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

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CHAPTER FOUR
DIS'l'RIBtJTION
4.1 INTRODUCTION
This chapter outlines factors 'cha.t largely determine the local
distribution of DuY'1JiZZaea. The distribution ot D. anta:rctica and
D. zuillana is described in detail, and an account of the "lOrld-wide
distribution of species is provided.
Earlier biog"eographical maps that included DurviZlaea (Knox
1960: Fig. 61; Zinova 1966: volol, pl.129) were on avery small scale
and did not supply the sources of the distributional records. In
this chapter are listed the records that have been used to compile
a more detailed and accurate map of species distributions. In general,
it confirms that of Knox. but includes biogeographical info:cm.ation
that has become available in the last sixteen years,
4.2 FACTORS RESPONSIBLE FOR THE LOCAL DISTRIBUTION OF DURVILLAEA
(a)
Horizontal distribution!
(i)
Wave force
Around Kaikoura Peninsula both D, antarctica and D. willana are
confined to areas permanently or periodically subjected to \i!ave action
rated subjectively by Rasmussen (1965) as IV or V (see Chapter 2 for
Rasmussen's scale). Most Durvittaea occurs in areas classed a,S IV
or V regardless of the state of the tide, or the dir€;"d.on and strength
of the wind. The most sheltered habitat on the Peninsula. where the
kelp grows ,is probably between the Fisheries Wharf and the Marine
Labora tory (Fig" 2,2)_ According to Rasmussen's mi'l.ps of \.,ave force,
this area receives grade IV and V waves during stx:nng northerlies
and grade III with gentle northerlies. With strong southerlies wave
action is aga.in IV and V, but it drops to as low as grade I when they
are weak.
Observations made elsey/here \-Jere similar" I have never seen
ei mer Dur>vitlaea species grmlling in places where wave aetj.on j_s
permanently less than grade IV., Morton and Miller (1960:302) stated