scholarly journals Ammonium cycling under a strong oxygen gradient associated with the Oxygen Minimum Zone off northern Chile (~23°S)

2005 ◽  
Vol 288 ◽  
pp. 35-43 ◽  
Author(s):  
V Molina ◽  
L Farías ◽  
Y Eissler ◽  
LA Cuevas ◽  
CE Morales ◽  
...  
Keyword(s):  
Oxygen Minimum Zone ◽  
Northern Chile ◽  
Oxygen Gradient ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Zooplankton diel vertical migration and downward C flux into the oxygen minimum zone in the highly productive upwelling region off northern Chile

2020 ◽  
Vol 17 (2) ◽  
pp. 455-473 ◽  
Author(s):  
Pritha Tutasi ◽  
Ruben Escribano
Keyword(s):  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Net Primary Production ◽  
Oxygen Minimum Zone ◽  
Zooplankton Biomass ◽  
Taxonomic Structure ◽  
Northern Chile ◽  
Minimum Zone ◽  
The Impact ◽  
Oxygen Minimum

Abstract. Diel vertical migration (DVM) can enhance the vertical flux of carbon (C), and so contributes to the functioning of the biological pump in the ocean. The magnitude and efficiency of this active transport of C may depend on the size and taxonomic structure of the migrant zooplankton. However, the impact that a variable community structure can have on zooplankton-mediated downward C flux has not been properly addressed. This taxonomic effect may become critically important in highly productive eastern boundary upwelling systems (EBUSs), where high levels of zooplankton biomass are found in the coastal zone and are composed by a diverse community with variable DVM behavior. In these systems, presence of a subsurface oxygen minimum zone (OMZ) can impose an additional constraint to vertical migration and so influence the downward C export. Here, we address these issues based on a vertically stratified zooplankton sampling at three stations off northern Chile (20–30∘ S) during November–December 2015. Automated analysis of zooplankton composition and taxa-structured biomass allowed us to estimate daily migrant biomass by taxa and their amplitude of migration. We found that a higher biomass aggregates above the oxycline, associated with more oxygenated surface waters and this was more evident upon a more intense OMZ. Some taxonomic groups, however, were found closely associated with the OMZ. Most taxa were able to perform DVM in the upwelling zone withstanding severe hypoxia. Also, strong migrants, such as eucalanid copepods and euphausiids, can exhibit a large migration amplitude (∼500 m), remaining either temporarily or permanently within the core of the OMZ and thus contributing to the release of C below the thermocline. Our estimates of DVM-mediated C flux suggested that a mean migrant biomass of ca. 958 mg C m−2 d−1 may contribute with about 71.3 mg C m−2 d−1 to the OMZ system through respiration, mortality and C excretion at depth, accounting for ca. 4 % of the net primary production, and so implies the existence of an efficient mechanism to incorporate freshly produced C into the OMZ. This downward C flux mediated by zooplankton is however spatially variable and mostly dependent on the taxonomic structure due to variable migration amplitude and DVM behavior.

Anammox bacteria and the anaerobic oxidation of ammonium in the oxygen minimum zone off northern Chile

2009 ◽  
Vol 56 (16) ◽  
pp. 1021-1031 ◽  
Author(s):  
Alexander Galán ◽  
Verónica Molina ◽  
Bo Thamdrup ◽  
Dagmar Woebken ◽  
Gaute Lavik ◽  
...  
Keyword(s):  
Oxygen Minimum Zone ◽  
Anammox Bacteria ◽  
Northern Chile ◽  
Anaerobic Oxidation ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Ammonia-Oxidizing β-Proteobacteria from the Oxygen Minimum Zone off Northern Chile

2007 ◽  
Vol 73 (11) ◽  
pp. 3547-3555 ◽  
Author(s):  
Verónica Molina ◽  
Osvaldo Ulloa ◽  
Laura Farías ◽  
Homero Urrutia ◽  
Salvador Ramírez ◽  
...  
Keyword(s):  
16S Rrna ◽  
Waste Treatment ◽  
Treatment Plant ◽  
Oxygen Minimum Zone ◽  
Rrna Gene ◽  
Ammonia Oxidizing Bacteria ◽  
Northern Chile ◽  
Clone Libraries ◽  
Minimum Zone ◽  
Oxygen Minimum

ABSTRACT The composition of ammonia-oxidizing bacteria from the β-Proteobacteria subclass (βAOB) was studied in the surface and upper-oxycline oxic waters (2- to 50-m depth, ∼200 to 44 μM O2) and within the oxygen minimum zone (OMZ) suboxic waters (50- to 400-m depth, ≤10 μM O2) of the eastern South Pacific off northern Chile. This study was carried out through cloning and sequencing of genes coding for 16S rRNA and the ammonia monooxygenase enzyme active subunit (amoA). Sequences affiliated with Nitrosospira-like cluster 1 dominated the 16S rRNA gene clone libraries constructed from both oxic and suboxic waters. Cluster 1 consists exclusively of yet-uncultivated βAOB from marine environments. However, a single clone, out of 224 obtained from the OMZ, was found to belong to Nitrosospira lineage cluster 0. To our knowledge, cluster 0 sequences have been derived from βAOB isolated only from sand, soil, and freshwater environments. Sequences in clone libraries of the amoA gene from the surface and upper oxycline could be grouped in a marine subcluster, also containing no cultured representatives. In contrast, all 74 amoA sequences originating from the OMZ were either closely affiliated with cultured Nitrosospira spp. from clusters 0 and 2 or with other yet-uncultured βAOB from soil and an aerated-anoxic Orbal process waste treatment plant. Our results reveal the presence of Nitrosospira-like βAOB in both oxic and suboxic waters associated with the OMZ but with a clear community shift at the functional level (amoA) along the strong oxygen gradient.

scholarly journals Underwater Glider Observations in the Oxygen Minimum Zone off Central Chile

2016 ◽  
Vol 97 (10) ◽  
pp. 1783-1789 ◽  
Author(s):  
Oscar Pizarro ◽  
Nadin Ramírez ◽  
Manuel I. Castillo ◽  
Ursula Cifuentes ◽  
Winston Rojas ◽  
...  
Keyword(s):  
Low Frequency ◽  
Oxygen Minimum Zone ◽  
Northern Chile ◽  
Underwater Glider ◽  
Central Chile ◽  
Southern Patagonia ◽  
Minimum Zone ◽  
Frequency Changes ◽  
Oxygen Minimum ◽  
Future Plans

Abstract Gliders have become an efficient and reliable oceanographic platform for measuring physical and biogeochemical properties of the seawater, and the global glider fleet is rapidly expanding. In Chile, glider observations have been carried out in very different oceanographic environments, from the mild upwelling region of subtropical northern Chile to the channels of southern Patagonia. Herein, we briefly present observations and results obtained in the oxygen minimum zone off Concepcion (∼36°30′S). Many new features have been observed in this region thanks to the relatively high resolution of the glider measurements. Future plans for the glider program include an oceanic time series off central Chile that will contribute to the regional observing system of the ocean and allow evaluations of low-frequency changes like those associated with El Niño and La Niña events.

scholarly journals Zooplankton diel vertical migration and downward C into the Oxygen Minimum Zone in the highly productive upwelling region off Northern Chile

2019 ◽  
Author(s):  
Pritha Tutasi ◽  
Ruben Escribano
Keyword(s):  
Community Structure ◽  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Oxygen Minimum Zone ◽  
Taxonomic Structure ◽  
Northern Chile ◽  
Daily Rate ◽  
Minimum Zone ◽  
The Impact ◽  
Oxygen Minimum

Abstract. The daily vertical movement of zooplankton, known as diel vertical migration (DVM), can enhance the vertical flux of carbon (C) and so contributing to the functioning of the biological pump. The magnitude and efficiency of this active transport of C may depend on the size and taxonomic structure of the migrant zooplankton. However, the impact that a variable community structure can have on zooplankton-mediated downward C has not been properly addressed. This taxonomic effect may become critically important in highly productive eastern boundary upwelling systems (EBUS), where zooplankton biomass becomes aggregated in the coastal zone, but comprised by a highly variable community structure (size-composition). In these systems, presence of a subsurface oxygen minimum zone (OMZ) can impose an additional constraint to vertical migration and so influencing the downward C export. Here, we address these issues based on a high-resolution zooplankton sampling at three stations off northern Chile (20°S−30°S) during November 2015. Automated analysis of zooplankton composition and taxa-structured biomass allowed us to estimate daily migrant biomass by taxa, amplitude of migration and daily rate of migration, defined as the daily exchange of biomass between the upper mixed layer and below the thermocline. We found that high biomass aggregates above the oxycline, associated with more oxygenated surface waters and this condition was more evident upon a more intense OMZ. Some taxa however, were found closely associated with the OMZ. We found that most taxa were able to perform DVM in the upwelling zone withstanding severe hypoxia. Even, several strong migrants, such as copepods Eucalanidae and Euphausiids, can exhibit a large migration amplitude (~500 m), remaining either temporarily or permanently during the day or night condition within the core of the OMZ and so contributing to the release of C below the thermocline. Our estimates of DVM-mediated C flux showed that migrant biomass (5099 ± 2701 mg C m−2d−1) may contribute with about 678 ± 465 mg C m−2d−1 to the OMZ system through respiration, mortality, and production of fecal pellets, implying the existence of a very efficient mechanism to incorporate freshly produced C into the OMZ. This downward C by zooplankton is however strongly depending on taxonomic structure due to variable migration amplitude and behavior affecting the daily rate of diel vertical migration.

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