|Longitudinal and seasonal pattern of insect emergence in alpine streams|
Füreder, L.; Wallinger, M.; Burger, R. (2005). Longitudinal and seasonal pattern of insect emergence in alpine streams. Aquat. Ecol. 39(1): 67-78
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588, more
Aquatic insects; Chironomidae [WoRMS]
|Authors|| || Top |
- Füreder, L.
- Wallinger, M.
- Burger, R.
Prevailing water sources and/or regional climate are known to have an important influence on hydromorphology and chemistry of high alpine streams, affecting biology and phenology of aquatic insects considerably. Seven reaches in two different stream types (glacial and non-glacial) in the European Central Alps were investigated along a longitudinal gradient above the tree line to elucidate community structure and emergence patterns of aquatic insects. Aquatic insect emergence was dominated by chironomid taxa in both streams (95.0% in the glacial vs. 90.5% in the spring-fed stream). Emergence rate was much higher in the non-glacial stream, with Chironomidae 638.9 ind. m-2 d-1 and EPT (Ephemeroptera, Plecoptera, Trichoptera) 20.3 ind. m-2 d-1 (annual mean), compared to the glacial stream (Chironomidae 132 ind. m-2 d-1 and EPT 7.0 ind. m-2 d-1). Whereas, in the glacial stream a richer and more diverse species composition was found at lower elevations, emergence rate and emerging taxa numbers were higher at higher altitude in the non-glacial stream. Seasonal comparisons also showed a significant difference between the two streams. In the glacial stream maximum emergence was in April/May, whereas, in the non-glacial stream in July. A comparison with similar studies carried out in alpine streams showed that abundance and biomass of emerging insects were relatively low in the glacial stream. The continuous emergence throughout the summer is another example of insect life-cycle adaptation to the harsh environmental conditions in glacial streams: most likely, emergence during the warmer summer months, where the probability of experiencing favourable climate conditions on land is higher than for the rest of the year, was an evolutionary advantage for many glacial stream taxa.