Biology Reference
In-Depth Information
12.4.2
Gracilaria salicornia
Gracilaria
species represent well-recognized sources of linear galactan polysac-
charide agar, widely used in industry for its excellent gelling or thickening abilities
(reviewed in Mehta et al.
2010
). Species of the genus
Gracilaria
such as
Gracilaria
salicornia
(C. Agardh) Dawson and
G. parvispora
Abbott, a highly valuable alga in
the Hawaiian markets, occur widely throughout the tropical Indian and Pacific
Oceans (Ryder et al.
2004
). Furthermore,
G. debilis
(Forssk
˚
l) Børgesen and
G.
salicornia
occur naturally at the west coast of India where they represent valuable
natural sources for superior quality agars (Oza and Zaidi
2001
; Mehta et al.
2010
).
Several
Gracilaria
species from various sources were intentionally introduced to
the Hawaiian Islands for aquaculture development (Russell
1992
).
Gracilaria
salicornia
has become a successful invader. After escaping from sea farms,
G.
salicornia
has invaded surrounding coral reef flats, either as unattached drift or
attached populations outcompeting corals, propagated mainly via fragmentation
(Smith et al.
2004
; Conklin and Smith
2005
).
Gracilaria salicornia
displays a
variety of biological traits that facilitate high yield cultivation but also make this
a potentially invasive species: e.g., high growth rates that can be sustained in
variable light regimes, the ability for vegetative dispersal, desiccation tolerance,
remarkable tolerance to a wide range of temperatures, salinities, chemical
treatments (commercial-grade herbicides and algaecides), and resistance to
herbivores (Rodgers and Cox
1999
; Smith et al.
2004
; Nelson et al.
2009
).
12.4.3
Eucheuma
and
Kappaphycus
spp.
Wild and farmed strains of the carrageenophytes
Eucheuma denticulatum
(Burman)
Collins et Harvey,
Kappaphycus alvarezii
(Doty) Doty and
Kappaphycus striatum
(Schmitz)
Doty ex Silva
have been intentionally introduced in more than 20
countries for mariculture purposes (Bulboa and de Paula
2005
; Hayashi et al.
2007
). These species represent the world's most important kappa-carrageenan
producing red algae (Ask and Azanza
2002
), a hydrocolloid that is widely used in
industry as a gelling and thickening agent. All, however, have been introduced to
Kane'ohe Bay in Hawai'i in 1974 for growth experiments and since then acciden-
tally escaped and established highly abundant populations on Hawaii's coral reefs
(Conklin and Smith
2005
). However, most introductions for cultivation have
occurred in the developing world and adverse impacts on the surrounding environ-
ment are not well studied (Zemke-White
2004
; Bindu and Levine
2011
).
Invasive traits that make these species ideal for farming are easy propagation and
dispersal by fragmentation and very high growth rate (doubling in size every
15-30 days). The improvement of growth performance in these species is an area
of active research (Luhan and Sollesta
2010
).
