120
J.E. Merrill
consideration should be given to the full range of available options along
this continuum.
On a worldwide basis, many different species of macroalgae are cultivated
(Waaland 1981; Ryther 1985; Perez et al. 1992). Most of the types cultivated
successfully on a commercial scale are those used for human food, particularly
in Asia (Abbott 1988). The best known examples include the red alga Porphyra
("nori"), and the brown algae Undaria ("wakame") and Laminaria
("kombu"); (Miura 1980; Waaland 1981; Arasaki and Arasaki 1983). Other
species have been cultivated as sources for valuable extractive products, e.g. the
red algae Eucheuma for caragheenan and Gracilaria for agar (Jansen 1979;
Hanisak and Ryther 1984; Bird and Benson 1987; Lewis et al. 1988).
Ideally, the species selected for cultivation would be one for which
commercial methods were already established, otherwise a potentially long
and costly "domestication" process might be required prior to commercial
scale cultivation. In most cases utilization of a locally occurring species will
be preferable to introduction of a nonnative species due to the current
intenstity of opposition to species introductions. Fortunately, many of the
most productive cultivated genera have very wide geographic distribution,
and it is therefore likely that for a given intervention target area, there will
be a useful local representative that can be brought into production with a
relatively modest research and development effort.
A key consideration in every example of seaweed farming is the selection
and optimization of a suitable substrate. The sea farm grounds are often in
areas where the same species would not otherwise occur because of the lack
of suitable substrate materials at the appropriate water depth. The exception to this principle is in tank or pond cultivation where vigorous water
mixing by aeration or other means allows free floating culture.
If we consider the conditions present in a typical bay or lagoon that is
subject to repeated green tide occurrences we know that, by definition, the
overall annual nutrient budget of the water system is excellent for support
of algal growth. These nutrients come either from current sources of runoff
and discharge or from mineral cycling processes within the sediments (cf.
Bianchi et al. 1988). In many cases, by providing a suitable substratum, and
by providing adequate inoculum, we can cause desirable species of seaweed
to dominate. As with any agricultural crop, however, it is essential to
understand the particular biological requirements of the target species in
order to successfully manage it under cultivation, especially if one of the
major objectives is to out-compete the green tide.
Some examples will serve to demonstrate typical methods of seaweed
cultivation and how these might be applied in eutrophicated bays and
lagoons.
J.E. Merrill
consideration should be given to the full range of available options along
this continuum.
On a worldwide basis, many different species of macroalgae are cultivated
(Waaland 1981; Ryther 1985; Perez et al. 1992). Most of the types cultivated
successfully on a commercial scale are those used for human food, particularly
in Asia (Abbott 1988). The best known examples include the red alga Porphyra
("nori"), and the brown algae Undaria ("wakame") and Laminaria
("kombu"); (Miura 1980; Waaland 1981; Arasaki and Arasaki 1983). Other
species have been cultivated as sources for valuable extractive products, e.g. the
red algae Eucheuma for caragheenan and Gracilaria for agar (Jansen 1979;
Hanisak and Ryther 1984; Bird and Benson 1987; Lewis et al. 1988).
Ideally, the species selected for cultivation would be one for which
commercial methods were already established, otherwise a potentially long
and costly "domestication" process might be required prior to commercial
scale cultivation. In most cases utilization of a locally occurring species will
be preferable to introduction of a nonnative species due to the current
intenstity of opposition to species introductions. Fortunately, many of the
most productive cultivated genera have very wide geographic distribution,
and it is therefore likely that for a given intervention target area, there will
be a useful local representative that can be brought into production with a
relatively modest research and development effort.
A key consideration in every example of seaweed farming is the selection
and optimization of a suitable substrate. The sea farm grounds are often in
areas where the same species would not otherwise occur because of the lack
of suitable substrate materials at the appropriate water depth. The exception to this principle is in tank or pond cultivation where vigorous water
mixing by aeration or other means allows free floating culture.
If we consider the conditions present in a typical bay or lagoon that is
subject to repeated green tide occurrences we know that, by definition, the
overall annual nutrient budget of the water system is excellent for support
of algal growth. These nutrients come either from current sources of runoff
and discharge or from mineral cycling processes within the sediments (cf.
Bianchi et al. 1988). In many cases, by providing a suitable substratum, and
by providing adequate inoculum, we can cause desirable species of seaweed
to dominate. As with any agricultural crop, however, it is essential to
understand the particular biological requirements of the target species in
order to successfully manage it under cultivation, especially if one of the
major objectives is to out-compete the green tide.
Some examples will serve to demonstrate typical methods of seaweed
cultivation and how these might be applied in eutrophicated bays and
lagoons.