Dietary and stable isotope (δ 13C, δ 15N) analyses in alpine Ephemeroptera and Plecoptera

350 210 Stroud Water Research Center

Füreder, L., C. Welter, and J.K. Jackson. 2003. Dietary and stable isotope (δ13C, δ15N) analyses in alpine Ephemeroptera and Plecoptera. Pages 39-46 in E. Gaino (editor). Research Update on Ephemeroptera and Plecoptera. University of  Perugia, Perugia, Italy.

Headwater streams are intimately tied to their water sources, regional climate, and stream-side and upland vegetation as they define abiotic and biotic conditions. In the case of alpine headwater streams, altitude is also a factor as it directly affects water sources, climate, and vegetation. While previous studies have elucidated longitudinal and seasonal patterns of community structure associated with changes in local environmental conditions in alpine streams, little is known about nutrients, and food availability and utilization. In the Austrian Central Alps, we studied physicochemical conditions, food resources (i.e., benthic CPOM and FPOM, DOM, seston, Aufwuchs) and bottom faunas in nine reaches that contrasted in stream type (glacial versus non-glacial systems), riparian vegetation (above and below the treeline), and season (autumn versus spring). Gut content and stable isotope (δ 13C, δ 15N) analyses were used to estimate the utilization of food in nine dominant species (Ephemeroptera – Baetis alpinus, Rhithrogena loyolaea, Rhithrogena nivata; Plecoptera – Dictyogenus fontium, Leuctra sp., Nemoura sp., Protonemura sp., Rhabdiopteryx alpina, Siphonoperla sp.). Gut content indicated detritus was the dominant food consumed in all streams. Stable isotope analysis suggests several species feed opportunistically on algae, especially in glacial streams. Thus, it appears that autochthonous production can be important in glacial streams, in spite of long snow cover, frequent flooding, and high turbidity.