Biology Reference
In-Depth Information
Several biological traits, related to life history and ecology of this ESU, are
likely to be a reason for its invasive success. Invasive
Codium
benefits from both
sexual and parthenogenetic proliferation as well vegetative propagation facilitated
via thalli fragmentation and dispersal. Furthermore, colonization and the persis-
tence of populations are facilitated by broad physiological tolerances to tempera-
ture and salinity regimes (B
´
gin and Scheibling
2003
).
12.5 Conclusions
The relocation of marine species with invasive potential represents extraordinary
challenges for marine ecosystems. In the future, the rate and range of introductions
is likely to increase with increasing volume and speed of maritime traffic and with
unprecedented changes in “recipient” environments by global climate change and
local habitat degradation. Anticipating and controlling potential invasions is easier
and more cost-effective than investing in posteriori management such as control
and eradication efforts (e.g., Hewitt et al.
2009b
).
The invasive seaweed species discussed in this chapter are recognized priority
pest species with a high potential for negative ecological and socio-economic
impacts (Doelle et al.
2007
). However, where these seaweeds are native, many of
them have long been exploited as valuable natural resources. The low capital costs
of seaweed farming, good economic returns, and high demand for seaweed products
in the world's market have led to intentional introductions of potentially invasive,
high yield taxa like
Kappaphycus
,
Gracilaria
, and
Undaria
spp. and the expansion
of farming areas, especially in developing and low-wage countries (Pickering et al.
2007
). The incentives to introduce high-yield taxa are significant and the risks of
intentional seaweed introductions have not yet been evaluated with cost-benefit
analyses that include ecological and socio-economic consequences. The seaweed
industry in the new millennium is predicted to grow with increasing demand for
traditional seaweed products and for new applications of seaweeds, e.g., for the
production of biofuels and bioactive compounds. Selective breeding and genetic
modification to produce better cultivars for these applications is likely to add
another dimension of uncertainty. New “super strains” with high invasive potential
may be introduced to new locations with unprecedented consequences or may
interbreed with con-specific native populations and increase their invasiveness.
The potential for controlled harvest has been suggested as a positive conse-
quence of seaweed introductions, especially in areas where invasive seaweeds have
established in high abundance and eradication or ongoing control is not economi-
cally feasible. However, stringent harvest regulations must be developed and
applied to prevent further translocation and spread of invasive seaweeds into
areas previously unaffected (see Schaffelke and Hewitt
2007
).
In application of the precautionary principle of environmental management,
preference should be given to the development of sustainable commercial seaweed
culture in regions where a species (sensu stricto) occurs naturally. Valuable marine
