Rotifer occurrence and trophic degree

Information on the distribution of planktic, periphytic and benthic rotifers from diverse waters in south and central Sweden was analysed for details on relationships to the trophic degree. Three factors were combined in order to get an estimation of the trophic degree: tot-P-content, electrolytic conductivity and content of dry matter. Indicators of oligotrophic and eutrophic environments are enumerated. As far as the planktic species are concerned, the results are largely compatible with those of earlier investigations (while the non-planktic forms were previously less known in this respect). Some eutrophy indicators have been reported as typical of saprobic environments.     

On limnic micro-crustaceans and trophic degree

A large material of planktic and semiplanktic microcrustaceans from different types of waters in south and central Sweden was computerized. The more frequent species were ranked according to phosphorus content (tot-P), electrolytic conductivity and content of suspended matter, searching for correlations with the trophic degree. With few exceptions, species indicating oligotrophy are found at lower factor values and those indicating eutrophy at higher values concerning all the abiotic factors considered.