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oxygen minimum layer
ovoviviparous mechanism of reproduction in which the offspring develop in
eggs inside the female body, and leaves the female animal as juveniles.
oxygen (0) the most abundant element in the earth's crust (46.4 %), followed by
silicon (28.2 %) and aluminum (8.3 %). After nitrogen the most abundant gas
(0 2 ) in the atmosphere of the earth (20.95 %). Physical constants: mol. weight
31.9988; density 1.429 g dm-3(gas 0 °C), 1.149 kg dm-3(liq. -183°C); melting
point -218.4 °C, boiling point -182.962 0c. Ozone (0 3 ) is formed by dis- and
reassociation of oxygen with UV light « 240 nm) at heights of 30 to 50 km
in concentrations of 20 ppm. The ozone layer effectively shields the lower
parts of the atmosphere from the destructive effects of short wave UV light
on living organisms. Space research has confirmed older spectroscopic evidence of very low free oxygen concentrations in the atmosphere of other
planets in the solar system. Under purely physical conditions low steady-state
oxygen concentrations are formed by photochemical dissociation of water
vapor and geological evidence points to an almost anoxic primordial atmosphere of the earth. The evolution of life allowed the gradual formation of an
oxic atmosphere and a hundredfold increase of oxygen pressure to the present level possibly took place in the last few hundred million years with the
development of plants capable of photosynthesis. The hydrosphere contains dissolved oxygen in about 1 % of the quantity present in the atmosphere.
oxygen demand the consumption of oxygen in incubated samples at a certain
constant temperature during a prescribed timespan. BOD (-tbiological oxygen
demand) values are frequently used as water quality indicators in the analysis
of natural waters. -tchemical oxygen demand (COD).
oxygenic photosynthesis -tphotosynthesis.
oxygen isotope ratios on earth the chemical element 0 consists mainly of isotope
16 0 (± 99.758 %), with minor amounts of isotopes 17 0 (± 0.038 %) and 180
(± 0.204 %). The H 2 0 in seawater contains 0 in roughly the same isotopic
proportions. Minor variations in the isotopic ratio 18 0/ 16 0 can largely be
ascribed to temperature effects. Another cause of the different ratios is the
slight difference in vapor pressure, causing higher 18 0/ 16 0 ratios in surface
waters with high evaporation, and lower ratios in deeper water. -tisotopes.
oxygen minimum layer water layer in the oceans below the euphotic zone, where, due
to settling of organic detritus and the presence of vertically migrating zooplankton during the day, bacterial oxygen consumption and respiration are
relatively high.
oxygen minimum layer
ovoviviparous mechanism of reproduction in which the offspring develop in
eggs inside the female body, and leaves the female animal as juveniles.
oxygen (0) the most abundant element in the earth's crust (46.4 %), followed by
silicon (28.2 %) and aluminum (8.3 %). After nitrogen the most abundant gas
(0 2 ) in the atmosphere of the earth (20.95 %). Physical constants: mol. weight
31.9988; density 1.429 g dm-3(gas 0 °C), 1.149 kg dm-3(liq. -183°C); melting
point -218.4 °C, boiling point -182.962 0c. Ozone (0 3 ) is formed by dis- and
reassociation of oxygen with UV light « 240 nm) at heights of 30 to 50 km
in concentrations of 20 ppm. The ozone layer effectively shields the lower
parts of the atmosphere from the destructive effects of short wave UV light
on living organisms. Space research has confirmed older spectroscopic evidence of very low free oxygen concentrations in the atmosphere of other
planets in the solar system. Under purely physical conditions low steady-state
oxygen concentrations are formed by photochemical dissociation of water
vapor and geological evidence points to an almost anoxic primordial atmosphere of the earth. The evolution of life allowed the gradual formation of an
oxic atmosphere and a hundredfold increase of oxygen pressure to the present level possibly took place in the last few hundred million years with the
development of plants capable of photosynthesis. The hydrosphere contains dissolved oxygen in about 1 % of the quantity present in the atmosphere.
oxygen demand the consumption of oxygen in incubated samples at a certain
constant temperature during a prescribed timespan. BOD (-tbiological oxygen
demand) values are frequently used as water quality indicators in the analysis
of natural waters. -tchemical oxygen demand (COD).
oxygenic photosynthesis -tphotosynthesis.
oxygen isotope ratios on earth the chemical element 0 consists mainly of isotope
16 0 (± 99.758 %), with minor amounts of isotopes 17 0 (± 0.038 %) and 180
(± 0.204 %). The H 2 0 in seawater contains 0 in roughly the same isotopic
proportions. Minor variations in the isotopic ratio 18 0/ 16 0 can largely be
ascribed to temperature effects. Another cause of the different ratios is the
slight difference in vapor pressure, causing higher 18 0/ 16 0 ratios in surface
waters with high evaporation, and lower ratios in deeper water. -tisotopes.
oxygen minimum layer water layer in the oceans below the euphotic zone, where, due
to settling of organic detritus and the presence of vertically migrating zooplankton during the day, bacterial oxygen consumption and respiration are
relatively high.