140
J . E . G . RATMONT
coastal species may be limited to neritic regions partly on nitrogen and
phosphate requirements, but equally on the relatively greater demands
for trace elements. In this connection Hulburt and Rodman (1963) have
suggested that the sporadic blooms of neritic species in the open sea
may be occasioned by the temporary presence of larger quantities of
iron or some similar nutrient which normally limit their distribution.
However, the experiments of McAllister et al. (1961) in which coastal
plankton species bloomed successfully indicated that trace metals (Fe,
Cu, Mn) were not limiting. It is probable that species have different
trace element requirements. Jones and Haq (1963) believe that blooms
of P h e o c y s t i s may depend on some minor nutrient. Tranter and Newel1
(1963) suggest that iron may be important in oceanic waters off
Australia. Pintner and Provasoli (1963) state that trace metal requirements are excessively low for the chrysomonads. Johnston (1964) also
believes that different species may have varied requirements. He has
emphasized the great importance of trace metals such as iron, manganese, copper, and molybdenum; under special conditions in a few areas
some of these elements may be temporarily limiting. Although in
northern seas sufficient quantities of these trace metals are normally
present, with the high pH of sea water they may be virtually unavailable to the phytoplankton cells. A chelating agent may therefore be of
the greatest significance in making the metals available. In the sea,
organic acids present in great dilution may act as such chelating agents.
This in turn focuses attention on dissolved organic factors in sea water.
6. Organic Requirements
Early experiments on the laboratory culture of marine algal species
proved fairly conclusively that even when nitrate, phosphate and trace
elements were supplied to the algae, growth was often impeded unless
some organic constituents were also present in the water. Work over
the last few years has shown an increasing number of organic substances which are mostly present at very low dilutions in the sea (cf.
Hood, 1963) (Duursma, 1961). Although most of these are extremely
difficult to identify, a recent review by Provasoli (1963) lists such
materials as carbohydrates, amino-acids, fatty acids, organic acids,
vitamins, and inhibitory substances as occurring in sea water.
The variety of organic substances present in sea water is remarkable.
Analyses by Tatsumoto et al. (1961) and by Park et al. (1962) have revealed some 17 or 18 amino-acids existing in surface and deeper ocean
waters. The studies of Koyama (1962) showed not only a variety of
amino-acids, but of carbohydrates, fatty acids, metallo-organic substances as well as vitamin compounds. Much dissolved organic material
arises from the decomposition of planktonic and nektonic organisms.
J . E . G . RATMONT
coastal species may be limited to neritic regions partly on nitrogen and
phosphate requirements, but equally on the relatively greater demands
for trace elements. In this connection Hulburt and Rodman (1963) have
suggested that the sporadic blooms of neritic species in the open sea
may be occasioned by the temporary presence of larger quantities of
iron or some similar nutrient which normally limit their distribution.
However, the experiments of McAllister et al. (1961) in which coastal
plankton species bloomed successfully indicated that trace metals (Fe,
Cu, Mn) were not limiting. It is probable that species have different
trace element requirements. Jones and Haq (1963) believe that blooms
of P h e o c y s t i s may depend on some minor nutrient. Tranter and Newel1
(1963) suggest that iron may be important in oceanic waters off
Australia. Pintner and Provasoli (1963) state that trace metal requirements are excessively low for the chrysomonads. Johnston (1964) also
believes that different species may have varied requirements. He has
emphasized the great importance of trace metals such as iron, manganese, copper, and molybdenum; under special conditions in a few areas
some of these elements may be temporarily limiting. Although in
northern seas sufficient quantities of these trace metals are normally
present, with the high pH of sea water they may be virtually unavailable to the phytoplankton cells. A chelating agent may therefore be of
the greatest significance in making the metals available. In the sea,
organic acids present in great dilution may act as such chelating agents.
This in turn focuses attention on dissolved organic factors in sea water.
6. Organic Requirements
Early experiments on the laboratory culture of marine algal species
proved fairly conclusively that even when nitrate, phosphate and trace
elements were supplied to the algae, growth was often impeded unless
some organic constituents were also present in the water. Work over
the last few years has shown an increasing number of organic substances which are mostly present at very low dilutions in the sea (cf.
Hood, 1963) (Duursma, 1961). Although most of these are extremely
difficult to identify, a recent review by Provasoli (1963) lists such
materials as carbohydrates, amino-acids, fatty acids, organic acids,
vitamins, and inhibitory substances as occurring in sea water.
The variety of organic substances present in sea water is remarkable.
Analyses by Tatsumoto et al. (1961) and by Park et al. (1962) have revealed some 17 or 18 amino-acids existing in surface and deeper ocean
waters. The studies of Koyama (1962) showed not only a variety of
amino-acids, but of carbohydrates, fatty acids, metallo-organic substances as well as vitamin compounds. Much dissolved organic material
arises from the decomposition of planktonic and nektonic organisms.