Primary production and community respiration in the Humboldt Current System off Chile and associated oceanic areas

Daneri, Giovanni; Dellarossa, Víctor; Quiñones, Renato A.; Jacob, Bárbara; Montero, Paulina; Ulloa, Osvaldo

doi:10.3354/meps197041

Cited by 340 publications

(240 citation statements)

References 8 publications

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“…The last experiment was conducted during 6 and 7 December 2002 during a ¢eld campaign onboard the RV 'Purihaalar' at a station located in Mejillones Bay (238S 73820'W; Figure 1A). The embayment and shelf stations were located close to Mejillones Peninsula; a nearshore area in£uenced by intermittent upwelling events and also one of the most biologically productive areas within the northern part of the HCS o¡ Chile (Daneri et al, 2000).…”

Section: Study Areamentioning

confidence: 99%

“…Water-column integrated PP was estimated from changes in the dissolved oxygen concentrations of light and dark bottle incubations. This procedure is fully described in Daneri et al (2000). Ambient BP was estimated from incorporation rates of L-[ 14 C]-leucine and transformation of the rates of incorporation of leucine into bacterial carbon was done according to Simon & Azam (1989).…”

Section: Field Measurementsmentioning

confidence: 99%

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Bacterial growth response to copepod grazing in aquatic ecosystems

et al. 2007

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The growth rate response of bacterial communities to the potential increase of dissolved organic matter (DOM) produced by the copepod Acartia tonsa was assessed in experiments conducted in three stations representing three contrasting aquatic environments (coastal embayment, shelf and ocean). Bacterial assemblages were inoculated in filtered seawater where A. tonsa had previously grazed. Utilization of DOM over time was evaluated after the addition of bacterial inoculums as the biomass changes in both ‘control’ and ‘copepod’ treatments. In the embayment and ocean a high bacterial growth was observed in the treatments with seawater where copepod were feeding. Additional field measurements of bacterial, primary production and zooplankton biomass support the idea that bacterial communities living in oceanic environments can be efficient to utilize the newly available substrate. Copepods play a key role not only as conveyors of carbon up through the classical food-web, but also generated significant amounts of bacterial substrate in the microbial loop food-web.

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Section: Study Areamentioning

confidence: 99%

Section: Field Measurementsmentioning

confidence: 99%

Bacterial growth response to copepod grazing in aquatic ecosystems

et al. 2007

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“…During austral spring-summer (SeptemberApril), a marked upwelling-favourable period driven by persistent southwesterly winds, ESSWs arrive at the coastal area off central Chile, impinging on one of the widest continental shelves in Chile (Sobarzo and Djurfeldt, 2004;Sobarzo et al, 2007). Throughout the upwelling season high primary production rates (Daneri et al, 2000) occur along with a large downward flux of organic matter, leading to an increase in respiration rates at depth (Montero et al, 2007). These conditions, coupled with the presence of already O 2 -deficient waters, and greater availability of electron donors and acceptors (as a result of the advection of inorganic substrates, local organic matter respiration, and autotrophic redox reactions), create steep gradients for O 2 and other chemicals, with the establishment of hypoxic-anoxic conditions at middle-bottom depths.…”

Section: Introductionmentioning

confidence: 99%

Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystem

2017

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Abstract. The upwelling system off central Chile (36.5 • S) is seasonally subjected to oxygen (O 2 )-deficient waters, with a strong vertical gradient in O 2 (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 N 2 and/or N 2 O, were studied using 15 N-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 15 N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N 2 -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 O 2 fluctuation between 270 and 40 µmol L −1 ) relative to the hypoxic bottom waters (< 20 µmol O 2 L −1 ). Different pathways were responsible for N 2 O 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 N 2 O production. The temporal and vertical variability of δ 15 N-NO − 3 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 substratesPublished by Copernicus Publications on behalf of the European Geosciences Union. 4796A. Galán et al.: Vertical segregation among pathways mediating nitrogen loss are responsible for substantial accumulation of N 2 O, 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.

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“…The width of the continental shelf provides a large surface area for material exchange and benthic-pelagic coupling in subsurface waters that can reach the surface via upwelling processes. The most significant consequences of this coastal upwelling are the fertilization of the photic zone, which sustains high primary production (3-20 g C m −2 d −1 , Daneri et al, 2000;Farías et al, 2004) and the outgassing of N 2 O . In late autumn and early winter, however, Sub-Antarctic Water (SAAW), high in dissolved O 2 and low in nutrients, occupies the uppermost part of the water column and northerly winds predominate, driving strong, efficient vertical mixing of the water column.…”

Section: Introductionmentioning

confidence: 99%

Chemolithoautotrophic production mediating the cycling of the greenhouse gases N2O and CH4 in an upwelling ecosystem

Farı́as¹,

Fernández

Faúndez³

et al. 2009

Biogeosciences

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Abstract. The high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N 2 O and CH 4 cycling associated with aerobic NH + 4 (AAO) and CH 4 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. Chemolithoautotrophy was studied at a time-series station during monthly (2007)(2008)(2009)) and seasonal cruises (January 2008, September 2008, January 2009) and was assessed in terms of the natural C isotopic ratio of particulate organic carbon (δ 13 POC), total and specific (associated with AAO and AMO) dark carbon assimilation (CA), and N 2 O and CH 4 cycling experiments. At the oxycline, δ 13 POC averaged −22.2‰; this was significantly lighter compared to the surface (−19.7‰) and bottom layers (−20.7‰). Total integrated dark CA in the whole water column fluctuated between 19.4 and 2.924 mg C m −2 d −1 , was higher during active upwelling, and contributed 0.7 to 49.7% of the total integrated autotrophic CA (photo plus chemoautotrophy), which ranged from 135 to 7.626 mg C m −2 d −1 , and averaged 20.3% for the whole sampling period. Dark CA was reduced by 27 to 48% after adding a specific AAO inhibitor (ATU) and by 24 to 76% with GC7, a specific archaea inhibitor. This indicates that AAO and AMO microbes (most of them archaea) were performing dark CA through the oxidation of NH

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Primary production and community respiration in the Humboldt Current System off Chile and associated oceanic areas

Cited by 340 publications

References 8 publications

Bacterial growth response to copepod grazing in aquatic ecosystems

Bacterial growth response to copepod grazing in aquatic ecosystems

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

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

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Primary production and community respiration in the Humboldt Current System off Chile and associated oceanic areas

Cited by 340 publications

References 8 publications

Bacterial growth response to copepod grazing in aquatic ecosystems

Bacterial growth response to copepod grazing in aquatic ecosystems

Vertical segregation among pathways mediating nitrogen loss (N&lt;sub&gt;2&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O production) across the oxygen gradient in a coastal upwelling ecosystem

Chemolithoautotrophic production mediating the cycling of the greenhouse gases N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; in an upwelling ecosystem

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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

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