salinities are as high as 240 parts per thousand. In 
some areas gold concentrations are over 600 times 
the ocean average. (Such discoveries could be 
important in ocean mining.) 
The Nansen bottle, developed in the 1890's, 
still is used to take samples for analyzing seawater 
salinity. Improved instruments are needed to 
sample and measure very deep waters quickly and 
easily. 
The mutual exchange of energy and material 
between ocean and atmosphere at the ocean 
surface depends largely on the chemistry of the 
topmost layer of water. The importance of diffu- 
sion processes near the deep ocean bottom is just 
beginning to be appreciated. In some cases these 
may be studied by such natural tracers as the 
upward diffusion of radium from the sediments 
into the bottom waters. Mixing mechanisms and 
rates between upper, intermediate, and deep ocean 
layers can be studied by artificial radioactive 
tracers as well as natural chemical tracers. 
(5.) Dissolved Gases Gases constitute about 0.25 
per cent by weight of ocean water, their solubility 
decreasing with increasing temperature or salinity. 
The most important and abundant gases in the 
ocean are oxygen, nitrogen, and carbon dioxide. 
Dissolved oxygen is of special interest to undersea 
systems because of its corrosive effect on mate- 
rials. Surface waters are usually saturated with 
dissolved oxygen. 
The amount of dissolved oxygen decreases with 
depth until an oxygen-minimum layer is reached at 
a depth of 2,000 to 3,000 feet. Below this oxygen 
content gradually increases until the bottom is 
reached. Very deep bottom waters frequently have 
an oxygen content approaching that of surface 
water. 
Dissolved oxygen indicates the age of deep cold 
currents entering from surface polar regions. This 
free oxygen is consumed by deep water marine 
life. In waters within the sediments, the oxygen 
content drops radically because of the activity of 
bacteria and bottom dwelling organisms. 
Nitrogen in seawater, occurring as free dissolved 
gas or in such compounds as nitrates, nitrites, and 
ammonia, is essential for living matter and deter- 
mines the growth rate of ocean plants. Sediments 
on the bottom often have only a small amount of 
organic nitrogen, correlating with the concentra- 
tion of organic matter in the sediments and in the 
VI-66 
overlying waters. Carbon dioxide occurs in rela- 
tively large amounts in seawater as carbonates and 
bicarbonates. 
Some ocean areas produce abundant gas bub- 
bles that greatly impede sound waves. In the 
Southern California Bight and in the Red Sea 
virtual curtains of gas continuously are rising 
from the ocean floor. In some areas of high 
productivity or of stagnation (like the Black Sea) 
deep waters produce hydrogen sulfide bubbles and 
contain little or no oxygen. 
(6) Hydrogen Ion Concentration (pH) Values of 
pH, a measure of hydrogen ion concentration 
range from zero (highly acid) through 7.0 (neutral) 
to 14 (highly alkaline). The carbon dioxide con- 
tent mainly determines the pH value of seawater. 
In the deep ocean it generally decreases from 
about 8.3 at the surface to 7.7 at depths between 
1,200 and about 3,000 feet, below which it rises 
to about 7.8. Values as low as 7.5 are found in 
areas of high biological activity because of carbon 
dioxide liberation. Near the shore, the pH may 
drop sharply due to introduction of fresh water 
streams highly charged with decaying vegetation 
and organic matter from the land. Sometimes a 
sharp drop in pH is found immediately above the 
ocean bottom because of carbon dioxide produced 
by such bottom organisms as bacteria. 
(7.) Oxidation-Reduction Potential (Eh) Organic 
matter also has a great effect on the Eh of water. 
(Eh, or oxidation-reduction potential, is a measure 
of the ability to accept or donate electrons, thus a 
measure of corrosiveness.) Seawater approximately 
six feet above sediment sometimes has Eh values 
of zero; below this level and into the sediment, Eh 
may drop as low as -300 millivolts. At the sea 
surface Eh usually is about +300 millivolts. Bot- 
tom topography strongly influences whether zero 
Eh occurs six feet above the bottom or below the 
sediment surface. Thus, site selection surveys for 
bottom habitats and installations are necessary to 
anticipate corrosion problems. 
(8.) Radioactivity Disposal of low-activity solid 
radioactive wastes in specified areas of not less 
than 6,000-foot depth is permitted. These wastes 
are sealed in containers and should cause no 
problems to underwater operations. 
