O
Obelia, 306
reproduction, 320
Ocean currents, ecological relations of:
animals, 858–869
plants, 782–792
Oceanic environmental province, 275, 278
animals, 821, 827
plants, 763
Oceanographic vessels, 331–333
Oceans:
areas, 13, 15
boundaries of subdivisions, 12
mean depths, 13, 15
volumes, 13, 15
Oikopleura:
feeding mechanism, 888
systematic position, 312
Okhotsk Sea, 733
Oozes, ecological importance of, 278
Organic constituents in Sediments, 949–951, 983–986
Organic environment, 879
Organic matter:
dissolved, utilization of, 911–913
in sediments, 951
chemical composition, 1010
decrease with depth in deposit, 1016
distribution, 1013–1017
factors determining amounts, 1012–1013
quantity, 1008–1010
sources, 951, 1011
Organic production in the sea, 925–926
commercial, 936–937
cycle of organic matter in the sea, 926
in different regions, 937–944
phytoplankton, 927–934
zooplankton, 934–936
Osmotic pressure, function of salinity and temperature, 66, 67
Osmotic relationships of body fluids:
fresh-water animals, 269
marine animals, 269, 271, 839
Oxidation-reduction potential, 211, 212
importance to accumulation of iron in sediments, 1032
importance to accumulation of manganese in sediments, 1031
in sediments, 995–997
Oxygen;
as an environmental factor, 869–873, 903, 913, 917
in organic matter in sediments, 1011
production and consumption of, as index of organic production, 933–934
production by plants, 767, 777, 933
Oxygen, dissolved:
depletion in interstitial water, 995
depletion in relation to nutrient content, 237
determination, 187
relation to pH distribution, 209
solubility, 189–191
Oxygen consumption, bacterial, as a measure of organic carbon, 250
Oxygen content (see under specific geographic regions):
oceanic deep-water, 746, 748, 752–754
Oxygen distribution (see under specific geographic regions):
conditions for stationary, 161, 162
related to deep-water circulation, 754
Oyashio, 721, 733
meeting Kuroshio Extension, 722
Oysters, reproduction of, 316, 324, 846–847, 857