engleski

Do alpine stream insects change their feeding habits in response to environmental change?

Due to global warming and glacier recession, alpine streams have received increased attention as sensitive indicators to climatic change. Alpine stream macroinvertebrates can adapt to climate-induced environmental changes by altering life histories and by feeding plasticity. This project enhanced our understanding of food-webs, feeding plasticity and distribution patterns of macroinvertebrates inhabiting alpine streams undergoing rapid glacial recession. Our first goal was to compare seasonal variation in isotopic (δ13C, δ15N) signatures (resource changes) among different alpine streams with contrasting riparian development. Study sites were selected based on an earlier study of food webs in the Val Roseg in 2001, allowing us to compare spatial patterns in resource acquisition in present food webs with those a decade ago. Despite major environmental changes that occurred in the catchment, the isotope results largely coincided with results in 2001. Macroinvertebrate δ15N values ranged from ca. -6.9 to 6.7, whereas δ13C values ranged from -33.5 to -18.4. Carbon isotope ratios showed that non-predator macroinvertebrates fed on biofilms and detritus at sites nearest glaciers, whereas they consumed more allochthonous-derived organic matter at downstream sites (indicating high feeding plasticity). Seasonal changes in δ13C signatures of non-predator macroinvertebrates corresponded with seasonal changes in biofilm δ13C, indicating that the energy base within alpine streams is primarily autochthonous. Lastly, biofilm δ13C was lower in the lake outlet and proglacial stream than in the main channel, suggesting different biofilm communities and/or carbon sourcing at sites near the glacier.

global warming; glacier recession; food webs; macroinvertebrates; stable isotopes

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