Tolerance Determination of Certain Benthic Invertebrates as Indicators in River Water Quality Monitoring

Abstract

River survey work which assessed biological and chemical status of over one hundred randomly selected rithron stations spanning four Water Authorities is documented. Water quality has been correlated with benthic macroinvertebrate distribution and alteration in community structure, with specific regard to caseless Trichopteran distribution recorded. Organic pollution, R. Tean, Staffordshire, and heavy metal pollution, R. Ystwyth and R. Rheidol, have been investigated in the field to further knowledge on the usefulness of caseless Trichopteran species as indicators and/or monitors of pollution. The tolerance of the larvae of the two species, Hydropsyche angustipennis and Rhyacophila dorsalis, to increased organic load was studied by experimentally simulating three different water qualities. Mixtures of high quality river water with sewage effluent were prepared at the Aston Hydrobiology Field Station at Checkley (R. Tean) Staffordshire, providing intermediate field/laboratory conditions. Major factors influencing Trichopteran distribution included temperature, dissolved oxygen, pH and heavy metals. Acute toxicity studies on H. angustipennis demonstrated the toxic effect of copper and zinc under variable conditions of water hardness, and the bioconcentration of zinc was demonstrated by the use of radioisotopes. Additional experiments investigated the acute toxicity of ammonia and two pesticides to the larvae. The effect of temperature, dissolved oxygen and pH on the respiration rate of H. angustipennis was investigated using an apparatus specially developed in the laboratory. A modified Rank Electrode served as a respirometry chamber, whilst a further part of the system delivered test water at different oxygen and pH levels, other parameters being kept constant. Using this method, the effect of individual parameters involved in pollution was investigated. Recommendations for the use of certain benthic macroinvertebrates for use in water quality monitoring are documented. Appendices contain data from field work investigations and relevant literature has been reviewed.