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BULLETIN OF THE BUREAU OF FISHERIES 
The chloride determinations were made to discover any relationship between 
the available chloride and the amount of plankton. The results suggest that a 
plentiful supply of chloride was always available, and that chloride was not a limiting 
factor. 
Along with these chemical determinations there were also made observations 
on temperatures and on turbidity. Turbidity, since it determines the extent to 
which sunlight can penetrate the lower strata of water, may have an important 
influence on photosynthesis. 
To attempt to analyze all the data that are presented in this report at the present 
time would seem premature to the writer. Although the data may seem impressive 
in volume, it is manifestly inadequate to explain and to correlate the physical, chem- 
ical, and biological processes that are taking place in a fish pond. An explanation 
which may hold true for one pond may not fare so well when the data from another 
pond are examined. The writer has, therefore, purposely refrained from drawing 
many hard and fast conclusions. A few conclusions that seemed warranted by the 
data presented in this report, as well as by other unpublished data, are given at 
the end of this paper. The writer hopes, however, that while this paper fails to solve 
the life processes of a fish pond, it may act as a stimulus for further work along this 
line. 
LITERATURE 
Various attempts have been made to link up the productivity of the sea and of 
bodies of fresh water with certain definite chemical elements. The dissolved phos- 
phorus has been designated as a limiting factor by Atkins and Harris (1924). They 
found that one pond which they studied contained 0.055 p. p. m. of dissolved phos- 
phorus in spring, and another pond contained 0.04 p. p. m. During the summer no 
phosphorus at all or only very small amounts were found. They concluded that the 
further growth of algse had been prevented by the exhaustion of the dissolved phos- 
phorus early in spring. 
Fisher (1924) reported that at the Bavarian Pond Fishery Experiment Station 
an increase in carp production was obtained when superphosphate or basic slag were 
used as fertilizers. Fertilizers rich in nitrogen and potassium but containing no phos- 
phorus also increased carp production, but to a very much lesser degree. Fisher 
concluded from these experiments that the available phosphorus was the limiting 
factor and that nitrogen and potassium were generally present in sufficient amounts 
and did not have to be added through the fertilizer. 
Brandt (1919) reported that the amount of soluble phosphorus in the surface 
water of the North Sea was smallest in May and June and largest in November and 
February. Atkins (1926) found that the dissolved phosphorus at various places off 
the coast of England reached a minimum in summer and a maximum in winter. The 
decrease in the soluble phosphorus in spring was proportionate to the increase in 
phytoplankton. 
Harvey (1926) found that the nitrate nitrogen was completely exhausted in the 
English Channel during August of 1925. In 1927 in summarizing our present knowl- 
edge of the productivity of the ocean this author concludes “There is an excess supply 
of the requirements for photosynthesis with the exception of phosphate and nitrate,” 
and “The fertility of an ocean will depend for the most part on two factors; namely, 
the length of time taken by the corpses of marine organisms and excreta to decay, and 
