A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...
A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...
A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...
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(c)<br />
St<strong>and</strong>ing crop Nas measured as weight per unit. area or unit<br />
length <strong>of</strong> shore. Plants were either bagged <strong>and</strong> weighed on 100 kCj<br />
spring scales, or by the trailer load on a:x:le scales.. The surface<br />
area <strong>of</strong> each belt transect at Tautuku was measured beccluse<br />
the surface was smooth <strong>and</strong> devoid <strong>of</strong> major irlCegularities, 11 scale<br />
dra.wing ':Jas made, <strong>and</strong> 'che area was measured with a<br />
polar<br />
planimeter. 011 broken shores such as i:he transect at Kean Point<br />
(Section 2,.6), ·the surface area inhabited by D. <strong>antarctica</strong> was more<br />
difficult to measure. 'l'he surface area <strong>of</strong> each rock <strong>and</strong> rock face<br />
had to be measured by marking the surface out in quadralaterals <strong>and</strong><br />
triangles. This was a tedious process but wa.s much more accurate than<br />
simply using a planar measurement.<br />
The area <strong>of</strong> rock covered by holdfasts was measured by assuming<br />
holdfasts were circular, <strong>and</strong> measuring' their diameter, using specially<br />
constructed calipers measuring up to 0.5 m. Many composite holdfasts<br />
ax:e, in fact, oval, in which case the mi'l:x:imum <strong>and</strong> minimum widths were<br />
measured <strong>and</strong> the mean <strong>of</strong> these two values used as the diameter.<br />
On most transects both the width <strong>of</strong> the DurvilZaea b<strong>and</strong> <strong>and</strong><br />
shore slope were meaBured. Mean \vidth \",",,5 obtained by measuring the<br />
distance between the highes·t <strong>and</strong> lowest holdfasts ;;l.t intc:i.."Vals across<br />
the transect. Shore slope \~as mea.sured with an inGlillometer.<br />
A:ceas 1, 5, 6, 7, 8, 9, 10 on Ta1Jtuku Peninsula (Figs 2.3; S.lO)<br />
were cleared at different seasons to see if there was any seasonal<br />
change in st<strong>and</strong>ing crop ox density.<br />
(d)<br />
Morphological variation:<br />
Preliminaxy investigations revealed that. mOTphology va:ded<br />
wi th wave force. Samples were therefore selec'b3d from are.a.s subj ected<br />
to a wide range <strong>of</strong> wave exposures.<br />
It was appreciated thai.: local variation in morphology, si:cmding<br />
crop ox densi ty could be as great or even grea.-ter than any li'iti tudinal<br />
variation in these features. When collecting samples at dif£e:tenl<br />
l.atitudes efforts \'leze therefore made to compare areas subjected<br />
to similar conditioHS, especially waV8 force. Samples rc.nged from<br />
Scott Point on the North Auckl<strong>and</strong> {'Test coast to Ri..ng.:>xinga on S·te"/a:ct<br />
isl<strong>and</strong>, a latitudinal interval <strong>of</strong> 12°30'.
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