caulerpa taxifolia in moreton bay - Centre for Marine Science ...

3.4.2 Experimental design
Caulerpa taxifolia in Moreton Bay
60 cores of C. taxifolia (106 mm diameter) were collected and washed and ground into
a homogeneous paste using an electric blender. This paste was applied to the surface of
the sediment of the pots of seagrass using a cut-off 60 ml syringe. Three treatments,
replicated in four tanks, were 1) control (no C. taxifolia extract added); 2) low dose of
C. taxifolia extract; and 3) high dose of C. taxifolia extract. The three cores of seagrass
in each tank were subjected to the same treatment to prevent contamination. The low
dose of C. taxifolia extract treatment consisted of the equivalent of one core of
C. taxifolia biomass per core of seagrass (30 ml of C. taxifolia extract), and the high
dose of C. taxifolia extract consisted of the equivalent of four cores of C. taxifolia
biomass per core of seagrass (120 ml of extract).
Prior to initiation of the experimental treatments, initial measurements were taken of
seagrass shoot density of each core, the number of leaves per shoot of 10 haphazardlychosen
shoots within each core, and the maximum leaf length of the longest leaf of 10
haphazardly-chosen shoots in each core. These measurements were repeated each
week for the three-week duration of the experiment. Fluorescence using the PAM
(pulse-amplitude modulated) fluorometer was also measured prior to experimental
treatments. Fluorescence was measured every three days for the duration of the
experiment. This experiment was terminated when it became apparent that the
seagrass cores, particularly those of Z. capricorni were experiencing stress that was
independent of the experimental treatments.
3.4.3 Effect of Caulerpa taxifolia extract on Zostera capricorni
Due to the variability of response of Z. capricorni in the experiment with three
seagrass species, the above experiment was repeated using only Z. capricorni and
with the following additional changes to the experimental design (Figures 7 and 8).
Larger cores were collected (36 in total; 150 mm diameter) and acclimation was
limited to one week in an attempt to reduce the stress to the seagrass that was apparent
after five weeks of acclimation in the previous experiment.
An additional 36 Z. capricorni shoots were haphazardly collected at the same time
and from the same area as the cores. These shoots were analysed for pigment
concentration, for comparison with shoots harvested from the experimental cores at
Jane Thomas -15-
Materials and Methods