226
A. D. BONEY
tive content of marine algae, and of changes associated with the growth
or reproduction of the plants concerned. Destructive diseases, fungal
and bacterial, can seriously deplete the seaweed crops. Sudden changes
in local conditions, such as water turbidity, can, if prolonged, upset the
balance which exists between growth of sublittoral algae and the browsing " pressure " of marine invertebrates. Sewage and toxic effluents are
features to be closely watched in the vicinity of " stands " of harvestable plants. Information on seaweed growth and supply of nutrients is
less clear-cut for large plant populations, although a good deal of data
me available on both mineral and organic nutrients and their effects on
the growth of young stages of algae. The increase in plant productivity as a result of the fertilization of a Scottish sea loch has been
reported (see summary in Newton, 1963). The cultivation of edible
Laminaria plants in the vicinity of porous containers of mineral salts,
as reported from China (p. 159), has shown that marked increases in
organic production can be obtained. To carry out similar methods on
a large scale with underwater beds of seaweed would require a detailed
knowledge of the currents in the immediate vicinity of the axeas under
cultivation.
One aspect for which there appears to be little quantitative data
concerns processes of " weeding " unwanted algae from underwater
beds of seaweed. Use of the self-contained breathing apparatus
should enable some progress to be made in this direction, and observations will need to be extended over some time to obtain the more
significant results.
Attempts have been made in recent years to investigate the effects
of cross-breeding between different species of marine algae in order to
obtain more valuable products. The methods pose appreciable difficulties of technique, e.g. the work carried out with the edible Porphyra
species. However, the methods evolved in studies on the " nursery "
growth of the very young stages make the practical applications of
such cross-breeding experiments at least a possibility.
Consideration must also be given to the important factor of conservation. Whilst with the shore fucoids, particularly Ascophyllum, some
degree of controlled harvesting is clearly necessary, the data are far less
clear-cut for other species. If the experience of the last two decades is
any guide, there will be'no slackening of demand for raw materials.
For example, a fivefold increase in the value of the annual output of
seaweed colloids was reported from the United States for the years
1945-1955 (Newton, 1963). Large-scale harvesting of some species,
e.g. Furcellaria fastigiata f. aegagrophih, has been carried out on an
increasing scale over the years without apparently seriously depleting
A. D. BONEY
tive content of marine algae, and of changes associated with the growth
or reproduction of the plants concerned. Destructive diseases, fungal
and bacterial, can seriously deplete the seaweed crops. Sudden changes
in local conditions, such as water turbidity, can, if prolonged, upset the
balance which exists between growth of sublittoral algae and the browsing " pressure " of marine invertebrates. Sewage and toxic effluents are
features to be closely watched in the vicinity of " stands " of harvestable plants. Information on seaweed growth and supply of nutrients is
less clear-cut for large plant populations, although a good deal of data
me available on both mineral and organic nutrients and their effects on
the growth of young stages of algae. The increase in plant productivity as a result of the fertilization of a Scottish sea loch has been
reported (see summary in Newton, 1963). The cultivation of edible
Laminaria plants in the vicinity of porous containers of mineral salts,
as reported from China (p. 159), has shown that marked increases in
organic production can be obtained. To carry out similar methods on
a large scale with underwater beds of seaweed would require a detailed
knowledge of the currents in the immediate vicinity of the axeas under
cultivation.
One aspect for which there appears to be little quantitative data
concerns processes of " weeding " unwanted algae from underwater
beds of seaweed. Use of the self-contained breathing apparatus
should enable some progress to be made in this direction, and observations will need to be extended over some time to obtain the more
significant results.
Attempts have been made in recent years to investigate the effects
of cross-breeding between different species of marine algae in order to
obtain more valuable products. The methods pose appreciable difficulties of technique, e.g. the work carried out with the edible Porphyra
species. However, the methods evolved in studies on the " nursery "
growth of the very young stages make the practical applications of
such cross-breeding experiments at least a possibility.
Consideration must also be given to the important factor of conservation. Whilst with the shore fucoids, particularly Ascophyllum, some
degree of controlled harvesting is clearly necessary, the data are far less
clear-cut for other species. If the experience of the last two decades is
any guide, there will be'no slackening of demand for raw materials.
For example, a fivefold increase in the value of the annual output of
seaweed colloids was reported from the United States for the years
1945-1955 (Newton, 1963). Large-scale harvesting of some species,
e.g. Furcellaria fastigiata f. aegagrophih, has been carried out on an
increasing scale over the years without apparently seriously depleting