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

51.
SECTION 4
COMMUNITIES
4.1 Introduction
Assemblages of animals are very· rarely present
as discrete groups with clear cut boundaries. Grouping
therefore must be inferred from consideration of the
interaction of the fauna with variotis physical and
chemical factors. The habitat must be shown to be
reasonably constant, supporting a stable population
before the existence of a community is considered. In
most regions one or more species seem to dominate samples,
and providing they are a permanent feature of the local
fauna, may be termed indicator species. Such species
usually have varying tolerances within the study' zone
and may serve to delimit communities. This approach may
not be valid where a rarer animal shows a very patchy
distribution at points where its' narrow requirements
are met· exactly.
4.2 Community concepts
The pioneer in benthic community ecology was
undoubtedly Petersen whose major publications '(Petersen,
1913 and 1914), set up basic principles which have been
used by most later inves gators as a starting point
for their own approaches. Since that time the recognition
of communities have become a basic aim of benthic
ecological studies. Two schools of thought have evolved,
the statistical and biological approaches. Petersen
was an adherent of the former with the aim of avoiding
subjective conclusions. Conclusions reached by his