A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

was heavily colonised~ On Area 7, for , the density of
D. antaPctica on old holdfast sites in
\'las 940 :!: 144/m2
t.o 70 ± in other areas. For this reason then, and
also because holdfasts cover up to 23% of the rock surface 2)
it is advantag'eous to remove hold£asts when harves·ting in aut:umn and
If this is not done, then most of the
which
settle on old holdfasts (Fig. 9. are later lost when the holdfasts
rot away. HO .... Jever. when in and su:mmeri it is
probably best to L!'!ave the holdfas'cs on the rock. If they oXe
scraped off, then the bare sites are colonised by seaweeds
such a.s Vlva, Enteromorpha, and a val: of red algae.
If are left, then the rock beneath the holdfasts becomes available
for recolonisatiol1 in the winter when are released.
(b)
1\'S mentioned
or part of the
lamina, do not
7 , methods that leave all
, or that involve the removal of most of tl1e
in any significant regeneration of tissue, and
ultimately cause both
and holdfaet to rot at·lay.
9.5
Only two areas of D. llaYia were and in both cases,
clearing was carried out in summer.
All plants were removed, but
holdfasts were left because they were too difficult to remove.
The
events which followed were in many \-J'ays similar to those which
followed removal of D.
in sm~er.
An area of 43 was cleared in the wilZana
belt near Parititahi Tunnel, Kaikoura, on 16 January 1~n3,
1 the flora was sparce, Below E L.W.S.
there were scattered specimens of Mapginapiella boryana,
variegata, Gl08sophora kunthii,
sp., Chaetomorpha dar~inii,
Pterocladia land Hymenena sp,
Between the holdfasl:s
above low water, there were patches of a PoZysiphonia spo,
of
~1ond~ia, CZadophora, Ballia and articulated corallines, and
a fet>l CaY'pophyllwn fle:x:uosum and
'I'he
ubiquitous, pale pink,
like (?)LitJ'lOtJwmnion was common.
"'-iter ilie red , and
tomorpha were bleached. fol1oT"ling autumn