UPWELLING AND THE PRODUCTION OF FISH
27 1
suggested that the turnover rate for phosphorus off the north-east coast
of England during the spring outburst amounted to perhaps two or
three times a month.
In general, the level of nutrients in an upwelling area never reaches
the very low level at which the algal reproductive rate might be reduced,
from the results of the plastic bag experiments. But progressing offshore, the nutrients do decrease. If the above interpretation is right,
this is because the residual quantity of nutrient decreases offshore, as
the stocks of algae decrease offshore. Reid's charts of phosphorus and
zooplankton extend the correlation to the areas of low algal stock in the
centres of the anticyclones, which suggests that the same processes
operate there. Then the algal stocks in the deep ocean may subsist on
regenerated nutrients. The implication is that the long-established
correlation between production and nutrients is a consequence of the
dependence of nutrient quantity on production and not the other way
round.
However, Wyrtki (1964) has estimated the production in the Costa
Rica Dome from the decrement of phosphorus during the period of upwelling and has found that the apparent use of phosphorus corresponds
fairly closely with the radiocarbon measurements. In the formulation
given above P, = P, - P, = BP, - ,P, - P,, which means that the
quantity taken up is proportional to that in living material, less regeneration. By analogy with a temperate cycle, regeneration may be
low in the rising water, as the production is increasing; then the
decrement of phosphorus in the rising water, P,, is proportional to that
in living material. A radiocarbon measurement at the surface would be
one of A stock, which, if the reproductive rate is constant (i.e. about
one division per day), is proportional to stock. So the association found
by Wyrtki is an expected one.
IV. DESCRIPTION OF A WELL-KNOWN UPWELLING AREA
A. The California current system
The best known upwelling area is that in the California Current,
which extends from off Baja California to off Washington State. A
special study was executed in the Gulf of Panama, which is not part of'
the California Current system (see p. 276).
During spring and summer, there is a high pressure system over the
Pacific, west of California, and a low pressure system over northern
Mexico, Nevada and southern California in the south-western United
States, SO winds blow between them, north-easterly, northerly or northwesterly ; and therc are locally very strong winds south of Point Con-
27 1
suggested that the turnover rate for phosphorus off the north-east coast
of England during the spring outburst amounted to perhaps two or
three times a month.
In general, the level of nutrients in an upwelling area never reaches
the very low level at which the algal reproductive rate might be reduced,
from the results of the plastic bag experiments. But progressing offshore, the nutrients do decrease. If the above interpretation is right,
this is because the residual quantity of nutrient decreases offshore, as
the stocks of algae decrease offshore. Reid's charts of phosphorus and
zooplankton extend the correlation to the areas of low algal stock in the
centres of the anticyclones, which suggests that the same processes
operate there. Then the algal stocks in the deep ocean may subsist on
regenerated nutrients. The implication is that the long-established
correlation between production and nutrients is a consequence of the
dependence of nutrient quantity on production and not the other way
round.
However, Wyrtki (1964) has estimated the production in the Costa
Rica Dome from the decrement of phosphorus during the period of upwelling and has found that the apparent use of phosphorus corresponds
fairly closely with the radiocarbon measurements. In the formulation
given above P, = P, - P, = BP, - ,P, - P,, which means that the
quantity taken up is proportional to that in living material, less regeneration. By analogy with a temperate cycle, regeneration may be
low in the rising water, as the production is increasing; then the
decrement of phosphorus in the rising water, P,, is proportional to that
in living material. A radiocarbon measurement at the surface would be
one of A stock, which, if the reproductive rate is constant (i.e. about
one division per day), is proportional to stock. So the association found
by Wyrtki is an expected one.
IV. DESCRIPTION OF A WELL-KNOWN UPWELLING AREA
A. The California current system
The best known upwelling area is that in the California Current,
which extends from off Baja California to off Washington State. A
special study was executed in the Gulf of Panama, which is not part of'
the California Current system (see p. 276).
During spring and summer, there is a high pressure system over the
Pacific, west of California, and a low pressure system over northern
Mexico, Nevada and southern California in the south-western United
States, SO winds blow between them, north-easterly, northerly or northwesterly ; and therc are locally very strong winds south of Point Con-