Temporal dynamics of production and ingestion of the dominant mayflies in a subtropical stream in China

We investigated temporal dynamics of secondary production and trophic basis for four dominant mayfly species in a second-order river of the Hanjiang River basin in Middle China from June 2003 to June 2004. The secondary production of the dominant four mayfly species, comprising nearly 90% of the total density of mayflies, was 14.45 g m⁻²  per year for Ephemera sp., 9.15 g m⁻²  per year for E. sinensis, 7.23 g m⁻²  per year for Leptophlebia sp. and 1.55 g m⁻² per year for C. nigropunctata. C. nigropunctata and Ephemera sp. had most of their production in winter (from January to March), while E. sinensis and Leptophlebia sp. produced in two intervals, from June to September (summer) and from December of the first year to March of the next year (winter). Overlap in temporal distribution of production among the four mayflies was generally high (>0.60), especially those of C. nigropunctata, Ephemera sp. and Leptophlebia sp. Overlap of Leptophlebia sp. and Ephemera sp. was >0.85. Patterns of the four food types (amorphous detritus, vascular plant detritus, fungi, and diatoms) for each mayfly varied significantly (P < 0.01) over time, and patterns of food ingestion between the four mayflies were also significantly different (P < 0.05–0.01). Among the four main food types, all mayflies used amorphous detritus the most, which constituted 53–96% of their diets and contributed 54–97% to their production. Thus, temporal changes in the food web for mayflies in Heizhuchong stream are quantitative rather than qualitative.