'
THE SEAS
_
'
certain nutrient salts dissolved in the water on which the
drifting plants depend for their growth. In localities where
these bodies are richest the plants will be most abundämt,
'
and, consequently, the animals which depend on
them for
their food supply.
A discussion giving the basic principles - ,
that underlie this plankton production will be found in
_,
Chapter XI ; it would be out of place to enlarge on: the
’,
problem here until the reader has made himself acquainted
.
with Some of the properties of sea waterthat are outlined
in- Chapter X.
'
.
’
In Plate 47 is given a chart of the North Atlantic Ocean
and surrounding seas, in which the density of plankton life
is shown diagrammatically. The richest areas are shown by
the
colouration, the regions of greatest density of life
being the deepest green.
The green colour gradually shades
off into blue which can be taken to represent a poverty
-
'
plankton organisms.
“
Having dealt with the geographical distribution of the
.
plankton, let us turn now to ConSider at what depths this
drifting life is to be found and where it is most abundaht.
Taking the plants rst,- consisting of the Diatoms and the
Peridinians, collections made by research vessels from
_
different depths show that it ”is only the upper water layers
of the sea, from the surface down to about one hundred
; j-_
fathoms, that contain…driftin'g plant life in any quantity.
_
-
A moment’s thought will satisfy anyone that this must
"
.
'
'
of‘necessity be the case, since all plants. are dependent on
_"
the sun’s light for their life and the deeper .We go into the ,
,
water'the less light is there present. - In,fact it has been
'
shown that at little more than ten fathoms in the English —
'
Channel o Plymouth the amount of light present is already
'
similarto that in the heart of ;an English wood.
In the
of the ocean the light can perf0rce
_
'
'
penetrate deeper, but it is certain that at a. depth of one
'
THE SEAS
_
'
certain nutrient salts dissolved in the water on which the
drifting plants depend for their growth. In localities where
these bodies are richest the plants will be most abundämt,
'
and, consequently, the animals which depend on
them for
their food supply.
A discussion giving the basic principles - ,
that underlie this plankton production will be found in
_,
Chapter XI ; it would be out of place to enlarge on: the
’,
problem here until the reader has made himself acquainted
.
with Some of the properties of sea waterthat are outlined
in- Chapter X.
'
.
’
In Plate 47 is given a chart of the North Atlantic Ocean
and surrounding seas, in which the density of plankton life
is shown diagrammatically. The richest areas are shown by
the
colouration, the regions of greatest density of life
being the deepest green.
The green colour gradually shades
off into blue which can be taken to represent a poverty
-
'
plankton organisms.
“
Having dealt with the geographical distribution of the
.
plankton, let us turn now to ConSider at what depths this
drifting life is to be found and where it is most abundaht.
Taking the plants rst,- consisting of the Diatoms and the
Peridinians, collections made by research vessels from
_
different depths show that it ”is only the upper water layers
of the sea, from the surface down to about one hundred
; j-_
fathoms, that contain…driftin'g plant life in any quantity.
_
-
A moment’s thought will satisfy anyone that this must
"
.
'
'
of‘necessity be the case, since all plants. are dependent on
_"
the sun’s light for their life and the deeper .We go into the ,
,
water'the less light is there present. - In,fact it has been
'
shown that at little more than ten fathoms in the English —
'
Channel o Plymouth the amount of light present is already
'
similarto that in the heart of ;an English wood.
In the
of the ocean the light can perf0rce
_
'
'
penetrate deeper, but it is certain that at a. depth of one
'