Biology Reference
In-Depth Information
22.1.3 Methods of Production and Technical Design
Quite a great amount of preliminary observations and experimental setups are
necessary for a commercially successful cultivation of seaweeds. To pick the
right choice of species thorough knowledge of the alga's often complicated life
cycle and a good control of the different life stages are crucial. Likewise local
weather conditions, the temperature range, wave action, currents, tidal amplitude,
and salinity levels must be appropriate for the respective target species. Further
factors to consider are nutrient supply in the water, water depth, and transparency to
maintain beneficial irradiance levels, which may, in the case of shallow water
farming, also be influenced by the color and composition of the bottom sediments.
Moreover, ideally, grazers should not be found in the vicinity of a farm and the
presence of epiphytes or other unwanted macroalgal species competing for light
and nutrients should have been tested before a commercial farm is ventured
(see also Chap.
11
by Potin).
Since the worldwide demand for seaweeds and their products could not be met
by simple collection from natural populations, several decades of effort have gone
into farming (Tseng
1984
,
1987
). A considerable number of technical variations in
cultivating seaweeds are presently used depending on species, local conditions, and
experience (Pereira and Yarish
2008
). Meanwhile cultivation methods comprise
not only single species cultures but also integrated multi-trophic aquaculture
(IMTA; Chopin et al.
2008
; Buschmann et al.
2008
).
22.1.3.1 Monocultures of Seaweeds
Basically, seaweeds are either “seeded” on ropes or nets (e.g.,
Porphyra)
or thallus
fragments are fastened on or pinched into ropes, which are subsequently fixed to
various suspended or floating culture structures (e.g.,
Gracilaria
). From Chile a
system to anchor
Gracilaria
cuttings in the sand is known and has also been
successful (Trono
1990
; Pereira and Yarish
2008
; FAO
2011c
: National Aquacul-
ture Sector Overview—NASO). Paddle wheel ponds that keep algae floating and
moving are a suitable device to grow the green
Ulva
to large quantities (Chopin
et al.
2008
; Butterworth
2010
).
“Nori” production comprising several species of the genus
Porphyra
is a big
business worldwide valued at US$ 1,400 million in 2008 according to the FAO
statistical yearbook 2010 (FAO
2010b
). After about 300 years of culture efforts
dependent on natural seeding, Baker (
1949
) discovered the conchocelis phase of
this genus. Only then could the present-day effective multistage culture system be
established (Pereira and Yarish
2008
,
2010
).
Porphyra
is mainly cultivated in
China, Japan, and Korea: Mollusk shells, mostly of oysters, are seeded with diploid
carpospores from preselected thalli and kept in large shallow indoor tanks for
approx. 5 months until under nutrient, temperature, and light control conchospores
are released by the conchocelis filaments. Appropriate spore density and agitation
