Benthos and Allochthonous Organic Matter in Streams

• Published in: Journal of the Fisheries Research Board of Canada
• Main Authors: Hynes, H. B. N., Kaushik, N. K., Lock, M. A., Lush, D. L., Stocker, Z. S. J., Wallace, R. R., Williams, D. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1974
• Subjects: Arctic; Canada
• Online Access: http://dx.doi.org/10.1139/f74-090; http://www.nrcresearchpress.com/doi/pdf/10.1139/f74-090

Investigations into the vertical distribution of stream animals by means of a coring technique have demonstrated that they could be found many decimeters down in the gravel; a maximum of 17% was found in the top 5 cm.Sampling of arctic streams revealed that chironomid larvae comprised 70–80% of the numbers in the benthos and that their rate of drift did not vary with the time of day.Life history studies of stream invertebrates have demonstrated clear seasonal patterns in Canada. Work has been done on several mayflies and stone flies, some Chironomidae, and two species of Gammarus. Currently the life histories of the stone flies of southern Australia are being investigated in which the seasonality is much less marked.After the experimental application of the blackfly larvicide Methoxychlor to two rivers, a catastrophic drift of invertebrates occurred and larvicide residues were detected up to 8 wk after application.Work on the decomposition of autumn-shed leaves in water has included the responses to temperature and to additional nutrients (N and P). The effect of nutrient addition was to increase the amount of nitrogen in the leaf after incubation, but temperature affected only the rate of decomposition. Determination of the relative importance of bacteria and fungi in decomposition, was studied with use of antibiotics, and food preference of Gammarus for several leaf species was determined.A considerable portion (up to 40%) of the autumn-shed leaf is water-soluble, and the way in which it is made available to stream animals was investigated. One process, its conversion into particles, appears to involve mechanisms similar to those found in soils, i.e. by formation of organic/metal complexes. Using infrared spectroscopy, attempts have been made to characterize the laboratory and field-produced particles. Field investigations have also demonstrated large-scale fluctuations, during only a few hours, of dissolved and particulate organic matter in the water.These findings are considered in relation to general stream ...