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

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however 1
the articulated corallines, Ballia, Chondria and Cladophora
expanded to form a red algal turf ben/een the holdfasts.
Ulva also
covered much of the rock in the lowe~ littoral. In the shallohPs,
Margina't'iella and Lessonia plants had grown much larger.
D. l.dllana holdfasts rotted more slo\J!ly than D. antaY'ctica holdfasts,
and most were still extant four-six months later when D.
W1:Uana \.... as releasing gametes (Chapter 6)" By this time the areas
between holdfasts were almost totally covered by other algae, so
that: there was very little substrate available for recolonisation
by D. willana. Thus very few small D. wiZZana plants appeared in
spring, and over the following summer (1973/74) there was no
significan'c regrowth of the kelp. During summer, many of the D.
willana holdfasts decayed, and the old holdfast sites were quickly
colonised by UZva. and to a lesser extent, GZos8opho't'a.
Some holdfasts in the subtidal rotted more slowly, and the
patches of bare rock beneath were therefore exposed later during
autumn and winter. These sites were colonised hy D. willana" By
November 1974, small patches of 2-3 em plants could be seen grm'ling
belOw ELWS.
There was no settlement of the kelp in the lower
Ii ttoral. These small plants \"ere I however 1 heavily grazed by
fish, so that by May 1976 (41 months after clearing) there was only
sligh tregrowth of D. wi llana.
Instead, the area was dominated by
M~gina~iella, Ca~ophyllum and Glo88ophora. Any D. willana plants
\>lere small (less than 0.5 m long) and cont ined to the subtidal regions
of the area.
It is not known whether a lawn-like sward of D. willana plants
would have developed if these areas had been cleared in the autumn
or winter.
The small clusters of plants which colonised some of the
subtidal holdfast sites, suggested that this \-Jas possible, if
g~azing by fish was less intensive.
The second and much more recent D. wi l lana clearance was at
(3 Ma .... r~17)
Tautuku, below Area 7 on First Slope\ Preliminary observations
BU9gest that a sequence of events very similar to that seen i'),t
Parititahi, is occurring in this area, although there is a noticeable
absence of the larger brown algae such as Mar>ginarieZta, Glossopho't'a,
Car>pophylZum and HaZopteris.