126
E. D. S. CORNER AND ANTHONY 0. DAMES
The euryhaline species Dunaliella tertiolecta would be expected to
compete successfully only when ammonia is available, the other three
species presumably being excluded, by their lack of salinity tolerance,
from the rock pools where Dunaliella is usually found.
Should the easily measured half-saturation constant for nutrient
uptake prove to be of general use for predicting the growth of phytoplankton, it is likely that many of the outstanding problems relating to
phytoplankton distribution could be explained. A great deal more
research in this field is obviously required.
VII. NITROQEN AND PHOSPHORUS LEVELS IN PHYTOPLANKTON
There is surprisingly little published information on nitrogen and
phosphorus levels in natural populations of marine phytoplankton.
The most detailed study remains that of Harris and Riley (1956) who
followed the changes in the chemical and species composition of the
phytoplankton in Long Island Sound over a period of a year. Their
data are reproduced in Table I (Section 111). Between March and
June, approximate doubling of the nitrogen and phosphorus contents
took place and was associated with the change from Skeletonem
costatum, as the dominant species, to the presence of substantial
numbers of dinoflagellates : a small decrease in the nitrogen : phosphorus
ratio also occurred. The change in the species composition probably
resulted from depletion of the available nitrate in March (Riley and
Conover, 1956), for McAllister et al. (1961) noted in their large-scale
cultures of natural, coastal phytoplankton populations that the dinoflagellates increased only after the nitrates had been completely utilized
(although in this case their presence appeared to cause an increase in
the nitrogen : phosphorus ratio in the phytoplankton).
Parsons et al. (1961) have provided data on the chemical composition
of 11 species of marine phytoplankton grown in culture, and their
results for nitrogen and phosphorus content are given in Table I1
(Section 111). Both elements were present in greater amounts in the
cultured phytoplankton than they were in the natural populations
examined by Harris and Riley; and, as mentioned earlier (see p. 112)
the nitrogen : phosphorus ratios varied considerably between species,
usually being much smaller than the accepted value of 16 : 1.
Although the higher concentrations of nutrients available in the
cultures of Parsons et al. (500 pg-atoms NO;-N/l; 50 pg-atoms
PO;--P/l) may have been the cause of the higher nitrogen and phosphorus levels in the phytoplankton, it should be noted that Strickland
et al. (1969) found that the nitrogen and phosphorus contents of cells
grown in large-scale cultures under near natural conditions were not
E. D. S. CORNER AND ANTHONY 0. DAMES
The euryhaline species Dunaliella tertiolecta would be expected to
compete successfully only when ammonia is available, the other three
species presumably being excluded, by their lack of salinity tolerance,
from the rock pools where Dunaliella is usually found.
Should the easily measured half-saturation constant for nutrient
uptake prove to be of general use for predicting the growth of phytoplankton, it is likely that many of the outstanding problems relating to
phytoplankton distribution could be explained. A great deal more
research in this field is obviously required.
VII. NITROQEN AND PHOSPHORUS LEVELS IN PHYTOPLANKTON
There is surprisingly little published information on nitrogen and
phosphorus levels in natural populations of marine phytoplankton.
The most detailed study remains that of Harris and Riley (1956) who
followed the changes in the chemical and species composition of the
phytoplankton in Long Island Sound over a period of a year. Their
data are reproduced in Table I (Section 111). Between March and
June, approximate doubling of the nitrogen and phosphorus contents
took place and was associated with the change from Skeletonem
costatum, as the dominant species, to the presence of substantial
numbers of dinoflagellates : a small decrease in the nitrogen : phosphorus
ratio also occurred. The change in the species composition probably
resulted from depletion of the available nitrate in March (Riley and
Conover, 1956), for McAllister et al. (1961) noted in their large-scale
cultures of natural, coastal phytoplankton populations that the dinoflagellates increased only after the nitrates had been completely utilized
(although in this case their presence appeared to cause an increase in
the nitrogen : phosphorus ratio in the phytoplankton).
Parsons et al. (1961) have provided data on the chemical composition
of 11 species of marine phytoplankton grown in culture, and their
results for nitrogen and phosphorus content are given in Table I1
(Section 111). Both elements were present in greater amounts in the
cultured phytoplankton than they were in the natural populations
examined by Harris and Riley; and, as mentioned earlier (see p. 112)
the nitrogen : phosphorus ratios varied considerably between species,
usually being much smaller than the accepted value of 16 : 1.
Although the higher concentrations of nutrients available in the
cultures of Parsons et al. (500 pg-atoms NO;-N/l; 50 pg-atoms
PO;--P/l) may have been the cause of the higher nitrogen and phosphorus levels in the phytoplankton, it should be noted that Strickland
et al. (1969) found that the nitrogen and phosphorus contents of cells
grown in large-scale cultures under near natural conditions were not