Seasonal and diel patterns of invertebrate drift in different alpine stream types

Abstract

SUMMARY 1. We examined the seasonal and diel patterns of invertebrate drift in relation to seston and various habitat characteristics in two each of four different kinds of alpine streams [rhithral (snow‐fed) lake outlets, rhithral streams, kryal (glacial‐fed) lake outlets and kryal streams]. Samples were collected at four times of the day (dawn, midday, dusk and midnight) during three seasons (spring, summer and autumn). 2. Habitat characteristics differed mainly between rhithral and kryal sites, with the latter having higher discharge and turbidity, lower water temperature, and higher concentrations of ammonium, and particulate and soluble reactive phosphorus. Seasonality in habitat characteristics was most pronounced for kryal streams with autumn samples being more similar to rhithral sites. 3. The concentration of seston was lowest in the glacial‐influenced lake outlets and slightly higher in the stream sites; no seasonal or diel patterns were evident. 4. The density of drifting invertebrates averaged less than 100 m−3 and was lowest (<10 m−3) at three of the four kryal sites. Taxon richness and diversity were lowest at rhithral lake outlets. Chironomidae dominated the drift as well as benthic communities and <30% of benthic taxa identified were found in the drift. 5. Drifting invertebrates showed no consistent seasonal pattern. However, density tended to be highest in spring at rhithral sites and in autumn at kryal sites. No diel periodicity in drift density was found at any site and the lack of diel pattern may be a general feature of high altitude streams. 6. Glacially influenced habitat parameters were a major factor affecting drift in these alpine streams, whereas no clear differences were observed between streams and lake outlets. Our findings indicate that invertebrate drift in alpine streams is primarily influenced by abiotic factors, and therefore, substantially differs from patterns observed at lower altitude.

Towards a definition of environmental niches in alpine streams by employing chironomid species preferences

“…Besides these biotic variables, we identified sediment load and electrical conductivity to be related to chironomid assemblage patterns. Conductivity might not be a primal stressor for invertebrates but differs significantly between rhitral and kryal stream sites (Hieber et al, 2003) and is significantly related to invertebrate patterns in recent studies (Mori et al, 2011;Brown et al, 2015). Although we did not quantify disturbance, we derived sediment load as a proxy for hydraulic stress, which integrates discharge and concentration of suspended solids.…”

The food niche overlap of five fish species in the Úpoř brook (Central Bohemia)

“…Moreover, not only fish prefer different habitats, but the way benthos use the water column is species-specific. Hieber et al (2003) pointed out that certain species of mayflies are often a part of drift (Rhitrogena sp., Baetis sp. ), while others, even though also often occurring in benthos, are almost non-existent in drift (Ecdyonurus sp.).…”

Settling distances of benthic invertebrates in a sediment mobilization simulation in semi-natural flumes

“…In temperate streams, invertebrate drift is represented mainly by larval stages of Ephemeroptera, Diptera Simuliidae and Chironomidae, Plecoptera and Trichoptera, which are the most common benthic taxa in such habitats (Brittain and Eikeland, 1988;Hieber et al, 2003). Catastrophic drift (sensu CULP et al, 1985) is usually associated with flood conditions, during which the substrate is physically disturbed.…”