A METHOD OF QUALITATIVE BIOLOGICAL RIVER SURVEY 247
Fig. 2. The inter-relationships of plants and animals with oxygen and
carbon dioxide
chemical interplay. Some of the more important are Calcium,
Magnesium, Sodium, Potassium, Iron and Chlorine. So closely
related are these chemical and biological cycles that it is impossible
to complete one cycle without frequent reference to the other.
Two environments exist in such a system; there is the internal
environment of the organism which possesses its own bio-physico-
chemical cycles and the external environment with which we are
interested. A study of the conditions existing external to an
organism will therefore, in part at least, reflect the internal
environment of the organism itself. The most important factors
affecting the complex life of a stream are: rate of flow, river bed,
temperature, pH, dissolved oxygen.
There must necessarily therefore be limitations to what I have
termed a "Biological River Survey". What I have attempted
is to try to find a relatively simple method of estimating animal
life in a stream or river. A method, which, due to its simplicity, is
readily reproducible and which will provide information enough
for the construction of a food cycle. A comparison between the
food cycles of areas polluted and unpolluted on the same river,
along with defined chemical and physical states of these sites can
then be used to diagnose a biological and chemical state of
pollution. As already emphasized, the factors which determine