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

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numerous narrow channels. On the Kaikoura coast, particularly
between Oaro and the Kahutara River, this t.ype of shore is periodically
subjected to the deposition of shingle and sand. \Vhen storms undercut
the road embankment further inshore, loose rna terial is depo S1 'ted
temporarily in the upper sublittoral and sublitt.oral fringe,. D.
willana la~minae and holdfasts are abraded, until the shingle and sand
is deposited elsewhere. This usually occurs before the plants are
seriously damaged. If the input of shingle was more·-or-less
continuous, then I am sure that small D. willana plants would be
unable to become established, and that. the holdfasts of large plants
l'lOuld be severely damaged.
Intolerance of D. willana to shifting deposits of shingle and
sand perhaps explains why this species is less common on the
Kaikoura Coast north of Kaikoura Peninsula, 'chan on the southern
coast. On the south side, the shore slopes very steeply. Within
1 km of the shore the depth is 200 ro. Shingle is quickly washed down
the slope, and is only temporarily deposited amongst the D. willana.
North of the Peninsula the shore slopes less steeply. Small deposits
of loose material are a permanent feature of the slLblittoral fringe
and upper sublittoral.
(v)
Salinity
In New Zealand, the only areas of open rocky coast that are
at least periodically immersed in brackish water «25°~o) occur near
river mouths. Both Du~viZZaea species grow within 0.5 kID of the
Kahutara River near Kaikoura. Salinity at the mouth of this river
is 22%0 (13 August 1975). Slightly further south (0.8 km) the
salinity ",as only slightly less than normal (32%0). Presu..I"tlably
much lower values would be obtained this distance from the river
mouth ... 1hen the river is in flood. Water samples collected at intervals
over the tidal cycle from amongst D. anta:t'etiaa growing a't the
mouth of the Tautuku River (August 1975) shO\\l'ed that the salinity drops
to 7" 4%'() '.\Then the tide recedes, and returns to normal shortly after
low wateL At the Nile RiVer, 20 Jan south of Cape Foulwind., both
species grm