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.

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.

Temporally invariable bacterial community structure in the Arabian Sea oxygen minimum zone

2014 ◽  
Vol 73 (1) ◽  
pp. 51-67 ◽  
Author(s):  
A Jain ◽  
M Bandekar ◽  
J Gomes ◽  
D Shenoy ◽  
RM Meena ◽  
...  
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Bacterial Community Structure ◽  
Arabian Sea ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Oxygen Minimum

Nematode community structure along a central Chile margin transect influenced by the oxygen minimum zone

2013 ◽  
Vol 78 ◽  
pp. 1-15 ◽  
Author(s):  
Carlos Neira ◽  
Ian King ◽  
Guillermo Mendoza ◽  
Javier Sellanes ◽  
Paul De Ley ◽  
...  
Keyword(s):  
Community Structure ◽  
Oxygen Minimum Zone ◽  
Nematode Community ◽  
Central Chile ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Macrofaunal colonization across the Indian Margin oxygen minimum zone

2013 ◽  
Vol 10 (6) ◽  
pp. 9451-9492 ◽  
Author(s):  
L. A. Levin ◽  
A. L. McGregor ◽  
G. F. Mendoza ◽  
C. Woulds ◽  
P. Cross ◽  
...  
Keyword(s):  
Community Structure ◽  
Oxygen Concentration ◽  
Sediment Cores ◽  
Oxygen Minimum Zone ◽  
Continental Margins ◽  
Benthic Community Structure ◽  
Oxygen Minimum Zones ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. There is a growing need to understand the ability of bathyal assemblages to recover from disturbance and oxygen stress, as human activities and expanding oxygen minimum zones increasingly affect deep continental margins. The effects of a pronounced oxygen minimum zone (OMZ) on slope benthic community structure have been studied in both the Western and Eastern Arabian Sea; however, little is known about the dynamics or resilience of these benthic populations. To examine the influence of oxygen and phytodetritus on short-term settlement patterns we conducted colonization experiments along two cross-OMZ transects on the West Indian continental margin. Four colonization trays were deployed at each depth for 4 days at 542 and 802 m (16°58′ N) and for 9 days at 817 m and 1147 m (17°31′ N). Oxygen concentrations ranged from 0.9 μM (0.02 mL L−1) at 542 m to 22 μM (0.5 mL L−1) at 1147 m. All trays contained local defaunated sediments; half of the trays at each depth also contained 13C/15N-labeled phytodetritus mixed into the sediments. Sediment cores were collected between 535 m and 1140 m for analysis of background (source) macrofaunal (> 300 μm) densities and composition. Background densities ranged from 0 ind. m−2 (at 535–542 m) to 7400 ind. m−2, with maximum values on both transects at 700–800 m. Macrofaunal colonizer densities ranged from 0 ind. m−2 at 542 m, where oxygen was lowest, to average values of 142 ind. m−2 at 800 m, and 3074 ind. m−2 at 1147 m, where oxygen concentration was highest. These were equal to 4.3% and 151% of the ambient background community at 800 m and 1147 m, respectively. Community structure of settlers showed no response to the presence of phytodetritus. Increasing depth and oxygen concentration, however, significantly influenced the community composition and abundance of colonizing macrofauna. Polychaetes constituted 92.4% of the total colonizers, followed by crustaceans (4.2%), mollusks (2.5%), and echinoderms (0.8%). The majority of colonizers were found at 1147m; 88.5% of these were Capitella sp., although they were rare in the background community. Colonists at 800 and 1147 m also included ampharetid, spionid, syllid, lumbrinerid, cirratulid, cossurid and sabellid polychaetes. Consumption of δ13C/ δ15N-labeled phytodetritus was observed for macrofaunal foraminifera (too large to be colonizers) at the 542 and 802/817 m sites, and by metazoan macrofauna mainly at the deepest, better oxygenated site. Calcareous foraminifera (Uvigerina, Hoeglundina sp.), capitellid polychaetes and cumaceans were among the major consumers. These preliminary experiments suggest that bottom-water oxygen concentrations may strongly influence ecosystem services on continental margins, as reflected in rates of colonization by benthos and colonizer processing of carbon following disturbance.

scholarly journals Macrofaunal community structure in the western Indian continental margin including the oxygen minimum zone

2010 ◽  
Vol 31 (1) ◽  
pp. 148-166 ◽  
Author(s):  
Baban S. Ingole ◽  
Sabyasachi Sautya ◽  
Sanitha Sivadas ◽  
Ravail Singh ◽  
Mandar Nanajkar
Keyword(s):  
Community Structure ◽  
Continental Margin ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Macrofaunal Community ◽  
Oxygen Minimum

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
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