144
J . E . G . RAYMONT
compounds which may be present in sea water and which may promote
the growth of phytoplankton, but three vitamins (cobalamine or vitamin B,,; thiamin or vitamin B,; and biotin) appear to be of more general
significance to a number of species (cf. Belser, 1963). The main producers of these vitamins are marine bacteria, but some algae apparently
synthesize vitamins; the red algae are often especially rich, though
there is some question as to whether these are not really accumulated
by these macrophytes (Provasoli, 1963). Kanazawa (1961) records a
considerable list of vitamin B complex from algae. The very fact that
some algae can synthesize vitamins underlines the point that phytoplankton species differ greatly in their precise requirements even for
these three vitamins. Since also it is only by most careful culture techniques that we can test for vitamin requirements, it is not surprising
that specific needs are known only for comparatively few phytoplankton
forms; the oceanic phytoplankton is particularly unknown in this
regard.
As regards vitamin B,,, the work of Provasoli and his colleagues
(e.g. Provasoli, 1958), of Droop (1957) and others, as summarized by
Provasoli (1963), suggest that a number of dinoflagellates and some
diatoms (e.g. Xlceletonema) all require vitamin B12. On the other hand,
some algae such as Rhodomonas, Dunaliella, Nannochloris, and Phaeodactylum do not require the vitamin. Presumably they synthesize it
from simpler substances. Species which require B,, show considerable
differences in their ability to grow successfully with various analogues
of this vitamin; how far such analogues occur in the oceans is unknown.
Differences in the spatial concentration of B,, or temporal variations
might, however, limit production. Investigations by Droop suggested
that a considerable amount, probably sufficient for the needs of the
algae, were present in inshore waters (5-10 mpg/l), but work by Cowey
(1956) in the North Sea and the Norwegian Deeps indicated that while
this order of concentration might be present in winter, in summer the
concentration fell to 1/10 of the value. Daisley and Fisher (1958) also
showed for the Bay of Biscay that the euphotic zone had only about
0.6 mpg/l as against about 4 times that value at intermediate depths
(from 200-2 000m). For the Sargasso Sea, Menzel and Spaeth (1962)
found only up to 0.1 mpg/l of vitamin B,, in the upper layers with some
seasonal variation; below 200m the concentration of about 0.2 mpg/l.
was relatively constant. Several authors therefore (e.g. Provasoli, 1963)
doubt whether sufficient B,, is always present for phyDoplankton,
especially in the open sea. Skeletonema as a main spring diatom has
been observed to reduce the vitamin B,, content of waters in Long
Island Sound appreciably, though the amount there is relatively large
(cf. Vishniac and Riley, 1961). Antia et al. (1963) obtained evidence
J . E . G . RAYMONT
compounds which may be present in sea water and which may promote
the growth of phytoplankton, but three vitamins (cobalamine or vitamin B,,; thiamin or vitamin B,; and biotin) appear to be of more general
significance to a number of species (cf. Belser, 1963). The main producers of these vitamins are marine bacteria, but some algae apparently
synthesize vitamins; the red algae are often especially rich, though
there is some question as to whether these are not really accumulated
by these macrophytes (Provasoli, 1963). Kanazawa (1961) records a
considerable list of vitamin B complex from algae. The very fact that
some algae can synthesize vitamins underlines the point that phytoplankton species differ greatly in their precise requirements even for
these three vitamins. Since also it is only by most careful culture techniques that we can test for vitamin requirements, it is not surprising
that specific needs are known only for comparatively few phytoplankton
forms; the oceanic phytoplankton is particularly unknown in this
regard.
As regards vitamin B,,, the work of Provasoli and his colleagues
(e.g. Provasoli, 1958), of Droop (1957) and others, as summarized by
Provasoli (1963), suggest that a number of dinoflagellates and some
diatoms (e.g. Xlceletonema) all require vitamin B12. On the other hand,
some algae such as Rhodomonas, Dunaliella, Nannochloris, and Phaeodactylum do not require the vitamin. Presumably they synthesize it
from simpler substances. Species which require B,, show considerable
differences in their ability to grow successfully with various analogues
of this vitamin; how far such analogues occur in the oceans is unknown.
Differences in the spatial concentration of B,, or temporal variations
might, however, limit production. Investigations by Droop suggested
that a considerable amount, probably sufficient for the needs of the
algae, were present in inshore waters (5-10 mpg/l), but work by Cowey
(1956) in the North Sea and the Norwegian Deeps indicated that while
this order of concentration might be present in winter, in summer the
concentration fell to 1/10 of the value. Daisley and Fisher (1958) also
showed for the Bay of Biscay that the euphotic zone had only about
0.6 mpg/l as against about 4 times that value at intermediate depths
(from 200-2 000m). For the Sargasso Sea, Menzel and Spaeth (1962)
found only up to 0.1 mpg/l of vitamin B,, in the upper layers with some
seasonal variation; below 200m the concentration of about 0.2 mpg/l.
was relatively constant. Several authors therefore (e.g. Provasoli, 1963)
doubt whether sufficient B,, is always present for phyDoplankton,
especially in the open sea. Skeletonema as a main spring diatom has
been observed to reduce the vitamin B,, content of waters in Long
Island Sound appreciably, though the amount there is relatively large
(cf. Vishniac and Riley, 1961). Antia et al. (1963) obtained evidence