TY - JOUR
T1 - Oxygen distribution and aerobic respiration in the north and south eastern tropical Pacific oxygen minimum zones
AU - Tiano, Laura
AU - Garcia-Robledo, Emilio
AU - Dalsgaard, Tage
AU - Devol, Allan H.
AU - Ward, Bettie
AU - Ulloa, Osvaldo
AU - Canfield, Donald E.
AU - Peter Revsbech, Niels
N1 - Publisher Copyright:
© 2014 The Authors.
PY - 2014
Y1 - 2014
N2 - Highly sensitive STOX O2 sensors were used for determination of in situ O2 distribution in the eastern tropical north and south Pacific oxygen minimum zones (ETN/SP OMZs), as well as for laboratory determination of O2 uptake rates of water masses at various depths within these OMZs. Oxygen was generally below the detection limit (few nmolL-1) in the core of both OMZs, suggesting the presence of vast volumes of functionally anoxic waters in the eastern Pacific Ocean. Oxygen was often not detectable in the deep secondary chlorophyll maximum found at some locations, but other secondary maxima contained up to ~0.4μmolL-1. Directly measured respiration rates were high in surface and subsurface oxic layers of the coastal waters, reaching values up to 85nmolL-1 O2h-1. Substantially lower values were found at the depths of the upper oxycline, where values varied from 2 to 33nmolL-1 O2h-1. Where secondary chlorophyll maxima were found the rates were higher than in the oxic water just above. Incubation times longer than 20h, in the all-glass containers, resulted in highly increased respiration rates. Addition of amino acids to the water from the upper oxycline did not lead to a significant initial rise in respiration rate within the first 20h, indicating that the measurement of respiration rates in oligotrophic Ocean water may not be severely affected by low levels of organic contamination during sampling. Our measurements indicate that aerobic metabolism proceeds efficiently at extremely low oxygen concentrations with apparent half-saturation concentrations (Km values) ranging from about 10 to about 200nmolL-1.
AB - Highly sensitive STOX O2 sensors were used for determination of in situ O2 distribution in the eastern tropical north and south Pacific oxygen minimum zones (ETN/SP OMZs), as well as for laboratory determination of O2 uptake rates of water masses at various depths within these OMZs. Oxygen was generally below the detection limit (few nmolL-1) in the core of both OMZs, suggesting the presence of vast volumes of functionally anoxic waters in the eastern Pacific Ocean. Oxygen was often not detectable in the deep secondary chlorophyll maximum found at some locations, but other secondary maxima contained up to ~0.4μmolL-1. Directly measured respiration rates were high in surface and subsurface oxic layers of the coastal waters, reaching values up to 85nmolL-1 O2h-1. Substantially lower values were found at the depths of the upper oxycline, where values varied from 2 to 33nmolL-1 O2h-1. Where secondary chlorophyll maxima were found the rates were higher than in the oxic water just above. Incubation times longer than 20h, in the all-glass containers, resulted in highly increased respiration rates. Addition of amino acids to the water from the upper oxycline did not lead to a significant initial rise in respiration rate within the first 20h, indicating that the measurement of respiration rates in oligotrophic Ocean water may not be severely affected by low levels of organic contamination during sampling. Our measurements indicate that aerobic metabolism proceeds efficiently at extremely low oxygen concentrations with apparent half-saturation concentrations (Km values) ranging from about 10 to about 200nmolL-1.
KW - Community respiration
KW - Eastern tropical Pacific
KW - Oxygen
KW - Oxygen minimum zone
KW - STOX sensor
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U2 - 10.1016/j.dsr.2014.10.001
DO - 10.1016/j.dsr.2014.10.001
M3 - Article
AN - SCOPUS:84934902894
SN - 0967-0637
VL - 94
SP - 173
EP - 183
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
ER -