The Influence of Substrate Stability on the Composition of Stream Benthos: An Experimental Study

Publisher Website
Google Scholar
Abstract
Artificial stones having identical surface area and complexity, but different specific densities, were placed in four Swedish stream riffles. The rate of movement of stones was assumed to be related to their density. Invertebrate colonization showed indications in agreement with the intermediate disturbance hypothesis although these were weak and not conclusive. More significant positive (22 and 38%) and negative (16 and 11%) correlations among pairs of the most common species were found in two of the streams than would have been expected by chance alone (2.5%) suggesting biotic interactions. In general, blackfly number positively correlated to species richness, and this correlation was probably related to the structuring effect of the cocoons of Prosimulium hirtipes which resemble moss. While some species (e.g. Eusimulium cryophilum and Polypedilium laetum) dominated the lightest artificial stones, others showed higher incidences on stones of intermediate (e.g. Agapetus ochripes, Hydropsyche siltalai and Polycentropus flavomaculatus) or high densities (e.g. Gammarus pulex and Rheotanytarsus spp.). The patterns may be interpreted as interspecific differences in colonization abilities or strategies.