Effects of frequent streambed disturbance on the diversity of stream invertebrates

Abstract

We conducted a field experiment to reveal the effects of frequent streambed disturbance on the diversity of stream invertebrates in a local habitat patch in a Japanese stream. We used wire mesh baskets as experimental substrata and manipulated five levels of disturbance frequency (every 2, 4, 8, 16 or 32 days) in order to describe the pattern of the diversity of the stream invertebrates under different disturbance frequency and to explore possible factors generating the pattern. The total abundance and taxon richness recovered during 8-day and 2-day periods between each experimental disturbance, respectively, indicating that the stream invertebrates were highly resilient to disturbance due to their high mobility. The evenness of the invertebrate community was high in streambed patches with frequent disturbance. Patterns of the absolute abundance among the different disturbance frequency treatments differed substantially among nine common taxa. The absolute abundance of the most common taxon, Chironominae, was low in streambed patches where the disturbance frequency was high and intermediate, suggesting their low colonizing ability owing to their low mobility, compared with other common taxa. These results suggested that the diversity, in terms of evenness, of stream invertebrates in a local habitat patch is maintained by frequent streambed disturbance when the most common taxon has low colonizing ability. Our study demonstrated that differences in colonizing ability, caused by different mobilities, among community members may have a prominent importance when investigating the relationships between disturbance frequency and the diversity of organisms that have high mobility and actively colonize an opened patch.