Abundance of Aquatic Insects (Trichoptera, Plecoptera, and Ephemeroptera) Immature and Adult Life Stages in Relation to Elevation and Water Flow on the Murinascia Grande River

Abundance of aquatic insects (Trichoptera, Plecoptera, and Ephemeroptera) immature and adult life stages in relation to elevation and water flow on the Murinascia Grande River Rikki Babuka Stuart Barker The immature and adult life stages of Trichoptera, Plecoptera, and Ephemeroptera in relation to elevation, water flow rates, and nutrient loading of the Murinascia Grande River, a small alpine river fed primarily by snow melt, in Val Piora, Ticino, Switzerland were studied during a 10 day period in July, 2014. Two sites were chosen along the river at different altitudes (1940 m ASL and 1981 m ASL), which also differed in the amount of nutrient input from runoff from nearby dairy cattle operations. The water flow rates, weather conditions, and air temperature were measured each day at each site while collecting specimens. The riparian vegetation was similar at both sites where the collections were made; willow (Salix spp.), was the dominant vegetation at both sites. Immature stages of the arthropods were collected with an aquatic sieving tool while disturbing the rocky substrate of the river, whereas adults were collected by a netting technique from vegetation and with UV-visible light traps each night. The abundance of immature stages of Trichoptera, Plecoptera, and Ephemeroptera were greater in slower moving water in the Murinascia Grande. The abundance of adult Trichoptera, Plecoptera, and Ephemeroptera was greater at the lower elevation site where vegetation was denser, and nutrient input greater. The study documented the differential diversity and density of these aquatic insects at two different sites separated by approximately 1 km, demonstrating that small differences in environmental conditions were correlated with variation in collection success. Overall, the study indicated the Murinascia Grande River was a productive location for investigating the bionomics of local aquatic insects. The study also showed the effects of nutrient input from manure runoff on the abundance of species found in the river. Furthermore, by using varied collecting techniques, it was determined that different techniques were most appropriate for the collection of the particular insect groups. Ephemeroptera nymphs were found most commonly in the river, and Trichoptera were the most abundant adults found in light traps. Finally, although all collecting techniques were successful at collecting aquatic insects, refinement of the techniques would be useful for more precisely estimating the diversity and density of these insects