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

50.
mud portions of the harbour. These principally are in
a strip extending from Ripapa Island to Quail Island.
The nature of this substrate seems to have been
determined and maintained by the tidal currents as
described in section two.
While the highest proportion of organic material
is found in the muds there is still a sufficient quantity
in the sandy muds to support the many detrital feeders
there.
The largest beds of filter feeding lamellibranchs
are also located along the current tracks. This is shown
particularly well by consideration of the distribution
diagrams of Chione stutchburxi and 'Myadora striata.
With the type of sediment divided into the three
classes; sandy, sandy mud, and muddy, there clearly
a change in the relative proportions of the three types
of animals; filter feeders, d~trital feeders, .illd
predators. Detrital feeders predominated in the muddy
regions, filter feeders in the sandy mud parts, and
there was a slightly higher proportion of filter feeders
in the sandy regions.
While the 24 indicator species were chosen for
their abundance and ability to 'show certain tendencies,
the species list shows that there were many other species
found although many were very rare. Most of the fauna
corresponds to that common throughout New Zealand in a
sheltered shallow water inlet such as Lyttelton •
. Similar associations were found by Powell (1937) in
Auckland and Manukau Harbours.