SEA WATER
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it is these bacteria that are responsible for the production
of the =sulphuretted hydrogen.
Such a condition is unique
in salt water.
Even in the very greatest depths in the
open ocean life is still possible.
For the absence of‘oxygen ,
is a result of stagnant conditions, and in the open ocean
'
such cannotbe the case owing to the continual circulation
of water in the great ocean-currents. .
While We breathe in oxygen
send ont into the air
.
again the product resulting from its utilization, Carbon
dioxide.
All animals are therefore constantly giving this
gas out—. to the surrounding water and it is everywhere
present.
At the same time it is used up again in the upper
layers by the oating plants which build up sugars out of
it under the action of sùn1ight, ”restoring oxygenonce more
to the water.
_
.
.
_
,
PHYSICAL
PROPERTIES
Water being the medium in which all marine animals
’
live, there are certain of its physical properties which
inuence the animals themselves or tend to modify the_
environment under which they live. ‘ On land, for instance,
the temperature of the air or the barometric pressure may
induce profound changesin our bodies.
-
'
The” surface temperature of the sea changes markedly
”from place to place.
In the tr0pics it is hot compared,
_
'
with the polar regi0ns; 'The highest temperature recorded
.
in the seais,1iinety—six- degrees Fahrenheit-in the Persian
Gulf and the lowest twenty-eight degrees Fahrenheit in
pôlar
BetW‘een these
limits all-temperatures
are to befound.
,
Albeit this range is Small compared with
the great temperature
differences which occur on land,
the highest being _one hundred and thirty—six degrees
.
'
Fahrenheit“ and
the lowœt minus ninety—f0uf degrees
'
Fahrenheit;
although the changesrare not as great