The benthic ecology and community structure in Lyttelton Harbour ...

59.
analysis had shown that there were two fairly well
def~ned
muddy and sandy communities.
Secondly it had to show some relationship to
the picture ~uilt up over the sampling period of, the
inhabitants and their affinities. One should regard
with skepticism a statistical method which yields
results that differ from the observed biological
situation.
Initially it was decided that there may be
4 groups distinguishable on the basis of sediment tYre.
The 40 s1 tes, were then grouped into four groups of ten
sites. These decisions were made on the sediment type
alone but the discriminant analysis program would take
into account the numbers of species and the organic
carbon content at each site as well.
The sites in the four groups, after being subjected
to this initial discriminant function analysis, were
re~~ssigned.
Instead of being four groups of ten the
number in each group were 4, 5, 24 and 7 respectively
(see table 2). The first of these groups, h21, h20,
n12~ g28, presented a puzzle since there seemed to be
no binding factor. The only possibility was that this
was brought about by an abundance of the shrimp
Pontophilus australis at these sites. This hypothesis
was arrived at by examining the raw data sheets.
The second group, j1S, jl0, j9, k8, i20,
comprised mostly the Chione stutchburyi bed. The last
of the'group i20, although not in the main bed
correspond to an isolated occurrence of Chione in the
middle harbour (see Fig 15).
The third group, g22, 920, h20, 112, m12, k12
k14, g14, g22, h6, 14, g9, hll, j5, hl0, j24, i24, h18,
g23, f23, i7, m1S, i13, h8, covered all of the sandy