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

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(iii) Turbidity
Despite the fact that D. wiZZana is less tolerant than D.
antarctica of very strong wave force, it does not extend further
than D. antarctica into semisbeltered waters. In 'c.hese regions {~he
sea is often murky, and it could be that Do willana is less tDlerant
of turbid conditions than D. antarctica. D, antarctica e~ctends
further than D. willana into muddy bays and harbours on Bal~s Peninsula.
Only D. anta:r>ctica grows at t.he moutb of the Tautuku :eiver. where the
~..rate:r
is invariably turhid,
(iv)
Substrate
Rock type has little effect on the local distribution of
Dur-villaea. with the notable exception of recently uplifted mud~
stones such as occur along the south Taranaki coast, almost any sort
of rock is colonised. The Kaikoura Peninsula shore consists of
alternate platforms of soft siltstone and hard limestone. Most
DurviZZaea grows on the siltstone, but this is mainly because most
of the areas subjected to grade IV and V waves are this rock type,
Hard limestone areas elsewhere on the Kaikoura coast support large
beds of DurvilZaea, D. antarctica has been seen gro",ing abundantly
on andesitic breccia (Piha), greywacke (Ohau Point), coarse basalt
(Banks peninsula.) , granite (Snares I.), sandstone (Tautuku), diorite
gneiss (Milford Sound and Resolution I.) and intrusive volcanic rocks
(near Riverton) . I have also seen this species growing on concrete,
steel, wood and even plastic substrata.
Both species are long-lived (Chapter 7), and the stability of
the substratum is more important than the rock type. Rock platforms
and cliffs are tbe best habitat, nlthough some stable boulder coast.s
support Durvillaea (Fig. 4.le). Large rocks or rocky outcrops 0n
shingle or sand beaches are suitable habitat for D. m~taX'ctica, but
rarely support D. wiZlana. On this type of shore there are constant
changes in beach level. Most D. antal'ctica are confined to tbe tops
of rocks because lower levels axe periodically buried in the beach"
cnd constantly scoured by sand or shingle. Occasionally, when rocks
are completely buried, the D. antarctica stipes appear to be growing
out of the sand" Buoyant D, antal'ctica laminae rarely become buried
in gxavel or sand. Only in semiahel'tered areas ,.;here honeycombing
is poorly developed do laminae sometimes become partly buried.
D, wiZZana grows most abundantly on gently sloping rock plat-'
forms, especially those studded "lith large rocks and dissected by