Nitrogen sediment fluxes in an upwelling system off central Chile (Concepción Bay and adjacent shelf) during the 1997-1998 El Niño

Muñoz, Práxedes; Salamanca, Marco; Neira, Carlos; Sellanes, Javier

doi:10.4067/s0716-078x2004000200009

Cited by 8 publications

(8 citation statements)

References 30 publications

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“…Whereas during normal years ammonium production is higherduring the upwelling-favourable, oxygen-depleted spring and summer period, carbon fluxes to the sediment decreased to low normal autumn/winter levels during the entire 1997-1998 EN (Gutiérrez, 2000;Grunewald et al, 2002;Graco et al, 2005). Ammonium production and NH + 4 fluxes during this period were lower than normal (Muñoz et al, 2004), indicating a tight pelagobenthic coupling during EN (Graco et al, 2005). Thioploca biomass was very low, and the filaments were withdrawn deeper into the sediment as a response to increased temperatures, oxygenation, reduced nitrate and lack of H 2 S (Schulz et al, 1999b).…”

Section: Oxygen Minimum Zone (Omz)mentioning

confidence: 89%

“…In addition, the collapse of the pelagic food web due to the lack of nutrients in the mixed surface layer leads to reduced POM input to the seafloor (Muñoz et al, 2004;. Off Concepción, reduced TOC, shifts in the sediment biochemical components, and a decrease in the "freshness" and quality of organic matter (sum of carbon, protein, carbohydrates, and lipids) were observed during EN 1997-1998 (Gutiérrez et al, 2000;Neira et al, 2001a;Sellanes and Neira, personal communication), together with increased dissolved oxygen in the bottom water (Gutiérrez et al, 2000).…”

Section: Oxygen Minimum Zone (Omz)mentioning

confidence: 99%

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El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

Gallardo²,

et al. 2006

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Abstract. To a certain degree, Eastern Boundary Current (EBC) ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O 2 exchange is restricted, it creates oxygen minimum zones (OMZs) at shelf and upper slope (Humboldt and Benguela Current) or slope depths (California Current). These hypoxic zones host a specifically adapted, small macro-and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H 2 S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between <100 and about 600 m, with decreasing thickness in a poleward direction. The OMZ merges into better oxygenated zones towards the deep sea, where large cold-water mega-and macrofauna occupy a dominant role as in the nearshore strip. The Benguela Current OMZ has a similar upper limit but remains shallower. It also hosts giant sulphur bacteria but little is known about the benthic fauna. However, sulphur eruptions and intense hypoxia might preclude the coexistence of significant mega-und macrobenthos. Conversely, off North America the upper limit of the OMZ is considerably deeper (e.g., 500-

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Section: Oxygen Minimum Zone (Omz)mentioning

confidence: 89%

Section: Oxygen Minimum Zone (Omz)mentioning

confidence: 99%

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

Gallardo²,

et al. 2006

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“…Methodological details concerning Thioploca , and macrofauna, and sediment biogeochemical processes are reported elsewhere (see Gutiérrez et al. 2000; Muñoz et al. 2004).…”

Section: Study Areamentioning

confidence: 99%

“…Hydrographic conditions during the study period are reviewed in detail elsewhere (Gutiérrez et al. 2000; Sellanes 2002; Muñoz et al. 2004), but are summarized briefly here.…”

Section: Study Areamentioning

confidence: 99%

ENSO as a natural experiment to understand environmental control of meiofaunal community structure

Sellanes

Neira

2006

Marine Ecology

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ProblemThe mechanisms controlling abundance and biomass of meiofauna in marine sub-littoral systems are still poorly known. The structure of a meiobenthic community is the product of an intricate network of abiotic factors, which interact with biotic factors like food availability, intra-and interspecific interactions and predation (Giere 1993). In spite of this inherent complexity, the temporal variation of meiobenthic communities in coastal systems might be quite predictable in relation to seasonal variation of primary production (i.e. food availability) and environmental conditions (e.g. temperature and oxygen) AbstractThe sediments of the Bay of Concepció n and the adjacent shelf underlie one of the most productive upwelling areas in the SE Pacific margin. Reports on factors controlling meiofaunal community structure in these kinds of organic-rich and oxygen-deficient habitats are scarce in the literature. In this study, five sites along a transect from the mid-Bay of Concepció n (27 m) to the outer shelf (120 m) were studied on fives dates (May, August, November 1997, and March and May 1998) in order to assess the dynamic relationships between sedimentary organic matter and metazoan meiofauna. The sampling period coincided with the 1997-1998 El Niño event. Sediment parameters investigated were the redox potential discontinuity depth, photosynthetic pigment concentrations (chlorophyll a and phaeopigments), organic carbon, nitrogen, total lipids, carbohydrates, and proteins. In general, lowest values of meiofauna abundance and biomass were found within the naturally eutrophic Bay of Concepció n and towards the shelf break, while maximum values occurred at intermediate depths. During the whole period, the meiofaunal abundance was negatively correlated with the concentration of most of the biochemical components of organic matter, as well as with the sediment phaeopigment content. However, positive correlations were found with chlorophyll a derived indices and with bottom-water oxygen content. Most of the sediment parameters displayed a seasonal cycle, but towards the beginning of 1998, an effect of the 1997-1998 El Niño was evident. Typical austral-summer (i.e. oxygen-deficient) conditions did not develop, and sedimentary parameters reflected a decreased input of phytodetritus. Along the transect, the magnitude of this effect on meiofauna varied among sites. An overall positive response, in terms of meiofaunal abundance was observed, probably due to the amelioration of low oxygen conditions in the sediment.

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“…Our study area, Station 18, is 20 km off the coast of central Chile ∼36 • S, over the continental shelf (40 km East to West in extension), where a combination of meteorological and oceanographic factors allows the generation of seasonal coastal upwelling, with low O 2 conditions, even anoxia, at mid depths (40-93 m bottom) (Muñoz et al, 2004;Sobarzo, 2004;Fuenzalida et al, 2009;Murillo et al, 2014). At this station, high rates of chemosynthetic production have been observed during the austral spring-summer periods (Farías et al, 2009), however, the organisms responsible for this production have not been identified.…”

Section: Introductionmentioning

confidence: 99%

Diversity and Transcriptional Levels of RuBisCO Form II of Sulfur-Oxidizing γ-Proteobacteria in Coastal-Upwelling Waters with Seasonal Anoxia

et al. 2017

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Seasonal wind-driven upwelling, high primary production in surface waters, and oxygen deficiency in subsurface waters characterize the coastal ecosystem of the subtropical eastern South Pacific (ESP), and shape the nature and dynamics of the microbial community structure and function. We investigated the diversity, abundance, and transcriptional levels of the gene encoding the large subunit form II of the RuBisCO enzyme (cbbM) in the pelagic microbial community at a continental-shelf site off central Chile over 2 years. We focused on cbbM genes affiliated with the sulfur-oxidizing γ-proteobacteria cluster, whose members are known to dominate in oxygen-deficient marine environments and are highly abundant in the study area. Phylogenetic analysis of cbbM sequences suggests the presence of a novel group of chemolithoautotrophs, closely related to the SUP05/ARCTIC96BD-19 clade. Through (RT)-qPCR, we studied the cbbM gene abundance and transcript dynamics over an annual cycle, finding a significantly higher number of cbbM copies per unit volume in months of active upwelling and at depths in which oxygen was scarce or absent. The same temporal pattern was observed at the transcriptional level. We also analyzed the relative expression of key genes for carbon, nitrogen and sulfur cycling in six metatranscriptomic datasets, for two characteristic periods within the annual cycle: the anoxic upwelling and the suboxic downwelling. Our results indicate that coastal waters of the subtropical ESP contain transcriptionally active populations of carbon fixing pelagic bacteria, whose dynamics is controlled, in large part, by fluctuations in oxygen levels. They also suggest that chemolithoautotrophic processes coupled to the sulfur and nitrogen cycles become increasingly important for the carbon economy of marine coastal waters as oxygen concentrations decline.

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Nitrogen sediment fluxes in an upwelling system off central Chile (Concepción Bay and adjacent shelf) during the 1997-1998 El Niño

Cited by 8 publications

References 30 publications

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

ENSO as a natural experiment to understand environmental control of meiofaunal community structure

Diversity and Transcriptional Levels of RuBisCO Form II of Sulfur-Oxidizing γ-Proteobacteria in Coastal-Upwelling Waters with Seasonal Anoxia

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