Tracking oxygen depletion in the Arabian Sea

2021 ◽  
Author(s):  
Rieko Kawabata
Keyword(s):  
Arabian Sea ◽  
Oxygen Depletion

scholarly journals Uptake of phytodetritus by benthic foraminifera under oxygen depletion at the Indian Margin (Arabian Sea)

2013 ◽  
Vol 10 (9) ◽  
pp. 15305-15335 ◽  
Author(s):  
A. J. Enge ◽  
U. Witte ◽  
M. Kucera ◽  
P. Heinz
Keyword(s):  
Continental Slope ◽  
Benthic Foraminifera ◽  
Arabian Sea ◽  
Isotope Labeling ◽  
Oxygen Depletion ◽  
Food Delivery ◽  
Short Term ◽  
Important Species ◽  
Minimum Zone ◽  
Species Specific

Abstract. Benthic foraminifera in sediments on the Indian margin of the Arabian Sea where the oxygen minimum zone (OMZ) impinges on the continental slope are exposed to particularly severe levels of oxygen depletion. Food supply for the benthic community is high but delivered in distinct pulses during upwelling and water mixing events associated with summer and winter monsoon periods. In order to investigate the response by benthic foraminifera to such pulsed food delivery under oxygen concentrations of less than 0.1 mL L−1 (4.5 μmol L−1), an in situ isotope labeling experiment (13C, 15N) was performed at the western continental slope of India at 540 m water depth (OMZ core region). The assemblage of living foraminifera (>125 μm) in the uppermost centimeter at this depth is characterized by an unexpectedly high population density of 3982 ind. 10 cm−2 and a strong dominance by few calcareous species. For the experiment, we concentrated on the nine most abundant taxa, which constitute 93% of the entire foraminifera population at 0–1 cm sediment depth. Increased concentrations of 13C and 15N in the cytoplasm indicate that all investigated taxa took up the labeled phytodetritus during the 4 day experimental phase. In total, these nine species had assimilated 113.8 mg C m−2 (17.5% of the total added carbon). The uptake of nitrogen by the three most abundant taxa (Bolivina aff. B. dilatata, Cassidulina sp., Bulimina gibba) was 2.7 mg N m−2 (2% of the total added nitrogen) and showed the successful application of 15N as tracer in foraminiferal studies. The short-term response to the offered phytodetritus varied largely among foraminiferal species with Uvigerina schwageri being by far the most important species in short-term processing whereas the most abundant taxa Bolivina aff. B. dilatata and Cassidulina sp. showed comparably low uptake of the offered food. We suggest that the observed species-specific differences are related to individual biomass of species and to specific feeding preferences. The high numbers of living foraminifera and their rapid response to deposited fresh phytodetritus demonstrate the importance of foraminifera in short-term carbon cycling under oxygen-depleted conditions. We propose that foraminifera at the studied site benefit from unique adaptations in their metabolisms to nearly anoxic conditions as well as from the exclusion of macrofauna and the resulting relaxation of competition for food and low predation pressure.

scholarly journals Impact of climate induced hypoxia on calcifying biota in the Arabian Sea : An evaluation from the micropaleontological records of the Indian margin

MAUSAM ◽  
2021 ◽  
Vol 62 (4) ◽  
pp. 647-652
Author(s):  
A.D. SINGH ◽  
S. DAS ◽  
K. VERMA
Keyword(s):  
Arabian Sea ◽  
Global Climate ◽  
Marine Ecosystem ◽  
Oxygen Depletion ◽  
Marine Biota ◽  
Low Oxygen ◽  
Hypoxic Environment ◽  
Minimum Zone ◽  
Abundance And Diversity ◽  
Poor Ventilation

High biological productivity combined with the poor ventilation produces severe oxygen depletion (hypoxia) in upper intermediate waters of the Arabian Sea. The naturally developed Arabian Sea oxygen minimum zone (OMZ) is one of the most pronounced low oxygen ocean environments known today. The OMZ impinges the Indian margin where oxygen concentration reaches values less than 0.05 ml/l leading denitrification. In recent studies, it has been observed that the OMZ strength has varied considerably in the past, in tune with the global climate change. But the effect of changes in natural mid-water hypoxic environment on the marine biota particularly of the eastern Arabian Sea is unknown. Here, we analyzed 30,000 yr record of temporal changes in two major groups of marine calcifying microfauna pteropods secreting aragonitic shells and foraminifera secreting calcitic shells in terms of abundance and diversity variations. This study will provide an insight into our understanding of potential impact of rising atmospheric CO2 on marine ecosystem.

scholarly journals Microbial diversity of the Arabian Sea in the Oxygen minimum zones by metagenomics approach

2019 ◽  
Author(s):  
Mandar S. Paingankar ◽  
Kedar Ahire ◽  
Pawan Mishra ◽  
Shriram Rajpathak ◽  
Deepti D. Deobagkar
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Arabian Sea ◽  
Community Dynamics ◽  
Oxygen Depletion ◽  
Oxygen Minimum Zones ◽  
Microbial Community Dynamics ◽  
Nitrate Reducers ◽  
Insight Into ◽  
Oxygen Minimum

ABSTRACTLarge oxygen depleted areas known as oxygen minimum zones (OMZ) have been observed in the Arabian Sea and recent reports indicate that these areas are expanding at an alarming rate. In marine waters, oxygen depletion may also be related to global warming and the temperature rise, acidification and deoxygenation can lead to major consequences wherein the plants, fish and other biota will struggle to survive in the ecosystem.The current study has identified the microbial community structure using NGS based metagenomics analysis in the water samples collected at different depth from the oxygen depleted and non-OMZ areas of Arabian Sea. Environmental variables such as depth, site of collection and oxygen concentration appeared to influence the species richness and evenness among microbial communities in these locations. Our observations clearly indicate that population dynamics of microbes consisting of nitrate reducers accompanied by sulphate reducers and sulphur oxidizers participate in the interconnected geochemical cycles of the OMZ areas. In addition to providing baseline data related to the diversity and microbial community dynamics in oxygen-depleted water in the OMZ; such analysis can provide insight into processes regulating productivity and ecological community structure of the ocean.

scholarly journals Uptake of phytodetritus by benthic foraminifera under oxygen depletion at the Indian margin (Arabian Sea)

2014 ◽  
Vol 11 (7) ◽  
pp. 2017-2026 ◽  
Author(s):  
A. J. Enge ◽  
U. Witte ◽  
M. Kucera ◽  
P. Heinz
Keyword(s):  
Continental Slope ◽  
Benthic Foraminifera ◽  
Arabian Sea ◽  
Isotope Labeling ◽  
Oxygen Depletion ◽  
Food Delivery ◽  
Core Region ◽  
Short Term ◽  
Important Species ◽  
Species Specific

Abstract. Benthic foraminifera in sediments on the Indian margin of the Arabian Sea, where the oxygen minimum zone (OMZ) impinges on the continental slope, are exposed to particularly severe levels of oxygen depletion. Food supply for the benthic community is high but delivered in distinct pulses during upwelling and water mixing events associated with summer and winter monsoon periods. In order to investigate the response by benthic foraminifera to such pulsed food delivery under oxygen concentrations of less than 0.1 mL L−1 (4.5 μmol L−1), an in situ isotope labeling experiment (13C, 15N) was performed on the western continental slope of India at 540 m water depth (OMZ core region). The assemblage of living foraminifera (>125 μm) in the uppermost centimeter at this depth is characterized by an unexpectedly high population density of 3982 individuals 10 cm−2 and a strong dominance by few calcareous species. For the experiment, we concentrated on the nine most abundant taxa, which constitute 93% of the entire foraminiferal population at 0–1 cm sediment depth. Increased concentrations of 13C and 15N in the cytoplasm indicate that all investigated taxa took up labeled phytodetritus during the 4 day experimental phase. In total, these nine species had assimilated 113.8 mg C m−2 (17.5% of the total added carbon). Uptake of nitrogen by the three most abundant taxa (Bolivina aff. B. dilatata, Cassidulina sp., Bulimina gibba) was 2.7 mg N m−2 (2% of the total added nitrogen). The response to the offered phytodetritus varied largely among foraminiferal species with Uvigerina schwageri being by far the most important species in short-term processing, whereas the most abundant taxa Bolivina aff. B. dilatata and Cassidulina sp. showed comparably low uptake of the offered food. We suggest the observed species-specific differences are related to species biomass and specific feeding preferences. In summary, the experiment in the OMZ core region shows rapid processing of fresh phytodetritus by foraminifera under almost anoxic conditions. The uptake of large amounts of organic matter by few species within four days suggests that foraminifera may play an important role in short-term carbon cycling in the OMZ core region on the Indian margin.

Low-temperature annealing of YBa2Cu3O7-x

1992 ◽  
Vol 50 (1) ◽  
pp. 88-89
Author(s):  
R.L. Sabatini ◽  
Yimei Zhu ◽  
Masaki Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Oxygen Diffusion ◽  
Diffusion Rate ◽  
Oxygen Depletion ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Microstructural Effects ◽  
Oxygen Diffusion Rate

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.

Protein content of 5 algae from Persian gulf and Arabian sea

Planta Medica ◽  
2010 ◽  
Vol 76 (12) ◽  
Author(s):  
N Ebrahimi ◽  
M Moein ◽  
S Moein
Keyword(s):  
Protein Content ◽  
Persian Gulf ◽  
Arabian Sea

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

Analysis and Modeling of Ambient Noise in Shallow Water of Arabian Sea

2012 ◽  
Vol 2 (6) ◽  
pp. 271-272
Author(s):  
Sudhir Pal Singh Rawat ◽  
◽  
Dr. Arnab Das ◽  
Dr. H.G.Virani Dr. H.G.Virani ◽  
Dr. Y.K.Somayajulu Dr. Y.K.Somayajulu
Keyword(s):  
Shallow Water ◽  
Arabian Sea ◽  
Ambient Noise

Fucoxanthin Content and Chemical Composition in Brown Seaweed, Nizamuddinia zanardinii (Phaeophyta) Collected from Mirbat, Southern Oman (The Arabian Sea)

2017 ◽  
Vol 19 (3) ◽  
pp. 259-270
Author(s):  
M. Chesalin ◽  
S. Al-Ghassani ◽  
V. I. Ryabushko ◽  
N. I. Bobko ◽  
E. Gureeva ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Arabian Sea ◽  
Brown Seaweed ◽  
Nizamuddinia Zanardinii
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