Interactions in Stream Leaf Packs: Effects of a Stonefly Predator on Detritivores and Organic Matter Processing

The influence of a common perlid stonefly predator, Diura nanseni, on the turnover rate of leaf material in leaf packs and their associated fauna was investigated in laboratory and field experiments in northern Sweden. In the laboratory experiment significant indirect effects of the predator were demonstrated upon leaf mass loss and the densities of two nemourid stoneflies, Nemoura avicularis and Protonemura meyeri. There was evidence of non-lethal effects on the two species expressed as increased wound frequencies and reduced condition. In the field experiment predator influence on leaf turnover rates was supported but there were no discernible effects on prey densities