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

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9 . 6 SUMMARY OF RESOLTS
D. antapctica quickly reestablished itself on areas cleared
autumn and winter, but on sites cleared at other times of
year, especially during the spring, regrowth "las very sloN_ This
was because a of other seaweedS covered the rock surface
and summer, and thus effectively prevented recolonisation
in the next \'linter.
Of the thousands of D. antapctica per square metre which
in suturon and "winter;"cihTy '"asm"fl1
perce survived for at least one year. Those survivors
however; grew dly and within two years the stand crop of the
swards was several times higher than normal. Some
ants reached 4 m in two years. First signs of
n9 were detected ayear, but it took at least two
years for to become fertile. Relatively few D. antarctica
in recolon
had discrete holdfasts, compared to the
20-40% recorded in natural beds; and the number of plants per
holdfast was
higher than in natural beds.
had the effect of increasing the growth
rate of small However, since composite holdfasts
wi th severed soon rotted, many small were subsequently
lost. l~growth on areas was not as fast as on areas where
the was cleared. The same wet weight of fronds as
obtained can be by reculling two or
three years later.
the second crop will contain few, if
any,
Recolonisation
\'las heaviest on the bare patches
of rock
'ii/hen holdfasts \'lere removed in autumn and winter.
If hm.,tever, the holdfasts were removed in spring and summer I then
opportunistic such as
the old holdfast
sites, and prevented their recolonisation
There was evidence of a h
Uaea.
mussels afte!'
D. antarct-ica was cleared" This .~J-'l""-­
canalicuZus. However, mussels appear to be able to the
cleared areas sQQsequently.
Recolonisation by' D, wit lana woul 1
probably be fastest on areas harvested autumn and wint:el::" ..
On areas harvested duxing ng a,nd
SU:lllme,t",
of the kelp can be e:npected to take several years.
the