208
A. D. BONEY
constitution of Laminaria saccharina and L. hyperborea. These biochemical changes have been summarized in earlier pages, and include
the change from the low mannitol and laminarin contents of late winter
to the higher values in late spring and in the summer and then, in
the case of mannitol, remaining relatively constant, whilst laminarin
tends to increase. Alginic acid is highest early in spring, but decreases
as summer progresses, and the protein reserves show a similar course.
In autumn the protein content increases again, and subsequently there
is a rise in the mannitol and laminarin reserves. The well known cycle
of changes in the nitrate and phosphate contents of the sea show two
annual peaks, e.g. in spring and autumn, and these cyclic changes have
been correlated by Black and Dewar (1949) with the major changes in
chemical content of the algae. They also suggested that the higher
summer temperatures may be of significance because of increased rates
of respiration; the depletion of nutrients and the accompanying
restriction of photosynthesis was considered to be of greater importance.
However, Bidwell et at?. (1958) observed that addition of inorganic
salts appeared to have little effect on the photosynthesis of Fucus
vuesicuZosus, and Macpherson and Young (1952) observed that the
fluctuation in mannitol content paralleled that of the sea temperature.
Whilst depletion of nitrate and phosphate may indeed be limiting
factors, it is also possible that other elements (of a'micronutrient
nature) may fall below a critical value and hence be significant.
Vitamin content of brown algae
Reference has already been made to use of brown seaweeds as
sources of meals for animal feeding (see also p. 215). This is in part due
to their vitamin content, and the results of studies on the seasonal
variation of certain of these are available. Thus, with the vitamin B
group, seasonal fluctuations in the niacin content have been described
from Norway (Larsen, 1958). For Laminaria hyperborea the minimum
quantity is observed in the winter, thence rising to a maximum in
April and May, and similar fluctuations are observed in the stipe and
frond. Results for Laminaria digitata and L. hyperbovea were much
the same. I n A8cophyllum nodosum the maximum content is found in
the spring, with a smaller peak in the winter, and with Fucus serratus
the maximum content is observed in late spring. I n both these species
the niacin content appears to vary with salinity (Larsen and Haug,
1958a), and younger tissues have a higher content. No significant loss
was observed on drylng the weed for preparation of the meal. For
Laminaria species the biotin content was also at a maximum in spring,
with a second peak in autumn, whilst with Fucus serratus the two
A. D. BONEY
constitution of Laminaria saccharina and L. hyperborea. These biochemical changes have been summarized in earlier pages, and include
the change from the low mannitol and laminarin contents of late winter
to the higher values in late spring and in the summer and then, in
the case of mannitol, remaining relatively constant, whilst laminarin
tends to increase. Alginic acid is highest early in spring, but decreases
as summer progresses, and the protein reserves show a similar course.
In autumn the protein content increases again, and subsequently there
is a rise in the mannitol and laminarin reserves. The well known cycle
of changes in the nitrate and phosphate contents of the sea show two
annual peaks, e.g. in spring and autumn, and these cyclic changes have
been correlated by Black and Dewar (1949) with the major changes in
chemical content of the algae. They also suggested that the higher
summer temperatures may be of significance because of increased rates
of respiration; the depletion of nutrients and the accompanying
restriction of photosynthesis was considered to be of greater importance.
However, Bidwell et at?. (1958) observed that addition of inorganic
salts appeared to have little effect on the photosynthesis of Fucus
vuesicuZosus, and Macpherson and Young (1952) observed that the
fluctuation in mannitol content paralleled that of the sea temperature.
Whilst depletion of nitrate and phosphate may indeed be limiting
factors, it is also possible that other elements (of a'micronutrient
nature) may fall below a critical value and hence be significant.
Vitamin content of brown algae
Reference has already been made to use of brown seaweeds as
sources of meals for animal feeding (see also p. 215). This is in part due
to their vitamin content, and the results of studies on the seasonal
variation of certain of these are available. Thus, with the vitamin B
group, seasonal fluctuations in the niacin content have been described
from Norway (Larsen, 1958). For Laminaria hyperborea the minimum
quantity is observed in the winter, thence rising to a maximum in
April and May, and similar fluctuations are observed in the stipe and
frond. Results for Laminaria digitata and L. hyperbovea were much
the same. I n A8cophyllum nodosum the maximum content is found in
the spring, with a smaller peak in the winter, and with Fucus serratus
the maximum content is observed in late spring. I n both these species
the niacin content appears to vary with salinity (Larsen and Haug,
1958a), and younger tissues have a higher content. No significant loss
was observed on drylng the weed for preparation of the meal. For
Laminaria species the biotin content was also at a maximum in spring,
with a second peak in autumn, whilst with Fucus serratus the two