Biology Reference
In-Depth Information
within 10 h and killed the alga via osmotic shock and cell lysis while having only
minor effects on native biota. Additionally, no fronds were present in salted areas
6 months later (Glasby et al. 2005a; O'Neill et al. 2007). Researchers determined that
the salting process worked best in cooler months when
C. taxifolia
died back natu-
rally and that a thick, continuous covering of salt worked significantly better than
salting discrete patches. For deploying salt, researchers compared hand dispersal vs.
using a hopper on a flat-bottomed boat. Although waters deeper than 5 m allowed for
too much horizontal dispersal in the water column for salting to be successful, in
shallower waters the hopper method cost $A7 per square meter (2005 values) (Glasby
et al. 2005a). Salt deployment by hand cost an average of $30 per square meter at the
same time. Glasby et al. (2005a) suggested that colonies should be mapped during the
warm season, followed by repeated salting of the infestations during colder months.
Glasby et al. (2005a) additionally calculated a cost of over $A60 million to cover all
C. taxifolia
in NSW with one application of salt, using the hopper method.
15.5.5
Other Treatments: Temperature Shock, Ultrasound,
and Genetic Control
A variety of additional methods to kill
C. taxifolia
under field conditions have been tried
unsuccessfully. While cold shock killed fragments in the laboratory (Williams and
Schroeder 2004), dry ice applications were not successful in the field. With dry ice, only
sublethal necrosis was obtained (Thibaut 2001). Likewise, when fragments of
C. taxifolia
in the laboratory were heat-shocked at 72°C for 1 or 2 h, the fragments died (Williams
and Schroeder 2004). However, underwater applications of hot water at or above 40°C
appeared to work initially, but recovery was observed after 3 weeks (Thibaut 2001).
Underwater welding devices to boil the plants also were not successful (Madl and Yip
2005). In situ application of ultrasound did not destroy plant tissue (Boudouresque et al.
1996). However, in a feasibility study for genetic control of
C. taxifolia
, Thresher and
Grewe (2004) stated that a species-specific biocide based on an enzyme critical for pho-
tosynthesis or osmoregulation could be developed and then delivered in pellet form.
15.5.6 Biological Control
Many scientists and managers hypothesize that the only hope for control of
C. taxifolia
will involve biological control. Thresher and Kuris (2004) suggested that most current
efforts to eradicate or control high-impact marine invasive species that are deemed
acceptable to stakeholders are low risk and publically acceptable, while biological
control remains more contentious for both social and political reasons. Thresher and
Kuris (2004) continue by stating that contentious possibilities will not occur on a large-
scale until scientists and managers learn more about biological control agents.
