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

70.
the posi on of the Lyttelton bed of Chione. There
a very abrupt change from the sandy region to a
mud ~ubstrate
which has been shown to be relatively
depauperate in species. Because of this there may he
little scope for migration in from surrounding regions
of competitive specieso This together with the physical
attributes of the region that seem to make it ideal
for the establishment of the Chione combines to crea t:e
a uniquely pure assemblage of animals. The density
of Chione is not exceptionally high, similar concentrations
having been found in a nearby estuarine habitat
(Voller 1972).
Powell found a definite correlation between
bottom type and the communities existing on them and
proposed that a succession was occurring with the
changing of the bottom from the original muddy state
of the harbour floor to a hard stabilized substrate
with the addition of shell -fragments.
Estcourt (1967) in investigating the fauna of
the sheltered parts of Marlborough Sounds was dealing
with a stable, well ~stablished muddy bottom. This
superficially bears some resemblance to the state of the
upper portions of Lyttelton Harbour but the fauna, rich
in northerp warmer water species,was generally almost
totally different. Chione stutchburyi was found at
only one station, although large numbers of dead
shells were dredged. Hemiplax hirtipes was present
but Vir.qularia gracillima was not found at any sites
sampled. The role of the ophiuroid Ophiomyxa brevirima
was taken in the sands by the northern species Amphiura
rosea and An norae. Golfingia cantabriensis, a
sipunculid taken in Lyttelton Harbour in very small
numbers was present as was the large horse mussel