Download (20MB) - Repository@Napier

species was significantly affected. C. edule, M. balthica and A. mucosa showed non-
significant changes in abundance between any of the plot types.
Sediment water, organic and silt/clay contents and granulometry - The mean
values for water content, organic content, silt/clay fraction, median phi and sorting
coefficient for the sediments at the start of the experiment, after 6 weeks and after 20
weeks are given in Figures 4.4(i-iii). At the start of the experiment there were no
significant treatment differences for any of the sediment variables measured. Six
weeks after the start of the experiment, the weed significantly increased the levels of
all of the measured sediment variables (One-way ANOVA and Tukey test). The net
plot was not found to be significantly different from the unmanipulated control for any
of the variables measured suggesting that there were no significant artefacts associated
with the plastic mesh for any of the measured sediment variables. This implies that
the sediment accumulation observed within the net plots was probably natural and not
due to the presence of the plastic mesh.
After 20 weeks, there were no longer any significant differences in water content,
organic content, silt/clay fraction, median phi and sorting coefficient between the
weed treatment and net plots. This suggests that the effects of the weed on the
sediment variables were short-lived, i.e., as soon as the weed started to disappear the
sediments began to return to ambient conditions.
94