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

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growth rate. D. anta~cti~a plants recolonising experimentally
cleared areas gre~1]
much faster at Tautuku than at Kaikoura Over a
period of three years.
Observations similar to these I have made concerning phenotyPic
variation of DurviUaea have been made by other workers for a.
of large brown algae I and their conclusions were similar. Wilrce
(1965) stated that the gross blade morphology of many species of
Lamina~ia is highly plastic and of little systematic value. In
Norway Sundene (1964) shmV'ed very conclusively by transplant
expel::iments that the breadth of Laminaria digitata blad.es was greatly
inf luenced by \1aVe force. He found that young specimens transplanted
from exposed places into relatively sheltered waters developed int.o
broad bladed forms thereby resembling forms native to sheltered
areas. Similar observations were made by Norton (1969) for
Saccorhiza poZY8chides (Lightf.) Batt. in Ireland and the Isle of Man.
In the northwest Pacific, Druehl (1966) noted that Lconinaria
setcheUii Silva exhibits considerable morphological variation
characterized by its blade becoming broad, and the degree of
dissection decreasing with transition from exposed to sheltered water.
In Nova Scotia Mann (1971) and Chapman (1973) showed that the
characters normally used to separate Lconinaria longicruris Lamour.
and L. agardhii Kjell.. ~V'ere unsatisfac>cory because they change with
age, with wave eXposure/ and because forms intermediate between the
two species were common. They found that stipe length and the
stipe proportion of total plant length decreased with diminishing wave
force. Mann showed that there were differences in stipe morphology
between populations at various depths, and Chapman noted that there
was a trend for stipe length to increase with depth.
Amongst the large brown algae, D. antaY'cticQ is :~he only species
t'lhich achieves buoyancy by the fo:r.:mation of honeycomb tissueo The
laminae of all other species are typically buoyed by discrete gas
filled vesicles. The trend for honeycombing, and hence buoyancy
to decrease with increasing shelter contrasts with what appears to
be a general trend amongs t: 'other brollffi alg a,e • Ascophyllum nodosum
is more buoyant in sheltered condi tions than in eJcposed places because
the frequency and the size of vesicles increases with diminishing
wave force (David 1927, David 1943 and pers. obs.). 'Powell (1963)
described 0. similar trend for F'ucus V88icuZosus. This apparent
contradiction is due to the t\V'o very different means {)f obtaining