An experimental study on the effect of elevated temperature on the heterotrophic and autotrophic food resources of aquatic insects in a forested stream

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Abstract
The effect of temperature on the heterotrophic and autotrophic food resources of aquatic insects was investigated in outdoor experimental channels and in the laboratory. Elevated temperatures in outdoor channels resulted in accelerated decay rates and accumulation of organic layers on introduced tiles. Heterotrophic activity (substrate respiration) increased with temperature in the laboratory for leaf strips, flocculent organic matter, and stone surface organic layers. Autotrophic activity (substrate photosynthesis) was greater in the laboratory for flocculent detritus (per milligram ash-free dry weight) than for stone surface organic layers. These results indicate that the primary food resources of shredder, collector, and scraper functional guilds are enhanced by elevated temperature, but also suggest that coarse particulate organic matter may disappear from the stream more quickly. The results also point out that substantial autotrophic activity occurs within flocculent organic detritus.