Small fly ash settling ponds (e.g. 2-yr life time) should not be used after they are ~87–90% full when effluents are released into lotic systems. When our pond was > 90% full, mayflies (Stenonema, Heptagenia, Paraleptophlebia), stoneflies (Acroneuria), and caddisflies (Cheumatopsyche) were significantly (α = 0.05) reduced in density, number of taxa, and diversity in the stream receiving system. Highly resistant coleopterans (e.g. Psephenus herricki) became the dominant species. Two to 10 mo were required for the insect community to recover after cessation of ash effluent. Potential lethal effects of fly ash may result from ash particles, heavy metal, and other elements (especially As and Se), and alkaline pH increases above 9.0. Which fraction of fly ash is most limiting to each insect group or species needs far more examination. Ash particle concentrations (total suspended solids, [Formula: see text]) were not acutely toxic in 96-h laboratory bioassays to sensitive mayflies (Stenonema pudicum) or resistant coleopterans (P. herricki), nor were heavy metals (Cd, Cu, Zn) at concentrations similar to those found in the fly ash effluent, although data are lacking to evaluate long-term (e.g. [Formula: see text]) effects. Alkaline pH exposures need more research, since the 96-h LC50 of 9.5 for S. pudicum was similar to pH values observed in the receiving stream during summer low-flow, high-temperature conditions when the ash pond was > 95% full.
The life history of the giant stonefly Pteronarcys dorsata was investigated in a warm water fourth order river in southwestern Virginia. The life cycle of P. dorsata was univoltine with emergence occurring mid-March to 1st week of April. Adults lived up to 42 days in the laboratory. Mean fecundity was 242 eggs with up to four separate egg batches produced. Eggs hatched in 23 to 38 days. Early nymphal instars were collected in the river in mid-June. Nymphs reached maximum size by late November or December. During the warm months nymphs were found in mats of Podostemum ceratophyllum (river weed) and through the winter months under large unembedded rocks or leaf packs. The diet consisted of diatoms and detritus. Higher water temperatures of longer duration in the Little River probably allowed this species to complete its life cycle in 1 year rather than the 2 to 4 years previously reported.
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