Some Factors Influencing the Distribution of Macro-Invertebrates in the Riffles of Organically Polluted Streams

Abstract

The literature relating to various aspects of fresh-water ecology has been reviewed. Special attention was paid to that dealing with’ limiting factors in fresh-water, methods of sampling bottom fauna, water pollution ecology and experimental work on fresh-water invertebrates. The effects of sewage effluent discharges on water quality and the riffle benthic community of a number of Midlands stream. were studied. The riffle community was sampled quantitatively and it was found that it was possible to relate different benthic communities to varying degrees of organic enrichment. The importance of seasonal changes in influencing distribution was observed and commented upon. Special attention was paid to the distribution of the Chironomidae in polluted waters, this group was found to be particularly abundant and different species varied in their tolerance of polluted conditions. In the laboratory, apparatus was constructed to study the effects of some of the factors associated with organic pollution on a number of Invertebrates associated with varying degrees of organic enrichment The factors investigated wore low dissolved oxygen concentrations, undissociated ammonia, dissolved carbon dioxide and potassium ortho-phosphates. It was found? that invertebrates associated with polluted conditions wore usually more tolerant of these factors than those found in good quality waters. Wherever possible the combined effect of these factors was studied and it was usually found to be more toxic An attempt was made to explain the distribution of the invertebrates observed from field work on the basis of the experimental results. In many cases it was found that the experimental results could explain the presence or absence of a species from a particular locality. Notes, are included on the biology of some common benthic invertebrates in relation to their use as indicators of organic pollution.