Effect of substrate stability and canopy cover on stream invertebrate communities

Abstract

Disturbance can be an important determinant of stream benthic invertebrate community structure. Whether this is a result of the direct loss of invertebrates, an alteration to the food base of the community by the disturbance, or a combination of both, is never clear. We examined this question by conducting a disturbance experiment under artificial cover where low light limited periphyton growth and minimised the effect of disturbance on periphyton abundance. The experiment was conducted using baskets of natural substrate in a spring‐fed Taranaki Ring Plain stream, Taranaki, New Zealand during February and March 2000. Baskets were placed in the open or under cover and half were disturbed every week for 4 weeks. The artificial cover dramatically reduced periphyton biomass. Presence or absence of cover was the primary determinant of what invertebrate taxa dominated in the baskets, most likely as a result of differences in food resources. The filter feeding Coloburiscus humeralis dominated numerically in the covered baskets, whereas the generalist grazers Deleatidium spp., Beraeoptera roria, Orthocladiinae, and Diamesinae dominated numerically in the open baskets. However, cover had no effect on the overall abundance and species richness of the experimental baskets but disturbance reduced abundance and to a lesser extent species richness.

Keywords:

• community structure
• cover
• disturbance
• diversity
• macroinvertebrates
• periphyton
• substrate stability