The role of drift and effect of season on macroinvertebrate colonization of implanted substrata in a tropical Australian stream

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Abstract
SUMMARY 1. Experiments using implanted substrata were conducted in Yuccabine Creek, a n upland stream in north‐eastern Australia which exhibits a strong seasonal pattern of discharge and temperature. The implanted substrata were either set in the stream bed or were raised in the water column. Three experiments were run, at different times of the year.2. Colonization rate was dependent on benthic abundance, mobility of the fauna and distribution of resources. The rates on embedded trays were similar in the late wet season and mid dry season, but colonization rate in the late dry season was greater.3. Drift alone could have accounted for all colonization in the late wet season, 63% of colonization in the mid dry season and less (unmeasured) in the late dry season. Drift acts to disperse early instars to patches of suitable habitat after the summer wet‐season peak in reproduction.4. Following the wet season, stream discharge decreases, benthic abundance increases, resources become more concentrated, and movements of animals in contact with the substratum play an increasingly important role in colonization.
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