marcela Cornejo
Keyword(s):  
Seasonal Changes ◽  
Bottom Water ◽  
Coastal Upwelling ◽  
Central Chile

scholarly journals Coastal Upwelling Front Detection off Central Chile (36.5–37°S) and Spatio-Temporal Variability of Frontal Characteristics

2018 ◽  
Vol 10 (5) ◽  
pp. 690 ◽  
Author(s):  
Vera Oerder ◽  
Joaquim Bento ◽  
Carmen Morales ◽  
Samuel Hormazabal ◽  
Oscar Pizarro
Keyword(s):  
Temporal Variability ◽  
Coastal Upwelling ◽  
Central Chile ◽  
Spatio Temporal ◽  
Front Detection

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.

АNNUAL DISTRIBUTION OF THE ORGANIC AND NUTRIENT SUBSTANCES IN WATER OF THE VERBNE LAKE (KYIV CITY)

2020 ◽  
pp. 41-47
Author(s):  
V.P. Osypenko ◽  
A.O. Morozova
Keyword(s):  
Seasonal Changes ◽  
Bottom Water ◽  
Oxygen Demand ◽  
Fulvic Acids ◽  
Component Composition ◽  
Aqueous Environment ◽  
Anthropogenic Pressure ◽  
Organic Substances ◽  
Ecological Features ◽  
Water Ph

The results of investigations of the dissolved organic substances and nutrients distribution in surface and bottom water of the Verbne lake in 2018-2019 are presented and analysed. In particular the annual values of the total dissolved organic substances content by parameters of permanganate and bichromate oxidizabilities are difined. Also the seasonal dynamics of such different organic compounds as humic acids, fulvic acids, carbohydrates and protein-like substance in surface and bottom water are considered. The concentration alterations of the nitrogen, phosphorus and silicon combinations of nutrients from seasonal factor are studied. The major hydrochemical characters of water (pH, dissolved oxygen concentration, degree of oxygen saturation of water, chemical oxygen demand) and their correlation with the seasonal changes of the general dissolved organic substances content and nutrient compounds are adduced. The traditional seasonal distribution of these organic substances indicates a good self-cleaning ability of the Verbne lake. The received results testify that the investigated Verbne lake belong to a evtrophic reservoir in which hydrobionts actively develop and there are important processes of accumulation and destruction of these substances that essentially influences on their component composition. The ecological features of the chemical composition of this water object are largely determined both by natural processes and anthropogenic pressure, which is manifested not only in the direct entering into the water products of human activity, but also indirectly, as a result of changes in the physical, chemical and biological factors in the aqueous environment. Monitoring of annual and seasonal changes of the total and components content dissolved organic substances and nutrients in the water along with other hydrochemical and hydrobiological indices makes it possible to assess the ecological state of water objects.

scholarly journals Chemolithoautotrophic production mediating the cycling of the greenhouses gases N<sub>2</sub>O and CH<sub>4</sub> in an upwelling ecosystem

2009 ◽  
Vol 6 (3) ◽  
pp. 6205-6247 ◽  
Author(s):  
L. Farías ◽  
C. Fernández ◽  
J. Faúndez ◽  
M. Cornejo ◽  
M. E. Alcaman
Keyword(s):  
Coastal Upwelling ◽  
Isotopic Ratio ◽  
Carbon Assimilation ◽  
High Availability ◽  
Electron Donors ◽  
The Other ◽  
Ch4 Oxidation ◽  
Central Chile ◽  
Gas Cycling ◽  
Upwelling Area

Abstract. Coastal upwelling ecosystems with marked oxyclines (redoxclines) present high availability of electron donors that favour chemoautotrophy, leading in turn to high N2O and CH4 cycling associated with aerobic NH4+ (AAO) and CH4 oxidation (AMO). This is the case of the highly productive coastal upwelling area off Central Chile (36° S), where we evaluated the importance of total chemolithoautotrophic vs. photoautotrophic production, the specific contributions of AAO and AMO to chemosynthesis and their role in gas cycling. Chemoautotrophy (involving bacteria and archaea) was studied at a time-series station during monthly (2002–2009) and seasonal cruises (January 2008, September 2008, January 2009) and was assessed in terms of dark carbon assimilation (CA), N2O and CH4 cycling, and the natural C isotopic ratio of particulate organic carbon (δ13POC). Total Integrated dark CA fluctuated between 19.4 and 2.924 mg C m−2 d−1. It was higher during active upwelling and represented on average 27% of the integrated photoautotrophic production (from 135 to 7.626 mg C m−2d−1). At the oxycline, δ13POC averaged -22.209‰ this was significantly lighter compared to the surface (-19.674‰) and bottom layers (-20.716‰). This pattern, along with low NH4+ content and high accumulations of N2O, NO2- and NO3- within the oxycline indicates that chemolithoautotrophs and specifically AA oxydisers were active. Dark CA was reduced from 27 to 48% after addition of a specific AAO inhibitor (ATU) and from 24 to 76% with GC7, a specific archaea inhibitor, indicating that AAO and maybe AMO microbes (most of them archaea) were performing dark CA through oxidation of NH4+ and CH4. AAO produced N2O at rates from 8.88 to 43 nM d−1 and a fraction of it was effluxed into the atmosphere (up to 42.85 μmol m−2 d−1). AMO on the other hand consumed CH4 at rates between 0.41 and 26.8 nM d−1 therefore preventing its efflux to the atmosphere (up to 18.69 μmol m−2 d−1). These findings show that chemically driven chemoautotrophy (with NH4+ and CH4 acting as electron donors) could be more important than previously thought in upwelling ecosystems and open new questions concerning its future relevance.

Intraseasonal variability of wind-forced coastal upwelling off central Chile (30°S)

2004 ◽  
Vol 24 (7-8) ◽  
pp. 789-804 ◽  
Author(s):  
José A. Rutllant ◽  
Benjamı́n Rosenbluth ◽  
Samuel Hormazabal
Keyword(s):  
Coastal Upwelling ◽  
Intraseasonal Variability ◽  
Central Chile

Detecting Subtle Seasonal Transitions of Upwelling in North-Central Chile

2015 ◽  
Vol 45 (3) ◽  
pp. 854-867 ◽  
Author(s):  
David A. Rahn ◽  
Benjamín Rosenblüth ◽  
José A. Rutllant
Keyword(s):  
Wind Stress ◽  
Large Scale ◽  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Biological Productivity ◽  
Wind Stress Curl ◽  
Two Phase ◽  
North Central ◽  
Central Chile ◽  
Upwelling Index

AbstractBiological productivity in the ocean along the Chilean coast is tied to upwelling that is primarily forced by equatorward wind stress and wind stress curl on the ocean surface. Southerly alongshore flow is driven by the southeast Pacific (SEP) anticyclone, and its intensity and position vary on a range of time scales. Variability of the SEP anticyclone has been linked to large-scale circulations such as El Niño–Southern Oscillation and the Madden–Julian oscillation. The actual timing, duration, and nature of the seasonal meridional drift of the SEP anticyclone are associated with the onset, demise, and strength of the local upwelling season. Seasonal variation is especially marked at the Punta Lavapié (37°S) upwelling focus, where there is a clear upwelling season associated with a change of the cumulative upwelling index (CUI) slope between positive and negative. The Punta Lengua de Vaca (30°S) focus typically exhibits upwelling year-round and has less distinct transitions, making it more difficult to identify an enhanced upwelling season. A two-phase linear regression model, which is typically used to detect subtle climate changes, is applied here to detect seasonal changes in CUI at Punta Lengua de Vaca. This method objectively finds distinct transitions for most years. The spring-to-summer transition is more readily detected and the slackening of the upwelling-favorable winds, warmer waters, and longer wind strengthening–relaxation cycles change the coastal upwelling ecosystem. While the spring-to-summer transition at Punta Lengua de Vaca could be influenced by large-scale circulations, the actual dates of transition are highly variable and do not show a clear relationship.

scholarly journals Benthic Foraminifera from Middle to Late Pleistocene, coastal upwelling sediments of ODP Hole 686B, Pacific Ocean, off Peru

1991 ◽  
Vol 9 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Kathryn A. Malmgren ◽  
Brian M. Funnell
Keyword(s):  
Late Pleistocene ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Water Oxygen ◽  
Minimum Zone ◽  
Water Depths ◽  
Oxygen Minimum

Abstract. Benthic Foraminifera from middle to late Pleistocene, (c. 600ka to 0ka), sediments of ODP Hole 686B, off Peru, show highest abundances and diversities during periods of cooler surface waters, (inferred from the Uk37 index), and enhanced upwelling, (inferred from the peridinacean/gonyaulacacean dinoflagellate cyst ratio). During the latest Pleistocene, (c. 160ka to 0ka), these periods are characterised by higher organic carbon contents in the bottom sediments, and occur during the odd-numbered, interglacial_18O stages. The benthic Foraminifera indicate deposition in 120 to 250 metres water depth for the earlier part of the record, (c. 600ka to c. 200ka), within the oxygen-minimum zone, with bottom water oxygen contents of <0.5 to 0.2 ml/l, (inferred from the dominance of Bolivinellina humilis). Deposition in water depths approaching those of the present day, (c. 450 metres), is indicated from c. 160ka onwards, with better oxygenated bottom water conditions, probably corresponding to the lower part of the oxygen-minimum zone.

Sign in / Sign up

Export Citation Format

Share Document