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

190
On areas cleared during spring and summer there was relatively
little, or no regrowth of D, antarctica for at least 3~
clearing,
Tautuku Area 9, for example, was cleared in early
years after
November 1973. Wi thin several days I many of the red and green alga;.e
left on the rock showed signs of bleaching'.
This applied
particularly to the foliose species and to Codiwn adhaerens.
weeks later, almost all the (?)Lithothcormion and a:cticulated
corallines were bleached, and the thalli of the larger foliose red
algae (with the exception of Pachymenia Zusorial were reduced to
basal remnants.
Five
This damage was only temporary, however, and the
same species, albeit as more stunted and tufty forms, soon began to
caver the rock (Fig. 9.l4d).
In addition, other algae, not normally
found i;unongs·t DlCt'Vi Zlaea hold£asts, invaded the cleared spaces.
UZva Zaetuca was the most important of these and quickly colonised
old ho;ldfast sites (Fig, 9 .14c) and bare patches in the upper two
thirds of the cle~red
areas.
Six months after clearing, much of area 9 was covered by
CoraZZina cuvieri, C, piZifera, BaZZia hirsuta, UZva laetuca and
PoZysiphonia sp.
'rhe last of these species formed large furry patches
on the bare areas, and on the paint-like algal patches in the upper
half of the kelp band. Patches or Chond:r>ia, GgZidium and clumps of
I
Pachymenia had expan~ed, and Porphyra coZumbina covered an upper
corner. SpZanchnidium Y'Ugosum \\]as scattered throughout, Only six
D, antarctica plants were found, and these were small specimens
which were missed When the area was cleared.
The overall appearance
of the site was similar in July 1974, except that there ~Ias
obvious increase in PoZysiphonia and UZva (Fig. 9.1, column 4) .
December, the PoZY8iphonia had disappeared, and the site was domina. ted
by a turf-like layer of articulated corallines (mid a'l.d lower third),
and Ulva (mid and upper third).
The Durvillaea plants had d1sappeaxed.
an
A similar sequence of events occurred on all o'thcr Tautuku
sites cleared during spring and surr~er (Fig. 9.1). The general
trend was for a decrease in the area of bare rock, and paint-like
alqae such as l-lildenbrandia,
by the expansion of a corCl.lline,·dominated
turf, and the settlement of such opportunistic species as VIva.
Area 6a, for example, the area suitable for DurviZZaea colonisation
decreased fram 64.3% to 22.0% in two years 0
were slight differences in i:be composi t.ion of
Admittedly, there
each
On
In