Technical highlights - Department of Primary Industries ...

Progress in 2010–11
Cabomba regeneration—
nutrients in solution
Cabomba regenerated readily from
single-node fragments, independent
of nutrient availability in the culture
solution (Figure 24.1 and Photo 24.1).
Only 4 weeks after fragmentation,
about 50% of all fragments grew
new shoots. Towards the end of the
experiment, there was a decrease in
cabomba health in the high and medium
nutrient concentrations due to excessive
algal growth. Overall this means that
cabomba does not depend on nutrients
available in the water to regenerate,
but is probably able to use internally
stored nutrients for initial growth.
Consequently, cabomba would be able
to establish from single-node fragments
even in habitats with low nutrient
availability (oligotrophic systems).
Cabomba establishment—
substrate types
The experiment was conducted from
March to December 2010. There was a
pronounced difference between cabomba
establishment in the mesocosms with
different substrate types. Cabomba
clearly prefers fine substrates (sand)
and did not establish well even in fairly
fine gravel (Figure 24.2). However, there
was a fairly high variability in cabomba
establishment, even within the same
substrate treatment, indicating that other
factors are also important. Nevertheless,
while two of the sand mesocosms were
completely filled with cabomba after
8 months (Photo 24.2), there was very
little establishment of shoots in other
substrate types. This clearly shows that
cabomba establishment is limited to
suitable substrates.
Photo 24.1 Cabomba fragments
Shoot wet mass (g m –2 )
1200
1000
800
600
400
200
0
sand fine gravel coarse gravel cobble
Substrate type
standard deviation
Figure 24.2 Cabomba establishment and growth, measured as shoot wet mass, as affected by
substrate type
Photo 24.2 A fine sand mesocosm with strong cabomba growth after 8 months
56 Technical highlights: research projects 2010–11