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Abstract
The effect of desiccation on epilithic algae was studied in two subtropical rainforest streams in south‐east Queensland, Australia. Diatom‐dominated algal assemblages on stream‐collected cobbles were subjected to desiccation periods of 15 and 30 days, followed by re‐immersion in the streams for 15 and 30 days. Algal assemblages in the two streams showed different responses to the desiccation and re‐immersion treatments, most likely the result of differences in the physical and chemical characteristics of the two stream ecosystems. Following the re‐immersion treatments, chlorophyll a was significantly reduced in one stream, with no significant changes recorded in ash‐free dry mass. In the second stream, epilithon ash‐free dry mass had increased significantly by the end of the re‐immersion period, while no significant effects of desiccation were measured. Results indicated that, at least in one stream studied, diatom assemblages on the experimental cobbles were not able to withstand short periods of desiccation (15 days) and did not recover after 30 days of re‐immersion in the streams. The results obtained here showed that desiccation must be considered an important factor controlling epilithon communities in streams.
