The ecology and proximate composition of some plants and animals in running waters were studied in an attempt to elucidate some aspects of the relationships between different trophic levels. Although algal communities almost always showed a spring bloom, apparently in response to increasing day length, the standing crop subsequently showed considerable variation. This was often attributable to such factors as either the direct or indirect effects of flooding or to the interactions between communities. No marked seasonal trends were observed in the amount of lipid found in algae from field collections, contrasting with the situation in the larval lamprey, a microherbivore. Algae generally made only a small contribution to the total organic fraction of the suspended and epilithic material. Although the microflora formed an important component of the diet of Asellus and Gammarus, only in the case of Paramecium were microphagus feeders apparently effecting the standing crop. Lampreys accumulated large neutral lipid reserves at the end of both the larval microphagous and adult carnivorous stages, an adaptation to the metabolic demands of the subsequent lengthy non-trophic phases. The vertical distribution, degree of motility and seasonal changes in the biology of various crustacean species were important in determining their use as a teleost food source. Other factors affecting fish feeding were hunting behaviour, visual acuity, mouth morphology and dimensions, and the temperature and turbidity of the water.
|Date of Award||1975|