T H E PRODUCTION O F MARINE PLANKTON
145
for considerable utilization of vitamin B,, in their culture experiments,
but biotin did not appear to be used. The work of Guillard and Cassie
(1963) suggests that phytoplankton B,, requirements may be slightly
greater than was first considered. Thus they find minimum needs for
both neritic and oceanic forms of about 5-18 molecules of B,, per cell,
as compared with 3 per cell suggested by Droop. These authors make the
interesting suggestion that B,, may be required by some phytoplankton
species only a t a particular stage in their life history; for example, by
Skeletonema at auxospore formation.
The absolute requirement for thiamin varies also from species to
species of marine phytoplankton. For example, Phaeodactylum and
Nannochloris, which do not require B,,, do riot need thiamin. On the
other hand, Skeletonema, which requires B1,, citn grow without the addition of thiamin. Pintner and Provasoli (1963) found that chrysomonads
generally required B, rather than BIZ. A sum :nary of the requirements
of various algae for B12, thiamin and biotin as given by Provasoli (1963)
is seen in Table 111. Vishniac and Riley (1961) found only barely
detectable amounts of thiamin, in contrast LO B,,, in the more open
water of Long Island Sound; such small concentrations could limit the
growth of species unable to synthesize the vitamin. We lack knowledge,
however, of the variations in concentration of growth promoting substances in the oceans and of the precise nutrient requirements of individual species so that it is not possible to imsess their exact role in
primary production. It seems likely that at times insufficient amounts
may be present, at least in the open sea far from land. The requirements
of neritic species also probably exceed that cbf most oceanic forms (cf.
Hulburt, 1962; Hulburt and Rodman, 1963) and, more generally, the
vitamin requirements of planktonic species probably play an important
part in spatial and temporal succession.
The whole array of dissolved organic substances may be of significance
in this connection. The production of extracellular substances imposes a
biological history on the water, and Lucas (1947, 1955, 1961) in particular has called attention to the great importance of this biological
conditioning to both phytoplankton and zooplankton. Several studies
of species succession have included conditioning of the water as one
factor. Lillick (1940), for the Gulf of Maine, thought that subtler differences due to conditioning of the water were responsible in part. Conover
(1956), describing a rather simila,r study of seasonal succession in Long
Island Sound, stated that conditioning of the water was an important
aspect of the species succession, and suggested that Schroederella was
particularly favoured by the products of blooming of earlier species.
Margalef (1958) has also called attention to t’he importance of external
metabolites. He describes three main phases i n a species succession, the
145
for considerable utilization of vitamin B,, in their culture experiments,
but biotin did not appear to be used. The work of Guillard and Cassie
(1963) suggests that phytoplankton B,, requirements may be slightly
greater than was first considered. Thus they find minimum needs for
both neritic and oceanic forms of about 5-18 molecules of B,, per cell,
as compared with 3 per cell suggested by Droop. These authors make the
interesting suggestion that B,, may be required by some phytoplankton
species only a t a particular stage in their life history; for example, by
Skeletonema at auxospore formation.
The absolute requirement for thiamin varies also from species to
species of marine phytoplankton. For example, Phaeodactylum and
Nannochloris, which do not require B,,, do riot need thiamin. On the
other hand, Skeletonema, which requires B1,, citn grow without the addition of thiamin. Pintner and Provasoli (1963) found that chrysomonads
generally required B, rather than BIZ. A sum :nary of the requirements
of various algae for B12, thiamin and biotin as given by Provasoli (1963)
is seen in Table 111. Vishniac and Riley (1961) found only barely
detectable amounts of thiamin, in contrast LO B,,, in the more open
water of Long Island Sound; such small concentrations could limit the
growth of species unable to synthesize the vitamin. We lack knowledge,
however, of the variations in concentration of growth promoting substances in the oceans and of the precise nutrient requirements of individual species so that it is not possible to imsess their exact role in
primary production. It seems likely that at times insufficient amounts
may be present, at least in the open sea far from land. The requirements
of neritic species also probably exceed that cbf most oceanic forms (cf.
Hulburt, 1962; Hulburt and Rodman, 1963) and, more generally, the
vitamin requirements of planktonic species probably play an important
part in spatial and temporal succession.
The whole array of dissolved organic substances may be of significance
in this connection. The production of extracellular substances imposes a
biological history on the water, and Lucas (1947, 1955, 1961) in particular has called attention to the great importance of this biological
conditioning to both phytoplankton and zooplankton. Several studies
of species succession have included conditioning of the water as one
factor. Lillick (1940), for the Gulf of Maine, thought that subtler differences due to conditioning of the water were responsible in part. Conover
(1956), describing a rather simila,r study of seasonal succession in Long
Island Sound, stated that conditioning of the water was an important
aspect of the species succession, and suggested that Schroederella was
particularly favoured by the products of blooming of earlier species.
Margalef (1958) has also called attention to t’he importance of external
metabolites. He describes three main phases i n a species succession, the